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2014, 33 (S2): 0-

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DAMAGE MODEL OF ROCK UNDER TEMPERATURE AND LOAD

ZHANG Huimei1，LEI Lina1，YANG Gengshe2

2014, 33 (S2): 3391-3396 doi: 10.13722/j.cnki.jrme.2014.s2.001

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The interior defect is random distribution in rock. The damage model of rock under coupling action of temperature and load was established by the damage mechanical theory，and the model parameters were determined. The evolutionary route of rock macro-mechanical properties induced by micro-structural damage was analyzed. The deformation and failure laws of rock were predicted and the rationality of damage model was verified. It is shown that the total damage evolutionary route under temperature and load coupling action reflects the whole process of closure，initiation，propagation and coalescence of microcrack in rock，and then the appearance of macroscopic crack and the disruption of rock. Under high temperature，the rock damage intensifies， which is displayed on the deterioration of the mechanical properties of rock on the macro level. With increasing of the confining pressure，the damage degree and deterioration decrease and the strain increases for the same extent of damage，which is manifested on the enhanced ability to resist destruction and the increased plastic deformation in macroscopic view.

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SEEPAGE CALCULATION MODEL FOR ROUGH JOINT SURFACE CONSIDERING FRACTAL CHARACTERISTICS

WANG Gang1，2，HUANG Na1，JIANG Yujing1，3，LI Bo3，WU Xuezhen1，ZHANG Xuepeng1

2014, 33 (S2): 3397-3405 doi: 10.13722/j.cnki.jrme.2014.s2.002

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Understanding hydro-mechanical behavior of single rock joints is a basic building block to assess several important properties of jointed rock mass associated with fluid flow，a representative one among which is mass transport in rock mass. The surface roughness plays an important role in the fluid flow behavior through a single rock joint，which has received extensive studies in the past a few decades，by using various approaches，such as JRC，statistical parameters and fractal dimension. An improved equation involving the relation between mechanical aperture and hydraulic aperture，with the employment of the fractal dimension of joint surface was proposed to evaluate the effects of surface roughness on the behavior of fluid flow through rock joints. To verify this equation，a number of coupled shear-flow tests for several artificial rock joint specimens with the surface characteristics of natural rock joints were carried out，and the evolution of mechanical and hydraulic apertures during shear processes were evaluated. The fractal dimension of each specimen was calculated using cubic covering method based on the measured surface topographical data. Compared with other commonly used equations，such as Zimmermans equation and Yeos correction equation，the proposed equation gives better fitting to experimental measurements，which may serve as an effective approach for quantitative estimation of the hydro-mechanical behavior of rock joints.

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STUDY OF DAMAGE TENSOR FOLDING MUTATION MODEL FOR FRACTURING ROCK MASS AND ITS APPLICATION

ZHAO Wanchun1，2，WANG Tingting1，FU Xiaofei1，2，GUAN Bing1

2014, 33 (S2): 3406-3411 doi: 10.13722/j.cnki.jrme.2014.s2.003

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In order to accurately describe the problems of fracturing rock mass damage mutation cracking up crack in the oil and gas field engineering，based on the changes of rock porosity，the rock mass damage variable is defined and the damage constitutive model in the process of rock mass deformation is established. Considering that the process of reservoir fracturing rock mass damage is the accumulation increasing and suddenly releasing of rock mass deformation energy，the folding mutation model of fracturing rock mass damage tensor type is established based on the principle of conservation of energy. The balance equation of fracturing rock mass damage mutation and the calculation model of energy release quantity of rock mass damage mutational damage are given. Combined with quartz sandstone and lithic sandstone characteristics of Sulige block of Changqing Oilfield，the change rule of energy release quantity of rock damage mutational damage under hydraulic fracturing is calculated，and a new method is provided for the study of the oil and gas field fracturing rock mass damage crack formation.

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STUDY OF rheologICAL TESTS AND ITS PARAMETERS IDENTIFICATION OF SOFT ROCK IN FRACTURED BELT

ZHANG Yu1，2，XU Weiya3，WANG Wei3，SHAO Jianfu3，GU Jinjian3

2014, 33 (S2): 3412-3420 doi: 10.13722/j.cnki.jrme.2014.s2.004

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Some fractured structures which compose of soft sandstone have been developed in a hydropower project. It has poor integrity and pore cementation contact，and the creep properties producing a significant impact on the deformation and stability of the dam under long term load. Based on the characteristics of loose organizational structure，high moisture content，poor physico-mechanical properties，the triaxial creep tests were carried out first. The results show that the soft rock has a significant creep property，and the creep curve is mainly divided into transient and steady creep. Increasing stress can aggravate the creep deformation，and the finally failure of the specimen shows the characteristics of large axial compression deformation，obvious volumetric ductility dilation and large steady creep rate. Secondly，the creep curves are described by taking three dimensional Burgers creep model. The parameters are identified with combination of Quasi-Newton optimized algorithms method. The selected model can describe the creep properties of soft rock correctly. The research results have important reference value for similar projects.

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SIZE EFFECT OF COMPRESSION STRENGTH AND END CONSTRAINT OF ROCKS BY DISTINCT ELEMENT SIMULATION

SUN Chao1，2，LIU Fang1，2，3，JIANG Mingjing1，2，3，CHEN He1，2

2014, 33 (S2): 3421-3428 doi: 10.13722/j.cnki.jrme.2014.s2.005

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In order to understand the size effect of compression strength of rocks caused by the end constraint conditions，a bond contact model of rocks based on micromechanical test data was implemented into the two-dimensional distinct element code for simulating the uniaxial compression tests of rock samples with different slenderness ratios under different constraint conditions. The simulation results were compared with theoretical solutions. The simulation results confirm that end constraint is one of the reasons causing the size effect of uniaxial compression strength of a homogenous rock sample，and the size effect disappears when the ends of the samples are frictionless. Under the same constraint conditions，the samples with a larger slenderness ratio break at a smaller number of bond breakage，so the uniaxial compression strength decreases with the increase of the slenderness ratio until it reaches a steady value when the ratio exceeds 2.0. The strength of rock samples with a small slenderness ratio increases with the increase of the friction coefficient of the ends of samples until it reaches a steady value when the coefficient exceeds 0.5. In addition，the number of bond breakages at failure and the proportion of bond compression-shear-torsion failure substantially increase with the increase of friction coefficient.

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STUDY OF MECHANICAL PROPERTIES OF RAW COAL UNDER HIGH STRESS WITH TRIAXIAL UNLOADING

LIU Quansheng1，LIU Kaide1，2，LU Xingli1，ZHU Jiebing3

2014, 33 (S2): 3429-3438 doi: 10.13722/j.cnki.jrme.2014.s2.006

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Based on the raw coal from B10 seam of －780 m in Huainan coal mine，unloading tests under high stress were carried out in the style of non-uniform velocity of unloading confining pressure and axial pressure synchronously，and the test results were compared with that of conventional triaxial experiments under the same confining pressure. The deformation，strength，parameters and failure characteristics of the raw coal under unloading were studied. The results show that：(1) From the unloading point，the deviatoric stress-axial strain curves pitch up abruptly，and its gradient increases. But compared with conventional triaxial curve，peak axial strain under unloading condition decreases apparently，yield process is obviously shorten and post-peak brittle failure characteristics is significant. (2) From the unloading point，the deviatoric stress - lateral strain curves fall abruptly，and its gradient decreases. The peak lateral strain is smaller than that of conventional triaxial curves. Before post-peak destroying，the stress drops slowly，and 3 changes greatly. While that of conventional triaxial curves fall rapidly，and 3 changes small. (3) From unloading point，the deviatoric stress-volume strain curves reverse left instantly，presenting the features of obvious dilatancy. And in the interval near peak point，the dilatancy is the strongest. However，except the conventional triaxial curves show dilatancy characteristics under low confining pressure conditions，the curves always extended right under high confining pressure，and presenting a continuous shrinkage state. (4) In the process of unloading，the deformation modulus E always reduces，and the damage factor D and Poissons ratio μ always increase. And the three change trend are gentle before peak，gradually increase after peak. Moreover，the E，D and μ all increase in general with the increase of initial confining pressure. (5) The failure modes of unloading coal samples are mainly shear failure，and rupture angle is in the range of 20°–32°，which increases in parabolic trend with the increase of confining pressure. Under the same initial confining pressure，the value of θ is less than that of the triaxial angle. (6) The shear strength parameters c of coal under unloading is less than that of the triaxial，and the value of is very close.

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EXPERIMENTAL STUDY OF MICROSTRUCTURE AND ROCK PROPERTIES OF SHALE SAMPLES

SHI Xian1，2，CHENG Yuanfang1，JIANG Shu2，CAI Dongsheng3，ZHANG Tao4

2014, 33 (S2): 3439-3445 doi: 10.13722/j.cnki.jrme.2014.s2.007

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The study of shale mechanical properties is very important for well completion and stimulation in shale gas reservoirs. Thus，the geomechanical properties of Paleozoic marine shale in Lower Yangtze Basin were studied. With the application of argon ion polisher，high-solution CT and scanning electron microscope，the shale samples were processed and their microstructures were observed. Besides，mineral compositions of this shale were analyzed by XRD technique. In order to get the compression characteristic of shale，the scratch and uniaxial experiments were performed. In addition，the loading and unloading situations were simulated under different effective stress conditions in order to reduce negative effects of natural fissures and rock relaxation. Finally，the multi-stage triaxial compression deformation experiment was performed on the triaxial rock testing system for calculating cohesive strength and inherent friction angle. The study of shale mechanical properties is very important for well completion and stimulation in shale gas reservoirs. Thus，a systematic experiments was performed on Paleozoic marine shale samples collected from Lower Yangtze Basin，and the microscopic structure，mineral compositions and the geomechanical properties of marine shale samples were studied. Testing result shows that except for shale sample with natural fractures，both the values of Youngs modulus and Poissons ratio increase with the increase of confining pressure. But in the unloading condition，the Youngs modulus increases with the decrease of confining pressure，whereas the Poissons ratio is greater than that in its loading condition. The inherent friction angle is within approximately 40°and the shale sample with high brittleness index tends to crack as fracture network according to the multi-stage triaxial compression test. This research is greatly helpful for the study of shale mechanical properties，and provides technical parameters for well completion design and stimulation.

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RHEOLOGICAL MODEL AND NUMERICAL SIMULATION OF JOINTED ROCK MASSES REINFORCED BY PASSIVE AND FULLY-GROUTED BOLT

LIN Yongsheng，HE Ji，CHEN Shenghong

2014, 33 (S2): 3446-3455 doi: 10.13722/j.cnki.jrme.2014.s2.008

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Based on the model of jointed rock masses reinforced by passive and fully-grouted bolts，a modified model of jointed rock masses reinforced by passive and fully-grouted bolts is proposed by introducing Nishihara model. This model pays attention to the importance of viscoelastic rheology of soft-rock and hard-rock interface. Based on the modified model，the elastic-viscoelastic-viscoplastic constitutive equation is established in a 3D FEM program. The modified model is verified by the laboratory test，and the result of the modified model is more comparable with the experimental result than the result of the former model. The results of case two show that the viscoelastic rheology of rock mass will cause the increase of bolt stress. When the other parameters are fixed，the smaller the viscoelastic rheological coefficient of rock mass is，the faster the bolt stress changes，and the smaller the viscoelastic modulus of rock mass is，the greater the final bolt stress is. Without considering viscoelastic rheology of rock mass in the analysis of bolts for reinforcement of rock mass，the bolt stress will be smaller than that when considering，so that the result of the analysis will be on the safe side.

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ADVANCES IN DEVELOPMENT OF COUPLED STRESS-FLOW TEST SYSTEM FOR ROCK JOINTS

XIAO Weimin1，2，XIA Caichu2，DENG Ronggui1

2014, 33 (S2): 3456-3465 doi: 10.13722/j.cnki.jrme.2014.s2.009

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The coupled stress-flow properties of rock joints，which have remarkable impacts on the stability of rock masses，have become a hot problem of rock mechanics in recent two decades. The most effective way to study the coupled stress-flow characteristics of rock joint is to perform laboratory coupled stress-flow tests. Hence，the coupled stress-flow test system that is able to achieve the true coupled stress-flow process can provide an important basis for these researches. In this paper，three aspects of advances in the development of coupled stress-flow test system at home and abroad are involved as follows. (1) The methods adopted to achieve constant normal stiffness(CNS) conditions during shearing process are summarized. (2) Advances in coupled stress-flow test of rock joint with only normal loadings are reviewed. (3) Recent advances in the development of coupled shear-flow test system for rock joints，which include the realization of flow boundary conditions，new sealing system of shear box and technologies to achieve high hydraulic pressure during coupled shear-flow test，are introduced. The advantages and deficiencies of different coupled shearing-flow test systems developed in recent years are analyzed in detailed，on the basis of which new challenges for developing new coupled shearing-flow test system are proposed by considering high stress and high hydraulic pressure conditions existing in deep underground excavation programs.

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EXPERIMENTAL STUDY OF FATIGUE CHARACTERISTICS OF LIMESTONE SAMPLES SUBJECTED TO UNIAXIAL CYCLIC LOADING WITH DIFFERENT FREQUENCIES

ZHAO Kai1，2，3，QIAO Chunsheng1，LUO Furong2，HAO Zhihong3

2014, 33 (S2): 3466-3475 doi: 10.13722/j.cnki.jrme.2014.s2.010

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For searching the impact of loading frequency on the fatigue life and deformation characteristics of rock，low cyclic fatigue tests of limestone were conducted under 0.5，1.0，1.5，2.0，2.5 and 3.0 Hz loading frequencies by using a MTS 810 dynamic test system. The results indicate that there are well linear relationship between fatigue life and loading frequency in double logarithmic coordinate and fatigue life increases with the raises of frequency. It is mainly due to the strong sensitivity of limestone for loading rate and uniaxial compress strength of limestone increasing with the improvement of loading rate. The axial deformation of limestone goes through three-stage evolution. The cumulative amount of deformation in the second and third evolution stages is almost independent of loading frequency. In the range of loading frequencies，the ultimate deformation of limestone samples in fatigue tests is controlled by uniaxial compressive stress-strain curve，the calculated relative error is nothing to do with loading frequency. The tests results under different frequencies indicate that ultimate deformation law of rock fatigue failure which is hardly impacted by load frequency is a universal law. The average strain increment of each cycle in the second evolution stage reduces with the increase of loading frequency. Combined with the law of limestone deformation evolution，a strain-increment-based fatigue life calculated model was proposed. The evaluation results of this model are more conservation than measured ones，and its parameters are easy to obtain.

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EXPERIMENTAL STUDY OF MECHANICAL PROPERTIES OF COAL CONTAINING GAS UNDER UNLOADING CONDITIONS

XU Youlin1，2，KANG Hongpu1，2，ZHANG Hui1，2，WANG Weizhong3

2014, 33 (S2): 3476-3488 doi: 10.13722/j.cnki.jrme.2014.s2.011

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Based on the triaxial stress thermal-hydro-mechanical coal containing gas system，unloading confining pressure experiments under different gas pressures and confining pressuresand speeds of unloading confining pressures，are carried out to study the influences of gas pressure，stress，speed of unloading confining pressure and their coupling conditions on the mechanical properties and the laws of roadway surrounding rock deformation and failure. The results show that：(1) The gas pressure has an obvious infulence on the coal elasticity modulus. The elasticity modulus decreases with the increase of gas pressure. (2) The confining pressure has an obvious infulence on the coal elasticity modulus. The elasticity modulus increases with the increase of confining pressure. (3) The speed of unloading confining pressure has an obvious infulence on the coal elasticity modulus. The elasticity modulus decreases with the increase of the speed of unloading confining pressure. (4) The time before deformation and failure increases with increase of confining pressure，decrease of gas pressure and the increase of speed of unloading confining pressure.

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METHOD OF QUANTITATIVE DETERMINATION OF JOINT ROUGHNESS COEFFICIENT

LI Hua，HUANG Runqiu

2014, 33 (S2): 3489-3497 doi: 10.13722/j.cnki.jrme.2014.s2.012

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In order to meet the measurement requirements of joint roughness coefficient(JRC) in the condition of engineering practice，statistical analysis and numerical simulation method were adopted to carry out the vector analysis of the Bartons standard roughness rating profile curves and some undulate shape of practical rock joints. Taking the measurement condition of joints surface morphology fully into account，relative waviness Ra and elongation R were determined to evaluate JRC. At the same time，the standard roughness rating profile curves were classified as flat，wavy and serrated. Eventually experiential formulas were established and expressed by images and the sensitivity of JRC relative to the change of R and Ra was analyzed and the Bartons standard roughness rating profile curves were expressed by functions. Consequently，the quantitative determination of JRC and the fast calculation of joint shear strength using JRC-JCS model can be achieved.

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STUDY OF ACOUSTIC EMISSION AND FRACTAL CHARACTERISTICS OF SOFT AND HARD COAL SAMPLES WITH SAME GROUP

GAO Baobin1，2，3，LI Huigui1，3，LI Lin1，3，WANG Xiaolei1，2，YU Shuijun1，3

2014, 33 (S2): 3498-3504 doi: 10.13722/j.cnki.jrme.2014.s2.013

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In order to study of acoustic emission and fractal characteristics of soft and hard coal with same group under uniaxial compression，focusing on group Yi soft and hard coal in Pingmei Group，an experimental study is carried out to investigate the acoustic emission characteristics of soft and hard coal with the same group in Pingmei group by using RMT–150C rock mechanics test system and CDAE–1 acoustic emission instrument，and analyze the fractal characteristics of the acoustic emission count sequence. The results show that phenomenon of the acoustic emission cumulative count surge appears the soft and hard coal samples in failure process under compression uniaxial. The average growth rate is 855.4 of soft coal and the average growth rate is 914.32 of hard coal. Phase space dimension has a certain influence on the correlation dimension，but the effect will be more and more smaller with increasing of the phase space dimension. The fractal dimension is relatively small of acoustic emission cumulative count sequence of the soft and hard coal at the initial loading stage，and at the near peak stress it will reach the maximum value，and then it will appear dump phenomenon，at last it can be used as a forewarning of the instability failure of coal body.

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NUMERICAL TEST VERIFICATION OF CONSTITUTIVE MODEL BASED ON THE GENERALIZED POTENTIAL THEORY

ZHONG Zhihui1，2，YANG Guanghua1，2，3，4，FU Xudong1，WEN Yong1，ZHANG Yucheng2，3，4

2014, 33 (S2): 3515-3522 doi: 10.13722/j.cnki.jrme.2014.s2.015

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From the mathematical principles，the generalized potential theory can be employed to create constitutive model of geomaterial directly. Compared with the conventional plasticity theory，creating constitutive model by the generalized potential theory has many advantages such as less assumptions，clearer mathematical basis，and better computational accuracy. This theory can also apply to general materials. The double surface model is a simple and practical constitutive model of the generalized potential theory. To explain its determination method and rationality，the particle flow code——PFC3D is used to make numerical tests to verify the double surface model. The verification process is as follows：first，creating an assembly of spherical particles as the sample of synthetic material，and simulating conventional triaxial tests of this sample by PFC3D；second，establishing the coefficients of the double surface model of this sample according to conventional triaxial test results；finally，predicting the behavior of this sample under triaxial tests with different stress paths by the double surface model. The analysis results prove that the double surface model has good prediction accuracy. Moreover，the determination method of the double surface model illustrated in this paper can apply to actual soils and other materials，which has certain reference value.

