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2009, 28 (S2): 0-0 doi:

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EXPERIMENTAL STUDY ON IMPACT OF WATER RATIO TO ADSORPTION OF LUMP COAL

FENG Zengchao，ZHAO Dong，ZHAO Yangsheng

2009, 28 (S2): 3291-3295 doi:

[PDF] 178 KB (914)

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In order to study the effecting degree on coal adsorption property of groundwater，the experiment begins with adsorption character coal samples under the condition of drought and water-bearing. These samples are fetched from No.3 coal seam in Lu¢an Tunliu Coal Mine. And then conclusions are as follows：(1) there is a logarithm relation between gas pressure and time，and the attenuation coefficient decreases with the increase of water-bearing ratio using adsorption of fixed-volume method；(2) there is an exponent relation between gas adsorption capacity and time；and (3) there also is a linearity relation between gas adsorption capacity and water-bearing ratio of coal samples，both of which are different from powder coal.

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CONSTITUTIVE RELATION FOR GAS-FILLED COAL CONSIDERING ADSORPTION

ZHU Jie1，2，JIANG Yaodong1，2，ZHAO Yixin1，2

2009, 28 (S2): 3296-3301 doi:

[PDF] 307 KB (945)

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The constitutive equation is given by means of a constitutive modeling approach based on the theory of mixtures. The volume fraction of each constituent of the saturated mixtures can describe pore structure of coal and connect constituent stress with true stress. Assuming isotropic elastic behavior and that the change of the elastic energy equals the change of surface energy，gas adsorption-induced coal swelling and the volume fraction of each constituent of the saturated mixtures are derived. Consequently，the stress-strain relation under triaxial stresses is derived. By comparing the stress-strain curves of coal containing different gas components，the effect of adsorption on the constitutive relation of gas-filled coal is analyzed. Meanwhile，the theoretical values from the proposed constitutive relation are compared with the experimental results. Results from the constitutive relation agree well with experimental curves. It is shown that the constitutive equations are able to describe the difference in deformation behavior with respect to gas adsorption，which is affected by the difference in gas adsorption and that the stress-strain relation，under the same porosity and pore pressure，even when the skeleton structure of the coal satisfies the Hooke¢s linear elastic constitutive relation.

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STUDY OF SEALABILITY OF CAVERN FOR NATURAL GAS STORAGE IN DEEP SALT FORMATION BASED ON COMPACTION-DILATANCY BOUNDARY OF SALT

CHEN Jianwen1，2，YANG Chunhe2，GUO Yintong2

2009, 28 (S2): 3302-3308 doi:

[PDF] 363 KB (926)

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Based on the feasibility analysis of compressed air energy storage in deep rock salt stratum in China，experimental study and theoretical analysis of sealability of rock salt cavern for energy storage are carried out. According to the datum of triaxial compression test for Yingcheng rock salt，the compaction-dilatancy boundary(CDB) of rock salt can be expressed by hyperbolic function for better applicability than the parabolic function，which often used for fitting the CDB of rock salt. Based on the analysis of the expression of compaction-dilatancy theory of rock salt in the principal stress space，the definition and expression of dilatancy approach index(DAI) are proposed. The sealability of rock salt cavern can be analyzed based on the compaction- dilatancy boundary(CDB) theory and a corresponding example is proposed.

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ANALYSIS METHOD FOR LANDSLIDE STABILITY

LI Shihai，LIU Tianping，LIU Xiaoyu

2009, 28 (S2): 3309-3324 doi:

[PDF] 649 KB (1741)

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Landslide stability is analyzed systematically based on progressive and dynamic failure of geological media. It is very complex to study the landslide according to specific phenomena and model tests. According to the damage degree of the mountains，the failure can be divided into several types，including intrinsic failure，partial re-failure, run-through failure，discrete failure and motive failure. The transition of the failure type is the process of the gradual failure of the mountains. The limitations of the limit equilibrium method，the finite element method and the discrete element method in analyzing the slope stability are analyzed comprehensively. The characteristics of the continuum-based discrete element method are introduced in detail. Landslide surface cracks should be considered as a basic parameter for analyzing landslide stability. The importance of study on motive failure is then described. It is specially emphasized that the engineering problems cannot be solved only leaning on the numerical simulation，and as a result，the effective approach to estimate the condition of mountains and to analyze the landslide stability should combine calculation models and monitoring results together.

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STUDY OF SURROGATE DATA METHOD FOR CHAOS IDENTIFICATION OF ROCK MASS DEFORMATION

WU Xiaosuo，JIANG Binsong，GUAN Yanhua，WANG Tao

2009, 28 (S2): 3325-3329 doi:

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Measured displacement time series is a combination of rock mass deformation and failure，and it has been used widely in stability analysis and predict of these rock engineering，such as slope，tunnel and underground opening etc.. Based on the measured displacement time series of rock mass，a random checking method is put forward using the substitute data produced by Fourier transformation. By this way，the limitations caused by judging whether the largest Lyapunov exponent is a negative and whether correlation dimension is an integer for chaos identification can be avoided. The application of the method of nonlinear chaos identification to the measured displacement time series of the roadway of Linglong mine and Zaolin landslide has acquired ideal results.

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STUDY ON MECHANISM OF PS-F GROUTING MATERIAL FOR SANDY CONGLOMERATE GROTTOES

GUO Qinglin1，2，WANG Xudong1，2，FAN Yuquan2，LI Zuixiong1，2

2009, 28 (S2): 3330-3335 doi:

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Many grottoes are excavated in sandy conglomerate poorly consolidated with a little calcareous/ argillaceous cementation on the Silk Road in China，also many cracks can be found on those grottoes. The further development of those cracks into cliff will cause collapse and devastating damage of rock of caves. PS-F grouting material has a perfect effect on crack grouting of conglomerate grottoes in China，but the mechanism research of PS-F grouting material is comparatively lagging behind. By X-Ray diffractometer(XRD)，scanning electron microscopy(SEM) and other analytical tools，the main component and micro-morphology of fly ash，the physical mechanism of PS with different moduli，and the contractibility，mechanical property and micro- morphology of PS-F grouting material with different viscosities and moduli are studied. Comparing above results，it shows that PS-F has good groutability. The strength of PS-F grouting material changes with PS viscosity and modulus，and a reasonable interpretation of mechanism on the PS-F grouting material is presented.

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TEST STUDY ON DEFORMATION FIELD EVOLUTION OF ROCK MATERIAL UNDER CYCLIC LOAD

WANG Jianguo1，WANG Zhenwei1，2，MA Shaopeng3

2009, 28 (S2): 3336-3341 doi:

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Study of the failure law of rock using deformation field evolvement methord is a significant project in rock mechanics deformation observation field，and it can put up the stress field of rock material intuitively during process of destruction. By using the deformation field monitoring system(GEO-Dscm system)，the deformation field evolvement has been observed in the failure procedure of rock material under cyclic load. The rock specimens are manufactured by marble plate，the cyclic loading is sine wave，with lower limit load and upper limit load are 10，130 kN respectively，the frequency is 0.04 Hz. The failure laws of rock material under cyclic loading are summarized according to the obersvation results of deformation failure process of multiple rock speciments. It is shown that the deformation of rock under cyclic loading experienced three stages：steady stage，localization stage and wreck stage. A law of deformation field evolution is shown that the severe deformation localization is occurred before rock failure and the deformation localization zone is formed. Along with the deformation concentration of localization zone，the macrocracks are occurred and the rock specimen is destroyed. Thus，a statistic which is used to describe the localization characteristic can indicate the process of deformation field evolvement. It will suddenly jump when the localization occures. For this reason，the statistics can indicat the failure of rock. It is expected that this methord can be used to predict and forecast disasters when field observation system is designed.

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EVOLUTIVE FEATURES OF THERMAL RADIATION OF TORTUOUSLY NON-CONNECTED FAULT IN THE LOADING AND INSTABILITY PROCESS

LIU Shanjun1，2，WU Lixin1，3，ZHANG Yanbo2，LI Guoliang2，CHEN Qunlong2

2009, 28 (S2): 3342-3348 doi:

[PDF] 1193 KB (791)

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To study the infrared anomaly features of tectonic activity and process of instability，the tortuously non-connected fault is selected as a physical simulation model，and the thermal infrared radiation(TIR) variation features of fault models are experimentally studied in the process of loading and instability by means of uniaxial loading system and TIR imaging system. It is revealed that：(1) with the stress increases periodically，a high-temperature anomaly point firstly appeared at the lower fault，and the temperature of the point gradually increases. When the fault is close to destabilization，two new high-temperature anomaly points appear alternately at the end of the rock bridge，and finally become a hot strip. Then two faults connect and are destabilized. There is a causality of the infrared radiation(IRR) anomaly feature of three high-temperature points and alternating evolution with the pre-sliding of fault，the stress concentration in the region of rock bridge and migration；(2) the average infrared radiation temperature(AIRT) of rock bridge region shows three-stage variation features manifested as AIRT is hardly changed at the low-stress stage，then increased slowly at the middle-stress stage and increased quickly at the instability stage. The rapid rise of AIRT after a short drop is an important precursor of fracture and instability；and (3) the difference of infrared radiation variation in different position is closely related to the stress property of different position. The united earth observation of multi-parameters，such as stress，strain and infrared radiation etc.，would be the key of analysis on tectonic activity and its disaster in the future.

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A PROBABILISTIC APPROACH TO EVALUATE PERMANENT DISPLACEMENT OF CAUSATIVE FAULTS

ZHAO Jisheng1，2，ZHOU Zhenghua2，3

2009, 28 (S2): 3349-3356 doi:

[PDF] 274 KB (903)

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A probabilistic approach to evaluate permanent displacement of causative faults is presented based on engineering seismic risk analysis frame work of Cornell，of which the parameters includes the fault model，probabilistic models for earthquake occurrence，the relations among of earthquake magnitude with rupture length，width and surface displacement. The parameters can be determined or verified by results of geophysical prospecting，inversion of kinematics source，historical earthquake data，site investigations and fault dating. In engineering technical points of view，the method adopts two suppositions，one is that all the potential earthquake of fault around the field point contributes to the earquake motion while only the fault contributes to the permanent displacement of the analysis field point；the other is that permanent displacement origins from only a few strong earthquakes on the fault，rather than strong ground motion origins from all earthquakes on the fault. The values of permanent displacement on Haiyuan fault in different probabilistic levels are given by using the data of seismic geology and characteristics of seismic activity. The objective of this research is to determine the value of permanent displacement of causative faults in different probabilistic levels，which have the same probabilistic levels of strong ground motion claimed on the code for a seismic design of buildings and the code for a seismic design of oil and gas steel pipelines of China. Based on the results，the engineers may take measures of to resist the displacement in pipeline and long bridge engineering to minimize loss caused by earthquakes.

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TEST STUDY ON COUPLING RELATIONSHIP BETWEEN PERMEABILITY CHARACTERISTICS AND STRESS OF OUTBURST COAL

ZHAO Hongbao1，2，YIN Guangzhi1，3，LI Xiaoshuang1，3

2009, 28 (S2): 3357-3362 doi:

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Based on the relationships of gas seepage speed with confining pressure and axial compression which are obtained by conventional triaxial test of gas seepage of outburst coal，the coupling relationship between the gas seepage speed and stress of outburst coal is discussed，and the relationships of gas seepage speed with confining pressure and axial compression with certain gas pressure are established and so is the equation of stress with seepage coefficients. The following results can be drawn. When the gas pressure and axial compression are determined，the gas seepage speed decreases as confining pressure increasing with the relationship of second-order curve relationship. When the gas pressure and confining pressure are determined，the relationship between the gas seepage speed and axial compression is fourth-order curve relationship，and the gas seepage speed of broken Briquette is larger than initial speed. A characteristic parameter，difficulty stress point of gas seepage，is proposed，which is useful for prevention of accidents of coal and gas Dutburst.