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STUDY OF MARBLE DAMAGE EVOLUTION LAWS UNDER UNLOADING CONDITIONS BASED ON NUCLEAR MAGNETIC RESONANCE TECHNIQUE

ZHOU Keping，HU Zhenxiang，LI Jielin，GAO Feng，WANG Mingqiu

2014, 33 (S2): 3523-3530 doi: 10.13722/j.cnki.jrme.2014.s2.016

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To study the damage characteristics of rock microstructure under unloading condition，the loading and unloading confining pressure tests on the marble specimens under different initial confining pressures and different unloading confining pressure ratios are conducted. The crosswise relaxation time T2 distribution，rock porosity and nuclear magnetic resonance imaging(MRI) are obtained by the nuclear magnetic resonance(NMR) technique. The results show that：(1) As the unloading confining pressure ratio increases，the T2 spectrum curves move towards right with the spectrum areas keeping increasing，and the porosity of the specimens increases，which indicates that the damage of specimens increases. (2) As the unloading confining pressure ratio increases，the spectral peaks of small microcracks move towards right，but the spectrum areas of small microcracks are relatively small，which indicates that the size of small microcracks increases and the number of small microcracks changes randomly. The influence of small microcracks is weak to the porosity of the specimens. There is a critical value near the unloading confining pressure ratio of 75%. When the unloading confining pressure ratio is below the critical value，new microcracks appear constantly in the specimens. When the unloading confining pressure ratio is above the critical value，the generation of new microcracks is limited. (3) As the unloading confining pressure ratio increases，the spectral peaks of big microcracks move towards right. The spectrum areas of big microcracks keep increasing and account for over 96% of all microcracks in the rock specimens，which indicates that the size and number of big microcracks increase and the change of big microcracks determines the porosity and damage of rock. (4) The development process of microcracks and fracture in the rock specimens is shown dynamically.

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RESEARCH OF PRE-REINFORCEMENT MECHANISM AND MODEL TEST OF TUNNEL-LANDSLIDE SYSTEM

WU Honggang1，YANG Tao2，MA Huimin1，ZHANG Hongli1

2014, 33 (S2): 3531-3538 doi: 10.13722/j.cnki.jrme.2014.s2.017

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When tunnels are constructed in landslide area，it would be inevitably to suffer from landslide impact. At present，few studies force on the interaction mechanism of tunnel-landslide. The tunnel excavation method has not been considered seriously by engineering as well as reinforcement measures. Focusing on the tunnel-landslide parallel system，pre-reinforcement mechanism and design philosophy of tunnel-landslide system are proposed. Taking Yangpoli tunnel on Wuhan-Guangzhou highway as a prototype，geomechanical model used to study the mechanism of engineering pre-reinforcement and processing pre-reinforcement is established. The variation of displacement and stability in tunnel-landslide system are explored carefully while excavating forward or reverse in the engineering pre-reinforcement condition as well as without pre-conditions. The test results show that the tunnel excavation direction has some impact on landslide stability that reasonable excavation direction is favorable. Reinforcement project has a very good role in the inhibition of landslide deformation. Landslides began deformation along with tunnel excavation，and the landslide thrust transfers gradually to reinforcement structure making the subsequent landslide displacement less than that unreinforced.

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RESEARCH ON RELATIONSHIP BETWEEN JRC OF BARTONS STANDARD PROFILES AND STATISTIC PARAMETERS INDEPENDENT OF SAMPLING INTERVAL

SUN Futing，SHE Chengxue，WAN Litai

2014, 33 (S2): 3539-3545 doi: 10.13722/j.cnki.jrme.2014.s2.018

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Ten standard joint profiles proposed by Barton is taken as the research object. Firstly，relationship between four statistical roughness parameters and sampling interval of the ten profiles is analyzed，and roughness power parameters are calculated by using power function to describe the relationship. Secondly，new computational formulas of JRC are established based on the power roughness parameters，it makes the JRC computational formulas no longer depends on sampling interval of joint profiles. Finally，an approximate method to estimate JRC is proposed and any sampling interval in a certain scope can be selected to measure the joint profiles. The new method to calculate JRC value has a certain theoretical innovation and good application prospect.

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RESEARCH ON MECHANICAL CHARACTERISTICS OF INTERLAYERED ROCK MASS UNDER UNLOADING CONDITION

XIONG Liangxiao1，2，YU Lijun3，YANG Changbin4，LI Tianbin2

2014, 33 (S2): 3545-3554 doi: 10.13722/j.cnki.jrme.2014.s2.019

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Take the interlayered rock mass composed of green schist and marble as subject of study，the numerical analysis of its mechancial characteristics under unloading condition was done by using FLAC3D. The research results show that the initial deviatoric stress has great effect on stress state and deformation when rock sample fails of confining pressure reduction test under constant axial stress. The stress increment ratio also has great effect on stress state and deformation when rock sample fails of confining pressure reduction test with increasing axial stress. The stress path has little effect on characteristics of strength and deformation of rock. The strength of interlayered rock mass is nearly not influenced by the stress path，but the deformation is significantly affected.

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EFFECT OF CORRELATION BETWEEN JOINT TRACE AND APERTURE ON HYDRO-MECHANICAL BEHAVIOR OF FRACTURED ROCK MASS

WU Yuexiu1，LIU Quansheng1，2，LI Jinlan1，HE Jun1

2014, 33 (S2): 3555-3562 doi: 10.13722/j.cnki.jrme.2014.s2.020

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The correlation between joint trace and aperture has an effect on the distribution and permeability of joint network. Finally，the hydro-mechanical behavior of fractured rock mass is influenced. Based on nuclear disposal project in Sellafield，the correlation between joint trace and aperture was studied when they followed the power-law distribution. With discrete element software UDEC，the effect of correlation between joint trace and aperture on hydro-mechanical behavior of fractured rock mass was analyzed. At the end，a calculation system was proposed to do the hydro-mechanical calculation for fractured rock mass considering the correlation between joint parameters. It is concluded that correlation between joint trace and aperture has a significant effect on hydro-mechanical behavior of fractured rock mass. When the correlation between joint trace and aperture was power-law function，permeability tensor and representative elemental volume(REV) of fractured rock mass increased.

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EXPERIMENTAL STUDY OF DEFORMATION AND ENERGY EVOLUTION LAW OF COAL UNDER CYCLIC LOADING

XU Jiang1，2，LI Bobo1，2，ZHOU Ting1，2，LIU Dong1，2，CAO Jie1，2，YE Guibing1，2

2014, 33 (S2): 3563-3572 doi: 10.13722/j.cnki.jrme.2014.s2.021

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Based on the self-developed triaxial servo-controlled seepage equipment for thermal-hydrological- mechanical coupling of coal containing methane，the experimental study of cyclic load of coal was performed on coal samples under different temperatures. The results are shown as follows：(1) The absorbed energy in axial direction U1 increases with the increase of axial stress，its converted into elastic strain energy Ue1 and consumed energy for radial deformation U3，and the dissipated energy Ud for plastic deformation or cracks in unloading stages，the radial elastic strain energy Ue3 produced by confining pressure is supplemented at the same time. (2) The absorbed energy U is positive，it decreases gradually with the increase of the cycle index，and it begins to flatten after the sudden drop between the first and the second cycle. In the same cycle，U decreases with the temperature increase，and it is the most stable in 70 ℃. (3) The absolute value of axial dissipated energy Ud1，radial dissipated energy Ud3 and the dissipated energy Ud decrease with the increase of the cycle index，and tend to stably. (4) The absolute value of conversion rate of Ud and Ue decrease with temperature increase，but the conversion rate of U3 has not changed much，the three forms of energy all decrease with increase of cycle index，and the absolute value of releasing rate of Ue is faster than Ud and U3.

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STUDY OF IMPERMEABILITY OF ROCK STRATUM BASED ON WATER INJECTIION TEST

HUANG Zhen1，JIANG Zhenquan1，CAO Dingtao2，LI Ting3

2014, 33 (S2): 3573-3580 doi: 10.13722/j.cnki.jrme.2014.s2.022

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Water injection test is a particularly useful technique to determine the impermeability of rock stratum. Based on Baodian coal mine，the data of water injection test were obtained and permeability coefficient of floor rock were deduced through high pressure water injection test. Based on the analysis of data，the results show that the curves of permeability coefficient and pressure are provided with a significant segmentation，which is stable before fracturing pressure and shows linear relationship with high regression coefficient after fracturing pressure. The relationship between permeability coefficient and water discharge is close to linear. Results show that if water discharge continue to rise，the permeability coefficient tends to increase；the impermeability of floor rock stratum can be judged by the calculated results of the critical impermeability strength. The result of the impermeability from highest to lowest is mudstone，siltstone，fine sandstone，limestone. The results make a important reference for safety-mining of follow-up working face.

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EXPERIMENTAL STUDY OF PRECAUTION TECHNOLOGY OF HEADING FACE COAL AND GAS OUTBURST BASED ON DYNAMIC CHANGES OF STRESS AND METHANE CONCENTRATION

JIANG Fuxing1，YIN Yongming1，ZHU Quanjie1，WANG Cunwen1，QU Xiaocheng1，2

2014, 33 (S2): 3581-3588 doi: 10.13722/j.cnki.jrme.2014.s2.023

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Research on the influential factors of coal and gas outburst，a precaution technology of heading face coal and gas outburst based on dynamic changes of stress and methane concentration is proposed，which is called the SMD method. The outburst fuzzy comprehensive prediction model is established by the drilling stress increments，gas pressure and the changes in characteristics of the methane concentration time series as the determination index，which is applied to determine the index value of heading face coal and gas outburst. Based on this，the monitoring and precaution system of coal and gas outburst is developed. The system is capable of real-time monitoring heading face dynamic changes of surrounding rock stress and the dynamic changes of the concentration of coal gas，and the continuous and real-time monitoring and precaution for the coal and gas outburst dangerous areas and danger severity could be implemented by the system. Through field application in mine，it is proved that the system can predict the precautions dangerous areas and dangerous levels accurately. In this way，the secure development of dangerous working faces with coal and gas outburst can be done.

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RESEARCH ON SHEAR STRENGTH CHARACTERISTICS OF SLOPE ROCK MASS ON PROJECT OF WATER DIVERSION FROM HAN TO WEI RIVER PROJECT

GUO Xifeng1，2，YAN Echuan2，WU Xiangchao1，YIN Jianmin1，HE Peitian1

2014, 33 (S2): 3589-3594 doi: 10.13722/j.cnki.jrme.2014.s2.024

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Sanhekou hydraulic project is one of the two potable water source projects of the water diversion from the Han to the Wei river project，and shear strength properties of the slope rock mass are the main rock mechanics. To research slope rock mass strength characteristics，many groups of in-situ direct shear test for different lithology and weathering degree rock mass were conducted on abutment slope，which loading paths and maximum pressure were the same as the conditions of the arch dam acting on the rock mass. By comprehensive analyzing 7 groups rock mass shear test results and 7 groups interface between concrete and rock shear test results，variation range of the shear strength parameters for different rock mass were put forward and influencing factors of test results，direct shear test failure characteristics were studied. At last，results and failure features of interface between concrete and rock shear test and rock mass shear test were contrasted.

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FRACTAL CHARACTERISTIC OF FRAGMENT SURFACE FROM ROCK BURST TEST BASED ON CONFOCAL LASER SCANNING MICROSCOPE

MA Aiyang，WU Faquan，SHA Peng，WANG Dingwei

2014, 33 (S2): 3595-3600 doi: 10.13722/j.cnki.jrme.2014.s2.025

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In order to obtain surface fractal characteristics of fragments from rock mechanics test，especially the two-dimensional fractal characteristics at yardstick below sub-millimeter，Projective Covering Method was utilized. Firstly，unloading damage phenomenon at cave waist was simulated by rock burst test，and then marble samples damage characteristic was studied. Secondly，3D surface data of fragments from rock burst test was acquired by Confocal laser scanning microscope. Surface area at different yardstick was acquired by Triangulation method and two-dimensional characteristic of fragments was analyzed. Thirdly，lower limit of yardstick was confirmed in surface area calculation by Projective Covering Method. Three conclusions were drawn. Firstly，surface area of fragment had multi-fractal characteristic at yardstick from 0.625 μm to 639.375 μm. Secondly，the distribution of surface areas growth rate was similar with normal distribution. At yardstick below 0.625 μm，increase of surface area was little，so 0.625 μm could be regarded as lower limit of yardstick in surface area calculating by Projective Covering Method. Thirdly，fracture analysis from scanning electron microscopy confirmed the lower limit of yardstick in surface area calculating and the multi-fractal characteristic of fragments.

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STUDY OF ADSORBED GAS SEEPAGE LAW IN COAL

FENG Zengchao，GUO Hongqiang，LI Guibo，ZHAO Jing，LU Zhaoxing

2014, 33 (S2): 3601-3605 doi: 10.13722/j.cnki.jrme.2014.s2.026

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With the increase of pore pressure，coal permeability changing in V shape. The critical pore pressure is the pore pressure corresponding to the minimum permeability. Results show that both sides of critical pore pressure are two different physical mechanisms percolation process. When pore pressure is less than critical pore pressure，flow mainly to slippage effect. The relationship between slip coefficient and confining pressure shows a V shape change. When pore pressure is greater than critical pore pressure，the gas flow in a linear flow-based. The relationship between reciprocal of permeability and square of pore pressure is linear. This study is important for a correct understanding from the mechanism of low permeability coal reservoir flow process.

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RESEARCH ON MICRO-FRACTURE MECHANISM OF MUDSTONE AFTER WET-DRY CYCLES

YANG Jianlin1，2，WANG Laigui1，LI Xilin3，ZHAO Guochao1

2014, 33 (S2): 3606-3612 doi: 10.13722/j.cnki.jrme.2014.s2.027

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By X-ray diffraction，mechanical experiments of mudstone and three-dimensional laser topography measurement instrument，the mudstone was characterized to investigate the micro-fracture mechanism of mudstone after wet-dry cycles. A series of data were obtained，such as composition，mechanical strength，topography of mudstone in the process of wet-dry cycles. More attention was paid to the micro-fracture mechanism of mudstone in wet-dry cycles. Results show that：Some microcline generates kaolinite after dry mudstone becoming wet. The uniaxial compressive strength of dry mudstone is 5.31 MPa，and it decreases to 0 MPa when the mudstone is put into water. With the increase of the number of wet-dry cycles，the quantity and width of cracks increase. Water molecules enter the space between unit cells of illite clay grains and water films form on the surface of clay grains，when the mudstone is wet. Some second porosity generates because of the physical and chemical effects of water when mudstone becomes wet，and the volume of mudstone becomes large also. Some cracks form in localized surface areas enriching clay grains of mudstone due to the different contraction velocities between surface and inner. The quantities and size of cracks increase upon the increase of the times of wet-dry cycles. The sample fractures when the cracks penetrate the whole sample.

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STUDY ON PHYSICAL SIMULATION EXPERIMENT FOR ANCHORAGE ROCK CREEP CHARACTERISTICS

XIN Yajun，GOU Panfeng

2014, 33 (S2): 3613-3624 doi: 10.13722/j.cnki.jrme.2014.s2.028

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Based on similar ratio characteristics of rock and bolt，creep experiment of similar simulation anchorage specimen was carried out on RLW–2000 rheometer，creep control equation on anchorage rock were determined，basic rheological parameters were inverse calculated，and creep experiment and theoretical curves were compared and analyzed. Results show that anchorage specimen have initial and stable creep in non-anchorage specimen stress(loading) level. With stress level improving，creep strain on non-anchorage and anchorage specimen is nonlinear increasing，and creep strain difference value is more and more. Creep strain is nonlinear decreasing with bolt amount increasing in same stress(loading) level and different bolting parameters，and strain different value is less and less. The long-term strength of anchorage rock improves with bolt amount increasing beside reasonable layout density. M-K-B anchorage body model has characteristics of instantaneous strain and steady creep. Creep experiment curve is consistent with theoretical curve of inverse calculation，and the results provide reference for anchorage rock creep control.

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FRACTURE MECHANICS ANALYSIS OF UNEQUAL CRACKS INTERACTION UNDER UNIAXIAL TENSION

XI Jingyi，CHEN Zhonghui，ZHANG Wei

2014, 33 (S2): 3625-3630 doi: 10.13722/j.cnki.jrme.2014.s2.029

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The interaction of different sizes of cracks in the rock is one of the key factors leading to the damage of rock. Aiming at the interaction problem of many unequal cracks existing in the rock mass，the expressions for the stress intensity factors at the crack tip of two collinear unequal cracks under far field tension were derived by Kachanov method. The interaction and the influence of two unequal cracks were analyzed. The stress intensity factors obtained by the expressions were in good agreement with the handbook of stress intensity factors. So it verified the rationality of the obtained expressions. Results show that the small crack almost has no impact on the large crack when its length is shorter than the distance between the cracks. The large crack begins to have obvious influence on the small crack when its length is longer than the distance between cracks. When the distance between two cracks reaches the length of large crack，the large crack almost has no influence on the small one.

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STUDY OF SHEAR STRENGTH PROPERTIES OF INTERFACES IN BEDDED SALT FORMATIONS BASED ON SEDIMENTARY CHARACTERISTICS

ZHANG Guimin1，LI Yinping2，LIU Wei2，ZHANG Guanghui1

2014, 33 (S2): 3631-3638 doi: 10.13722/j.cnki.jrme.2014.s2.030

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The interfaces in bedded salt formations have a critical influence on the stability and tightness of underground gas/oil storages. Relying on the geological and test data of Yunying salt mine in Hubei province，the shear strength properties of the interfaces were firstly analyzed，and then two strength models for dominant interfaces were revealed，finally the failure mechanism was discussed. Results show that：(1) Most of the interfaces of bedded salt formations formed by chemical deposition are strong，such as interface between rock salt and argillaceous anhydrite. The strengths of mechanical deposition interfaces are lower，specifically interfaces between mudstone and rock salt. Weak interfaces normally appear at the sudden transition interfaces. (2) Two shear strength models were proposed respectively for the graduate transition interfaces and discrete discontinuous interfaces. Especially gradual transition interfaces are similar to functionally graded materials(FGM) while sudden transition interfaces can be treated as the contact surface between rock salt and interlayer. (3) Gradual transition interfaces could transfer the additional force resulted from the inconsistent deformation between salt rock and interlayer，thus not prone to breakage. However，the sudden transition interfaces cannot. The analysis reveals the relationship between sedimentary characteristics and shear strength of bedded salt formations，which provides important references for the design and construction of underground gas storage in bedded salt formations.

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PERTURBATION SOLUTIONS FOR ELASTO-PLASTIC PROBLEMS OF CIRCULAR TUNNEL UNDER UNEQUAL COMPRESSION

HOU Gongyu1，LI Jingjing1，ZHAO Weiwei2，LIU Ying1，CHEN Zhichao1，TIAN Le1

2014, 33 (S2): 3639-3647 doi: 10.13722/j.cnki.jrme.2014.s2.031

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The perturbation solution of axisymmetric round well under unequal compression in two directions was studied. The elastic stress distribution considering the second order infinitesimal and analytic dynamics of elasto-plastic boundary line was raised，and the perturbation solution through engineering example was analyzed. Results show that elasto-plastic boundary line is similar to ellipse，tangential stress and radial stress are equal in certain angles，and the stabilized value of is greater than in-situ stress(). Research results are analyzed through the example of project，and compared with Д. А. Galindo solution to prove the reliability of the perturbation method，which are remarkably consistent.

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DISSOLUTION EXPERIMENT AND NUMERICAL SIMULATION ANALYSIS FOR CONDENSATION WATER ON CARBONATE ROCKS

ZHANG Ao1，FANG Yun2，CHEN Jianping3，FAN Zilong3

2014, 33 (S2): 3648-3656 doi: 10.13722/j.cnki.jrme.2014.s2.032

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In order to protect stone relics from the infraction of condensation water，it is necessary to study the mechanism of condensation water. Based on dissolution experimental methods，the dissolution of condensation water on carbonate rocks was stimulated with the self-made static and dynamic experimental system. Considering CO2 concentration，temperature and humidity，the effect of different factors on the dissolution process was analyzed and the mass loss，microstructure，water change，and etc. were tested during the experiment process. Finally，the process of dissolution was stimulated by the numerical software Phreeqc to verify the accuracy of simulation experiment. Static and dynamic simulation experiments show that condensation water dissolves carbonate rocks increasing with CO2 concentration and the dissolution of limestone is greater than dolomite. In the dynamic simulation experiment of vapor condensation，dolomite dissolution and rock porosity are significantly increased because the microscopic vapor is strong intrusive. Dissolution process and calculated dissolution depth are consistent with numerical simulation results. Dissolution curve shows quadratic indicating that preliminary dissolution is faster and post-dissolution is gentler. Calculated dissolution depth of limestone is 0.027 6 mm and the dissolution depth of dolomite is 0.013 6 mm in a year.