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THEORETICAL ANALYSIS AND EXPERIMENTAL STUDY ON
PERMEABILITY OF GAS-BEARING COAL

TAO Yunqi1，2，XU Jiang1，CHENG Mingjun1，LI Shuchun1，PENG Shoujian1

2009, 28 (S2): 3363-3370 doi:

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From the basic defination of the porosity，the absorption gas expansion，thermoelastic expansion of coal matrix and the influnce caused by gas pressure on coal matrix body dirtortion are considered fully. After showing the function relation between coal porosity and volumetric strain，temperature，and gas pressure，by using Kozeny-Carman equation，the dynamic evolvement model of permeability which is comprehensively influenced by effective stress，temperature，and gas pressure is established before expansion and under the condition of compression. Correlative test data show that this model has good applicability，and can reflect the development of the porosity under certain condition. The study shows that：porosity development degree and permeability of coal have good consistency，and the permeability increases as the porosity development degree increases；when temperature and gas pressure are fixed values，porosity reduces as the effective stress increases，meanwhile the tendency of the reducement is more obvious when the effective stress is smaller；when the effective stess and gas pressure are fixed values，porosity reduces as the temperature increases，however，its decrescent extent is basically not influenced by effective stress；when temperature and effective stress are fixed values，the permeability of coal reduces rapidly firstly and slowly whereafter with gas pressrure increasing. The study of the relationship between gas-bearing coal permeability and effective stress，temperature and gas pressure provides the theoretical foundation for the study of multi-field coupling problem including temperature field. It gives technical support for increasing efficiency of gas drainage in high temperature mine.

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NUMERICAL SIMULATION AND TEST STUDY ON MECHANICAL PROPERTIES EVOLUTION OF HIGH-PRESSURE WATER INJECTION COAL SEAM

ZHANG Chunhua1，2，LIU Zegong1，2，WANG Baishun1，2，LI Lianchong3，ZHU Xinghu4

2009, 28 (S2): 3371-3375 doi:

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In order to get the rule of the cranny development，stress field evolution and the high-pressure water flowing in the coal seam from a microscopic view，besides fieldwork experimentation about the high-pressure water injection in the coal seam of working face 721 in Qinan Coal Mine，numerical simulation is studied by the RFPA2D-Flow code developed on the basis of the solid-flow coupling dynamic model，in which the heterogeneity characteristics of the mechanical properties of coal and rock and the nonlinear evolution characteristics of gas permeability in stressed coal and rock are considered and incorporated. According to the numerical simulation，the seepage ability of the coal body around the infusing borehole becomes greatly stronger as a result of its gradual damage and cranny expanding under the effect of the high pressure water. The value of the maximal seepage parameter of the coal body could increase from 0.5 m/d to 1 580.0 m/d and 14 times averagely in part. According to the fieldwork experimentation，after adopting the high-pressure water injection technology，the width of the stress-relaxed zone at the front of the working face increases form 2.5 m to 3.5 m and the stress concentration zone moves to the deeper position for 1.0 m，which shows that the effect of the high-pressure water injection on eliminating the coal and gas outburst is comparatively considerable.

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TEST STUDY ON CREEP CHARACTERISTICS OF DAM FOUNDATION ROCKFILL OF XILONGCHI LOWER RESERVOIR

LI Haifang1，ZHANG Qincheng2，XU Zeping1，WEN Yanfeng1，CHEN Ning1

2009, 28 (S2): 3376-3382 doi:

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The creep behaviors and models of Xilongchi main rockfill and dam foundation gravel are studied through triaxial creep tests. The factors and value range of creep model parameters are analyzed. Based on the test results，the axial and volumetric creep characteristics can be described by a power function in which model parameters are determined by test for creep characteristics. With the stress level increasing，the initial axial creep a of the main rockfill increases while the axial creep strain exponential b decreases obviously，which can be described by exponential function and linear function respectively. The change ranges of the other parameters are achieved by the test results.

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STUDY ON QUIET PERIOD AND ITS FRACTAL CHARACTERISTICS
OF ROCK FAILURE ACOUSTIC EMISSION

YIN Xiangang1，2，LI Shulin3，TANG Haiyan2，PEI Jianliang1

2009, 28 (S2): 3383-3390 doi:

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Through the load test of rock，different rocks are tested and the mechanical and acoustic emission(AE) characteristics of rocks are studied. Stress-strain curves，AE accumulative total number and AE rate of rock failure are gotten. And AE features including the relationships between AE and time，AE and stress are studied. This study discusses emphatically the AE quiet period of the loading processes to those rocks whose plastic deformation is obvious. In this AE quiet period，the stress increment will be diminished in unit time when stress approaches to peak value strength and it will need more time. Moreover，AE rate will be declined and AE quiet period will also appear in this stage. But for those rocks whose plastic deformation is not obvious，this AE quiet period will not appear. In addition，by fractal theory，the AE values of different stress rates especially at quiet period are calculated and analyzed. It is found that the fractal values are lower in initial loading stages and increase gradually along with stress，about at the 40% of stress rate，fractal values begin to fall down. The fractal values go down to the minimum near the peak value stress and foreshow rock failure. Furthermore，combined with indoor experiment，some problems of in-situ monitoring and prediction are discussed，It gives the theoretical basis and methods for in-situ rock mass monitoring and forecast by AE technology.

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NUMERICAL ANALYSIS OF SIZE SCALE，INNER HOLE AND END RESTRAINT EFFECTS OF ROCK SAMPLES

GUO Baohua

2009, 28 (S2): 3391-3401 doi:

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The influences of mechanical parameters of rock mass，strain-softening methods，mesh density and loading rate on stress-strain curves are analyzed with FLAC3D. Size scale，inner hole and end restraint effects are then studied based on optimized parameters. When post-peak softening modulus，dilation angle or mesh number increase，tensile strength or loading rate decreases，and softening section of uniaxial compressive stress-strain curves becomes sharper. A Λ-shaped failure form is generated near one end of the sample，and slenderness ratio has no obvious effect on strength when ends are free. For fixed-end sample，an X-shaped shear band is created in the middle part，and the strength is larger than that of free-end sample under the same confining pressure；however，the strength doesn't vary with slenderness ratio when slenderness ratio is greater than 2. On the contrary，both strength and average modulus decrease with slenderness ratio when the latter is less than 2. When the diameter of inner hole increases，average modulus has no obvious change，strength under the same confining pressure increases，and softening section of post-peak curve becomes steeper. The yield zones of intact sample and the hollow one propagate both from the centre to the side of the cylinder sample，and yield surfaces like two cones with the same peak value are formed in hollow sample ultimately. Simulated and test results agree with each other well，and this approach could be used for design and analysis of rock mass engineering.

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STUDY ON LONG TERM STRENGTH OF PILLAR ROCKMASS AT YUNGANG GROTTOES

YANG Xiaojie1，PENG Tao2，LI Guigang2，LIU Jian1，WU Jiajia1，ZHANG Fan1，ZHANG Baotong1

2009, 28 (S2): 3402-3408 doi:

[PDF] 615 KB (1131)

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Based on the uniaxial creep experiment with step-loading，the long term strength of pillar rockmass before grottoes No.9，10，20 at the world culture heritage Yungang Grottoes is studied and the long term mechanical properties is also evaluated. The results show that：(1) the pillar rockmass mainly composed of sandstones is with a good geological environment such as a single type of rock and good structure without developed joint. (2) the long term strength of the medium coarse-grained sandstones is lower than that of the medium-grained and medium fine-grained sandstones. The reasons for these are that the medium coarse-grained sandstone is argillaceous cementing and it contains montmorilonites which easily make reactions with water molecules resulting in the rockmass joints relatively developed. and (3) under condition of high moist content，the long term strength of the medium coarse-grained sandstones is about 20.22 MPa dropping 44.31% than that under condition of low moist content，and the safety stability factor of the pillar rockmass is 15.4 if the maximum stress numerical value(1.31 MPa) occurs on the upper of the western pillar of the grotto No.10. It is suggested that the rehabilitating should be implemented as soon as possible for the protection of the grottoes from the rain erosion and weathering. The maximum quality the pillar rockmass can bear can be a reference for related departments of architectural design and relics protection. The study results and suggest possess guiding significance for protecting Yungang Grottoes.

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NUMERICAL SIMULATION OF STEADY/UNSTEADY FLOW
IN FRACTURED ROCK MASSES

ZHANG Li，LIU Xiaoyu，LI Shihai

2009, 28 (S2): 3409-3416 doi:

[PDF] 533 KB (974)

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A numerical model of steady/unsteady flow in fractured rock mass is developed. On the one hand，by using Monte Carlo technique，an intact rock is cut into 3D irregular block elements in term of the statistical distribution of density，orientation，position，size and aperture of fractures. A 3D fracture network is then constructed，which is composed of fracture elements between adjacent rock elements. The hydraulic properties are attached to the fracture elements. On the other hand，the fracture elements are discretized into triangular mesh，and the flow finite element equations are derived based on the variational principle. The dynamic relaxation technique in discrete element method is introduced to solve the permeability field without assembling the global matrix. Finally，the reliability and applicability of the program are validated by typical examples.

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NUMERICAL CALCULATION OF ROCK BREAKDOWN PRESSURE DURING HYDRAULIC FRACTURING PROCESS

REN Lan1，ZHAO Jinzhou1，HU Yongquan1，RAN Yijun2

2009, 28 (S2): 3417-3422 doi:

[PDF] 211 KB (1227)

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Based on the coupling theory of fluid seepage and rock stress-strain in porous media，the numerical calculation equation for rock breakdown pressure during hydraulic fracturing process is deduced，and a new calculation method is proposed. The method considers fully the coupling effect of rock deformation and fluid seepage. Numerical calculation technique of finite element method is used，and it can simulate the distribution of effective stress around well bore with time and space under injection of fluid into the formation. Therefore，not only rock breakdown pressure can be calculated，but also rock breakdown time can be obtained. The theory of breakdown pressure numerical calculation overcomes many disadvantages of conventional analytic calculation method on breakdown pressure. For example，conventional analytic calculation method can¢t calculate accurately the breakdown pressure for the rise of fluid pressure which leads to aggravation of stress around well bore，exact rock breakdown time，and so on. The buildup of the calculation theory realizes breakthrough of numerical calculation of rock breakdown pressure and improvement of calculation accuracy，and a new theory and method are found for rock breakdown pressure of fracturing process.

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STUDY ON FRACTAL PROPERTY OF FRACTURED ROCK MASS CONSIDERING SEEPAGE CHARACTERISTICS

ZHANG Yanhong1，2，CHAI Junrui1，3

2009, 28 (S2): 3423-3429 doi:

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Both the fissure connectivity and density are the important influencing factors of seepage characteristics in fractured rock mass. In order to meet the needs of seepage study in fractured rock mass，based on the theory of fractal geometry，the method to calculate fractal dimension of fractured rock mass considering fissures connectivity and their density after simulating out the fissures network by Monte Carlo technique is proposed. Moreover，the relationship between information dimension and permeability coefficient of rock mass is presented，so the permeability tensor of anisotropic fractured rock can be deduced directly by its geometry parameters and information dimension. Further results from project case as follows：(1) when considering the role of seepage coupling with stress，the rock mass permeability given by capacity dimension is 2 times more than that by information dimension，it shows that calculating permeability with capacity dimension will exaggerate the volume of seepage in rock mass；and (2) the value of information dimension can accurately describe how the fissure density affects fluid flow in fractured rock mass，because the bigger value of information dimension always shows the more quantity of interconnected fissures and the more permeability capacity in rock mass.