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EXPERIMENTAL STUDY OF STRENGTH CHARACTERS OF SATURATED RED SANDSTONE ON NEGATIVE TEMPERATURE UNDER TRIAXIAL COMPRESSION

SHAN Renliang1，2，YANG Hao1，GUO Zhiming1，LIU Xiaodong1，SONG Liwei1

2014, 33 (S2): 3657-3664 doi: 10.13722/j.cnki.jrme.2014.s2.033

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Saturated red sandstones，as the research subjects from 500–600 meters deep of Meilinmiao mine in Ordos，in China，were tested respectively by triaxial compression in the condition of different temperatures(10 ℃，－5 ℃，－10 ℃，－15 ℃) and different confining pressures(0，4，8，12 MPa). Results show that：(1) When temperature range from 10 ℃–－15 ℃，the triaxial compressive strength of saturated red sandstones increase with the temperature dropping down，and present exponent relation. Elastic modulus increase and present linear relation；Friction angles increase while cohesive strengths c decrease，as temperature reduce. (2) When confining pressures change between 0–12 MPa，triaxial compressive strengths of saturated red sandstones increase with the confining pressures increasing，show the linear relation and still follow Mohr yield criterion. Elastic modulus，peak axial strain and peak radial strain increase with the increment of confining pressures. (3) Under the experimental conditions，the Poisson ratio are less affected by the confining pressure，but significantly affected by temperature，more attentions should be paid to the impact of temperature on Poisson ratio；The elastic modulus E is affected greatly by temperature and significantly by confining pressure. The temperature is the main factor affecting the elastic modulus and the confining pressure is the secondary consideration. Compared with Poisson ratio，the value of the elastic modulus is easily affected by external environment. (4) The failure modes of saturated red sandstone specimen are affected by temperature and confining pressure significantly. However，these are two different failure mechanism. Temperature decreases result in rock particles gravity reduction，and pore ice increases the pore friction area，then increases the friction；With the confining pressure increasing，it is due to the formation of micro-cracks inside the rock，that cohesive strength declines，at the same time，increases vertical component force，coming from rising confining pressure，on the fracture surface，thereby，increases the friction.

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FRACTURE EVOLUTION AND STRENGTH CHARACTERISTICS OF BEISHAN DEEP GRANITE UNDER COMPRESSION CONDITIONS

ZHAO Xingguang，MA Like，SU Rui，WANG Ju

2014, 33 (S2): 3665-3675 doi: 10.13722/j.cnki.jrme.2014.s2.034

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Acoustic emission(AE) and strength characteristics of the Beishan granite at depth under uniaxial and triaxial conditions were investigated using a servo-hydraulic compression machine and a real-time AE measurement system. Based on the experimental results，complete stress-strain curves associated with 3D AE event distribution characteristics were analyzed. The fracture evolution mechanisms of the rocks at different loading and deformation stages were revealed，and the confining stress dependent behaviors of the three characteristic stress thresholds(i.e. crack initiation，crack damage and peak strengths) were discussed. The research results indicate as follows：(1) At low confining stresses(0–2 MPa)，the rock sample tends to present dispersive mircocracking or axial splitting throughout each loading stage，which is agreement with the dense distribution of AE events throughout the rock，indicating that certain amount of cohesion strength of rock is lost. With increasing confining stresses，a gradual transition from axial splitting failure to shear failure can be observed. The distributions of incremental AE events indicate that the maximum gradient of crack growth occurs at the strain softening stage，which corresponds to the maximum dilation rate in the stress-strain curve；(2) Using the proposed cumulative AE hit method in combination with stress-strain measurement data，the crack initiation strength can be identified accurately. Compared with the crack damage strength，the crack initiation strength is less sensitive to confining stress，especially for low confinements；(3) A single failure criterion is not sufficient to describe the complete failure envelope. Hence，a bi-segmental representation of the Hoek-Brown strength envelope is suggested for the Beishan granite.

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THEORETICAL ANALYSIS FOR RHEOLOGICAL CHARACTERISTICS OF SURROUNDING ROCK AND ON-SITE MONITORING IN LONGSHOU MINE

WANG Hongjiang1，LI Gongcheng1，WU Aixiang1，YI Haibao2，SUN Wei1，WANG Xiaoning1，HE Jianyuan3

2014, 33 (S2): 3676-3681 doi: 10.13722/j.cnki.jrme.2014.s2.035

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The rock mass rheological characteristics of Longshou mine were studied by FLAC3D numerical analysis software. The results show that the rock creep rate increases and rock damage，deformation and failure process accelerates with the increase of confining pressure. The impacting law of confining pressure on rock rheological properties is revealed. The deformation of surrounding rock mainly presents as dilatancy deformation after peak strength，and the sensitivity of confining pressure is more obvious when the confining pressure is lower. While the confining pressure is less than 4 MPa，the affecting degree reaches to 70%–80% of rock volumetric strain. The on-site monitoring of bolt stress and roadway deformation is conducted to explore the rock mass rheological rule and supporting effect. The results indicate that the anchoring force is just 9.15%–33.79% of the anchoring capacity，insufficient to suppress the rock deformation. The deformation rate is 0.043–0.149 mm/d and has a slowing down trend，but the amount of deformation increases gradually，with a greater horizontal convergence than the vertical of that，which is not conducive to the stability of surrounding rock，so the appropriate reinforcement measurements should be adopted.

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DEFORMATION ANALYSIS FOR SHIELD TUNNEL UPPER CROSSING BY CLOSE RANGE LARGE SECTION PASSAGEWAY

HE Meide1，2，LIU Jun3，LE Guiping4，ZHANG Dingli1，WANG Mengshu1

2014, 33 (S2): 3682-3691 doi: 10.13722/j.cnki.jrme.2014.s2.036

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During the upper crossing construction process in the project of a certain large section pedestrian passageway upper crossing the running shield tunnel of Beijing subway line No.10，the vertical displacements of shield tunnel structure，the horizontal convergence displacements of shield tunnel structure and the vertical displacements of track bad structure were monitored and analyzed. In this section，the minimum distance was 1.97 m and the CRD method of shallow tunneling was applied. The site monitoring results show that：(1) The deformation of existing subway tunnel structure due to the large section passageway construction is mainly resulted from up floating. The vertical displacement of shield tunnel structure varies from －0.10 to 4.10 mm；the horizontal convergence of shield tunnel structure ranges from －0.03 to －1.80 mm；while the vertical displacement of track bad structure is from －0.30 to 2.90 mm. And the deformations of tunnel structure and track bed structure are coordinating. (2) The variations of three monitoring indices are consistent. They all experience four stages，the upward rapidly area，the down abruptly area，the fluctuating decreased area and the later fluctuating stability area. After completing the tunnel face of passageway，the up floating deformation rate of tunnel structure is significantly increased. When grouting from the floor of passageway，however，it is obvious that grouting controls the up floating deformation of tunnel. When the grouting is completed，the up-floating deformation rate of tunnel structure becomes flat. After the secondary lining of passageway is completed，the tunnel overall is sinking with fluctuation because of the load above shield tunnel increase，and finally reaches stable. The analysis result of this project shows that grouting from floor of passageway can significantly control up floating，which can be applied in the similar projects.

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DYNAMIC DEVELOPMENT CHARACTERISTICS OF CAVING ZONE OVERBURDEN STRATA IN FULLY-MECHANIZED MINING STOPE UNDER ONE-PASS MINING

XIONG Zuqiang1，WANG Xiaolei2，LIU Chengwei 1，LI Huigui1

2014, 33 (S2): 3692-3698 doi: 10.13722/j.cnki.jrme.2014.s2.037

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Taking Sihe No.2 mine as the experimental mine，by using the equipment which is sealed two ends by capsules in borehole，affused measurable water between the two capsules and borehole televiewer observation system，overburden caving zone height of mining overall height in one times is monitored and analyzed through the digital relationship of fractures around mining such as change of dip angle，numbers and width，depth and width，numbers and depth. At the same time，similarity model experiment of fracture development character is carried out. The results show that caving zone height changes from 4.1 to 4.8 m. The fractures with small angle and middle width after mining are in the majority. With increase of the mining of working face，the numbers of fractures increase linearly. The fractures cluster region mainly focuses near the coal wall. The fractures density distribution curves of overlying strata like sanke-shapes.

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TIME-FREQUENCY ANALYSIS METHOD OF AMPLIFICATION EFFECT OF ACCELERATION OF HIGH AND STEEP HILL WITH TWO-SIDE ROCK SLOPES

YANG Changwei1，2，ZHANG Jianjing1，LIU Feicheng1

2014, 33 (S2): 3699-3706 doi: 10.13722/j.cnki.jrme.2014.s2.038

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Based on the elastic wave theory，the force balance differential equation is established by using the horizontal slice method. The time-frequency analysis method of the amplification of accelerations of the high steep hill with two-side slopes is derived，and the reasonability of this method is verified by the results of shaking table test and numerical simulation. This method not only can consider the effect of the three factors of the seismic wave which are peak ground acceleration，frequency and duration on the amplification of accelerations of the high steep hill with two-side slopes，but also can illustrate the whiplash effect of the slope theoretically.

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DISTRIBUTION CHARACTERISTICS OF GROUND MOTION AND DYNAMIC STRESS RESPONSE OF VALLEY SLOPES UNDER BLASTING LOADING

SHI Yucheng1，2，3，LU Yuxia1，2，3，HE Shaolin1，SUN Junjie1，2，3，LIU Xingwang1，LIU Kun1，2，3

2014, 33 (S2): 3707-3717 doi: 10.13722/j.cnki.jrme.2014.s2.039

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According to the seismic records，ground motion parameters are significant difference on various parts of alpine and gorge region，where earthquake damage investigation shows the damage is more serious than wide flat terrain and secondary disaster occurs frequently. In order to reveal the mechanisms of action，characteristics of blasting ground motion and the corresponding dynamic stress response，the blasting ground motion test for a loess valley slope located in Gaolan County，Lanzhou is carried. The testing analysis shows that：(1) Ground motion on the slope is obviously controlled by topography，especially in the cove(QZH14) on upper part of slope，where the PGA is higher than nearby observation points due to the wave superposition. (2) The response spectrum of blasting shows two attributes of ground motion on the slope and the foot of valley-bimodal pattern the former and unimodal pattern the latter. On the slope，long period component attenuates slowly with the hypocentral distance increasing. (3) There is a apparent correspondence between ground motion and its dynamic stress response，higher amplitude of ground motion，larger dynamic stress response. Due to the topographic effect and the geotechnical structure，inner stress response of the slope emerges significant variation in different depths rather than increasing or reducing trend with the distance of macro-epicenter increase. It suggests that the development degree of earthquake induced geological disasters are affected by the parameter variation of strong ground motion on the slope，which is usually determined by various factors，amplitude，frequency characteristics and incidence angle of seismic wave etc.

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NUMERICAL SOLUTIONS OF COMPOSITE STIFFNESS AND TRI-PARAMETER METHOD FOR CALULATION OF ANTI-SLIDE PILES

ZOU Shengtang，DAI Zihang

2014, 33 (S2): 3718-3723 doi: 10.13722/j.cnki.jrme.2014.s2.040

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In order to more reliably calculate the displacements and internal forces of anti-slide piles，the pile-soil composite stiffness under combined action and subgrade resistance tri-parameter method is presented to calculate anti-slide piles. Based on this method，numerical solution of link finite element is established. According to the measurements of displacements and bending moments of an engineering pile pushing test，the pile-soil composite stiffness under combined action and subgrade resistance tri-parameter are back analyzed. Then the calculation results obtained by finite element analysis are compared with the measurements of pile displacements and bending moments under different load grades. The results show that the horizontal resistance parameters of rocks and soils are nonlinear. With the increase of pile displacements caused by larger loads，the horizontal subgrade resistance parameters obviously decrease and the pile-soil composite stiffness under combined action diminishes to a certain extent.

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A PHENOMENON OF ANCHORAGE GROUT INTERLAYER WITHOUT SOLIDIFICATION IN TWENTY YEARS AND ITS REASONS ANALYSIS

REN Aiwu1，WANG Yanshu2，FAN Haizhu3，JIA Zhixin1，WANG Yujie1，JIANG Zhaoqun2

2014, 33 (S2): 3724-3729 doi: 10.13722/j.cnki.jrme.2014.s2.041

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A phenomenon of grout interlayer without solidification was founded in the in-situ anchor excavation experiment at Manwan hydropower. Three test methods were applied to resolve the problem，which were XRD，SEM and embedded closed hydration tests. Through analyzing the results of tests，some conclusions are achieved. The anchorage grout with the unsolidified interlayer shows just like a sandwich，which is composed of three parts. The up and down parts are hardwares，and the central part is a soft interlayer about 1–2 cm thick. The interlayer is linear extended in the mortar inclusions from the beginning to the end. Many tricalcium silicates are founded in the grout interlayer by XRD and SEM tests. The results indicate that the unsolidified phenomenon is closed to early stage of the cement hydration reaction process. It is proven by the indoor airtight hydration test and XRD results that just embedded closed condition and containing clay in cement can not lead to unsolidified phenomenon.

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RESEARCH ON RHEOLOGICAL BEHAVIOR FOR CEMENT GROUT CONSIDERING TEMPERATURE AND HYDRATION TIME EFFECTS

LIU Quansheng，LU Chaobo，LIU Bin，LU Xingli

2014, 33 (S2): 3730-3740 doi: 10.13722/j.cnki.jrme.2014.s2.042

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Grout rheological type is the foundation of grouting diffusion model research. Under different conditions of water cement ratio(W/C)，temperature，hydration time and the rheological properties of ordinary portland cement grout were investigated by rotary viscometer. The results show that：(1) When temperature is 20 ℃–50 ℃，the effect laws of temperature on the shear force under the same shear rate change with W/C. The shear force increases with the rise of temperature when W/C of 0.5 and 0.7. However，the shear force decreases with the rise of temperature when W/C of 1.0，1.5 and 2.0. (2) The shear force under stirred up condition increases with the increasing of hydration time at the same shear rate，and the higher of the temperature，the bigger of the increment of shear force. (3) The rheological pattern of cement grout does not change too much under the different temperatures and hydration times when the temperature is 20 ℃–50 ℃. (4) The flow pattern of cement grout is controlled by W/C. The cement grouts with W/C of 0.5 and 0.7 are power-law fluid with yield stress. With the increase of temperature and hydration time，the yield stress and consistency factor shows increasing trend. While the flow behavior index decreases with the increase of temperature and hydration time. When W/C is 0.7，the non-linear relationship between shear force and shear rate is not so significant. So the rheological behavior can be simplified to Bingham rheological model，which fits the test data point very well. When W/C is 1.0，the rheological behavior of cement grout displays Bingham fluid with unapparent yield stress，which can be considered as a Newtonian fluid and use Newtonian rheological equation to describe its rheological behavior. When W/C is 1.5 and 2.0，the cement grouts are Newtonian fluid. When W/C is 1.0，1.5 and 2.0，the dynamic viscosity of cement grout decreases with the increasing of temperature，while it increases with the increasing of hydration time.

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EXPERIMENTAL STUDY OF DECREASING BLASTING VIBRATION TECHNOLOGY WITH DIGITAL DETONATOR IN URBAN SUBWAY

YANG Renshu1，2，CHE Yulong1，SUN Qiang1，GAO Xiangtao1

2014, 33 (S2): 3741-3750 doi: 10.13722/j.cnki.jrme.2014.s2.043

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According to the problems of urban subway under-passing building closely，taking the Qingdao subway as engineering background，the electronic detonator tests with different forms of cut hole are carried out and the blasting vibration is monitored. The monitored results show that the delay time of electronic detonator is accurate，and the blasting vibration velocity can be controlled effectively by blasting hole by hole and disturbing the damping which is achieved by setting up the reasonable delay time of electronic detonator. Comparing the different forms of cut hole，when the parallel rhombus cut of empty hole is adopted，the empty hole as free surface could provide compensation space to reduce the clamping force and reduce the blasting vibration velocity. The test results prove that with the parallel rhombus cut of empty hole blasting，the time interval of cut holes should be greater than 30 ms，the time interval of satellite holes should be greater than 8 ms，and the time interval of periphery holes should be greater than 4 ms. With the wedge cut hole blasting，the time interval of cut holes should be greater than 3 ms，the satellite holes and periphery holes could be 8 ms，and the time interval of bottom holes should be greater than 4 ms. The comparison of particle vibration velocity in the three coordinate directions show that the vibration velocity in z direction is the biggest and it plays a dominating role in the vibration wave.

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DISTRIBUTION CHARACTERISTICS OF GEOSTRESS FIELD IN XINCHANG ROCK BLOCK OF CANDIDATE BEISHAN AREA FOR HIGH LEVEL RADIOACTIVE WASTE REPOSITORY IN CHINA

ZHAO Xingguang1，WANG Ju1，MA Like1，SU Rui1，JIN Yuanxin1，CHEN Qunce2，AN Qimei3，QIN Xianghui2

2014, 33 (S2): 3750-3759 doi: 10.13722/j.cnki.jrme.2014.s2.044

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Beishan area in Gansu Province is the first potential area for the construction of Chinas high-level radioactive waste(HLW) repository. To know the magnitude，orientation，and distribution characteristics of geostresses in the regional rock block，geostress measurement using a single loop hydraulic fracturing system is carried out in the Xinchang sub-area of the Beishan area. Based on the information in borehole log and acoustic borehole televiewer image，a total of 81 hydro-fracturing tests and 19 fracture impression tests are successfully conducted in four sub-vertical boreholes at depths ranging between 0 and 700 m below the ground surface. The obtained stress data provide a comprehensive view of the state of geostresses in the Xinchang sub-area. To make the hydro-fracturing results accuracy and reliable，three different methods are used to determine the instantaneous shut-in pressures according to the pressure-time history records. The measurement results indicate that the geostress components increase with depth. Within the measurement depth range，the maximum horizontal principal stress is generally larger than the vertical stress，and has a maximum value close to 25 MPa，reflecting that the regional stress filed is dominated by tectonic horizontal stress rather than by the overburden load. On the other hand，the relationship between the ratio of the maximum principal stress to vertical stress and depth shows that there exists a possible transition of regional stress field from tectonic stress dominated to weight stress dominated in deep ground. In addition，the orientation of the major horizontal stress in the Xinchang sub-area is dominantly in the NEE direction，which is in general agreement with that of regional tectonic stress field deduced from movement of the earths plates. This confirms the reasonability of the geostress data obtained from the present stress measurement campaigns. The measurement results provide stress boundary conditions for the design and stability assessment of HLW disposal systems in the Beishan area，and provide meaningful geostress information for further research on stress field distribution of northwestern China.

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FORCED THRUST MECHANISM OF FAULT MUTATION IN DEEP MINING

LI Tie1，2，WANG Jinan1，2，LIU Jun3

2014, 33 (S2): 3760-3765 doi: 10.13722/j.cnki.jrme.2014.s2.045

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In Laohutai coal mine，it occurred that normal fault was activated and varied into thrust fault movement，and strong mining earthquake energy release was produced during deep mining. The mechanical mechanism was explored by using microseismic monitoring and focal mechanism solutions，combining field investigation，in-situ stress measurement and three-dimensional numerical experiments. Analysis and conclusions: coal mining resulted in activation of faults，and the action mode of mining stress led the mode of fault movement. changing the fracture mechanisms of original fault；deep normal fault was mined in hanging wall after crossing fault in footwall，and the change of the direction of normal fault motion was caused by mining induced concentrated stress，forcing thrust motion，accompanied by the releasing of strong mining earthquake energy，and barriers and asperities can be sheared，also it may initiate second main-earthquake；the details about preventing normal fault catastrophe should be dynamically determined，according to the mode of action of stress during mining；by equipping with high-precision microseismic equipment，tracing analysis on spatial distribution of rock rupture sources and failure mechanism，the tendency of mining induced fault activation and variation can be caught out ahead of time，so that precaution will be taken promptly.