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TEST STUDY OF OIL WELL BREAKDOWN PRESSURE UNDER BLASTING LOADING

WU Feipeng，PU Chunsheng，CHEN Dechun，XIE Xinqiu

2009, 28 (S2): 3430-3434 doi:

[PDF] 296 KB (797)

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Based on the problem of the quantitative description of blasting well breakdown pressure，19 experiments on rock cracking with three kinds of tensile strengths under 5 loading rates are carried out by the rock dynamic cracking simulation device. The experiments verify that the device can simulate the reservoir conditions of a center open hole with the boundary conditions of constent pressure while giving a test of rock fragmentation by water pressure impact on the small simulation hole immediately. It can offer the loading rate bellow 153.17 MPa/ms，which can simulate the real blasting fracturing condition completely. The regression analysis of experimental data shows that the difference of dynamic and static breakdown pressures with the loading rate shows a very good logarithm relationship，and the regression model presents a calculation error of 0.95%. The research results can help to ascertain minimum peak pressure in the design of detonation pressure and enhance the production of universal application and the success rate.

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基于单轴受压的岩石三轴应变指标确定方法研究

LAI Yong1，ZHANG Yongxing2

2009, 28 (S2): 3435-3441 doi:

[PDF] 229 KB (734)

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Based on the uniaxial compression，the strength index of rock under triaxial compression can be determined with Mohr criterion or Heok-Brown criterion，however，there has been not a proper method to determine the index of strain. According to the characteristics that the vary grads of microcrack density is a constant at rock¢s elastic limit point(the damage threshold value)，the macro- and meso-damage composite models have been set up，according to the correlation between the critical value of damages on rock¢s stress-strain curve and the damage threshold value，the critical value of damage at the elastic limit point under different confining pressures has been derived from the microcrack density on the damage threshold and the vary grads of microcrack density at the elastic limit point under uniaxial compression，and the rock peak strength may be given by the Mohr-Coulomb criterion or Heok criterion under different confining pressures，and then the index of corresponding strain has been gained. The calculative formula of determining the index of triaxial compression by the index of uniaxial compression has been derived. The rationality of the formula has been proved by calculation case and experiments.

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STUDY ON EFFECTS OF INITIAL STRESS ON STRESS WAVE PROPAGATION AND BLOCK MOVEMENT LAW

FAN Xin1，2，WANG Mingyang2，SHI Cuncheng1

2009, 28 (S2): 3442-3446 doi:

[PDF] 227 KB (1006)

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The effect of initial stress on velocity of wave propagation in rock is analyzed by theoretic models and test results. The shapes of stress wave including particle stress，displacement and velocity with different initial stresses under the condition of explosion disturbances are studied by method of numerical simulation，and the basic law of initial stress effect on wave propagation is obtained. The movement model of structural block under the effect of explosion is built. The relative displacement of single block with different initial stresses is studied through increasing calculating and analyzing the numerical model. The results show that：(1) the velocity of wave propagation in rock increases rapidly under low initial stress，and tends to be constant under high initial stress；(2) the radial stress and displacement at the same distance will decrease with increasing of initial stress rapidly，and the wave shape will become narrow；and (3) the relative displacement of single block has inverse ratio to the value of initial stress.

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SIMULATION OF PROPAGATION OF EXPLOSIVE STRESS WAVE IN INELASTIC REGION OF GRANITE BY IMPROVED RDCDMC

YAN Bo1，ZENG Xinwu2，CAI Qingyu2

2009, 28 (S2): 3447-3451 doi:

[PDF] 211 KB (879)

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Based on the properties of rock different from concrete under blasting loads，the state equation of RDCDMC is improved. The volumetric deformation of plasticity is taken into account in the definition of tension and the tension-failure rule is adopted. The results of numerical simulations for explosion-induced wave by tamped mili-explosive charge indicate that the improved model is capable of describing the response of the inelastic region of granite and available in numerical simulations on propagation of stress wave.

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STUDY ON STRENGTH CHARACTERISTICS OF SLATES BASED ON HOEK-BROWN CRITERION

LIU Yaqun1，LI Haibo1，LI Junru1，WANG Xuechao2，LIU Bo1，Xie Bing1，3

2009, 28 (S2): 3452-3457 doi:

[PDF] 190 KB (1139)

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The Hoek-Brown empirical strength criterion is based upon the assumption that the rock mass is isotropic and has widely been used for design and safety assessment of underground and slope engineering. A common problem will be encounted in rock mechanics involving the determination of the strength of schistose or layered rock masses such as slates，shales or rock masses containing dominant discontinuities. Because the failure of these anisotropic rock masses is controlled by one or two discontinuities，the Hoek-Brown criterion can not be directly applied to analysis of such issues. So the criterion must be evolved for this purpose. On the basis of detailed study on Hoek-Brown criterion，the definition of intact rock pieces for layered rock mass is evolved and an important parameter in Hoek-Brown criterion，the uniaxial compressive strength of intact rock pieces¢ is proposed to be used for characterizing the variation of slates strength with schistosity orientation. A method of utilization of Hoek-Brown criterion to assess the strength of layered rock is then introduced. According to the proposed method，uniaxial and triaxial compression tests of slates in the West Route of South-to-North Water Transfer Project are conducted. Based on the experimental results，the related parameters and Hoek-Brown criterion for different layer directions of slates are determined. The variation of uniaxial compressive strength of slates with layer directions is also studied and the general Hoek-Brown criterion for the layered slates is then established. In addition，the triaxial compressive strength of slates under confining pressure of 10，15，20 and 25 MPa are predicted. The study results in this paper can provide references for similar projects.

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COMPREHENSIVE MECHANICAL MODEL OF RESERVOIRS OF CARBONATE SALT ROCK AFTER ACID-FRACTURING DAMAGE AND ITS APPLICATION

ZHANG Guangqing，CHEN Mian

2009, 28 (S2): 3458-3463 doi:

[PDF] 286 KB (785)

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Based on the characteristics of acid fracturing and the relationship of solid deformation and liquid flow，a comprehensive model for production testing is proposed，which includes intact region，etched region and propped fracture. The effects of effective stress on fluid parameters are different in different zones. Based on elasticity mechanics，for intact and etched regions，a model for change of porosity is established，and fracture conductivity tests are conducted to obtain a model of permeability change with effective normal stress. It is found that，for specific proppants，the change pattern of permeability of propped fracture changes when the closure stress exceeds compressive strength of etched rock which shows a permanent damage by proppant embedment. Considering the difference of three zones，a solid-liquid coupling algorithm is presented to calculate the distribution of effective stress. The measured data agree well with model results by field application.

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TEST ON GRANULES FLOW PARAMETERS OF ORE DRAWING WITH STOCHASTIC MEDIUM THEORY

TAO Ganqiang1，YANG Shijiao1，REN Fengyu2

2009, 28 (S2): 3464-3470 doi:

[PDF] 209 KB (1065)

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The traditionally measuring method of granules flow parameters in the stochastic medium theory of ore drawing(SMTOD) has certain insufficiency. Because of uncertainty and randomness of granules movement in the process of ore drawing，there is great error in measuring the granules flow parameters. Besides，the flow performance of index granular is different from experimental granular. Moreover，the existing solution method of granules flow parameter is deduced by equation between drawn-quantity and height of drawn-body，and the shape of granules drawn-body measured by this method is different far from actual one. Based on experiment，by improving production and placement method of index particle，a new measurement method to test the granular flow parameters by drawn-body equation is proposed. Four kinds of loose bodies from two mines are used to measure flow parameters. The experimental result indicates that granules flow parameters obtained by the new method match well with those of actual situation. Moreover，the new method is used in Beiminghe Ore Mine to determine rational stope structure parameters，and good technical and economic target is obtained. The recovery ratio and depletion ratio is 90% and 11% respectively. Field application also indicates that the flow parameter of stochastic medium theory of ore drawing can reflect flow characteristics of caved ore and rock well. The new method for measuring granules flow parameters can significantly improve the adaptability of SMTOD in engineering application.

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MECHANICAL ANALYSIS OF CLOSING SHAPEOF CRACK INDUCED BY WATERFRAC TREATMENT

YAN Tie，LI Wei，BI Xueliang

2009, 28 (S2): 3471-3476 doi:

[PDF] 344 KB (1022)

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In recent years，extensive attention is poured into the waterfrac treatment for its simple application and low fracturing costs，and it has already made an obvious effect to increase the yield for the fracturing in some low permeability reservoirs. It is well known that the effect on waterfrac treatment mainly comes from the roughness and relative shear moving in the crack surfaces，but the theoretical researches are not so many on the crack closing shape of waterfrac treatment，and there are not some effective theories to guide the construction in oil field. Based on the full inspection of the relevant literature at home and abroad，the fracture characteristic is analyzed for the waterface treatment and the crack closing shape is analyzed with the mechanical methods. The shear strength models are established for waterfrac treatment under the partial crack opening and shear moving of the crack surface. It reveals the mechanism and the reasons for increasing well production from waterfrac treatment and it will also provide a theoretical basis for the future constructional design in waterface treatment.

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A NEW REPRESENTATION METHOD FOR THREE-DIMENSIONAL SURFACE ROUGHNESS OF ROCK FRACTURE

ZHANG Peng1，LI Ning2，CHEN Xinmin1

2009, 28 (S2): 3477-3483 doi:

[PDF] 557 KB (1074)

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Based on T. Belem¢s theory for three-dimensional surface roughness，the local aspect concept is introduced，which is closely related to the directions of shear and seepage. By defining the local tilt angle and aspect after the three-dimensional geometric shape discretization，the JRC estimation method of the three-dimensional surface roughness parameters for describing the characteristic of anisotropy is proposed and compared with traditional methods，which can reflect the obvious anisotropy of rock fracture well for grasping the association characteristics of surface geometric characteristics¢s effect on its mechanical characteristics of rock fractures，while the deviation of the JRC result of traditional method neglecting anisotropy is 15%–35% with actual situation.

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STUDY ON DISTRIBUTION LAWS OF ROCK DENSITY

WANG Xuhong1，2，FENG Zengchao1，LIU Zhonghua1，2

2009, 28 (S2): 3484-3489 doi:

[PDF] 471 KB (1289)

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Five rock samples are scanned by μCT225KVFCB test system. The most advanced high-precision microscopic CT test system，and the distribution laws of rock density are studied for the target of ray attenuation coefficient. The results show that the rock micro-element density distribution accords with Weibull distribution. It has obvious aggregation for 90%–95% of the element density of rock distributed in a very narrow range，which provides 30%–40% of density range. In these mainly regions，the particle density of rock accords with normal distribution.

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STUDY ON ROCKMASS DETERIORATION AND CHANGES OF POROSITY AND PERMEABILITY IN DOUBLE-POROSITY MEDIUM UNDER HYDRAULIC FRACTURE BASED ON DAMAGE THEORY

ZHAO Wanchun1，AI Chi1，LI Yuwei1，GUO Boyun2

2009, 28 (S2): 3490-3496 doi:

[PDF] 251 KB (963)

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Firstly，according to the mechanism of rock damage of hydraulic fracturing for oil reservoir，considering the changes of matrix porosity and micro-cracks volumes after loading on rock，the tensor damage variable of rock damage is defined by using the changes of matrix porosity and microfracture volumes，and the rock damage deterioration model of hydraulic fracturing is obtained based on damage theory. Secondly，assuming the dynamic evolution of microfracture of the process of hydraulic fracturing satisfies with the Logistic fork standard model，the microfracture dynamic evolution model is established based on the damage theory and according to energy conservation principle of hydraulic fracturing，the internal relation among the volumetric strain，medium porosity and damage variable of the process of rock damage evolution is determined. Finally，the model of matrix porosity and the evolution of permeability tensor of Microfracture for hydraulic fracturing rock is established. Taking the well named 29–3，4 in Jilin oil field for example，the traditional method and the new one are implemented as modules into finite element software to simulate productivity to verify the advantage of new model. The comparison result shows that the new model is more suitable for practical situation.