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ANALYSIS OF SLIDING FAILURE MECHANISM OF GENTLY INCLINED BEDDING COMPOUND ROCK MASS SLOPE UNDER HYDUAULIC PRESSURE

XIA Kaizong，CHEN Congxin，LIU Xiumin，ZHOU Yichao，CHEN Guanwen，SONG Yafen

2014, 33 (S2): 3766-3775 doi: 10.13722/j.cnki.jrme.2014.s2.046

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An example taken from Yiba highways Pengjiawan slope(landslide) with overlying accumulation and inter-beddings of soft and hard rock，based on analysis of formation and evolvement of slope(landslide) bedding-slip failure due to hydraulic drive，the effect mechanism of groundwater on rock slope stability is discussed. By analysizing the effect of groundwater hydraulic pressure characteristics on slope，it is pointed out that groundwater hydraulic pressure including the dynamic water pressure of accumulation layer，and the fissured hydrostatic tension，the uplift force on potential sliding surface and the dynamic water pressure of inter-beddings of soft and hard rock. The dynamic water pressure of accumulation layer associated with obliquity of rock layer，and hydraulic pressure of inter-beddings of soft and hard rock are all decided by water filling at the back edge of the fissure；equations for calculating the critical water highness in the splay fracture and the critical rainfall intensity are developed. The bedding-slip failure criterions of rock slope are put forward，that is，the slope will lose its stability once the water highness of the splay fracture or the critical rainfall intensity reaches to a critical value. Through calculation and analysis，the proposed formula is proved to be reasonable，and it is also concluded that the decrease in slope stability under the influence of groundwater is mainly related to hydrostatic pressure and uplift force instead of its penetration.

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RESEARCH AND MANUFACTURE OF numerical control MECHANICAL SIMULATION TESTING SYSTEM FOR MOVEMENT EVOLUTION OF STRATA STRUCTURE AND ITS APPLICATION

GUO Weijia，LI Yangyang，FAN Weilin，ZHU Xuejun，WANG Hailong，SUN Xizhen

2014, 33 (S2): 3776-3782 doi: 10.13722/j.cnki.jrme.2014.s2.047

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According to the defects in physical similar material simulation test that cant meet some engineering requirement，the NC mechanical simulation testing system for deformation simulating the evolution of rock structure movement was developed.The development principles，main structures and function characteristics are given detailedly in this paper. The system can easily be operated，and has characteristics such as high automation，stable testing process，convenient disassembly and installation，good repeatability，which have been proved through laboratory test. The NC mechanical simulation testing system is superior to similar material simulation experiment for its laying difficulty，molding technology and forming quality is difficult to control，the long test cycle，materials can't be used repetitively，and is easily affected by external factors. The NC testing system can show the space structure evolution process of the overlying strata by mining，the corresponding relation between strata fracture mutations and stress field，the law of elastic deformation energy accumulation and release above the coal pillar intuitively.

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STUDY OF MECHANISM OF LANDSLIDE INDUCED BY RAINFALL IN GENTLY INCLINED RED STRATUM IN EAST SICHUAN BASIN

ZHANG Ming1，HU Ruilin2，YIN Yueping3，WU Ruian1

2014, 33 (S2): 3783-3790 doi: 10.13722/j.cnki.jrme.2014.s2.048

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Gently inclined red stratum widely distributes in East Sichuan Basin. Dip angle of this type of stratum is always between 3° and 10°，which is far less than the friction angle between bedding planes. In theory，the bedding landslide is unlikely to occur in red stratum. But in fact，rainfall induced landslide in gently inclined red stratum occurs frequently，which leads to a huge threat to the local people. Taking Qingning landslide in Da County，Sichuan province as an example，the geological model through field investigation and exploration is built；then analyzes the seepage field and static water pressure distribution before the landslide；a slope stability was analyzed based on the results of above seepage analysis. In order to obtain the characteristics of pore water pressure and shear resistance，the sliding zone soil is sampled to conduct ring shear test. The results indicate that landslide is due to coupled action of water pressure and shear resistance decreasing of sliding zone soil. The horizontal pushing force and vertical uplifting force due to rainfall infiltration initiated the landslide to deform and slid slowly，and then shear resistance decreasing of sliding zone soil led to the rapid sliding. Furthermore，a long rainfall and then a strong rainfall are deemed to be the necessary condition of landslide. Conclusions of this paper are the new findings in this field and can supply theoretical support for landslide forecasting and prevention in East Sichuan Basin.

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DISPLACEMENT PREDICTION OF SLOPE BASED ON IMPROVED GREY-TIME SERIES TIME-VARYING MODEL

ZHANG Zhenghu1，2，YUAN Mengke1，2，DENG Jianhui1，2，XUE Shouning3

2014, 33 (S2): 3791-3797 doi: 10.13722/j.cnki.jrme.2014.s2.049

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Cause and evolution law of the displacement of slope are very important for the evaluation of the stability of slope. Based on fuzzy uncertainty and random uncertainty and a certain regularity of deformation parameters，improved grey-time series time-varying prediction model，in which grey theory and traditional time series analysis method are combined，is established on gray model by double smoothing correction. Improved GM(1，1) is utilized to extract the trend term of the displacement of slope. After the extraction，the displacement time series becomes a stable series，which could be processed by ARMA or AR model. According to the detect data update，the model parameters are continuously modified of equal intervals in accordance with real-time tracing algorithm. As a test，the prediction model is used in inlet slope engineering of Huangjinping hydropower station and left abutment slope engineering of Changheba hydropower station. The model test show that relative error between predicted and measured value is mainly less than 5%. The model is of high precision and is of great significance to understand the development trend of the displacement of slope and study the dynamic stability of slope.

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STUDY OF SHAKING TABLE TEST FOR HIGH SLOPE RETAINING STRUCTURE ON HIGHLY SEISMIC REGION

LIU Changqing1，2，JIANG Chusheng3，LIANG Yao3，LI Xiang1，2

2014, 33 (S2): 3798-3802 doi: 10.13722/j.cnki.jrme.2014.s2.050

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Based on the worksite of Yuxi to Mengzi railway which is located on the strong seismic region of 8 degree intensity，the shaking table test was carried out to simulate the dynamic field situation caused by shear wave. The force acting on the pile，the acceleration in the soil and the deformation at pile top of single pile and double row pile retaining structure under different earthquake accelerations are tested. And the comparisons of support effect for the single pile and the double row pile anti-slide structure are analyzed. It shows that distribution of the total earth pressures and the dynamic earth pressures acting on the back of the piles are the same. And the value of single pile is 1.5 to 2 times greater than that of double row pile structure for the same position. Under the same earthquake acceleration，the peaks of acceleration in the soil of single pile structure is greater than that of double row structure，and the settlement of pile top at the low pile of double pile structure is less than that of single pile structure. The support effect of double row pile retaining structure is better than single pile retaining structure on strong seismic region.

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INFLUENCE OF ANISOTROPIC PERMEABILITY OF ROCKMASS ON STABILITY OF UNDERGROUND OIL STORAGE CAVERNS

SONG Kun1，2，YAN Echuan2，GAO Liantong2，LIANG Jiajia3

2014, 33 (S2): 3803-3809 doi: 10.13722/j.cnki.jrme.2014.s2.051

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Underground oil storage caverns are the main mode to strategic crude oil storage in the world，which is the underground rock caverns below ground water level and prevented leakage by water sealed. And the permeability of surrounding rock mass would affect the stability of caverns，especially the anisotropic. Taking an oil storage caverns as a case，which is the first large oil storage project in China. Based on calculation of permeability tensor of Granitic Gneiss，the groundwater pressure distribution，flow velocity，displacement and stress in the surrounded rock was gained with different anisotropic permeabilities by finite element method(FEM). And the factor of safety of rock caverns was obtained by strength reduction on the Generalized Hoek-Brown criterion. It shows that anisotropic permeability of Granitic Gneisses has a significant effect on the groundwater pressure and flow velocity in surrounding rock，which the pressure increase linearly and flow velocity decrease logarithmic with increase of permeability anisotropy ratio. It has no effect on displacement and negligible on stress of surrounding rock. But it has a greater impact on factor of safety of rock caverns，which is general decreased with anisotropy ratio increased. It has some theoretical and engineering values to stability evaluation of underground water sealed oil storage caverns.

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STUDY OF EARLY WARNING MECHANISM OF DEBRIS FLOW ALONG RAILWAY LINE IN MOUNTAINOUS AREAS

LI Chaoan，WANG Liangwei，LIAO Kai，FAN Rong

2014, 33 (S2): 3810-3816 doi: 10.13722/j.cnki.jrme.2014.s2.052

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The paper analyzes the formation mechanism，the movement characteristics and the disaster mode of debris flow. Combine with the formation，movement and the disaster mechanism of the debris flow disaster along the mountain railway line，it considers the four parameters，such as the rainfall of the debris flow area，the rainfall infiltration depth of the source area，the infrasonic information and the ditch mud position as the key parameters of the debris flow disaster early warning in the mountains. Secondly，it establishes the debris flow early warning mechanism along the mountain railway line. According to the scale of itself and the characteristics of debris process，then combine the anti-disaster ability of railway itself，and from the railway safety requirements，it divides the debris flow disaster early warning of mountain railway line into four types，such as the prompt warning，the formation of early warning，the non-disaster early warning and the disaster warning. And establishing the critical value of early warning indicators，the system warning process and the distribution options for the key parameters from the four aspects which containing the drainage area rainfall，the rainfall infiltration depth of the source area，the infrasound and the ditch mud of debris flow. Finally，the paper introduces the test situation in the field of this monitoring and early warning system. Through the field test，it is found that it is feasible of this debris flow disaster warning method along the mountain railway line and it has good application prospects.

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SEVERAL ISSUES ON SIMPLY-CONSTRUCTED WELL OF ELECTRIC TUNNEL WHEN TUNNELS FOLLOWED BY WELL EXCAVATION

MO Haihong1，2，YANG Chunshan1，2，CHEN Junsheng1，2，BAO Shufeng1，2

2014, 33 (S2): 3817-3824 doi: 10.13722/j.cnki.jrme.2014.s2.053

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The simply-constructed well which is no inner supporting，efficient and circular was proposed. The comparison between simply-constructed well and conventional scheme was conducted and parameters sensitivity analysis of the well to segment deformation was conducted with finite element method as well as the key technology of structures design was explored. The results show that the construction technology，feasibility and influence on surrounding environment of simply-constructed well are superior to conventional one. The project cost of simply-well is only 7% of the conventional scheme，so it greatly saves the cost. It will form unstable structure when local segments were broken and segment deformations greatly increase. The influencing scope of the deformation is manifested on the snap rings and two segment rings on both sides，so it should add temporary supports for spilt ring and four segment rings which are obviously affected to ensure structures safety. The effect of well thickness and soft soil on segment deformation is significant，while the effect of the diameter and spilt rings is very small. It suggests that the size of working well should not be big on the premise of meeting the requirements of global stiffness and clearance.

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ANALYSIS OF STRESS MECHANISM OF PILE COMPOSITE STRUCTURE BASED ON SOIL ARCH TEST

LIANG Yao1，JIANG Chusheng1，LI Qinghai1，LI Fei1，ZHAO Xiaoyan2

2014, 33 (S2): 3825-3828 doi: 10.13722/j.cnki.jrme.2014.s2.054

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At the southwest mountain areas，the composite structures，such as piles and retaining wall，plank wall，soil nailing wall，were applied to support high engineering slopes. Because of the soil arch effection，the soil pressure of the composite structure are redistributed. Considering the influence of soil friction angle，the contrast tests using the soil arch test machine(the patent No. is ZL200910058441.6) were conducted. The differences between those tests were soil friction angle，pile space and pile section dimension. The shape of soil arch，the soil pressure distribution caused by soil arch were analyzed. The equations of height and axis of soil arch considering the soil friction angle were suggested. A case history，considering soil arch effect，the support structure composited by piles and retaining wall was analyzed. Considering the effect of soil arch，a calculation method of potential slip surface and soil pressure on the retaining wall was put forward，and compared with the tradition method.

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APPLICATION RESEARCH ON BAMBOO OF SUBGRADE IN PRELIMINARY ENGINEERING FOR DRILLING

ZHANG Lingling1，WEN Hua1，ZHANG Zhiwei2

2014, 33 (S2): 3829-3833 doi: 10.13722/j.cnki.jrme.2014.s2.055

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The road of preliminary engineering for drilling is characterized by short period，overloading and subgrade diseases seriously. So the bamboo，as the reinforced material，is instead of geogrid used to improve the subgrade. The applicability of bamboo is verified by interfacial friction test and triaxial test of reinforced earth. At the same time，there is a comparative analysis between bamboo and geogrid. The results show that：(1) The tensile strength of bamboo is about 20 times higher than that of geogrid and the elastic modulus is about 30 times than that of geogrid，but the elongation of bamboo is only 1/6 times smaller than that of geogrid. It is satisfied for tensil strength as the reinforced material. (2) For the same amount reinforced earth，the interfacial friction strength of bamboo reinforced earth is bigger than that of geogrid reinforced earth. Because the surface roughness of bamboo is relatively higher than geogrid，its certain radian and thickness can provide lateral restraint for soil and its high tensil strength and low elongation has good stability and binding character. And more，iron wire using for bending bamboo can enhance the connect between bamboo and earth. (3) Peak strength and residual strength of bamboo reinforced earth can greatly improve and the peak strain interval increases comparing with geogrid. For the same strength，the strain value of bamboo reinforced earth is smaller than geogrid reinforced earth.

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TUNNELING IN SQUEEZING GROUND CONDITIONS：WITH A CASE STUDY OF YANMENGUAN RAILWAY TUNNEL

XU Zailiang1，SUN Yuanchun1，2

2014, 33 (S2): 3834-3839 doi: 10.13722/j.cnki.jrme.2014.s2.056

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Squeezing rock refers to weak rock under high grostress，so squeezing ground conditions conclude high grostress and weak rock，it means large convergences of the tunnel walls. Squeezing ground conditions have posed and continue to pose a major obstacle to the construction of tunnels through mountains. The Yanmenguan railway links the city of Datong to Yuanping in China through the Hengshan mountains. The tunnel is 14.1 km long with a two lane horse-shoe section，which is excavated in Archean plagioclase gneiss and granitic gneiss at depths of up to 820 m below surface，and extreme squeezing problems have been encountered，especially in sections of DK121+203–DK121+175. Based on analysis of engineering geological conditions，stability of surrounding rock and deformation monitoring，it is found that：(1) The sections of DK121+203–DK121+175 locate at fracture zones of ancient metamorphic rocks. (2) Rock mass quality and geostress conditions are key factors for the stability of surrounding rock. (3) Surrounding rock deformation sharply increased mainly due to excavation of middle，under bench and invert. (4) The effect is obvious to control surrounding rock deformation by strengthening the primary support and radial grouting behind primary support.

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STUDY OF COLUMN-HEMISPHERICAL PENETRATION GROUTING MECHANISM BASED ON POWER-LAW FLUID

YANG Zhiquan1，HOU Kepeng1，CHENG Yong2，YANG Bajiu2

2014, 33 (S2): 3840-3846 doi: 10.13722/j.cnki.jrme.2014.s2.057

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Grouting method is a common way to the engineering practices，grouting diffusion mechanism is the key factor which make it applied successfully in engineering. Carrying out theoretical analysis and experimental researches，diffusion radius of hemispheroid and diffusion length belongs to cylinder of column-hemispherical penetration grouting mechanism based on power-law fluid are deduced，at the same time the scope of application and method to determine the parameters are analyzed respectively. Then they were validated by means of designing indoor grouting experiments. Experiment results show that diffusion radius of hemispheroid，diffusion length belongs to cylinder of actual measurement values in the indoor grouting experiments have about 30%–35% differences with that of theoretical values calculated by column-hemispherical penetration grouting mechanism based on power-law fluid，but they are all within the acceptable error limits. Because the international and domestic researches on them were seldom reported，therefore，research achievements may not only can provide strong theoretical basis for perfecting the penetration grouting mechanism，but also play a reference guiding role for the theoretical research，design and construction on grouting technique.

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ROCKBURST HAZARD PRE-EVALUATION TECHNOLOGY BASED ON WAVE VELOCITY STRUCTURE DETECTION OF COAL BED SURROUNDING ROCK

WANG Shuwen1，2，MAO Debing1，2，PAN Junfeng1，2，LIU Shaohong1，2，LANhang1，2

2014, 33 (S2): 3847-3855 doi: 10.13722/j.cnki.jrme.2014.s2.058

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In order to achieve rockburst hazard pre-evaluation of working face，the concept of coal bed surrounding rock wave velocity structure is proposed，and its characteristic parameters are velocity size，velocity gradient，smallest distance of velocity anomalies to roadways，which are closely related to rockburst hazard. The rockburst hazard evaluation model based on characteristic parameters is constructed，and the classification method of rockburst hazard rating is determined. By kinetic theory of seismic waves，scoal source wave propagation characteristics in the special layered structure of roof-direct roof-coal seam are analyzed，indicating that velocity structure can be got by seismic first break travel-time CT technology. The research results were applied to working face 069–2 at Gushan coal mine. Practice shows that the evaluation results can be used for the formulation and implementation of protection measures.

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AN INVESTIGATION INTO SHEAR STRESS DISTRIBUTION AROUND HOLLOW GROUTING ANCHOR CABLES

LI Guichen1，2，3，SUN Hui1，2，ZHANG Nong1，2，WEI Yinghao1，2，ZHANG Lei1，2

2014, 33 (S2): 3856-3864 doi: 10.13722/j.cnki.jrme.2014.s2.059

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Hollow grouting anchor cables(HGAC) integrates tail resin anchorage and full-size grouting anchorage. The shear stress between anchor agent and borehole surface in HGAC possesses distinct pattern compared with that of traditional tension concentrated anchor cables. By simplifying the mechanical model around the grouts and using the analytical solutions of Kelvin problem and Boussinesq problem，theoretical formulas of shear stress of the grouts between anchor agent and borehole surface was derived based on the theory of elasticity. FLAC3D was also used to simulate shear stress distribution around anchor cables pre- and post- grouting. The results showed that the shear stress curve present bimodal distribution along the axial direction of anchor cable. Drawing force has limited effect on the shear stress distribution of the cable tail part. It has been found that shear stress and its concentration of the end anchored segment and the grouting anchored segment were respectively proportional to the pretightening force and the drawing force，while the shear stress and its concentration of the whole anchor cable was inversely proportional to the pore diameter within certain ranges.

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MINING-INDUCED RELEASE OF ENERGY FROM ROCK AND MECHANISM ON CATASTROPHIC FAILURE

XUE Dongjie，ZHOU Hongwei，ZHONG Jiangcheng，HUANG Yaming

2014, 33 (S2): 3865-3872 doi: 10.13722/j.cnki.jrme.2014.s2.060

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Mining-induced mechanical behavior of rock depends on the changing stress state，which is different from the intrinsic mechanical behavior. The mining-induced mechanical triaxial test has been designed based on the distribution of stress state during the excavation. The characteristics of released energy in strain softening process have been discussed by the contrast between conventional and mining-induced mechanical triaxial test from theory-based view. Furthermore，the composition of energy storage induced from in-situ stress is discussed with result that the critical value of necessary energy for destruction is far less than the traditional results. It is reasonable to explain the mechanism on dynamic failure of coal or rock. And there is one from the new thinking of mechanism on outburst that at the shallow depth dynamic failure may also occur，which means that the high in-situ stress is the dominant factor of energy storage，also a necessary condition for dynamic failure but not sufficient condition.

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EFFECT OF SLIDING PLANE MECHANICAL PARAMETERS ON LANDSLIDE STABILITY——A CASE STUDY OF JIWEISHAN ROCKSLIDE IN WULONG，CHONGQING

GE Yunfeng1，2，3，TANG Huiming1，XIONG Chengren4，WANG Liangqing1，WU Yiping1

2014, 33 (S2): 3873-3884 doi: 10.13722/j.cnki.jrme.2014.s2.061

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In order to investigate the influence of mechanical parameters of sliding plane，normal stiffness JKN，shearing stiffness JKS，internal friction angle ，and cohesion c，on the rockslide stability，the numerical simulations were conducted based on the orthogonal design method and 3D discrete element software 3DEC，the displacements concerning a monitoring point located in the front of sliding block were chosen as indicator in the orthogonal experiment. The analysis of variance shows that：(1) JKS and of sliding plane have a significant effect on the displacement of monitoring point along all of X，Y，and Z direction，as for the c and JKN，it seems that they have a limited influence on the displacement. (2) According to the influence degree on the rockslide stability，the order for 4 mechanical parameters may be arranged by JKS＞＞JKN＞c(for horizonal displacement)；JKS＞＞c＞JKN(for vertical displacement). The next research was focused on the most dangerous case among the 16 cases，in the initial stage of failure，for the horizontal displacement(EW)，the key block mainly moves to the east cliff due to the support from the rock mass，the amount of displacement for key block is much larger than that for driving block. For the horizontal displacement(SN) and vertical displacement，the displacement for driving block is bigger than that for key block. It can been seen that the key block slides down to the cliff following by driving block，numerical simulation results make a good agreement with the real situation.

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EVALUATION OF EARTHQUAKE SLOPE FAILURE ALONG A WEAK LAYER

DENG Jianliang1，2，XU Qiang2，KOSEKI Junichi3

2014, 33 (S2): 3885-3890 doi: 10.13722/j.cnki.jrme.2014.s2.062

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The earthquake-induced large displacement of slope containing a weak layer was calculated by extended Newmark with Sweden method(extended NS method). In the methods，the effects of excess pore water pressure and the change of sliding plane geometry on displacement are rationally evaluated. The details of extended NS method were described. A comparison between extended NS method and extended NJ method was performed on a calculation example. The characteristics of these two methods were described. In addition，the effects of ground water level，internal frication angle and slice width on the calculated horizontal displacement were evaluated.

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STABILITY AND CONTROL OF SURROUNDING ROCK IN ULTRA-HIGH ROADWAY

XU Lei1，WU Huankai2，LI Bo3，XIAO Tongqiang4

2014, 33 (S2): 3891-3902 doi: 10.13722/j.cnki.jrme.2014.s2.063

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In order to investigate ground control of ultra-high roadway. The ultrahigh segment(section：5.25×8 m) of No. 5205 rail roadway in a mine was selected as research object，the surrounding rock response characteristic in the process of height from 3.5 m to 8 m was simulated by UDEC. Research results show that：(1) Deviatoric stress increases in shallow part and decrease in depth；Deviatoric stress maximum in sides decreases，also the maximum in roof and floor increases and transfers to the deeper；Deviatoric stress change degree：sides＞roof＞floor. (2) Surrounding rock deformation scope：sides＞roof＞floor and its maximal deformation increasing amount：roof＞sides＞floor. (3) Fracture fields are all distributed as semi-ellipse，which has fracture transfixion area，fracture area and microfracture area from the shallow to the deep. It shows that balanced arch contour become larger with roadway height increasing by analyzing balanced arch. That is the maximum un-stable width of sides，roof caving arch height and roof pressure are all increaseing. Realiszed that：(1) Anchor group effect reduces surrounding rock bulking deformation. (2) Diagonal cable could be anchoraged in the shoulder and bottom angle no fracture areas through un-stable triangle block. (3) High performance and pretension bolt support can enhance mechanical parameters such as internal friction angle，which could reduces balanced contour. Based on this，the combined support technology of high strength and high pre-stressing bolt net bar and sides diagonal cable beam is proposed. Self-stabilization period of ultra-high roadway is 10 days，roof-to-floor relative convergence is 104 mm，both sides relative convergence is 150 mm，the total roof separation is 3.5 mm.

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SAFETY EVALUATION OF RAILWAY TUNNEL LINING BY FUZZY PATTERN RECOGNITION

YANG Yanqing1，GAO Yongtao1，HE Shaohui2，QI Falin2，3

2014, 33 (S2): 3903-3910 doi: 10.13722/j.cnki.jrme.2014.s2.064

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There are many qualitative and quantitative indices which are of uncertainty，ambiguity and complexity for safety evaluation of operating railway tunnel. In order to obtain a more reasonable evaluation result，the method of fuzzy pattern recognition for the safety of operating railway tunnel lining is proposed. The method that the forty-four indexes are divided into four gradations deals with the relationship between the qualitative evaluation indices and the quantitative evaluation indices. The calculation result shows that the evaluation results obtained by this method coincide with the results by the method of empirical judgments. The method reflects the roles of different indices in the process of various safety evaluation，makes up for the deficiency of traditional method based on empirical judgments，and will have some guidance significance for the further research on safety evaluation of railway tunnel.

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Study oF deformation characteristics of tunnels traversing adjacently under shield tunnels by shallow tunneling method

LI Qianqian1，ZHANG Dingli1，FANG Qian1，LI Dong2

2014, 33 (S2): 3911-3918 doi: 10.13722/j.cnki.jrme.2014.s2.065

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Using shallow tunneling method，tunnels between Pinganli and Beihaibei of Beijing Metro Line 6 traverse adjacently under Line 4 which is a shield tunnel. To obtain the deformation law of existing structures and ground surface settlement，the measured displacement of ground surface settlement and existing structures were analyzed. The research shows that：(1) For the stratum in non-crossing part，the maximum values of settlement decrease with the increase of buried depth of tunnel. If center distance between two tunnels is less than 2D，the surface subsidence is “single groove” shaped，otherwise the surface subsidence is “double grooves” shaped. In the crossing part，deformation of existing structures is “double groove”shaped，the surface subsidence is “single groove”shaped. (2) The maximum ground surface settlement of existing structures are 7.32 mm and 6.69 mm. The values of V are 0.36%，0.45%，the values of K range from 0.41 to 2.43. (3) The maximum ground surface settlement in crossing part is about 24%–27% of that in-non crossing part and the value of K is about 1.2–2.3 times. The research result can provide reference to the similar engineering.

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RESEARCH ON AXIAL FORCE DISTRIBUTION OF ROCK BOLTS UNDER TOP EXPLOSION

WANG Guangyong1，2，GU Jincai3，ZHANG Xiangyang3，SHAN Furong1，ZHOU Jianwei1

2014, 33 (S2): 3919-3923 doi: 10.13722/j.cnki.jrme.2014.s2.066

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In order to design new rock bolts improving explosion resisting capacity of tunnels reinforced by rock bolts，the axial force distribution under top explosion was studied by the model test and numerical analysis. Based on the model test，rock bolts of vault bore pressure and tension，according to axial stress distribution along the bolts on vault，the peak tension and peak pressure increased firstly，and then decreased，and the maximal peak pressure was near to anchorage，while the maximal peak tension was near to anchor head. According to numerical analysis，at the same time，the pressure had no difference significantly except that the pressure of anchorage and anchor head was small. The tension of three bolts on vault from anchorage to anchor top increased firstly，and then decreased，and the maximal peak tension was near to anchor top. The pressure and tension of other bolts also had no difference significantly，whose strength was smaller than that of vault.

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DISPLACEMENT CHARACTERISTICS OF BASALT SURROUNDING ROCK MASS

HUANG Qiuxiang1，YAN Jingjing2，WANG Jialin1，DENG Jianhui3

2014, 33 (S2): 3924-3931 doi: 10.13722/j.cnki.jrme.2014.s2.067

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Aiming at the problem of deformation and stability about rock mass，with underground powerhouse caverns of a hydropower station hosted in basalt rock mass as background，taking three chambers(the generator chamber，the main transformer chamber and the tail water surge chamber) as objects of study，based on monitoring results during construction，surrounding rock mass deformation magnitude distribution and spatial distribution in underground powerhouse chambers are analysed firstly，then by means of geological information combining with excavation and construction progress，the law of in-depth and by-time are analysed，at last the deformation characteristics of basalt rock mass during construction are summarized，and the effect of the inner beddings of the basalt on surrounding rock displacement is analyzed at mean time. The research results show that，with structural surface enriched，but mosaic structure in basaltic，effects of structural surface on surrounding rock mass deformation are not obvious. Most parts of surrounding rock displacements are within 20 mm，and within the scope of 15 m depth the rock mass displacement presents flexibility state，and deformation developed continuity with depth，such kind of rock mass can be considered as a homogeneous medium. Construction is the main factor that affects the development of deformation，and along with excavation carried out，the surrounding rock displacement shows developing trend like step.

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NODE QUASI-STATIC STABILITY ANALYSIS OF ROCK SLOPE UNDER EXCAVATION BLASTING BASED ON UDEC

ZHENG Yun1，CHEN Congxin1，ZHU Xixi1，PAN Zhengyi2，OU Zhe1，ZHOU Yichao1，XIA Tianyou1

2014, 33 (S2): 3932-3940 doi: 10.13722/j.cnki.jrme.2014.s2.068

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A node quasi-static method to calculate the safety factor of rock slopes under blasting case is given. Potential sliding surface slope position，failure mode and safety factor of slopes undertaking the blasting loads can be obtained by the node quasi-static method. The node quasi-static method consists of three parts. Firstly，secondary development on UDEC4.0 is conducted based on the FISH language embedded in UDEC4.0，and the calculation program considering the attenuation law of blasting vibration peak acceleration with blast center distance and elevation difference is written. Secondly，strength reduction calculation program is written based on the basic principles of strength reduction. Finally，choosing the discrimination method for slope critical state，and a new slope failure criterion that utilizes the maximum node displacement duration curve to determine the slope critical state is proposed in this paper. Through comparing with the calculation results obtained by UDEC system procedure，the correctness and feasibility of the node quasi-static method is verified. Finally，the node quasi-static method is applied to the blasting design and stability evaluation of Yunfu pyrite open-pit slope.

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IMPERMEABLE GROUTING MECHANISM AND PARAMETER ANALYSIS OF FRACTURE ROCK IN LONGMEN GROTTOES

LIU Xiangyou1，ZHAI Guolin2，FANG Yun2，FAN Zilong3

2014, 33 (S2): 3941-3947 doi: 10.13722/j.cnki.jrme.2014.s2.069

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Combined with rock fracture grouting theory，through the investigation of rock fissure，the adoption of low alkali compound injection slurry，on-site rock fracture grouting test and analysis of Longmen grottoes rock fracture grouting mechanism，the Longmen grottoes fissure grouting process parameters and construction technology were put forward. According to the grouting test result analysis，pulp slurry belongs to Bingham fluid，under the condition of low pressure grouting，grout in rock fracture movement status to laminar flow. Analysis field grouting cracks opening，minimum irrigation crack width characteristic value of alpha is 0.5 mm. Test results show that the crack width and water-cement ratio approximate assumes the inverse proportion relationship. When fracture opening width less than the minimum fracture width characteristic value of alpha，even though the water cement ratio is very big，grouting is also impossible. The grouting pressure and time has a significant impact of the test hole grouting volume.

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STUDY OF SLOWLY UNLOADING P-WAVES CAUSING DISCRETE FRACTURE MECHANISM

ZHU Zheming1，2，LIU Kai1，2，KANG Jiming1，2，ZHANG Xiaoyan1，2

2014, 33 (S2): 3948-3955 doi: 10.13722/j.cnki.jrme.2014.s2.070

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Slowly unloading P-waves and its function on this phenomenon has been investigated，and corresponding experimental study and numerical study have been implemented. A defected rock model around an excavation under the action of a slowly unloading P-wave is established，and the slowly unloading P-wave is induced by the impact of a steel plate. The simulation results show that if the strength of the slowly unloading P-wave is in a certain range，the phenomenon of discrete failures may occur in rock mass，and the phenomenon of zonal disintegration may be observed in the surrounding rock. And the rectangle stress waves cannot induce the phenomenon of rock discrete fractures.

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ANALYSIS OF SLIPPAGE AND FRACTURE CHARACTERISTIC ON ROOF INTERFACE OF UNDERGROUND HORIZONTAL SALT CAVERNS

HAO Tiesheng，LIANG Weiguo，ZHANG Chuanda

2014, 33 (S2): 3956-3966 doi: 10.13722/j.cnki.jrme.2014.s2.071

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Based on the characteristics of horizontal salt caverns，bedding plane slip and fracture between roof and cap rock are analyzed. A theoretical analysis of stress distribution around the salt caverns is presented，and discusses the normal stress and shear stress acting on the roof interface. Considering several main factors，such as the depth of salt caverns，friction angle，roof thickness，cavern pressure，as well as the radius of the caverns，it develops a rule based on the Mohr-Coulomb criterion to limit slippage and fracture characteristic of the roof interface. According to a example，it also analysis the relationship between the factors mentioned above and slippage and fracture of the roof interface，and then the range of damage on the roof interface is determined. The results will be helpful to the construction and operation of salt caverns.

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ANISOTROPIC AND WATER SENSITIVITY PROPERTIES STUDY OF SCHIST DEFORMATION PARAMETERS IN NORTHWEST OF HUBEI PROVINCE

WANG Zhangqiong，YAN Echuan，HUANG Xiangjia，WANG Qi

2014, 33 (S2): 3967-3973 doi: 10.13722/j.cnki.jrme.2014.s2.072

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In order to study anisotropic and water sensitivity properties of schist in northwest of Hubei province，Uniaxial compressive test on samples of Wudang Group schist，Tongsheng tunnel，Shiyan—Fangxian expressway，that with schistosity inclination of 0°，45° and 90° respectively is carried out. The results show that：Schist shows obvious anisotropic and water sensitivity properties，in the same state of water content，modulus of elasticity is 90°＞0°＞45°，Poisson ratio of natural state is 45°＞0°＞90°，and saturated state is 90°＞0°＞45°. In the same state of schistosity inclination，the modulus of elasticity of natural samples is larger than saturated samples，and Poisson ratio is related to schistosity inclination. Poisson ratio of saturated sample is equal to native state，when schistosity inclination is 0°，saturated sample is larger than to native state when schistosity inclination is 45°，and saturated sample is less than to native state when schistosity inclination is 90°. The main failure mode is press off，shear and split off when schistosity inclination is 0°，45°and 90° respectively. The main reason that schistosity inclination and water content has significant effect on deformation parameters and deformation and failure mode of schist is that，the different relationship between spatial orientation of schistosity and axial force direction，which caused obvious differences of contribution that of schistosity surface to schist deformation. The results can be reference for design，excavation，reinforcement and water-proof treatment of tunnel.

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SAFETY EVALUATION FOR STABILITY OF UNDERGROUND POWERHOUSE SURROUNDING ROCK BASED ON CATASTROPHE THEORY

ZHAO Yu1，ZHANG Jianwei1，YUAN Shufang2

2014, 33 (S2): 3973-3978 doi: 10.13722/j.cnki.jrme.2014.s2.073

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Deformation of surrounding rock of underground powerhouse with nonlinear characteristics is the reflect of various factors of hydropower station system. According to the deformation monitoring data of surrounding rock of Taian underground powerhouse，the rate of deformation is considered as a series of special solution of the nonlinear dynamic model，and then to inverse the nonlinear dynamic model. Using catastrophe theory，the cusp catastrophic model of surrounding rock deformation rate is established，and the stability of the surrounding rock is analyzed，and then the instability process of surrounding rock is further revealed. Study shows that the surrounding rock of Taian underground powerhouse is stable，and the result is consistent with the numerical calculation. It shows that this method is reasonable and effective，and provides a reference for similar projects.

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SLOPE EXCAVATION QUALITY EVALUATION BASED ON THREE-DIMENSIONAL LASER SCAN DATA

HU Chao1，ZHOU Yihong1，2，3，ZHAO Chunju2，3，PAN Zhiguo2，3，FENG Chengcheng2，3

2014, 33 (S2): 3979-3984 doi: 10.13722/j.cnki.jrme.2014.s2.074

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Hydraulic slope excavation usually have some characteristics such as huge face and tight period，high quality requirements and so on. The problems of traditional slope excavation evaluation method was analyzed，and then a three-dimensional laser scanning technology method for the slope excavation quality evaluation was presented. By using a random sample consensus algorithm，Bursa-Wolf models and other efficient algorithms to establish a method for slope excavation data acquisition，process flow. By analyzing the characteristics of the slope data，the point cloud data storage and management mechanism by implement relational databases based on B-tree and its expansion structure were established. Then according to the characteristics of slope evaluation excavation method，two evaluation methods were proposed：cross-sectional quality evaluation and excavation plane quality evaluation. The practical application proves that this method can rapidly evaluate and control the excavation quality，which can greatly improves the quality control excavation of efficiency and the level of information.

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RESEARCH ON FILLING BODY STRENGTH AND RHEOLOGICAL PROPERTIES OF MIXED FILLING MORTAR WITH UNCLASSIFIED TAILINGS AND ROD MILLING SAND IN JINCHUAN MINE

YANG Zhiqiang1，2，GAO Qian1，WANG Yongqian2，CHEN Dexin2，BA Duoheng2

2014, 33 (S2): 3985-3991 doi: 10.13722/j.cnki.jrme.2014.s2.075

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The research on mixed filling materials including unclassified tailings and rod milling sand was conducted due to the serious lack of rod mill sand in Jinchuan mine. Based on the experiments of filling body strength and rheological properties for different ratios of mixed filling mortar with unclassified tailings-rod milling sand，revealed the relationship between filling body strength and the ratios，average particle size and uniformity coefficient and determined the reasonable ratio of Unclassified Tailings and Rod Milling sand was 3∶7 which apply to underhand drift cut-and-fill method in Jinchuan mine. The research shows that the compressive strength of 7 d and 28 d bleeding and sedimentation rate were precede rod milling sands. This research achievement provided important technical support to industrialized application of unclassified tailings in Jinchuan mine and laid the foundation of the utilization of waste resources and environmental protection.

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NONLINEAR ANALYSIS ON LOAD TRANSFER MECHANISM OF WHOLLY GROUTED ANCHOR ROD ALONG ANCHORING SECTION

HUANG Minghua1，ZHOU Zhi2，OU Jinping1，2

2014, 33 (S2): 3992-3997 doi: 10.13722/j.cnki.jrme.2014.s2.076

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A novel nonlinear shear-slipping model of anchor rod according to load-displacement curve in the pullout test was established. Based on this model，the nonlinear differential equation of load transfer was established and the analytical solutions of axial force and shear stress were developed. The features of this model as well as the axial force and shear stress distributions along the anchor rod were analyzed. Results indicate that this model gives a peak value in its curve. With the slip increases，the shear stress initially goes up to the peak value then decreases，that is，this model characterizes the softening behaviors of anchorage interface reasonably. Under the pulling load，the anchorage interface undergoes three stages including elastic bonding stage，elastic-plastic deformation stage and rapidly softening stage. With the increase of pulling load，the shear stress distribution evolves from a monotone decay curve into a single peak curve and the influencing zone of the shear stress expands into far end gradually. Under the ultimate limited state，the whole anchorage interface softens rapidly into failure. The developed solutions are suitable for analyzing axial force and shear stress along anchor rod undergoing various stages，which provides theoretical reference for researches on the load transfer mechanism of wholly grouted anchor rod.

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REVIEW OF SLOPE MICRO-SEISMIC MONITORING IN OPEN-PIT MINE

LI Jian1，2，3，WU Shunchuan1，2，GAO Yongtao1，2，XIE Yuling1，2，JI Maowei1，2

2014, 33 (S2): 3998-4013 doi: 10.13722/j.cnki.jrme.2014.s2.077

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By analyzing the advantages and disadvantages of existing monitoring technology in open-pit mines，the unique advantages of micro-seismic monitoring technology in rock failure information collection and analysis were described. By detailing the development and current situation of micro-seismic slope monitoring technology，and combining with the instances analysis of micro-seismic slope monitoring abroad，it was indicated that the technology can not only implement the slope surface displacement prediction with 30–45 days in advance，determine the slope active geological layers internal，the rock slope failure mechanism inside，but also explain the influence on the rock mass slope inside by human activities and natural environment changing with the number of micro seismic events，torque，energy development trends and other forms of quantitative interpretation. At last，the problems of software and hardware equipment，influence assessment of underground water，precision of micro-seismic events location，noise filtering and the identification of signals arrival were put forward when it was applied in open-pit mine，and the improvement and application prospect in future were discussed.

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SKEWNESS ANALYSIS AND FORECASTING OF SURFACE SUBSIDENCE CAUSED BY TUNNEL EXCAVATION IN QINGDAO

YUAN Changfeng，YUAN Zijin，LIU Shibo，LI Guolong，LI Liang

2014, 33 (S2): 4014-4019 doi: 10.13722/j.cnki.jrme.2014.s2.078

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The laws and prediction of surface subsidence induced by jointed rock excavation are investigated based on the measured data of surface subsidence caused by tunnel excavation in the connection point of Qingdao Jiaozhou bay tunnel. Geological and mathematical models that considering the joint geometric forms are established. Using stochastic medium theory，probability of rock falling totally after unit excavation is analyzed. Meanwhile，probability distribution function of surface rock is deduced and settlement prediction formula of rock unit is established. According to the convergent monitoring results around the hole，sedimentation coefficient of rock unit is back analyzed by which surface subsidence caused by tunnel excavation on the field is forecasted. Results show that the surface subsidence rules caused by the shallow large-span hardrock tunnel excavation conform to the laws of discrete binomial distribution. The Gamma distribution prediction model is used when n≥10. Results from the model prediction agree well with those actual monitoring data of surface subsidence that caused by the Qingdao city subway tunnel excavation. The proposed model provides some insights for designing and construction monitoring.