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NUMERICAL ANALYSIS AND RESEARCH ON SURROUNDING ROCK STABILITY OF LATERAL KARST CAVE TUNNEL

TAN Daiming1，QI Taiyue2，MO Yangchun2

2009, 28 (S2): 3497-3503 doi:

[PDF] 575 KB (980)

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In combination with the construction process of karst cave tunnel of Zhongdian Highway，by using the finite difference software FLAC3D，the surrounding rock stability of karst cave beside the tunnel is simulated，and the numerical calculation results and field monitoring results are compared. The results indicate that after the tunnel is excavated，the surrounding rock is converged toward the karst cave and the tunnel. The surrounding rock between the karst cave and the tunnel is converged in opposite direction and is also the more dangerous zone. The plastic zone of the surrounding rock mainly concentrates around the tunnel and the two sides of karst cave while the top and the bottom of karst cave have little plastic zone. The surrounding rock between tunnel and karst cave possibly brings large deformation and rock mass failure because of stress concentration，and its stability is focused seriously. The conclusion can be used for reference for the design，construction and research of similar tunnels.

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ARTIFICIAL BOUNDARY FOR SEISMIC ANALYSIS AND ITS APPLICATIONS IN LS-DYNA

CHEN Wanxiang1，GUO Zhikun1，YUAN Zhengru1，CAI Wenli2

2009, 28 (S2): 3504-3515 doi:

[PDF] 1003 KB (1867)

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Local artificial boundary of seismic analysis is widely used in time-domain finite element method for its good feasibility and high numerical stability. A new equation for three-dimensional viscoelastic artificial boundary based on the theories of expansion wave(P-wave) motion and shear wave(S-wave) motion in spherical coordinate system is presented by introducing the constitutive relation of linear elastic infinite media and mixing the planar waves and the far-field scattered waves. A new numerical simulation technology for seismic responses is developed by introducing the equivalent boundary element into the finite element method and translating the seismic acceleration into the equivalent nodal force of boundary element on the bottom of the model. Finally，as a numerical example of seismic analysis for civil defense structure，the influences of elastic，transmission，viscoelastic boundary on the results are conducted by LS-DYNA. It is indicated that the viscoelastic artificial boundary is simple and can be easily used. The problems of seismic input and simulation of ground response are solved，and the elastic resume capability and energy radiation effectiveness of half infinite media outside the artificial boundary can be simulated very well. The validity of the proposed method is verified by the numerical example.

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NUMERICAL ANALYSIS OF TEMPERATURE FIELD DURING REPLACEMENT OF SHIELD TAIL BRUSH BY FREEZING METHOD

HU Xiangdong1，2，CHENG Yeer1，2

2009, 28 (S2): 3516-3525 doi:

[PDF] 916 KB (990)

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A 3D finite element analysis of the temperature field by freezing method adopted in the preparatory plan for the shield tail brush replacement after long-distance excavation in the Shanghai Yangtze River Tunnel is given to show the feasibility and reliability of the special program of the freezing method. According to the shield tail brush replacement plan by freezing method，in conformity to the geological conditions，structure of the shield machine and the segments and the thermo-dynamical properties of the sealant-grease and other related media，with the replacement technology taken into account，the temperature field during the tail brush replacement process is computed by the software ANSYS for analysis of the growth ratio，the thickness development and the watertightness of the frozen soil zone. The results demonstrate that the frozen soil ring can come into a closure state in a short time after the freezing process starts and then develop steadily. It is also shown that the frozen body will be weakened when the segments of the temporary ring are removed but it can soon go on growing and turn into a safe state. The conclusion is that the tail brush replacement plan by freezing method is feasible and reliable.

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TYPES AND SELECTION CRITERIA OF PROBABILITY DISTRIBUTION OF ROCK AND SOIL PARAMETERS

ZHANG Jizhou，MIAO Linchang

2009, 28 (S2): 3526-3532 doi:

[PDF] 320 KB (1431)

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The types of probability distribution of rock and soil parameters have lots of effects on the risk assessment and reliability analysis in geotechnical engineering. So it is a primary work to study rock and soil parameters. Based on the background and physical meaning of various probability distributions，all of them are approximately classified into five series by Bernoulli distribution series，Poisson distribution series，extreme value distribution series，central limit distribution series，and distribution series using for statistical analysis. Subsequently，the factors that affect the uncertainties of rock and soil parameters as random variables are studied. As a result，the central limit distribution series are considered more reasonable for soil parameters. Based on there，the characteristics of normal and lognormal distributions of central limit distribution series are compared in detail. Then，a selection criteria that normal distribution is chosen when coefficient of variation less than 30% and skew coefficient less than 0.025 and lognormal contrarily is recommended. In addition，the distribution which is more suitable for Poisson¢s ratio is also studied. Finally，a statistical case is studied to illustrate the validity of the viewpoint. It is believed that the research results have important reference values for the risk assessment and reliability analysis in geotechnical engineering.

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STABILITY ANALYSIS OF LOOSE SURROUNDING ROCK WITH SHALLOW OVERBURDEN BY A DISCRETIZATION FINITE ELEMENT METHOD

LI Ning，ZHU Caihui，YAO Xianchun，HE Min

2009, 28 (S2): 3533-3542 doi:

[PDF] 613 KB (859)

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The caving mechanism is simulated by FEM and DFEM to simulate ground arch respectively based on the inlet and outlet of the diversion tunnel of Ludila hydropower station. It is close to actual situation by combining the characteristics of caving load of loose medium and FEM which can consider the interaction of supporting structure and surrounding rock. The results show that the caving mechanism of underground cavern of loose medium with shallow overburden in lower stress area is simulated well by proposed DFEM，and it is close to practical engineering and important to the design and analysis of engineering.

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ANALYTICAL SOLUTION FOR PLASTIC DEFORMATION PRESSURE AROUND A DEEP CIRCULAR OPENING BASED ON GENERALIZED HOEK-BROWN FAILURE CRITERION AND ITS TERNARY NONLINEAR REGRESSION MODEL

ZENG Qianbang1，2，WANG Enzhi1，2，WANG Sijing2，3

2009, 28 (S2): 3543-3549 doi:

[PDF] 271 KB (913)

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When = 1，a closed-form solution of the plastic deformation pressure in elastic-perfectly plastic surrounding rock obeying the generalized Hoek-Brown failure criterion around a deep circular opening is obtained. Employing the easily-obtained parameters of surrounding rocks，a binary linear regression model for the variation of the maximum plastic deformation pressure with the relative initial stress and the normalized Geological Strength Index(GSI) is established，and so is a ternary nonlinear regression model for the variation of the relative plastic deformation pressure with the relative initial stress，the relative plastic radius and the normalized GSI. The two models can supply a reliable approach for predicting the plastic deformation pressure.

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RESEARCH ON CREEP PARAMETERS OPTIMIZATION OF SALT BED
IN DEEP GAS STORAGE GROUP

ZHAO Kelie1，YANG Haijun2，CHEN Feng1，YANG Chunhe1

2009, 28 (S2): 3550-3555 doi:

[PDF] 285 KB (819)

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Based on the monitoring data of the pressure change in the observation well obtained during the operation process of the Jintan gas storage group，the first salt rock gas storage group in China，the volume shrinkage deformation of the cavity is studied through the observation of the brine pressure change in the cavity of the rock-salt cavity，and thereby the major creep parameters of the creep constitutive model of the salt bed in the gas storage region is back analyzed to make the calculation results conform to the actual status，and the problem that the numerical calculation is hard to be verified in the underground gas storage is solved. By combining the theoretical analysis and test，the monitoring method of observation well，by which the volume shrinkage deformation of the cavity can be derived，is provided and verified. The research results can be applied to research such as the prediction of the long-term volume shrinkage in the operation process of salt rock gas storage and the prediction of the ground surface settlement，and also offer the technical support for the long-term stability and safe operation of the salt rock gas storage group.

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MODEL OF DEDUCING ONWARDS AND REVISING DISPLACEMENT OF TUNNEL SURROUNDING ROCK BASED ON SINGULAR VALUE DECOMPOSITION AND IMMUNE CLONE BP NETWORK

XUE Yuan1，2，HU Dan3，ZHAO Qihua4

2009, 28 (S2): 3556-3563 doi:

[PDF] 264 KB (816)

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Aimming at the two ubiquitous，typical and difficult problems about the false noise of monitoring displacement can¢t be rejected effectively and partial important preliminary displacement values may be lost for the reason that monitoring points can¢t be installed with the pushing of tunnel face in monitoring displacement of tunnel surrounding rock，the model of deducing onwards and revising displacement of tunnel surrounding rock based on singular value decomposition and immune clone BP network is put forward. The result of instance indicates that de-noising，deducing onwards and revising monitoring displacements of tunnel surrounding rock by this model can reach a good effect. The model can provide real and reliable data for judging the stability of tunnel surrounding rock.

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FINITE DIFFERENCE ANALYSIS FOR CONSTRUCTION OPTIMIZATION OF LITTLE DISTANCE SUBSEA TUNNELS IN QINGDAO CITY

YU Liyuan，LI Shucai，XU Bangshu

2009, 28 (S2): 3564-3570 doi:

[PDF] 237 KB (892)

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The subsea tunnel engineering that lies at Jiaozhou Bay in Qingdao is introduced，as well as the research status of little distance parallel tunnels in China. The section ZK5+607 which is located in the fault f3–1 is chosen as a typical cross section，and a three-dimensional model(215.0 m×86.1 m×100.0 m) for numerical analysis is established according to geometrical parameters and geological information of the typical cross section. The concrete lining is considered while the rigid arch is converted into concrete lining through a equivalent mode. 12 construction schemes are constituted according to the space temporal relationship between construction steps，the excavating method，the length of drivage cycle，the space distance among each working face and the overburden thickness of each tunnel. Then these schemes are simulated with FLAC3D program. The spacial curves of vault sinkage values after working faces for a given scheme are studied，and some conclusions and suggestions which will benefit construction and survey are obtained. By analyzing vault sinkage values of working faces，the maximum principal stresses in concrete lining，as well as the disturbance of neighborhood tunnels and volumes of plastic zones，the reasonable scheme is chosen. The rationality of recommendatory thickness of overburden is validated via contrasting five cases of overburden thickness. Eventually，in order to definitude the positions of the maximal construction interaction cross section that should be concerned in construction and monitoring，displacements of key points along the ministrant tunnel and distributing of major pricinple stress are given.

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WHOLE SPACE COMPREHENSIVE ADVANCED GEOLOGICAL PREDICTION TECHNIQUE FOR SHALLOW-BURIED SECTION OF TUNNEL UNDER COMPLICATED GEOLOGICAL CONDITION

LEI Mingfeng，PENG Limin，SHI Chenghua

2009, 28 (S2): 3571-3576 doi:

[PDF] 469 KB (946)

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Taking Guanchong tunnel on Hengyang Yanling expressway as engineering background，a whole space comprehensive advanced geological prediction scheme for shallow-buried section of tunnel under complicated geological condition is established by technical means of surface spatial differential detection combined with tunnel face TSP203 system. Then it is tested and applied in this project as an example. The prediction result shows that the formations along tunnel are mainly fully weathered to strong weathered slate with rock broken zones，abundant groundwater and potential slip surface. Even more，the range between spandrel and vault stretches into the gravel clays. All of these are unsafe for tunnel construction and suggests carrying out pre-supporting by using f108 mm pipes with the length 40 m. By comparing the results of prediction and in-situ measurement，the whole space comprehensive advanced geological prediction scheme has encouraged prediction effect.

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ESTIMATION OF ULTIMATE BEARING CAPACITY OF SINGLE PILE
WITH GOLDEN SECTION

YANG Yuwen

2009, 28 (S2): 3577-3584 doi:

[PDF] 274 KB (903)

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Due to the limitations of estimation methods，it is always difficult to determine proper values of vertical ultimate bearing capacity of single pile Qu for these piles which are not reaching failure states during pile load tests. A new approach is proposed to assess Qu rationally. The exponential functions are used to fit the relationship between load exerted on top of tested piles and the corresponding settlements. The upper bound value Q0 for Qu is defined and designated to the point within the curve of fitting functions where the tangent slope is equal to 0.129 mm/kN. In the range of zero to Q0，the golden section is adopted to obtain the value of Qu. The rationality of this new method is proved through the application of engineering.

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EXPERIMENTAL RESEARCH ON RESILIENT MODULUS OF REMOLDED SOIL BASED ON WATER CONTENT AND FREEZE-THAW CYCLES

MAO Xuesong，HOU Zhongjie，WANG Weina

2009, 28 (S2): 3585-3590 doi:

[PDF] 188 KB (1056)

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To simulate the effect of natural environmental factor on the mechanical performance of artificial filling subgrade，the experiments were carried out on the remolded soil and the changing law of the soil resilient modulus with water content and the numbers of freeze-thaw cycles were studied. By the static molding method，the soil sample was compacted from the optimal water contents. The water content of the soil sample was changed by drying and humidification process. After different freeze-thaw cycles，the unconfined resilient moduli of the soil sample were tested respectively. The experiments show that for the compacted soil from the optimal water content，the first change of water content is key factor to affect the resilient modulus of the soil. The change of resilient modulus is most sensitive to water content of 8%–17%. The resilient modulus of the soil with different water contents decrease，totally with the increase of the numbers of the freeze-thaw cycles. However，the resilient modulus tends to be stable after six freeze-thaw cycles. With the same numbers of freeze-thaw cycles，the decreasing magnitude of resilient modulus reduces with the reduce of water content during the drying process after the soil is compacted and remolded；while the decreasing magnitude keeps steady during humidification process.

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EVALUATION OF STATE OF ANTI-SLIDE PILES BASED ON
INCLINOMETER DATA

SHEN Yongjiang1，2，SUN Hongyue1，SHANG Yuequan1，LI Huanqiang1，WANG Yingchao1

2009, 28 (S2): 3591-3596 doi:

[PDF] 219 KB (847)

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The lateral displacements of anti-slide piles are monitored using inclinometer. The internal forces of anti-slide piles were estimated through back analysis of the lateral displacement and then compared with the design internal forces. The operation state of the anti-slide piles could be deduced from the internal forces，which may be divided into the stable state，the limit security state and the instable state. In the stable state，the anti-slide pile still contains certain margin of safety；in the limit state，the anti-slide pile fully plays its role，and it is in the critical state of invalidation；in the instable state，the anti-slide piles cannot meet the required standard，which may lead to the failure of the anti-slide，therefore，the monitoring should be strengthened and the new reinforcement measure is needed. The anti-slide piles in project are in the stable state by back analysis based on data.

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APPLICATION RESEARCH OF MICRO-SEISMIC MONITORING TECHNOLOGY TO GEOSTRESS HAZARDS IN DEEP MINING

TANG Shaohui1，PAN Yi1，HUANG Yinghua1，JI Xuewen2

2009, 28 (S2): 3597-3603 doi:

[PDF] 671 KB (1057)

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The 8th ore body of Huize mineral field is buried in depth of 1 000 m. The ore body exists in crush belt which is controlled by more than 10 faults with the complicated conditions. According to the actual situation during mining，digitalized 24-channel micro-seismic monitoring system was established，which has functions of seismology quantitative analysis and visualization interpretation. The composition and performance of micro-seismic monitor system were described. Using blasting to locate the accuracy of micro-seismic monitoring system for three tests，it is found that the source location error is the 3.16～6.78 m within the scope of monitoring，This result which are achieved from the expected aim proves that the monitoring system can supply monitoring requirements in mine ground pressure. The system has already been formally put into use in August 2007. On the basis of monitoring data in six months，the laws of the activities of ground pressure in 8th ore body are generally summed up after analyzing parameters，such as various characteristics of vibration waveforms，the time sequence characteristics of b value of micro-seismic events and the geostress drop parameters.

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RESEARCH ON CONSOLIDATION WAVE IN GROUTED ROCK BOLT STRUCTURE SYSTEM

ZHANG Changsuo1，LI Yi1，ZOU Steve2

2009, 28 (S2): 3604-3608 doi:

[PDF] 185 KB (801)

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Theoretical analysis，numerical simulation and experimental testing are used to study the velocity of consolidation wave in grouted rock bolt with different anchoring qualities. Fresh concrete with different ages is used to simulate different anchoring strengths in experimental testing. In the numerical simulation，various values of elastic modulus and Poisson ratio are used to simulate different anchoring qualities. Numerical simulation results agree with experimental results，both of which show that velocity of consolidation wave in grouted rock bolt are related to the anchoring strength of fresh concrete. At lower strength of fresh concrete，the velocity of consolidation wave decreases with the increase of strength；at higher strength，the velocity of consolidation wave increases with the increase of the strength. The essence of the phenomena is explained with numerical simulation，which shows that the changes are brought by the P wave and fluctuation of interfacial wave of the bolt and grouted medium.

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COMPREHENSIVE RESEARCH OF CRITICAL ANCHORAGE LENGTH PROBLEM OF ROD OF ANCHORAGE STRUCTURE

ZENG Xianming，LIN Dalu，LI Shimin，ZUO Kui，XU Xiaohua，DU Ningbo

2009, 28 (S2): 3609-3625 doi:

[PDF] 469 KB (1159)

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The critical anchorage length refers to the limit anchorage length of the rod of anchorage structure in certain soil and rock. If the rod length exceeds this length，the bearing capacity will not obviously increase，but if the rod length doesn¢t reach this length，the bearing capacity can be further improved. In recent ten years，the relevant problems of critical anchorage length are researched in China，and many results have been obtained. The typical research results have reviewed and analyzed. It is emphasized that it is still short of systemic study，and this problem has not been solved and is still under discussion. The critical rod anchorage length is a common phenomenon. This problem needs further study on the current design methods based on the average shear stress theory，and will result in the ultimate change of traditional anchorage structure design concepts. For the discovery of the critical anchorage length phenomenon，it is about 10 years earlier in foreign countries than in China. However，as the term of critical anchorage length with distinct concept，it should be focused on.

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PRELIMINARY EVALUATION OF STABILITY OF XIAOJIAQIAO DAMMED LAKE IN ANXIAN COUNTY，SICHUAN PROVINCE

HE Bingshun，DING Liuqian，WANG Yujie，XU Wenjie，ZHAO Yufei

2009, 28 (S2): 3626-3631 doi:

[PDF] 389 KB (1096)

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The Xiaojiaqiao danmed lake in Anxian County，Sichuan Province was considered as one of the most dangerous lakes induced by “5·12” earthquake. The height of damming object was 65～75 m with a volume of 2.5 million m3，and its maximum reservior capacity was about 20 million m3. The new technology LiDAR had been used in the topographic measurement which had provided precise and prompt topographic information for the dammed lake disaster mitigation design and its stability evaluation. Based on the LiDAR and preliminary geological investigation，the structural factor，which was beneficial for the landslide dam stability，was pointed out by comparison of old and new topographic maps of the landslide lake before and after the earthquake. The physico-mechanical index of damming object had been selected by experience and back analysis. According to the seepage computation and stability analysis，the two failure modes which were slide and seepage had been excluded，while the overtopping and scouring on top of the landslide dam may become governing factor leading to a dam breach for dammed lake.

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RESEARCH OF MINING BASED ON MICROSEISMIC MONITORING TECHNOLOGY IN HIGH-STRESS AREA

YANG Zhiguo1，YU Runcang2，GUO Ran3，WANG Linghui4

2009, 28 (S2): 3632-3638 doi:

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Dongguashan Copper Mine is one of the deepest metal mines with rockburst proneness in China at present，and the highest stress is 38 MPa. In order to control rockburst and establishing mining strategy in high stress area，the Dongguashan Copper Mine has installed an ISSI miroseismic monitoring system in 2005. The system can timely monitor change of the state of stress or strain in rockmass induced by mining. The layout of the seismic monitoring system in Dongguashan Copper Mine is descried. Then the time-spatial distribution of seismic events in a period of time is analyzed. By using visual tools of JDI the relative convergence area of seismic events in initial mining district is delineated combining with the causes according to practical mining underground. Also，some methods of identifying dangerous of rock mass project in underground are proposed，which is verified by the actual events. According to research results，the working procedure to analysis of rock mass induced by mining based on microseismic monitoring technology in high-stress area is developed，which can provide a basis for safety of mine production.

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ANT COLONY CLUSTERING RADIAL BASIS FUNCTION NETWORK MODEL FOR INVERSE ANALYSIS OF ROCKFILL DAM

KANG Fei，LI Junjie，XU Qing

2009, 28 (S2): 3639-3644 doi:

[PDF] 238 KB (887)

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An ant colony clustering radial basis function neural network model for parameter inverse analysis is proposed by combining the ant colony clustering algorithm with radial basis function(RBF) networks. In the new model, the radial basis function centers are searched by the ant colony clustering algorithm which utilizes the probability transfer characteristic of ant foraging clustering behavior. The sum of scatter degree obtained by the ant colony clustering algorithm is smaller than that obtained by the traditional K means clustering algorithm, thus more reasonable radial basis function centers can be searched so as to obtain the nonlinear mapping relationship between the parameters to be inversed and the displacements measured at certain points in the dam. Inverse analysis is performed to a concrete faced rockfill dam；the results show that the new neural network model can solve the inverse analysis problem of rockfill dams efficiently，which outperforms BP neural network model and K means RBF neural network model.

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STUDY OF CONDUCTED WATER TRACER OF INTERSECTING FAULT OF LOWER BEDROCK OF EARTH-ROCKFILL DAM

LIN Tong1，2，CHEN Jiansheng1，3，CHEN Liang3

2009, 28 (S2): 3645-3652 doi:

[PDF] 374 KB (806)

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The seepage amount of one reservoi in the city of Shenzhen is about ten times of designed one till 2007，and the seepage condition is rather complex. In order to find out the reason of seepage and ascertain the position of seepage passage，seepage condition of the dam was analyzed. Firstly，the tracer was used to investigate temperature field and velocity field of the dam，and then the abnormity seepage area was found. Secondly，according to the abnormity seepage area and data of the piezometric tube，it is clear that seepage occurred in lower bedrock，and it happened to be a concentration passage. Finally，combining with the geological conditions and construction situations，it is confirmed that the intersecting fault in lower bedrock of earth-rockfill was the main concentrating seepage passage，and the concept seepage model of dam was established. The comprehensive analysis is an effective way to investigate the dam seepage，which can avoid using single method and has a certain engineering significance.

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A NEW TOTAL STRESS METHOD FOR CALCULATION OF
STRESS AND DEFORMATION OF CORE IN ROCK-FILL DAMS

BI Qingtao1，2，YIN Zongze1，2，DING Shuyun3

2009, 28 (S2): 3653-3658 doi:

[PDF] 213 KB (744)

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A new total stress method and test method are presented to simulate consolidation degree of core in rock-fill dams. And its model parameters can be achieved by consolidated undrained compressibility test. The consolidation deformation can be calculated by new method. The superiority of new method is confirmed by model parameters test and stress-strain calculation for Shuangjiangkou dam.