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RESEARCH ON DAMAGE CRACKING FOR ROCK AND SOIL AGGREGATE USING CALCULATION MESO-MECHANICS

WANG Yu1，2，LI Xiao1

2014, 33 (S2): 4020-4031 doi: 10.13722/j.cnki.jrme.2014.s2.079

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According to the geological origin and meso-structure properties of rock and soil aggregates(RSA)，RSA is viewed as complicated material consisted of three partition：rock blocks，soil matrix and rock-soil interface. The calculation meso-mechanics for RSA is proposed. Cracking failure simulation for RSA，the morphology，distribution，grain composition and rock percentage of rock blocks should not only be considered，but also structure of soil aggregates and rock-soil interface be considered. The primary failure reason for RSA is the elasticity mismatch，essence of failure is the initiation，propagation，penetration of cracks. Problems to be solved using meso-mechanics to explore the meso-damage process in RSA，finding proper methods to describe evolution rule of cracking. Exploring the response of RSA to force field and environment effect，continuum mechanics，statistical damage mechanics and calculation mechanics should be integrated to analysis mesoscopic deformation，damage and cracking，and develop mesoscopic constitutive model for RSA and simulate failure mechanism for rock and soil aggregates. It can clearly clarify the meso-damage mechanism for RSA，which can provide theory assistant to disaster prevention and mitigation.

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ANALYSIS OF LATERAL RESPONSE OF BORED PILES BASED ON CONCRETE DAMAGED PLASTICITY MODEL

CAI Zhongxiang1，LIU Shannan2，GAO Chengyong1，HOU Shengnan1

2014, 33 (S2): 4032-4040 doi: 10.13722/j.cnki.jrme.2014.s2.080

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The lateral bearing capacity of piles is an important parameter for horizontal deformation of building and seismic checking of piles. The determination of test pile is under free-head condition. However，the widely used pile-raft foundations provide a strong constraint for the rotation of pile head. Linear solutions of differential equation for single piles are available and implemented in the traditional design methods. Thus，a numerical analysis is presented to study the behavior of laterally loaded pile based on the concrete damaged plasticity model. After validation with the in-situ test of bored piles in shanghai typical soft soil，the vertical load，reinforcement ratio and fixed-head constraint are considered for the lateral bearing capacity of bored piles. The analysis show that vertical load is benefit for the lateral bearing capacity of piles due to compressive stress. The increment of reinforcement ratio can increase the lateral bearing capacity to some extern，and mainly improve the ductility of piles. The constraint of pile head can increase the bearing capacity to a large extern. The increment factor from the numerical simulation has a significant difference with the m method based on elastic reaction assumption，and further study is hoped in the in-situ test.

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STUDY OF MOISTURE CONTENT MIGRATION OF RED CLAY AND STRATIGRAPHIC STRUCTURE INVERSION ANALYSIS IN SHALLOW BURIED TUNNEL

LU Gao，LI Ning，ZHU Caihui，CHEN Lijing，QIN Jiajia，LIU Xinxing

2014, 33 (S2): 4041-4048 doi: 10.13722/j.cnki.jrme.2014.s2.081

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In geotechnical engineering，the moisture content of shallow embedded soil directly affects mechanical property in the surrounding rocks and crucial important issue of the stability of tunnel. Based on the characteristics of ground penetrating radar(GPR) is sensitive to the water in soil，sampling red clay from tunnel face，adjusting the moisture content of experimental samples from 10% to 30%，and scanning it by variety of frequency of GPR. In consequence，a relationship of moisture content of red clay and the speed of GPR wave is set up. Through continuous monitoring for many times，the moisture content of surrounding rock are obtained by geological radar scanning，and the mechanical parameters as well as its changes related to the moisture content within the detection ranges are predicted. Therefore，moisture content distribution and mechanical parameters of tunnel excavation are revealed as the excavation process of changes occurring in the course of migration，and give a rapid quantitative assessment on the stability of tunnel.

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DYNAMIC STABILITY EVALUATION FOR ROCK STRUCTURE AROUND UNDERGROUND CAVERN BASED ON FRICTIONAL ENERGY ON JOINTS

WANG Shuai1，SHENG Qian2，ZHU Zeqi2，FU Xiaodong2

2014, 33 (S2): 4049-4055 doi: 10.13722/j.cnki.jrme.2014.s2.082

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Due to stability of rock structure is controlled by the joint，frictional energy on joints is proposed as an indicator of stability evaluation for rock structure around underground cavern. Relying on the underground cavern of Dagangshan hydropower station，numerical simulations with discrete element method are performed for different combinations of joint orientation，joint spacing and joint friction angle. Stability of rock structure is checked based on frictional energy and dynamic response of joints respectively. The applicability of friction energy on joints is discussed. Results show that the index proposed can be applied to evaluate the shear destruction of rock structure around underground cavern which can reflect failure rate，failure history and damage size of rock structure；consequent joints with inclination of 60° and consequent joints cutting at lower position of high sidewall are less favorable to the dynamic stability of rock structure.

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STUDY OF TOPOGRAPHY FACTORS INFLUENCE ON MOTION PARAMETERS FOR SEISMIC SLOPE-TOE LANDSLIDES

FAN Xiaoyi1，2，TIAN Shujun1，DUAN Xiaodong1，ZHANG Youyi1

2014, 33 (S2): 4056-4066 doi: 10.13722/j.cnki.jrme.2014.s2.083

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Slope-toe landslide is a typical disaster induced by the Wenchuan earthquake. The influential factors of topography，including length of sliding surface above slope toe(L′)，landslide gradient()，angle of slope toe() and gradient of landslide accumulation() were considered. The maximum vertical motion distance(Hmax)，maximum horizontal motion distance(Lmax)，horizontal motion distance under the slope toe(L) and equivalent fraction coefficient(Hmax/Lmax) were studied by the orthogonal，range，variance and regression analysis. The L′ is the most important and significant influence factor on Hmax and Lmax which the landslide volume is from 1×104 m3 to 1×106 m3. Among the influence factors on Hmax/Lmax，the is the most important one and the and are the significant influence factors. The is the most important factor on Lmax and L of landslides with the volume more than 1×106 m3 and significant influence factor on L of landslides with volumes more than 1×105 m3. The landslide volumes from 1×104 m3 to 1×106 m3，the topography factors play more consistent role on the factor combinations of the landslide maximum motion parameters，and it is different on the landslides with the volumes more than 1×106 m3. These results could provide references for determining the influence and significant of topography factors on the motion parameters of slope-toe landslides，and it is a practical significance to the prevention and mitigation of slope-toe landslides.

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STUDY OF THE PERMISSIBLE VALUE OF UPWARD FLOATING FOR SEGMENT IN SHIELD TUNNEL CONSTRUCTION

YE Junneng1，LIU Yuan2，3，4，CHEN Renpeng2，3，TANG Lujun2，3

2014, 33 (S2): 4067-4074 doi: 10.13722/j.cnki.jrme.2014.s2.084

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The excessive upward floating of segment in shield tunnel construction would cause the ring joints stretched，dislocated and segment damaged. At present，there are few researches on the permissible value of upward floating for segment in shield tunnel. By using finite element software ABAQUS，a 3D numerical model for the analysis of upward floating which could consider the impact of dislocation and stretched deformation of spring join was founded. The upward floating deformation at different segments and the deformation of spring joints were analyzed. Results show that upward floating of segment can be divided into three stages：the linearly developing stage，the arc-shaped developing stage and the deformation stabilized stage. The main deformation of joints is dislocation in the linearly developing stage and tensile in arc-shaped developing stage. A formula for the permissible value of upward floating for segment in shield tunnel which is affected by the permissible dislocation value and permissible tensile value of spring joint was obtained. The permissible value of segment upward floating of Ningbo and Shenzhen metro whose structure of segment are different were compared，and result shows that the structure of segment has great impact on the permissible value of upward floating.

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ISSUES AFECTING GROUND SUBSIDENCE INDUCED BY COVERED EXCAVATION FOR LARGE CROSS-SECTIONAL TWIN TUNNEL UNDER EXISTING STRUCTURES

WANG Dongyuan1，QU Huihong1，LI Wenbo2

2014, 33 (S2): 4075-4085 doi: 10.13722/j.cnki.jrme.2014.s2.085

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Based on a real project Jiaomen West Station in Beijing，details of two-dimensional finite element model for numerical analyses of surface ground subsidence are presented. Interpretation methods for parameters of soil-cement mixtures used to reinforce and pre-support excavation are proposed. Further numerical studies on the design and construction issues which significantly affect the ground subsidence caused by covered undercutting are then conducted. The study concludes that the proposed methodology to interpret the parameters of soil-cement mixtures is valid by comparing the simulation results and observed data. Moreover，the settlement trough under existing station structures is still in line with overseas research for Greenfield single tunnel，unconfined compressive strength of soil-cement mixture 1.5 MPa to 2.0 MPa is capable of making the excavation stable. The study also indicates that the surface ground subsidence has a correlation with pillar width.

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SIMULATION TEST OF METRO TUNNEL PARALLELS GROUND FISSURE WITH SHORT DISTANCE

HE kai1，PENG Jianbing1，2，HUANG Qiangbing1，2，WU Ming1，2

2014, 33 (S2): 4086-4095 doi: 10.13722/j.cnki.jrme.2014.s2.086

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Model test and numerical simulation were applied to study the metro tunnel parallel to ground fissure in short distance based on Xian metro line 3. The condition of 30 m between tunnel and ground fissure was utilized in model test. Numerical calculations about six groups of working conditions were carried out in distance of 5–50 m. Based on displacement，stress distribution and macroscopic deformation，destruction characteristics of tunnel and soil mass were analyzed in detail. The influencing mechanism of metro tunnel parallel to an active ground fissure was revealed. Combined the results of physical model test with numerical simulation，the condition of metro tunnel through in hanging wall parallel to ground fissure by 30 m is feasible and safety. Moreover，the safety distance between parallel metro tunnel and ground fissure was proposed.

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A NON-EQUIDISTANT TIME SERIES MODEL AND ITS APPLICATION IN TUNNEL VAULT CROWN DISPLACEMENT PREDICTION

HE Yabo，LIANG Cheng

2014, 33 (S2): 4096-4101 doi: 10.13722/j.cnki.jrme.2014.s2.087

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Based on the non-equidistant and non-stationary time series data in practical engineering，total displacement can be divided into trend term displacement and stochastic term displacement. The displacement prediction model of tunnel wall rock can be established by time series analysis. Cubic-spline interpolation method is used to process the non-equidistant time series data. On this basis，GM(1，1) grey model is used to forecast the trend term displacement，and autoregressive model is used to forecast the stochastic term displacement. Total displacement is obtained by adding the calculated predictive displacement value of each term. Taking Huayingshan tunnel for example，it is shown that the result could better reflect the development trend of vault crown settlement displacement value based on the comparative analysis of measured and predicted displacement-time curves. Results demonstrate that the established non-equidistant and non-stationary time series decomposition model is feasible and effective in the wall rock displacement prediction of practical tunnel engineering.

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INFLUENCE OF HEAVY RAINFALL CHARACTERISTICS ON SATURATED-UNSATURATED SLOPE FAILURE

ZHANG Sherong，TAN Yaosheng，WANG Chao，YU Mao

2014, 33 (S2): 4102-4112 doi: 10.13722/j.cnki.jrme.2014.s2.088

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Based on surveying and summarizing typical domestic landslide disasters，a saturated-unsaturated slope model was generalized and the software platform of ABAQUS was applied to solve the model by method of a coupled analysis of transient seepage field and stress field under the infiltration of heavy rainfalls. Combined strength reduction technique to analyze the slope stability under transient seepage，and safety factors of the overall stability were gained，proposing and implementing the evaluation method of failure approach index(FAI) by coupling of seepage and stress fields，revealing slope rock mass strength reserve，the degree of damage and criticality of non-rupture areas to explore the impacts of heavy rainfall characteristics on slope failure mechanism and stability from various angles. Results showed that：(1) Heavy rainfall will lead stress levels to deteriorate in the slope free face particularly lower rock mass，with easily bring about flow erosion damage and partial collapse. (2) The effect of rainfall patterns on time and space evolution of pore pressure，deformation response，safety factors and FAI is obvious，pore pressure and deformation are positive correlation to different raininesses. (3) Pore pressure will increase gradually under the long duration rainfall with low intensity and easily lead to deep slide damage. The slope toe is the first failure region under the short duration rainfall with high intensity. (4) Rain intensity is inversely proportional with the safety factor which is reduced by approximately 17% when raininess varies from 12 mm/h to 36 mm/h，which affects the extent of failure parts and criticality in non-rupture parts，and high-intensity rainstorms make it easier for the slope toe slippage.

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RESEARCH ON FAILURE MECHANISM OF ANTI-SLIDING MICROPILES BASED ON ELASTOPLASTIC MODEL

XIN Jianping1，2，ZHENG Yingren1，2，TANG Xiaosong1，2

2014, 33 (S2): 4113-4121 doi: 10.13722/j.cnki.jrme.2014.s2.089

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The failure mechanism of micropiles in rock-soil slope，rock slope and soil slope was obtained based on strengthen reduction and the finite difference program FLAC. Solid elements and Mohr-Coulomb ideal elastoplastic model were used for piles on the purpose of getting the failure state. The microplies getting into plastic state based on its mechanical characteristics，then the failure mechanism of micropiles from failure state，deformation and internal force were analyzed. Safety factor and failure mode of slopes reinforced by microplies are obtained. Then a model test of soil slope reinforced by micropiles is compared with its 1∶1 numerical simulation and the results conform to each other. It shows that the numerical simulation method is correct and can be utilized for slope prototype calculation. Results indicate that the failure mechanisms of micropiles in different types of slopes are completely different. For mixed rock and soil slope，bending shear failure in sliding zone and bending failure above sliding zone happens to piles. For rock slope，the failure of piles is mainly shear failure in sliding zone. For soil slope，bending failure of piles happens on both sides of sliding zone.

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RESEARCH ON SAFETY FACTOR COMPUTATION OF LANDSLIDE BASED ON VECTOR SUM-DISCONTINUOUS DEFORMATION ANALYSIS METHOD

FU Xiaodong，SHENG Qian，ZHANG Yonghui

2014, 33 (S2): 4122-4128 doi: 10.13722/j.cnki.jrme.2014.s2.090

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Discontinuous deformation analysis(DDA) is a new limit equilibrium computation method，which has satisfied three convergences including convergence of equilibrium equations，convergence of open-close iterations for all contacts and convergence of the maximum displacement for static computations. The two-dimensional vector sum analysis method had been introduced in DDA，and the Vector SUM-DDA method was proposed. Considering the dynamic iterations and contact force computation in DDA，the method of slide direction and safety factor were detailed. Several numerical examples of the landslide，including a planar sliding face and a rounded sliding face，computed by Vector SUM-DDA method. Comparing to the solutions of the theoretical analysis and the limit equilibrium analysis，results show that the new method is reasonable to calculate the safety factor of landslide. The Vector SUM-DDA method calculates the safety factor based on true stress field and the integrations of slide or resistant force has reflected the concept of sliding vector.

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RESEARCH ON COUNTERMEASURE OF CONSTANT RESISTANCE AND LARGE DEFORMATION COUPLING SUPPORT OF RETURN AIR COURSE SOFT ROCK ROADWAY IN XINAN COAL MINE

SUN Xiaoming1，2，WANG Dong1，2，YANG Jun1，2，XU Huichen1，2，LIU Zongquan1，2，CHEN Feng1，2

2014, 33 (S2): 4129-4139 doi: 10.13722/j.cnki.jrme.2014.s2.091

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To solve the destruction phenomena of non-linearity large deformation in the +535 m return air course soft rock roadway of Xinan coal mine，such as serious floor heave，side wall shrinking and roof sinking，situ engineering geomechanics analysis，indoor physical mechanic property research and three-dimensional numerical simulation were adopted. And a thorough study involving the deformation failure mechanism of the return air course soft rock roadway of Xinan coal mine was developed. The type of deformation mechanism of this soft rock roadway was confirmed and transferred successfully. The support form of constant resistance and large deformation bolt + metal net + floor anchor pipe + steel fiber reinforced concrete was proposed and used in practice successfully in Xinan coal mine. Practice was proved that the coupling technology based on constant resistance and large deformation bolt could effectively transfer the deformation mechanism，absorb the deformation energy accumulated in surrounding rock，cut off the plastic sliding force of floor heave and ensure the total safety of the roadway.

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CHARACTERISTICS AND AN EXPERIENTIAL MODEL OF ELECTRICAL RESISTIVITY OF STABILIZED SOILS

ZHANG Dingwen，CAO Zhiguo，LIU Songyu

2014, 33 (S2): 4139-4144 doi: 10.13722/j.cnki.jrme.2014.s2.000

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Electrical resistivity measurement is a useful and popular method to assess the quality of stabilized soils due to its economical，non-destructive and continuous measurement advantages. In order to evaluate the characteristics and influence factors of electrical resistivity of stabilized soils，a series of electrical resistivity tests of stabilized soils specimen after various curing periods were carried out. Cement，admixture of ground granulated blast furnace slag and lime，admixture of pulverised fly ash and lime were used to stabilize clay. The results indicate that increase of hardener agent contents results in the electrical resistivity of stabilized soils increasing. The electrical resistivity of stabilized soils also increases with the increase of curing periods，but the electrical resistivity gain rate is reducing. A synthetical parameter is proposed to represent the influences of porosity，degree of saturation，hardener agent content and curing periods on electrical resistivity of stabilized soils. The Archie′s electrical resistivity model is modified by replacing the porosity by the synthetical parameter，and the modified Archie model can represent the characteristics of electrical resistivity of stabilized soils.

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FORECASTING MODEL OF GRAIN SIZE GRADING CURVES OF COARSE-GRAINED MATERIALS BASED ON DISCARDING RATIO

CHANG Shuai1，2，XU Riqing1，2

2014, 33 (S2): 4145-4152 doi: 10.13722/j.cnki.jrme.2014.s2.000

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To construct a forecasting model of grading curve of coarse-grained materials considering breakage，particle breakage is divided into three stages. And the new concept of discarding ratio Rk is introduced in the model-building process. By investigating the relationship of discarding ratio with confining pressure，dry density and particle size with the breakage test results of quartz sandstone，gneiss，mixture of sandstone and slate，breccias and sandy conglomerate，it is indicated that on the simplified hypothesis of geometric progressional distribution，there is a linear relationship，which has a slope turning point between Rk and σ3，for different granular materials when particle size and confining pressure vary in the ranges of 10–60 mm and 0.0–1.6 MPa，respectively. By exploring the particle breakage of well-rounded sandy conglomerate，it is found that 3-Rk relationship becomes linear globally while particle size is less than 10 mm and confining pressure ranges from 0.0 to 1.2 MPa. Considering the combined effect of confining pressure，strength of mother rock and original particle size，it is concluded that the variation of discarding ratio is unanimous for the breakage of gneiss，mixture of sandstone and slate，weak weathering quartz sandstone with the same grain group once particle size changes from 10 to 60 mm. Thus a prediction formula for estimating discarding ratio is presented，and the ranges of its parameters are given preliminarily，which makes possible the forecast of soil grain size grading curve of coarse-grained materials based on the concept of Rk.

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SAFETY RISK EARLY-WARNING STANDARD OF FOUNDATION PIT IN COMPLEX ENVIRONMENT DURING EXCAVATING

GU Leiyu1，HUANG Hongwei2，CHEN Wei3，GONG Gupei1，WANG Defa1，YANG Hui1

2014, 33 (S2): 4153-4162 doi: 10.13722/j.cnki.jrme.2014.s2.000

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When in the vicinity of building or other complex conditions，the excavation safety risk warning standard need to be able to accurately quantify the associated economy and the environment safety of the project. Based on the risk theory，the design method of the excavation safety risk early-warning standard in the complex environment was put forward. To determine the design parameters，the probabilistic characteristics of the relationships between the risk warning indicator and ground deformation were analyzed. The interaction between building and foundation was studied by numerical analysis. Consequently，the relationships between building deformation parameters and risk early warning indicator were confirmed. The analysis method of damage to the building was proposed，and then，the design method of the safety risk early warning standard was determined. This design method is able to flexibly analysis the complex combinations of environmental factors. So it can over a wide range. With the classification warning mechanism，the dynamic early-warning standard can be designed during excavation. Confirmed by the practical engineering，the early-warning standard can more accordant to the engineering practice.

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LABORATORY RESEARCH ON MIGRATION OF EU(III) IN COMPACTED GMZ BENTONITE-SAND MIXTURES

ZHOU Lang，ZHANG Huyuan，CHEN Hang，YAN Ming

2014, 33 (S2): 4163-4167 doi: 10.13722/j.cnki.jrme.2014.s2.095

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Radionuclides will diffuse to the outside after the overpack has been destroyed in the high level radioactive waste(HLW) disposal. The diffusion coefficient of radionuclides in buffer backfilling material plays an important role in evaluating the property of the engineering barrier of disposal repository in HLW disposal. Taking 2.0×10－5 mol/L of Eu(III) solution as influent，the migration of Eu(III) in compacted GMZ bentonite-sand mixtures is studied under the conditions of convection，diffusion and adsorption；and the migration progress is modeled by the convection-dispersion equation. The fitting curves can fit the test data very well，which confirms the validity of experimental method. The effective diffusion coefficients and apparent diffusion coefficients of Eu(III) in compacted GMZ bentonite-sand mixtures are De = 1.62×10－12–4.87×10－12 m2/s，Da = 1.44×10－14–9.41×10－14 m2/s，respectively. And then，the effect of sand ratio on apparent diffusion coefficient is discussed. The research results can be used to forecast the relationship between migration length of Eu(III) in buffer backfilling material with time and provide a reference for the design of buffer backfilling material for HLW disposal in China.

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DISCUSSION ON MECHANISM OF SEISMIC LIQUEFACTION OF SATURATION LOESS IN SHIBEI TABLELAND，GUYUAN CITY

WANG Qian1，2，WANG Jun1，2，WANG Lanmin1，2，WANG Ping1，2，ZHONG Xiumei1，2

2014, 33 (S2): 4168-4173 doi: 10.13722/j.cnki.jrme.2014.s2.096

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On the basis of the dynamic triaxial liquefaction test of the loess samples which were taken from the Shibei tableland，Guyuan city，the characteristics of dynamic strain and pore water pressure of loess which at different layers are studied under the different levels of dynamic loads，the mechanism of the loess liquefaction in Haiyuan earthquake is analyzed. Moreover，the liquefaction criterion of saturated loess is discussed according to the special properties of loess. The results show that the development of pore water pressure influenced by various factors which contains dynamic load，grain composition，plasticity indices when the saturated loess liquefaction. It has the nature of hysteretic relative to the development of dynamic residual strain，so it often can not reach the effective confining pressure. However，the characteristics of dynamic residual strain development mainly by the influence of the initial void ratio，and increasing sharply when it exceeded 3%. Therefore，the dynamic residual strain reach to 3% can be chosen as the critical value of the saturation loess liquefaction.

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EXPERIMENTAL EFFECT CONTRAST BETWEEN PHC AND CFG PILE-RAFT COMPOSITE FOUNDATION IN HIGH SPEED RAILWAY BASE TREATMENT

SHEN Yupeng1，2，MAO Yuanfeng1，JING Peng1，CHENG Wanhui1，TIAN Yahu1，2

2014, 33 (S2): 4174-4180 doi: 10.13722/j.cnki.jrme.2014.s2.097

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Through analyzing the differences of bearing capacities of a single pile，pile-soil load distribution and variation characteristics of the load and settlement in the different times，PHC and CFG piles raft composite foundations are compared when applied to treat the foundations of Beijing-Tianjin intercity railway. The results show that PHCs bearing capacity of single pile is obvious higher than the CFGs，about 1.33 times，and the settlement in PHCs section is smaller than CFGs. The results appear that the pile-soil stress ratio is about 17–47，and load ratio is 0.56–0.78 in PHCs section. The pile-soil stress ratio is 12–25，and load ratio is 0.42–0.59 in CFGs section. It is said that the PHC piles can bear more load than the CFG，the soils in PHCs section will bear less load than CFGs. In summary，PHC piles are used to as a ground treatment not only to ensure pile-forming effect，but to reduce the load on soil between two piles in soft foundations，and to decrease the total settlement of composite.

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EXPERIMENTAL STUDY OF VACUUM PRELOADING COMBINED REINFORCEMENT WITH ELECTRO-OSMOSIS IN SOFT CLAY GROUND

WANG Jun1，2，ZHANG Le3，LIU Feiyu4，FU Hongtao1，2

2014, 33 (S2): 4181-4192 doi: 10.13722/j.cnki.jrme.2014.s2.098

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An electro-osmosis combined with closed vacuum preloading indoor model test was conducted on the soft clay using a self-developed apparatus. Vacuum pressure under the sealing membrane and the plastic drainage board，the change of soil drainage，current intensity and potential were monitored in real-time. After the test，surface subsidence，vane shear strength，moisture content，pH valves of soil and conductivity were measured in the different parts of the soil. The results show that the treatment effect of the combined method is better than that of vacuum preloading alone. Under the combined application，vacuum preloading and electro-osmosis can promote each other. The increase value in anodic resistance is greater than that in cathodic region. The increase of cathodic resistance is primarily related to the changes in soil composition and moisture，and the increase of anodic resistance is primarily related to the increase of interface resistance and the decrease of moisture content. The water can be discharge effectively and the reinforcement effect is improved significantly through the electro- osmosis cathode constituted with plastic drain board and metal electrodes.

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VERTICAL VIBRATION CHARACTERISTICS OF LARGE-DIAMETER END-BEARING PILE IN LAYERED SOIL

REN Qing，GAO Zhanshi，LU Hongyong

2014, 33 (S2): 4193-4202 doi: 10.13722/j.cnki.jrme.2014.s2.099

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Large-diameter end-bearing pile is widely used in offshore engineering and high-rise building. The classical plane-strain model of soil is reviewed and its limitations are discussed. An improved model is developed on the basis of plane strain model，which can consider the coincidence of lateral and vertical vibration. The proposed model is proved to be correct after comparing with classical solutions. And then，the above model is introduced into vertical vibration model to discuss dynamic impedance and axial force of large-diameter end-bearing pile in layered soils. After analysis of the slenderness ratio，hysteretic damping ratio，soil Poisson's ratio，pile-soil relative stiffness and pile-soil relative density，it can be concluded that slenderness ratio，soil Poisson's ratio and pile-soil relative stiffness are the key factors for dynamic impedance of large-diameter end-bearing pile. Finally，the present model is supported by three-dimensional finite element method in predicting dynamic response of large diameter monopile foundations used in offshore wind farm and cross-sea bridge，which shows that the present model can give more reasonable guidance on vibration of large-diameter end-bearing pile.

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NONLINEAR FINITE ELEMENT ANALYSIS OF CONSOLIDATION FOR VERTICAL DRAINED GROUND WITH PARAMETERS DETERMINED FROM GDS CONSOLIDATION PERMEABILITY TESTS

DENG Yuebao1，XIE Kanghe2，LI Feifei2，LIU Ganbin1

2014, 33 (S2): 4203-4210 doi: 10.13722/j.cnki.jrme.2014.s2.100

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A series of widely accepted non-linear constitutive models，which can be fully gained from the conjoined consolidation permeability test by GDS advanced consolidation testing system，are firstly introduced. These models contain the piecewise linear e-lgp model，the linear e-lgk model and Hansbos non-Darcy flow model，where e is the porosity，p is the loading pressure and k is the permeability. Then，the parameters acquisition process for these models is recommended with the presentation of conjoined consolidation permeability test for Ningbo soft soil by GDS. Next，the finite element equations considered these nonlinear models are deduced based on the classical Biots consolidation theory. The corresponding computing program is presented in detail. The reliability of the program and its theoretical basis is verified through the comparison with an existing numerical method. Lastly，example analysis for vertical drained ground with layered soft soil is carried out and the influences of the permeable boundary，non-Darcy flow，smear effect and loading size on consolidation are studied. It is found that the influence of the permeable boundary is obvious，while the influences of non-Darcy flow and smear effect are not obvious. The influence of loading size is more complicated，which will accelerate or slow down the consolidation rate.

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EXPERIMENTAL RESEARCH OF EFFECT OF GRANULE SHAPE ON SHEAR MODULUS AND DAMPING RATIO OF GRAVEL

SUN Tian1，2，CHEN Guoxing1，2，WANG Binghui1，2，LI Xiaojun2，3

2014, 33 (S2): 4211-4218 doi: 10.13722/j.cnki.jrme.2014.s2.101

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The effects of effective confining pressure，consolidation ratio，gravel content and grain breakage on the shear modulus and damping ratio of gravel have been studied. However，only little work focused on the effect of the granule shape. Thus，the dynamic triaxial tests under different confining pressures were performed on the gravel specimens to investigate the effect of the granule shape on the shear modulus and damping ratio using a hollow cylinder apparatus(HCA)，which is developed by GDS Instruments Ltd.，United Kingdom. These specimens were made by two kinds of gravel(i.e.，with angular and round grains) with the same grain composition and relative density 45%. The results indicate that the gravel with the round shape has a higher shear modulus than that with the angular one when the confining pressure is higher than 300 kPa or the shear strain amplitude is greater than 7×10－4. The gravel content(content of grains，whose diameter is bigger than 5 mm) corresponding to the maximum shear modulus is called the critical gravel content P5cr，and the P5cr of the angular sample is higher than that of the round one. Conversely，the damping ratio of the angular sample is greater than that of the round one when the shear strain amplitude is larger than 2×10－4.

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FIELD RESEARCH ON DRAINAGE SYSTEM OF VACUUM PRELOADING TECHNOLOGY FOR FRESH HYDRAULIC RECLAMATION SILT

BAO Shufeng1，2，DONG Zhiliang2，MO Haihong1，CHEN Pingshan2

2014, 33 (S2): 4218-4226 doi: 10.13722/j.cnki.jrme.2014.s2.102

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For fresh hydraulic reclamation silt foundation，after improvement of no-horizontal-sand-drainage vacuum preloading technology，soil strength increases only a little，and the effective improved depth is very small. In view of this，soil engineering properties was analyzed and summarized of fresh hydraulic reclamation silt from different area，it is showed that high content of clay particles and strong hydrophilic minerals are one of major reasons why the drainage efficiency of vacuum consolidation drainage system is very low. Then，based on a project on shallow ultra-soft soil improvement in Gaolan seaport area in Zhuhai seaport，following the design principle of vacuum drainage system，a field experiment research was carried out of optimizing the vacuum drainage system. It was concluded that：(1) Based on transfer properties of vacuum degree inside the drainage system，it was better of scheme 3 (PVC filter tube-interspersed and fixed-common PVD) and scheme 4(horizontal integral PVD-matching connector-vertical integral PVD). (2) Based on transfer properties of vacuum degree among soil particles，scheme 4 was most advisable. Finally，some further suggestions were provided in future research.

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NUMERICAL MODELLING OF BIAXIAL COMPRESSION TESTS FOR GRANULAR MATERIALS WITH INHERENT ANISOTROPY USING DEM

TONG Zhaoxia1，ZHOU Min1，ZHANG Lianwei2，YAO Yangping1

2014, 33 (S2): 4227-4232 doi: 10.13722/j.cnki.jrme.2014.s2.103

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The deformation of granular materials with inherent anisotropy is dependent on the principal stress direction relative to the bedding plane. In order to investigate the micro deformation process of anisotropic granular materials with discrete element method(DEM)，a numerical model was verified by two series of biaxial compression tests firstly. The experiments were conducted on the ideal 2D ellipse-shaped iron rods under three cell pressures and four different major principal stress directions. On this basis，the development of shear band under four different major principal stress direction loadings was studied by analyzing the particle displacement and rotation at different deformation stages. Further，the long axis orientation of particles and void ratio inside and outside shear band were investigated. It was found that，under the loading with different major principal stress directions，the long axis orientation of particles inside the shear band tends to approach the same direction，and the same tendency was also found for the void ratio inside the shear band.

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STRENGTH OF UNSATURATED LIME-TREATED EXPANSIVE CLAY IN HEFEI

WANG Mingwu，QIN Shuai，LI Jian，XU Peng

2014, 33 (S2): 4233-4238 doi: 10.13722/j.cnki.jrme.2014.s2.104

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Lime-treated expansive clays in semiarid area are in typical unsaturated state. Consequently，to ensure the rational design of foundation treatment，and safe operation，research on shear strength is of great significance. Herein，Based on scanning electron microscope(SEM) technology，digital image processing technology，and unsaturated GDS triaxial stress path system，microstructures，soil-water characteristic curves (SWCC) and strength of improved expansive soil with 7% lime in Xinqiao airport of Hefei were discussed. And strength properties of unsaturated lime-treated expansive clay were also further investigated by means of macro-micro comprehensive methods. It is found that microstructure in lime-treated expansive soil appears obvious harsh granular texture. The diameters were mainly from 0.52 to 7.80 μm，and pore area was less than 4 μm2. The measured SWCC behaves hysteretic characteristics between drying test and wetting test，and the air-entry suction is bigger than that of undisturbed expansive clay. Under the same amount of cell pressure，the higher suction the larger the peak strength and residual shear strength were. Moreover，for tests with the constant suction，residual shear strength increased with increasing cell pressure. The volume strains in the procedures of suction balance and shearing appeared differently.

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LABORATORY ANALYSIS OF SEISMIC SUBSIDENCE OF LOESS SUBGRADE OF HIGH-SPEED RAILWAY UNDER RANDOM SEISMIC LOADING

WANG Jun1，2，3，WANG Qian1，2，3，WANG Lanmin1，2，3，WANG Ping 1，2，3，CHAI Shaofeng1，2，3

2014, 33 (S2): 4239-4245 doi: 10.13722/j.cnki.jrme.2014.s2.105

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In this paper，through the synthetic random seismic wave of seismic risk analysis in different sections of a passenger dedicated line was input dynamic triaxial apparatus，and taken seismic subsidence experiments on undisturbed loess for samples. The seismic subsidence characteristics of the undisturbed loess in different sections of the passenger dedicated line are studied. According to the seismic subsidence test results，prediction method based on loess seismic subsidence test is used to judge whether loess seismic subsidence will occurred on the loess subgrade of passenger dedicated lines in future earthquake. Moreover，the prediction results of 50 years beyond the probability of 10% and 2% are provided respectively. The results show that the loess in HYCD，TGCD and LBCD sites belongs to seismic subsidence loess. The critical dynamic stress for seismic subsidence is about 70 kPa. The reasonable and effective foundation seismic measures should be taken，based on the size of the amount of loess seismic subsidence. While the loess from YSCD site belongs to non-seismic subsidence loess. Loess seismic subsidence in the research area mainly occurred in the Q3 loess when moderate and strong earthquake occurred.

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BAMBOO REINFORCEMENT TECHNOLOGY IN IMPROVED SILTY CLAY ROAD SUBGRADE

LEI Ting，WEN Hua，ZHANG Lingling，YAO Yong

2014, 33 (S2): 4246-4251 doi: 10.13722/j.cnki.jrme.2014.s2.106

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Bamboo reinforced soil technology has been widely applied to foundation reinforcement engineering due to its advantages of environmental friendliness and economy. Taking the low-grade highway subgrade improvement of oil well site in Xingwen County，Southern Sichuan as example，the feasibility of bamboo reinforced silty clay technology was discussed and silty clay highway subgrade cross sections reinforced with bamboo were designed and constructed. The basic physico-mechanical parameters of bamboo wood，silty clay and pulverin silty clay were obtained by means of experiments，and mixing ratios，20% pulverin or 6% lime，of improved silty clay were determined. Then，Based on FLAC3D，the optimal subgrade cross-section dimensions of the bamboo reinforcement silty clay were determined，and the best bamboo layer distance is 1.0 m. Finally，the rebound deflection values(2.69 mm) of the subgrade was measured with the monitoring technology. It is shown that the rebound deflection of the subgrade can match the requirements of the low-grade highway subgrade，and it is feasible that bamboo bars are applied in reinforced silty clay low-grade highway subgrade.

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MICROSTRUCTURE AND DEFORMATION PROPERTIES OF POLLUTED CLAY BY Pb2+ CHEMICAL SOLUTION

LU Haijun1，LIAO Zhuwei1，WANG Qi1，ZHAO Ying2，CHEN Wei1

2014, 33 (S2): 4252-4257 doi: 10.13722/j.cnki.jrme.2014.s2.107

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The microstructure and deformation properties of clay was affected by the migration of Pb2+ chemical solution. In order to investigate surface morphology and pore structure of polluted clay by Pb2+ pollutant，the scanning electron microscope(SEM) test and low-temperature N2 adsorption test were carried out. The results of microstructure tests show that pore of undisturbed clay is small. The soil particles are mainly lamination arrangement. Pore size of polluted clay is mainly near 10 nm，and secondary pore increases. The arrangement of soil particles transformed lamination to point-point under chemical solution. A series of tests are conducted，unconfined compressive strength test，direct shear test and consolidation test，to research deformation properties of polluted clay. The unconfined compressive strength，shear strength and consolidation properties of undisturbed clay were affected obviously by Pb2+ chemical solution. The unconfined compressive strength of polluted clay decreased with increasing of Pb2+ pollutant concentration. The shear strength index(c，) of polluted clay decreased with an increase of Pb2+ pollutant concentration. As Pb2+ pollutant concentration increased，void ratio(e) of polluted clay increased，compressibility coefficient() and compression index() increased，but compression modulus() decreased.

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EXPERIMENTAL STUDY OF STABILITY OF PILED FOUNDATION WITH THERMOSYPHONS OF POWER TRANSMISSION TOWER ALONG QINGHAI—TIBET RAILWAY IN PERMAFROST REGIONS

JIANG Daijun1，2，WANG Xu2，LIU Deren2，XIA Qiong2

2014, 33 (S2): 4258-4263 doi: 10.13722/j.cnki.jrme.2014.s2.108

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Power transmission towers along Qinghai—Tibet Railway line ran across permafrost regions. Frost uplifting failure of pile foundation is a prevail problem in permafrost regions. The Wangbu section in Qinghai—Tibet railway was selected as a test section for studying the application effect of thermosyphons in piled foundation of power transmission tower. Combining with the test section the field test and observation for the piled foundation with thermosyphons had been continued for two years. The changing rules of ground temperature field around pile，deformation at the top of piles，curves for ground temperature，negative accumulated temperature and permafrost table are obtained for both piled foundation with and without thermosyphons. The observed results show that in the piled foundation with thermosyphons the cooling effect is obvious，the frost- uplifting amount can be decreased，and the stability is better than that of the common piled foundation.

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PRELIMINARY ANALYSIS OF INFLUENCE OF SOIL MODELS ON SEISMIC RESPONSE OF SOIL-STRUCTURE INTERACTION SYSTEM

WANG Guobo1，YU Yanli2，JIANG Cangru2，HE Wei2

2014, 33 (S2): 4264-4270 doi: 10.13722/j.cnki.jrme.2014.s2.109

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The soil is usually simplified as an elastic half space model and its influence is replaced by springs and dashpot elements，which is the most common method for soil-structure interaction(SSI) problem. The computation parameters of spring and dashpot elements are determined by soil impedance functions. But this is not the case in practical engineering because soil is not always a half space. Focusing on this problem，the aim of the paper is to study the influence of different soil modes on seismic response of soil-structure interaction system. Three kinds of soil models are considered，which are elastic half space model，stratum-over-rigid model and stratum-over- half-space model. The influence of different models on impedance functions are analyzed qualitatively firstly based on the formulas. Then the natural frequency，structure acceleration response and response spectra of structure acceleration are computed and analyzed by two specific cases. It is showed from the calculation results that the static stiffness impedance values from three models have some differences，but the dynamic stiffness impedance values are almost the same，and hence the influence of different soil models on system natural frequency and seismic response are not significant. The research results can provide references to the preliminary seismic design of soil-structure dynamic interaction system.