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A NEW QUADRATURE POINT DETECTION ALGORITHM IN MESHLESS CALCULATION

LIU Hongsheng1，XING Zhongwen1，YANG Yuying2

2009, 28 (S2): 3659-3665 doi:

[PDF] 575 KB (887)

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Background cell integration method is widely used to implement numerical integration in meshless computation，in this procedure，the relationship between quadrature points and the problem domain must be assured. Radial method is commonly used when the boundary is complicated. However，the complexity of the algorithm is increased while several line sections are parallel，which results in low efficiency. In order to fasten the quadrature point detection，the matrix method is proposed to implement the detection through calculating the determinant of matrix，and furthermore，a new data structure—sparse matrix is presented；each element in this sparse matrix stores the following information associated with the nodes such as the distance between the node and its neighbor，the number of the node and radius of the node influence domain and the computational cost of determination of matrix can be decreased dramatically by sparse matrix. As a result，an advanced algorithm，which can fasten the quadrature point detection more quickly，is generated. Numerical results show that this algorithm can fasten the quadrature point detection sharply and therefore improve the efficiency of meshless numerical computation.

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TIME DOMAIN DAMPING-EXTRACTION METHOD FOR
INTERACTION OF UNBOUNDED MEDIA WITH
FRACTIONAL-ORDER

CHEN Yonghui1，2，WANG Xinquan3，ZHOU Xingde4

2009, 28 (S2): 3666-3672 doi:

[PDF] 268 KB (748)

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Based on the dynamic equations with fractional order(FO)，the damping-extraction method for structure- media with FO is studied. Firstly，the time domain basic formula of the damping extraction method of dynamic structure-media interaction with FO is deduced. Secondly，the uncoupled dynamic equations of dynamic structure-media interaction with fractional order are determined and then transformed into transfer functions expression according to mode transform. Thirdly，the acquired FO transfer functions are expressed as integrated order ones approximately by Oustalop differential filter algorithm. Fourthly，the all transfer functions are written as state equations form and assembled as an entity state-output equations，the corresponding interaction forces can also be solved by the four-order Runge-Kutta algorithm. Finally，two examples are utilized to demonstrate the feasibility of the proposed method.

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ANALYSIS OF INFLUENCED REGIONS AND CHANGE TREND FOR ROCK MASS DISPLACEMENT DUE TO MINING OF IRON ORE IN SOFT ROCK STRATA

LI Wenxiu1，ZHENG Xiaoping2，WANG Jing1

2009, 28 (S2): 3673-3678 doi:

[PDF] 271 KB (908)

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In north mining area of Guanzhuangdong Mine，in which the sublevel caving was used，although the buildings are beyond the ground subsidence influence criteria，there has been widespread evidence of deformation of land surface far away from the mining area. Combining with analysis of north mining area of Guanzhuangdong Mine analysis，laws and characteristics of rock mass displacement and deformation caused by the deep mining of iron ore in soft rock strata are given. Both observed and theoretical analysis show that the subsidence of overburden layer is characterized by uniform and entire compression，displacement and deformation. And the surface deformation is continual and slow with a long duration of movement due to deep mining of iron ore in soft rock strata.

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IMPACT OF 3D SLIP SURFACE′S SHAPE ON FACTOR OF SAFETY

LU Kunlin1，2，ZHU Dayong1，XU Qiang2，YANG Yang1

2009, 28 (S2): 3679-3685 doi:

[PDF] 320 KB (853)

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Based on the assumption of the modification of normal stress over the slip surface，the solution to the factor of safety is derived by iteration，according to the equilibrium conditions of the slope. Regarding the slip surface as a curved surface yielded from a family of power function rotating on y-axis，slip surfaces of different shapes are obtained by changing the values of the power function′s power. Accordingly，by discussing the impact of the slip surface′s shape on the factor of safety，the results reveal that the factor of safety is the single-valued function of power and its minimum value exists as well. As a result，the critical slip surface is obtained by optimizing the value of power，and the change law of the relationship between the value of power and the length of the sliding mass is analyzed. At last，the end effect of 3D slope is also discussed. It is demonstrated that the presented method can derive smaller factor of safety；the value of power corresponding to the critical slip surface decreases slightly and then increases gradually with the increase of length of the sliding mass. The analysis reveals that the end effect can be neglected when the length of the sliding mass is bigger than the height of the slope by 10 times，and it is proportional to the internal friction angle，inversely proportional to the cohesive stress and does not has close relation with the change of the slope inclination.

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FEM CALCULATION OF HIGH INLET SLOPE OF DIVERSION TUNNEL
ON RIGHT BANK OF CHANGHEBA HYDROPOWER STATION

SHE Chengxue，CUI Xuan

2009, 28 (S2): 3686-3691 doi:

[PDF] 365 KB (935)

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Because of the limit of landform of damsite，the inlet slope of the diversion tunnel of the Changheba hydropower station has to be designed vertically with the biggest height of 148m. This situation is seldom to meet at home and abroad，and its deformation，stability issues related to the success of the project diversion program is very important to the construction of the hydropower station. To know the stability of the slope as well as the effectiveness and reasonability of reinforcement，the FEM is used to model the excavation and reinforcement process of the slope，and the deformation，yield zone and the bolt stress distribution are obtained. Especially，the analysis of the impact of cracks and fissures for the slope deformation，yield stress，as well as anchor. The strength deduction method is also used to calculate the safety factor of the stability. Finally，some conclusions are discussed which are helpful to guide the excavation and reinforcement of the slope.

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STUDY ON EXCAVATION DISTURBED ZONE IN SURROUNDING
ROCK OF TUNNEL WITH VARIOUS TBM DRIVING RATES

LENG Xianlun，SHENG Qian，ZHU Zeqi，ZHANG Yonghui

2009, 28 (S2): 3692-3698 doi:

[PDF] 723 KB (947)

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On the basis of results of the loading and unloading triaxial tests with various unloading rates，Hoek-Brown empirical strength criteria is used to fit slate mechanical parameters including cohesion and friction angle. The numerical simulation method of the TBM driving process is put forward by studying driving characteristics of TBM. The FLAC3D program，which contains loading and unloading criteria，is adopted to analyze the excavation disturbed zone and stability in surrounding rock of tunnel with various TBM driving rates. The results show that when driving rate is greater，the excavation disturbed zone in surrounding rock is smaller，and the surrounding rock is more stable；the deformations of surrounding rock are uniformly distributed after excavation；in the radial direction of tunnel，three zones are obviously shown with displacement and stress variation including strongly varied zone，weakly varied zone and stable zone；along the tunnel radial direction，the maximum principal stress gradually changes from uniaxial to biaxial and triaxial，and the second deviatoric stress invariant forms a closed stress concentration zone which is called “stress dike”，which is helpful to rock breaking；the excavation disturbed zone of tunnel varies with TBM driving rates. When the speed increases 100%，the excavation disturbed zone decreases 64%，from 1.1 m to 0.4 m.

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FORECASTING OF ROCK MECHANICAL BEHAVIORS
BASED ON PSO-SVM MODEL

XU Fei1，2，XU Weiya1，2，LIU Kang3，CHEN Xiaopeng3，WANG Dikai3

2009, 28 (S2): 3699-3704 doi:

[PDF] 192 KB (1308)

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It is difficult to describe the complex nonlinear relationship between all kinds of geological factors of rock and their mechanical behaviors. A new model for forecasting the mechanical behaviors of rock is proposed by combining the particle swarm optimization(PSO) and the support vector machines(SVM)，which is support vector machine based on particle swarm optimization(PSO-SVM). The model，on one hand，uses the nonlinear characteristics of SVM to establish the nonlinear relationship between geological factors of rock and their mechanical behaviors. On the other hand，the penalty factor and kernel function parameter of SVM are optimized by PSO，by which the accuracy of the parameters used in the model is ensured as well as the precision of forecasting result. The model is applied to forecast the coefficient of compressibility of rock and the result is compared with that of back propagation neural network(BP-NN). It is shown that the forecasting precision of PSO-SVM is higher than that of BP-NN，which indicates that the model here is feasible and effective.

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DETERMINATION OF PARAMETERS FOR UNEQUAL-RATE
UNSTEADY FLOW DOUBLE-EXTRACTION WELL PUMPING TEST

YUAN Hua1，2，ZHANG Qinghe1，2

2009, 28 (S2): 3705-3711 doi:

[PDF] 299 KB (1284)

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Conventional fitting curve method and linear graphic method which could be used in aquifer parameters inversion for single well unsteady pumping test are transformed based on superposition principle，and then are applied in double extraction well unequal-rate，simultaneous unsteady flow pumping test with only one observation well. Taking Pudong working shaft of Shanghai South Xizang road river-crossing tunnel for example，according to the actual layout of well point，a particular type curve is plotted，then the transformed curve method，linear graphic method and numerical method are respectively used to determine the hydrological parameters. Moreover，the accuracy and main error sources of these three methods are compared. The results show that the hydrological parameters obtained by transformed linear graphic method are more accurate；if observation well is arranged adjacent to extraction wells，the measured drawdown curve at the initial stage of pumping test may be steeper，and eventually reduces the accuracy of inversed hydrological parameters.

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DETERMINATION WARNING METHOD FOR PROGRESSIVE FAILURE
PROPAGATION OF SLIDING ZONE OF DAYANTANG TALUS LANDSLIDE

LI Di，LI Yiming，ZHANG Man

2009, 28 (S2): 3712-3720 doi:

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A new determination warning method for progressive failure propagation of sliding zone on talus landslide is proposed. The new method is able to quantitatively forecast the whole process of sliding failure propagation，including direction and velocity of sliding failure propagation，the corresponding date of the sliding failure，as well as the extent of landslide failure. Firstly，the properties of failure propagation for single-point failure，linear failure and planar failure on sliding zone are systematically presented. The complete relative deformation-time process curves on single-point failure propagation under shearing load are obtained. The curves mentioned above are similar to complete stress-strain process curves obtained with stiff and servo-controled loading testing machine. It is discovered that sliding failure is at the beginning of bottom wall，and then successively from bottom wall up to top wall in vertical direction，and from front to back side of landslide in horizontal direction. Secondly，those mechanisms of failure propagation properties are illustrated mainly in four respects，including stratification of sliding zone，lithological character of formations，mechanical properties of formations，and general principles of rock mechanics. Thirdly，according to those mechanisms，a new quantitative warningmethod(PFPW) is established，which is based on the analysis of relative deformation process curves on sliding zone. The standard of the failure is peak value of change curves of relative deformation and time. The objective of warning is to forecast each failure phase for progressive failure propagation. Based on the results，it is convenient to forecast the date，position and extent of failure，as well as velocity of propagation.

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DETERMINATION OF KEY POSITIONS OF STRATA CONTROLLING IN ROCKS BETWEEN COAL SEAMS FOR UPWARD MINING

FENG Guorui1，YAN Xu1，WANG Xianxia2，KANG Lixun1，ZHAI Yingda1

2009, 28 (S2): 3721-3726 doi:

[PDF] 181 KB (897)

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In accordance with upward mining for left-over coal owing to some historical reasons or complex geological conditions，the key technology in upward mining was proposed to control the strata，and its breakthrough point was to determine key position in rocks between strata. Because key strata structure among coal seams in upward mining has evolved to face-contacted block structure，appropriate parameter matrix was established based on block theory and its discrimination matrix is figured out in view of which the block in face-contacted block structure had high intensity and stiffness. The friction face among blocks was similar to a plane，and the structural face run through the block，and structural instability was caused by the shear slip of the block along contact faces. Vector analysis method was employed to determine the mobile block in key strata structure between coal seams in upward mining. Furthermore，the specific determination method for key position in rocks of strata controlling between coal seams for upward mining was explored by means of virtual tangential net slipping force，which provides a solid foundation for further exploration of strata structure between coal seams and technology system of upward mining .