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NUMERICAL SIMULATION RESEARCH ON PROLONGATION DUNCAN-CHANG MODEL FOR SEASHORE SOFT SOIL

YU Jin1，2，LI Tianbin2，ZHENG Chunting1，CAI Yanyan1，3，TU Bingxiong1，MU Kang1

2014, 33 (S2): 4271-4281 doi: 10.13722/j.cnki.jrme.2014.s2.110

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The control convergence factor θ was introduced to propose a prolongation model which could avoid the mathematical defect of Duncan-Chang model. It is proved that the Duncan-Chang model is one exception of prolongation model with the value of θ equal to 2. The prolongation model is revealed to be more suitable for simulating seashore soft soil which has strong nonlinear deformational behavior. A two-dimensional finite element program was presented using the C++ language based on the traditional Duncan-Chang model and the new prolongation model. Conventional triaxial compression tests of seashore soft soil were carried out using the new program. The results show that，θ is negatively correlated with the convergence rate of prolongation model curve when the initial tangential modulus and limit deviatoric stress were set. By changing the value of θ，the stress-strain curve with the convergence rate greater or less than that obtained from Duncan-Chang model can be derived from the prolongation model. With the same axial strain，the axial stresses of the whole specimen and the radial strains of the central units would increase with the reduce of the control convergence factor. So the minimal safety factor of the sample units would reduce. Under the same confining pressure，the control convergence factor was negatively correlated with the volume strain change. For the same volume strain，the larger the confining pressure，the more significant influence the control convergence factor would be.

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LABORATORY TEST STUDY OF CREEP BEHAVIOR OF SANDY

YANG Qi1，2，LENG Wuming1，NIE Rusong1，ZHOU Wenquan1，ZHU Wenbing1

2014, 33 (S2): 4282-4286 doi: 10.13722/j.cnki.jrme.2014.s2.111

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The high speed railway has strict limitation for foundation settlement，The creep test was performed to investigate the creep deformation law of the compressible soil layers beneath pile toe of the high-speed railway bridge and to obtain the creep model and its parameters. The soil samples were explored from sandy soil layer beneath super-long pile toe and stressed by high-pressure. Its stress-strain-time curves under multilevel pressure were obtained from high-pressure confined compression test. It is found that the compression deformation experience the three stages of instantaneous deformation，consolidation deformation and damped creep deformation and that sandy soil behaved as non-linear creep characteristics for the negligible influence of pressure on creep modulus. A compute program of CPF was developed to determine the creep model and its parameters. The results indicate that the deformation characteristic of the sandy soil could preferably be simulated by the Schiffman viscoelastic model. The valuable reference are provided to calculate post-construction settlement of pile foundation with sandy soil layer beneath the pile toe.

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EXPERIMENTAL RESEARCH ON BEARING BEHAVIOR OF PRESTRESSED ANCHOR AND DETERMINATION OF SLIP SURFACE IN DEEP EXCAVATION OF WEAK ROCK

YANG Xiaohui1，2，ZHU Yanpeng1，2，GUO Nan1，2，HUANG Xuefeng1，3

2014, 33 (S2): 4287-4298 doi: 10.13722/j.cnki.jrme.2014.s2.112

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In order to research the bearing behavior of prestressed anchor，determine the most dangerous slip surface potentially in deep excavation of weak rock，this research conducted the internal force test of the prestressed anchor evenly arranged along with steal under different tensile forces during excavation by making advantage of large deep excavation projects of Xining railway station first time and compared the distribution and transfer law of rod bolt axial force in free section with fixed section in detail. The research shows that：(1) Without pulling force or during different tensile forces，the distribution and transfer law of rod bolt axial force is different from elementary knowledge which are more complicated than that in soil or rock excavation. (2) The appearance and movement of the neutral point of lateral friction force in anchor arm are in consistence with those of the most potentially dangerous slip surface. Therefore，location of most potentially dangerous slip surface and anchor arm threshold length in a deep excavation can be determined. (3) Structural bolting design needs to consider the maximum deformation as well as the bearing capacity under the local condition；lengths of the free section and anchorage calculated in accordance with this research should be optimized by the principle of“meeting the threshold length of anchorage，the longer the free section，the better anchoring effect，the shorter anchoring section，the more economical”. (4) Anchor force and deformation possess time-space effect in construction of deep excavation；its suggested that after construction，the soon prestressed anchor is prestressed the better；Each depth excavation of up layer can be appropriately increased，while the low should be appropriately reduced. (5) During the initial anchoring period or higher tonnages of prestressing imposed on the anchor，the greater loss of prestressing occurs；changes in anchor prestressing can be divided into the four stages：First，decreasing of prestressing. Second，fluctuating. Third，gradual increasing. Fourth，stabilizing. Results of this research can be used as the research and design reference for the similar studies.

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RESEARCH ON LOESS SITES SHEAR WAVE VELOCITY INFLUENCING FACTOR BASED ON FUZZY-GRAY RELATIONAL ANALYSIS

WANG Ping1，2，3，WANG Qiang1，2，3，WANG Jun1，2，3，WANG Qian1，2，3

2014, 33 (S2): 4299-4304 doi: 10.13722/j.cnki.jrme.2014.s2.113

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The shear wave velocity of loess，in some loess site near Linxia city of Gansu province，was tested through the single-hole method and transient Rayleigh wave method respectively. Together with the laboratorial results of basic properties of loess，the development laws between shear wave velocity and test method，initial void ratio，saturation，natural density and depth were analyzed for high-saturated loess. Based on the fuzzy-gray relation theory，the contribution rates of each influencing factors to the shear wave velocity of loess were studied. It is shown that the value of shear wave velocity is tested less by the single-hole method than the transient Rayleigh wave method；that the value of shear wave velocity is decreasing with the increase of initial void ratio and saturation，but the increasing rate of shear wave velocity become larger. Along with the increase of natural density and depth，the increasing trend of value of shear wave velocity become gentle，but the increasing rate of shear wave velocity has a decreasing trend. It is concluded by relation analysis that the soil saturation has the greatest impact on the shear wave velocity，while depth is the second important factor；and that the influences of soil natural density and void ratio to shear wave velocity are equivalent.

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Theoretical solution of ultimate bearing capacity of deep rectangle foundation

Shao Guojian，Zhou Xuan，Hu Feng

2014, 33 (S2): 4305-4311 doi: 10.13722/j.cnki.jrme.2014.s2.114

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Most of the existing ultimate bearing capacity theories can only be used in deep strip foundation. There are less researches on the three dimensional problems of deep rectangle foundation that are often encountered in practical engineering so far. According to the static equilibrium of rigid-plasticity body，a new analytical solution of deep square foundation is presented. With considering the bearing capacity factors of cohesion and density of soil，the analytical universal solution of deep rectangle foundation is received combined with the analytical solution of deep strip foundation. The relationship between bearing capacity factors Nc，Nq and ratio of length and width of deep rectangle foundation in different internal friction angle of soil and the relationship between bearing capacity factors Nc，Nq and internal friction angle of soil in different ratio of length and width of deep rectangle foundation are investigated when the ratio of depth and width of foundation is two. And the relationship between bearing capacity factors Nc，Nq and ratio of depth and width of foundation in different internal friction angle of soil are investigated when the ratio of length and width of foundation is two. The results show that the changing trend of the curve of bearing capacity factors Nc，Nq are almost the same，but the value of bearing capacity factors are different when compared with the semi-empiric formulas. The value of Nc are almost the same，on the other hand，the difference of the value of Nq is obvious. There will be more researches to do to perfect the semi-empiric formulas.

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MEASUREMENT AND PREDICTION OF THERMAL PROPERTIES OF BENTONITE-SAND MIXTURES AS BUFFER BACKFILLING MATERIALS FOR HIGH LEVEL RADIOACTIVE WASTE

CHEN Hang1，ZHANG Huyuan2，GUO Yongqiang2，YAN Ming1，CHEN Xiaoning1

2014, 33 (S2): 4312-4320 doi: 10.13722/j.cnki.jrme.2014.s2.115

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In geological repository，high level radioactive waste(HLW) will decay and release heat to the buffer backfilling materials in the long time. Thermal property of bentonite buffer can be significantly improved by addition of sand so as to avoid thermal degradation of buffer backfilling materials. In this paper，mixtures of GMZ001 bentonite as major ingredient and quartz sand as an additive were compacted to measure the thermal data by Hot Disk TPS2500s Thermal Constants Analyzer. The effects of dry density，sand ratio and water content on the thermal property of the mixture were analyzed，and theoretical predictions of thermal conductivity were discussed. Test results show that thermal conductivity of the mixtures increases with the increase in dry density and sand ratio，respectively，especially at higher water contents. The thermal diffusivity of the mixtures is found to have a similar variation tendency to thermal conductivity. From the classic thermal resistance theory，calculation formulas for thermal conductivity of pure bentonite are adopted to predict the thermal conductivity of bentonite-sand mixtures. By comparison between predicted and measured values，the applicability of prediction theory is discussed.

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A NONLINEAR DILATANCY MODELS EXTENTION AND VALIDATION FOR COARSED-GRAINED SOILS

PAN Jiajun，CHENG Zhanlin，RAO Xibao，CHEN Yun，XU Han

2014, 33 (S2): 4321-4325 doi: 10.13722/j.cnki.jrme.2014.s2.116

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Based on hypoelasticity，three-module incremental nonlinear stress-strain relationships of a nonlinear dilatancy model for coarsed-grained soils under triaxial stress condition is generalized into a three-dimensional stress-strain relationship，and both tensor form and matrix form are given for finite element implementation. The nonlinear dilatancy model is implemented by user subroutine UMAT on ABAQUS finite-element software. The coarsed-grained soils of a rockfill dam sit is selected，conventional large scaled triaxial consolidated drained shear tests under saturated conditions with different confining pressures were calculated by ABAQUS for the coarsed-grained soils，the comparison between calculation results and tests results has been employed to validate the tensor form and matrix form and the subroutine.

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EXPERIMENTAL RESEARCH ON MECHANICS CHARACTERISTICS AND MECHANISM OF SILTY SOIL MODIFIED BY POLYMER MATERIAL

DONG Jinmei1，2，ZHU Hua1，BIAN Jiang1，GAO Hongmei1

2014, 33 (S2): 4326-4334 doi: 10.13722/j.cnki.jrme.2014.s2.117

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Silty soil is modified by polymer material from aspects to improve water stability. Indoor direct shear test and unidirectional compression test were conducted to research shearing strength and compressive deformation characteristics before and after submerging. Testing results show that (1) J1–6 proportion silty soil，compared with common silty soil，has a better shearing strength. After submerged，PAM cohesion polymerization decreases，and strength decreases. Compression deformation is great because PAM is capable of playing a role in lubrication. (2) G2–5 proportion silty soil can improve shearing strength at some extent and reduce compression deformation. After submerged，crumb structure and aggregated structure are desctroyed. Decreased strength，increased deformation and bad hydrolytic resistance are showed. (3) Because of combined action of sodium silicate and PAM，GJ6–9 proportion modified silty soil has a high polymer material protection layer on the surface，which greatly improve the cohesion and internal friction angle and also has a better hydrolytic resistance and less deformation. Through the research of effects of modifying agents and its mixture amount as well as submerging conditions on shear strength and compressive deformation，the best proportion is determined and degradation behavior under submerging condition is grasped.

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STUDY OF MICROFABRIC AND CONSTITUTIVE RELATION OF GRANULAR MATERIAL

DONG Qipeng1，2，YAO Hailin1，LU Zheng1，ZHAN Yongxiang1

2014, 33 (S2): 4334-4342 doi: 10.13722/j.cnki.jrme.2014.s2.118

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Coarse aggregate multi-scale study is mainly to establish the connection between fabric，contact forces，branch vector and constitutive relation，through probability statistics method for the direction and magnitude of the coarse aggregate orientational tensor. It gets a certain number of unit vector directional of contact probability distribution density function(fabric) and moment tensor by the method of statistical probability. The fabric tensor spread out three different forms polynomial expressions using least-square method to determine correlation coefficients. Three types of fabric tensor and the known data expression of statistics the relationship are set up. Orthogonal decomposition is used to make expansion independent with each other. Coarse aggregate stress expressions which included microstructure parameters fabric，contact force and branch vector are built. Compared with steel balls triaxial test and numerical calculation contrast macro-mesoscopic stress，two results are consistent. The simulation results indicate that second-rank contact normal density distribution function give reasonable approximations. A theoretical basis has been established for numerical simulation and the stress expressions for coarse aggregate microscopic parameters under the condition of three dimensional stress-contact force-fabrics.

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NUMERICAL ANALYSIS FOR ROADBED HEAT INFLUENCE IN QINGHAI—TIBET ENGINEERING CORRIDOR

YI Xin1，2，YU Wenbing1

2014, 33 (S2): 4343-4350 doi: 10.13722/j.cnki.jrme.2014.s2.119

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The heat influence law for structure in Qinghai—Tibet engineering corridor is significant to the new path selection of structure and keeping old structure stable. On the basis of same temperature boundary condition，taken height and width of embankment as impact factor，control equation which involved phase change and finite element method was applied，and heat influence law along the Qinghai—Tibet engineering corridor were studied. Results indicate that heat influence limit of embankment is highly sensitive to height and width of embankment. Width is positively correlated with heat influence limits while height is negatively correlated with. After 50 years，with the same height of 1.5 m，heat influence limit of 8 m wide embankment is 5 m smaller than that with 21.5 m wide embankment；with the same 21.5 m width，heat influence limit of 1.5 m high embankment is 2.3 m bigger than that with 5 m high embankment. And heat influence limits is obviously affected by north and south slopes effect：heat influence limits at south side is distinctly bigger than that at north side at the same time. Insulation board can weaken heat influence limits to some extent，but the effect is limited.

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ELASTO-PLASTIC DEFORMATION BEHAVIOR OF INTACT CLAY SUBJECTED TO PRINCIPAL STRESS ROTATION

YAN Jiajia1，2，ZHOU Jian1，2，LIU Zhengyi1，2，GONG Xiaonan1，2

2014, 33 (S2): 4350-4358 doi: 10.13722/j.cnki.jrme.2014.s2.120

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A series of undrained pure principal stress rotation and cyclic principal stress rotation tests were carried out on intact clay using a hollow cylinder apparatus. The magnitudes of mean principal stress，shear stress and intermediate principal stress parameter were kept constant during principal stress rotation. The elastic parameters were obtained from the cyclic loading-unloading tests. The elastic and plastic deformation behavior of intact clay induced by pure principal stress rotation was studied. The direction of the plastic strain increment was investigated. Test results show that both the elastic and plastic strain are induced by principal stress rotation alone in undrained condition，the directions of the elastic and plastic strain increment deviated from the principal stress axis. The development of strains is influenced by the intermediate principal stress parameter. The non-coaxial plastic behavior of soil will be overestimated if the influence of elastic strain is not taken into consideration. The plastic strain induced by principal stress rotation depends on both the coaxial and non-coaxial plastic mechanisms.

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APPLICATION OF STATIC DRILL ROOTED PRECAST NODULAR PILE IN SOFT SOIL FOUNDATION AND CALCULATION FOR BEARING CAPACITY

ZHOU Jiajin1，GONG Xiaonan1，WANG Kuihua1，ZHANG Rihong2，YAN Tianlong2

2014, 33 (S2): 4359-4366 doi: 10.13722/j.cnki.jrme.2014.s2.121

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The static drill rooted nodular pile has lots of advantages such as high bearing capacity，high technology content and environment protection. In the application to some soft soil areas in the southeastern coast of China，the construction costs of the nodular piles was decreased by 10% compared to that of the bored piles，and the mud emission was largely reduced by using the static drill rooted method. Through the analysis of a test pile，it is found that the skin friction of the nodular pile is about 1.05–1.10 times that of the bored pile，while the standard of the precast pile is more appropriate with calculating the pile tip resistance of the nodular pile，and a reduction coefficient is applied. Combining the result of test pile and the literatures as well as standard in Japan，a simplified calculation formula was proposed. In order to verify the reliability of the proposed formula，test nodular piles in two projects were calculated using the formula. The calculated results fit the test results well. Therefore，the proposed formula could provide some reference for the actual engineering.

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CALCULATION METHOD STUDY OF SETTLEMENT PROCESS OF HIGH FILLING CHANNELS IN SOUTH-TO-NORTH WATER DIVERSION PROJECT

ZHANG Yu，CHEN Shanxiong，YU Fei，XIONG Shudan，DAI Zhangjun

2014, 33 (S2): 4367-4374 doi: 10.13722/j.cnki.jrme.2014.s2.122

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The settlement process of high fill channel is difficult to predict in the south-to-north water diversion project. The influence of filling height H，elastic modulus E and Poisson's ratio on the channel were clarified with ANSYS FEM. The lateral deformation correction coefficient K1 and the additional settlement correction coefficient K2 were proposed，and the compression modulus of filled soil was corrected during the loading process. And a calculation method which was applicable to the settlement process of high fill channel was established on the basis of layered summation method. The settlement of channel based mainly on the consolidation settlement Sj in the process of grading load Pi which mainly produce creep deformation Ss when the grading load Pi remains constant. The method has less calculating parameters，and the impact of the lateral deformation，the additional settlement and the compression modulus changing with depth are considered. The settlement process and the total settlement，which start from the channel filling until stable during the post-construction settlement，could be properly calculated out by the method. A visualization application was compiled based on the calculation method in Matlab7.0，which could reasonably simulate and predict the settlement process of high fill channel under the application of grading load，and provide a quick and practical guidance for the design and construction of high fill channel.

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EXPERIMENTAL STUDY OF BEARING CAPACITY OF SINGLE PILE IN LARGE THICKNESS Q2 LOESS GROUND

ZHU Yanpeng1，2，DONG Yunxiu1，2，BAO Zexue1，2，MA Tianzhong1，2，LAI Chunjing1，2

2014, 33 (S2): 4375-4383 doi: 10.13722/j.cnki.jrme.2014.s2.123

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Research on the performance of pile for the weak or non-collapsible Q2 Lishi loess layer is very scarce. In order to determine the pile Q2 Lishi loess layer thickness on the large pile in loess area，the single pile static load test was carried out. Concrete strain gauges and reinforcement stress meter are arranged on test piles，and soil pressure cells were installed on pile bottom to test internal forces on-site. Results show that：(1) Distribution of axial force of pile and lateral friction along the pile is not only related to pile top load，but also related to the nature of pile side soil. (2) When the ratio of pile top load and limit value of pile top load is less than 0.80(Pt/Pu＜0.80)，pile top settlement is mainly caused by the elastic compression of pile；when Pt/Pu≥0.80，endpoint soil subsidence Sb should be considered when calculating the pile settlement. (3) Standardized coefficient of the simplified method of synthetic factor value slants big，it is recommended to take = 0.44 in the region of the same type as the pile of calculation parameters. A new way was put forward by using amount of pile body compression to estimate the settlement of single pile in terms of simplified method and linear method.

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EMPIRICAL ESTIMATES OF MAXIMUM DYNAMIC SHEAR MODULUS OF SATURATED FINE SAND IN JINGJIANG LEVEES

JIANG Jiwei,RAO Xibao，ZHANG Wei，PAN Jiajun，WANG Zhanbin

2014, 33 (S2): 4384-4390 doi: 10.13722/j.cnki.jrme.2014.s2.124

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The saturated fine sand with alluvial origin in Jingjiang levees was collected，and specimens were reshaped refer to the in-situ tests results. Combining with the actual consolidation ratio Kc(Kc≈1.6)，the dynamic triaxial tests were conducted to research the characteristics of dynamic shear modulus，and then a suitable empirical formula was explored to estimate the maximum shear modulus. Results show that：Under the condition of same relative density(Dr)，the release velocity of dynamic shear modulus will slow down with the increasing of confining pressure；However，when Dr changes from 0.5 to 0.6，the decay curves of dynamic shear modulus can match well with the same confining pressure；Based on the empirical estimate formula，relative density and standard penetration test blow count are taken into account respectively to estimate the maximum shear modulus of saturated fine sand. Compared with the testing results，it is verified that the formula can estimate the maximum shear modulus of this kind of saturated fine sand well.