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APPLICATION OF MULTI-ATTRIBUTE DECISION AND D-S EVIDENCE THEORY TO WATER-INRUSH DECISION OF FLOOR IN MINING

HAN Jin1，SHI Longqing1，ZHAI Peihe1，LI Shucai2，YU Xiaoge1

2009, 28 (S2): 3727-3732 doi:

[PDF] 205 KB (934)

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In view of characteristics of coal mine water-inrush from floor containing a lot of uncertain factors and time-location randomness，the multi-attribute decision-making theory in the prediction of water-inrush from floor applied research is explored. With case statistics and expert analysis，the weights are governed to the factors which affect water-inrush from floor. The fusion rule is established for water-inrush probability ratio，and a new method of water-inrush probability ratio is put forward for water-inrush from floor. It provides a technique for decision- making water-inrush from floor with water-inrush probability ratio. Based on the D-S evidence theory，the frame of discernment including water-inrush，critical condition，no water-inrush and uncertain information，is proposed and the water-inrush integration decision-making model is established considering aquifer water-bearing ratio，structure ratio，water-resisting layer thickness ratio，underground water pressure ratio and underground pressure ratio as evidences. With the practical application examples in Feicheng coal field，it shows that the degree of confidence of water-inrush probability can be improved and indeterminacy is reduced by several times of information fusion，and the validity and feasibility of proposed model are proved.

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ANALYTICAL RESULT OF CONSOLIDATION OF LOOSE-FLEXIBLE PILE AND LOOSE-RIGIDITY PILE COMPOSITE FOUNDATION

SHANG Xinsheng1，LIN Yinfei2，WANG Mingcheng3，XIE Dingyi4，SHAO Shengjun4

2009, 28 (S2): 3733-3738 doi:

[PDF] 174 KB (820)

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Taking into account the role of daub effect of loose pile and the weaken effect of other piles on drainage channels，on the basis of the stress conditions based on equilibrium equations and continuity equation under the conditions of consolidation，analytical solution of loose-flexible piles combination and loose-rigid pile combination of the composite foundation is obtained by the assumption that the infinite series solution. Examples of comparison between numerical and analytical results show that the basic analytical solution agrees well with numerical solutions. The consolidation speed of the composite foundation is relevant to the permeability coefficient and the compression modulus. The composite foundation consolidates rapidly when it has large permeability coefficient and the compression module. The results show that the proposed method is feasible.

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“M” METHOD MODIFICATION BASED ON FUNCTION TO SOLVE CU INDEXES OF OVERCONSOLIDATION COHESIVE SOIL

LIU Xun1，FENG Xiaola1，CHENG Yun1，ZHOU Chenghao2，TAN Wei3

2009, 28 (S2): 3739-3745 doi:

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As a result of excavation and unloading of foundation pit，the state of passive zone soil body in front of diaphragm wall was transformed from the normal consolidation to the overconsolidation. At the same time，the indexes of consolidated undrained triaxial shear test(CU) of cohesive soil will be changed，therefore，the calculational theory of elastic foundation beam could be modified. Based on the relationship among over- consolidation ratio(OCR)，undrained shear strength and overburden pressure，the relationship between undrained shear strength and CU indexes was introduced and a function used to solve the CU indexes of overconsolidated soil in condition of several layers was derived gradually. Then the function was applied to the “m” method calculation theory of elastic foundation beam. A new modified m value calculational method was set up which considers the effect of the overconsolidated cohesive soil in the passive zone after excavation and unloading step by step. The result of finite element calculation of Wuhan Yangtze River tunnel indicates that CU indexes and m value of each cohesive soil layer in a certain depth below the excavated surface both increase in different degrees with increasing of OCR value. In particular，the indexes and value in silt increase greatly. In addition，the displacement of diaphragm wall calculated by the new modified method was close to the actual measurement results.

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PERMEABILITY OF SATURATED SOFT CLAYS AND ITS EFFECTS ON ONE-DIMENSIONAL LARGE STRAIN CONSOLIDATION

LI Zhihui，CHEN Xiaoping，ZHOU Qiujuan

2009, 28 (S2): 3746-3752 doi:

[PDF] 424 KB (954)

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Based on laboratory seepage pressure tests of saturated soft clays in Nansha，Guangzhou，the permeability of saturated soft clays under different consolidation and seepage pressures are systematically investigated. The effects of loading and unloading conditions on permeability are analyzed，and experience formulae are given to define void ratio and permeability coefficient. Testing results reveal the permeability law of saturated soft clays under different hydraulic gradients and the seepage failure characteristics. Based on experiments and large strain consolidation equations with displacement as variable，the effects of initial seepage coefficient on large strain consolidation are studied. It is shown that the nonlinear compressibility and permeability need to be considered in large strain consolidation calculation of soft foundation.

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RESEARCH ON GROUND SEDIMENTATION CRITERION OF XI¢AN LINE-2 SUBWAY UNDER CIRCUMVALLATION

LI Ning，GU Qiangkang，ZHU Caihui，SU Lihai

2009, 28 (S2): 3753-3761 doi:

[PDF] 655 KB (1048)

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Taking the Xi¢an line-2 subway as an example，the city wall is simulated with special discrete finite element method to analyze the capacity of withstanding the deformation of the city wall from the point of deformation and mechanics. The proposed finite element method can reflect the tensile or shear damage along the mortar，brick-soil interface and existing crack. Finally，the controlled sedimentation parameters for the Xi¢an city wall are proposed. The results can provide engineers with references to the underground construction nearby the ancient building.

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IMPACT OF CONSTRUCTION VIBRATION ON MOGAO GROTTOES IN DUNHUANG

ZHANG Mingquan1，WEN Lingli1，WANG Xudong2，GUO Qinglin2，SHI Yucheng3

2009, 28 (S2): 3762-3768 doi:

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In order to protect the cultural relics of Mogao Grottoes in Dunhuang and to reduce potential safety hazards，the following engineering measures were planned：grotto cliff strengthening，repairing and rebuilding of the plank road on the grotto cliff，and comprehensive prevention of wind-blown sand hazards. Among the above measures，drilling vibration in the process of cliff strengthening will have the strongest impact on the safety of the grottoes. In order to understand the propagation of drilling vibration and its impact on grotto safety，the tests dynamic parameters and drilling vibration behavior of the grotto rock mass were carried out. The results show the following：(1) longitudinal wave velocity in the country rock of the Mogao Grottoes is between 1 100 and 1 930 m/s；(2) the sympathetic vibration frequency of the rock mass is between 75 and 90 Hz；(3) longitudinal wave velocity is greatly affected by the spatial distribution of grottoes；(4) the peak values of vibration speed tested at a distance of 1，2，and 3 m from the borehole are mostly between 0.1 and 1.0 mm/s；and(5) the highest vibration speed recorded during high-pressure impact drilling is 6.01 mm/s. If the strict protection standard of 0.1 mm/s is used to evaluate the effect of drilling vibration on the grottoes，it is clear that drilling vibration will have a harmful impact on the grottoes. Therefore，low-pressure(0.8～0.9 MPa) and low-speed(≤0.4 m/min) drilling and appropriate protective measures must be adopted to reduce or eliminate the harmful effect of drilling vibration on the grottoes.

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RESEARCH ON SPATIAL DISTRIBUTION AND RELATIONS OF SALINITY AND MOISTURE CONTENT INSIDE ROCK MASS OF LOW-LAYER CAVES IN DUNHUANG MOGAO GROTTOES

GUO Qinglin1，2，3，WANG Xudong1，2，3，XUE Ping2，3，ZHANG Guobin2，3，FAN Zaixuan2，3，
HOU Wenfang2，3，ZHANG Zhengmo2，3

2009, 28 (S2): 3769-3775 doi:

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Dunhuang Mogao Grottoes，the very famous world culture heritage，was chiseled in the cliff face of alluvial grit etching by the Daquan River in the Quaternary Period. Undergone natural and human factors，caves of Mogao Grottoes have many diseases and deteriorations including flaking，detachment and disruption；especially the caves of low-layer are most serious. Cave 98，one of the most valuable and representative diseases of low-layer caves in the Five Dynasties(AD914—AD935)，is selected as an example. Like all other caves in Mogao Grottoes，it has been affected by the natural environment. From the hole drilled at the lower portion of the western wall without painting，samples obtained for salinity analysis. The temperature and humidity are measured inside the hole. The analysis of electrical resistivity data from south to north of the lower portion of the western wall indicates that the soluble salt contents of the rock mass are mainly vitriolic and chloride，mainly concentrated between the surface and the depth of 35 cm. Water condensation occurs in the rock mass at depth of 125 cm. Inside the rock mass，there is close correlation between relative humidity and salinity. When moisture content rises，salinity drops. Due to the high humidity and abundant supply of salt，the salinity of the western wall，which is backed by the main cliff structure，is higher than the other walls，and it is more sensitive to changes in the environment. These achievements have provided a scientific basis for conservation wall paintings.

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PRELIMINARY DETECTION OF GROUTING EFFECT ON DELAMINATED WALL PAINTINGS IN TIBET ARCHITECTURE

WANG Wanfu1，2，3，4，ZHAO Linyi1，2，3，4，YANG Tao2，MA Zanfeng1，3，4，5，
LI Zuixiong1，3，4，
FAN Zaixuan1，3，4

2009, 28 (S2): 3776-3781 doi:

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The detachment is one of the most critical diseases of ancient architecture murals at Tibet，and the area of detachment murals make up more than seventy-five percent of the total area of diseases murals. Based on working out measurable evaluation for the phenomenon of detachment murals and its repairing effect，the distribution of detachment murals were detected by ground-penetrating radar at the Potala palace，furthermore the reflection characters of electromagnetic wave were analyzed in detachment murals. For the detachment murals，PS materials of some moduli and concentrations were grouted into the detachment area. During one year for maintenance，the distribution of the detachment murals was detected by ground-penetrating radar again. It shows that the reflection signals of electromagnetic wave are strong in the stone-wall before grouting the detachment area，but after grouting the detachment area，it can not be detected between layers due to the detachment area felted for whole by PS material. It indicates that the grouting technology of PS material can effectively repair the detachment murals，and ground-penetrating radar can accurately improve the status of detachment and its repairing effect.

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PERFORMANCE TEST OF COMPATIBLE SLURRY GROUTING INTO SOIL FRACTURE AT ANCIENT CITY OF JIAOHE

YANG Tao1，LI Zuixiong1，2，3，WANG Wanfu2，3

2009, 28 (S2): 3782-3788 doi:

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The PS-(F+C) slurry is prepared by mixing PS(Potassium Silicate in optimum modulus) as binding ingredient，fly ash(F) generated from thermal power plant and pulverized native raw soil(C) at the ancient city of Jiaohe as filling substance，and sodium fluosilicate as treatment agent，its initial setting time is obtained and the shrinkage behavior of its concretion is monitored. The uniaxial compressive strength of PS-(F+C) grouting material is tested at different ages and the influencing factors for its strength. Treatment temperature，amount of sodium fluosilicate，modulus of PS，concentration of PS and water-ash ratio are also discussed. Furthermore，the durability experiment including its resistance to water，to cyclic freezing-thawing，to saline crystallization in porous PS-(F+C) grouts and to aqueous alkali is carried out. It is shown that the slurry of PS-(F+C) with good workability is more compatible with the soil mass at the ancient city of Jiaohe because of adding native raw soil in a half weight of fly ash，and it shrinks less for the spherical bulking material of fly ash. Its treatment process is moderate and controllable，the linear shrinkage of its concretion with a PS to filling material ratio by weight of 0.60 is about 2.6%，the long-term strength is overwhelmingly determined by PS concentration，and its durability is pretty good. High ambient temperature is a positive impact factor that enhances the strength of air hardening PS-(F+C) grouts in its treatment process，so that it is a proper decision to execute the grouting practice in hot summer. Such slurry will be used in grouting reinforcement of fractured soil mass at the ancient city of Jiaohe to prevent further erosion by running water through fractures.

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STUDY ON CONSTRUCTION TECHNIQUES OF A NOVEL BAMBOO-STEEL COMPOSITE ROCK-BOLT

REN Feifan1，2，CHEN Wenwu1，2，ZHANG Jingke1，2，LIANG Shouyun1，2，
HE Faguo1，2，WANG Guan3，CUI Kai1，2

2009, 28 (S2): 3789-3794 doi:

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Firstly，anchorage mechanism of composite rock-bolt was discussed. The special characteristics of the analytical solutions of shear stress and axial stress distribution were developed. Secondly，relying on the anchoring projects of the cliff of Jiaohe Ancient City，the construction techniques have been systematically optimized based on understanding general situation of the study area and anchorage mechanism of the composite rockbolt as well as failure modes of the cliff，including the location of anchor hole，hole-creating，lifting rock-bolts，installing rock- bolts，grouting，installing anchor devices，blocking the anchor holes，imitation of ancient surface，and curing the rock-bolts. The research results provide scientific basis for popularizing this new type rock-bolt for the preservation projects of cultural relics in the arid-semiarid regions，and it has a referential meaning for similar anchoring projects.

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RESEARCH ON PREVENTION COUNTERMEASURE AND MAIN GEOENVIRONMENTAL CAUSE OF LARGE-SCALE ANCIENT SITES IN SOUTH CHINA

LIU Yourong1，CHEN Zhongxing2，ZHOU Lizhen1

2009, 28 (S2): 3795-3800 doi:

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Geo-environment characteristics and disease types of the sites located in watery rock and soil in South China were analyzed for the prevalent geological diseases were water-caused trouble，instability of the surrounding rock and the change of environment. Among the diseases，water-caused trouble was primary important，so the key of the conservation measure was to control the water. Since the cultural site is regarded as primary source，its conservation engineering is different from the ordinary geotechnical engineering. The conservation measures are decided by the geo-environmental condition of the site. Then basically technical scheme and the key technical problem of the conservation engineering are proposed. The mausoleum site of Yue Kingdom in Yinshan was taken as an example. After analyzing the hydrogeological conditions，the stereographic projection and the block limit equilibrium method are adopted to calculate the stability of the slope in the tomb pit. Drip of the polymer chemical material and short anchor to reinforce the slop are proposed. Finally，the hydrogeological model of the site region is extablishedestablished，and method of waterproof blanket and blind ditch to control the water is proposed. It was proven by practical engineering.

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STUDY OF MAGNETIC MATERIAL PROPERTY OF GEOMECHANICAL MODEL TEST IN ELECTROMAGNET FIELD

LUO Xianqi1，GE Xiurun1，CHENG Shengguo2，ZHANG Zhenhua2，TANG Kai2

2009, 28 (S2): 3801-3807 doi:

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Geomechanical engineering problems were studied and stimulated using the principle of electromagnet force field to simulate gravity field in geomechanical model test based on electromagnet force system. Geomechanical problem can be studied by the model test of electromagnet force. In the model，the time and the geometric dimension are reduced with times，the acceleration of gravity g is amplified with times，the similarity ratio of the other basic material physical parameters all are 1. Prototype material in this geomechanical model test is chosen on the basis of electromagnet force theoretically，and it will provide convenience in model test operating. MageticMagnetic property of material is one of the key problems. The choice and basic property of geomechanical model test based on electromagnet force were introduced according to mixture and magnetic property of material. Magnet property of each mixture was studied to combinate need of geomachnical geomechanical model test. The relation between magnet force and magnetic strength and influence of moisture content were reseachedresearched with remagnetization and demagnetization. The electromagnet force is propositional to magnetic field gradient. A–200 magnetic powder¢s magnetic force multiple reaches 20.92 under 563.2 mT magnetic field intensity with mixture ratio 40% in remagnetization；C–180 magnetic powder¢s magnetic force multiple reaches 23.94 under 569.6 mT magnetic field intensity with mixture ratio 30% also in remagnetization. Based on the data from contrast tests，the selected two types magnetic powders can be considered as model material in the geomechanical experiments.

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EXPERIMENTAL STUDY ON CHARACTERISTICS OF DEFORMATION AND STRENGTH OF UNSATURATED CLAY

ZHANG Fangzhi1，2，CHEN Xiaoping1

2009, 28 (S2): 3808-3814 doi:

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A series of triaxial tests were carried out using double-cell triaxial system for unsaturated soils to investigate the behavior of volume change，yield and strength of unsaturated clays. The stress paths included drying with isotropic stress，isotropic compression and shearing with controlled suction. The results show that the clay exhibited an elasto-plastic shrinkage upon drying with low suction，indicating the existence of the suction- increase(SI) yield locus. During isotropic compression，the yield stress increases with increase of suction and the loading collapse(LC) yield curve changes parabolically. Increasement of net normal stress has more significant effect on the behavior of volumetric change than that of matric suction. The stress-strain relationship depends on the combinational style of net normal stress and matric suction，and suction enhances the stress-strain stiffness feature during triaxial shear test. Under conditions of different values of constant suctions，the effective friction angle is approximate a constant，and cohesion coefficient versus suction relationship is approximately linear.

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EXPERIMENTAL STUDY OF REDUCTION COEFFICIENTS a AND b OF CEMENT-SOIL PILES COMPOSITE FOUNDATION

LIN Yixi1，ZHANG Weili2，3，HUANG Liangji1，CAI Jian3

2009, 28 (S2): 3815-3820 doi:

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The calculational formula for bearing capacity of single pile with coefficient a and bearing capacity of composite foundation with coefficient b are shown in Technical Code for Construction Foundation Treatment. In order to get the value scopes of a and b which are suitable for this region and provide revision data for future code revision，the reinforcement treatment of representative silt soil foundation is carried out by means of cement-soil mixing pile in the Pearl River Delta area. And then，the load test is performed on single pile，natural foundation and four cement-soil mixing piles composite foundation，which is set with four kinds of thickness cushions. Based on analysis and calculation of the test data，the value ranges of the reduction coefficient a and b in the bearing capacity formula in the code are modified. Finally，the influence of cushion thickness on the bearing capacity of composite foundation is analyzed. It is suggested that the value range of cushion thickness is 200–400 mm，which can provide reference for design of cement-soil mixing pile composite foundation in the Pearl River Delta area.

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EXPERIMENTAL RESEARCH ON EFFECT OF SALT CONTENT ON STRENGTH OF TINY-PARTICLE CLAY

LIANG Jianwei1，2，FANG Yingguang1，2，CHEN Song1，2

2009, 28 (S2): 3821-3829 doi:

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For further study on the physicochemical mechanism of the inferior feature of tiny-particle clay such as coastal saline soil，and research on the influence of surface micro-electric field on the strength of tiny-particle clay，and shear strength，the liquid and plastic-limit tests were conducted on artificial soft soil including bentonite，kaolinite-bentonite mixed soil and quartz under a series of salt contents namely different ion concentrations of pore water. The cation exchange capacity and specific surface area were tested to obtain the surface potential of particle，and the relationship between shear strength and surface potential was proposed. The test results show that the surface potential of particle is changed with soluble salt ions through diffused double layer，and due to the variable thickness of bound water，the deformation resistance among particles changes. As a result，the strength of soil is influenced in macroscopic viewpoint. Based on the seaport saline soil foundation improvement project on Bubiyan island，Kuwait，tests were conducted on the strength and Atterberg limit of the local coastal saline soil. The research confirmed that the mechanism and rule of the influence of ion concentration of pore water on the strength of artificial soil are applicable to natural tiny-particle clay，providing theoretical explanation and experimental basis for the inferior features of saline soil in microscopic view.

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MICRO-STRUCTURE OBSERVATION AND ANALYSIS OFN GUANGZHOU
SOFT SOIL DURING CONSOLIDATION PROCESS

ZHOU Hui1，2，FANG Yingguang1，2，YU Changjiang3

2009, 28 (S2): 3830-3837 doi:

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Environmental scanning electron microscope(ESEM) was used to observe microstructures and their changes of soft soil samples of a typical soft soil district of PRD in consolidation test from Guangzhou Jinsha Delta. By analyzing the micrographs of soft soil obtained from consolidation test，characteristical parameters of the microstructure such as scale，shape，orientation of structural units and holes under the different consolidation pressure were obtained. At the same time，computer image processing software was used to analyze quantitatively the laws of some micro-structural parameters including microporosity，the distribution angle of the soil structural units and holes. In accordance with the analytical results from microscopic observation，some valuable conclusions were presented as follows：with the increasing consolidation pressure，the soil structural units increases constantly，microporosity decreases，and the shape of aggregates in the perpendicular direction to the pressure is longer，and the orientation of soil structural units increases and the fractal dimension of pore distribution has been a downward trend and in stability gradually.

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APPLICATION TO BEARING CAPACITY OF ROCK-embededEMBEDDED UNDER-REAMED UPLIFT PILES

ZHOU Zhiguo1，TANG Mengxiong1，DONG Xiaobin1，WANG Zhongkai2

2009, 28 (S2): 3838-3843 doi:

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When different weathered sandstones and mudstones are inter-embedded at different buried depths，and the weathered rock maximum strength is smaller than 14.4 MPa，it is difficult to find a suitable pile-end depth according to technical code for building pile foundations. Under-reamed uplift piles are constructed by rotary rig in different weathered sandstone and mudstone in South China. Rock-embededembedded under-reamed uplift piles are instrumented with strain gauges to measure the axial load distribution at all load increments. Based on the testing data，the crack and the deformation of shaft are discussed. The results show that the ultimate uplift capacity of pile is effected affected by pile friction and enlarged base of pile. The pile friction could be calculated considering that it is variable with pile length. The ultimate uplift capacity of pile is mainly effected affected by enlarged base of pile. Testing data show that the ultimate uplift capacity of pile is also decided by the critical displacement which is limited by the above building structure. To get larger ultimate load capacity of pile，it is useful to decrease the cracks and the deformation of pile under the pulling force such as constructing a short and large-diameter pile. Some methods such as vertical prestressed anchor are suggested to reduce the crack of shafts.

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DISCUSSION ON SEVERAL PROBLEMS FOR RETAINING AND PROTECTION DESIGN OF EXCAVATION

JIN Yabing，LIU Jibo

2009, 28 (S2): 3844-3849 doi:

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The problems for calculational methods of active earth pressure of inclined excavation slope plane and the horizontal anchor spring coefficient of pile-anchor retaining and protection structure，and whether considering the friction between pile and soil or not on calculating active earth pressure are discussed，and these calculation formulas are deduced. The active earth pressure of inclined excavation slope plane can be directly calculated using the formula on the limit-equilibrium theory，no need first to calculate the Rankine¢s active earth pressure and then amend the result. The vertical displacement of pile-anchor retaining and protection structure generally does not occur to anchored bearing，so the axis extension of anchor is assumed equal to the horizontal extension of anchor，and it is rational to calculate the horizontal anchor spring coefficient on this assumption. The deduced formulas are compared with the formulas in code by calculation examples. Both engineering case and the calculating results of the examples show that the calculating active earth pressure using the formula in code is more than the calculating active earth pressure without considering the friction between pile and soil，and the calculating horizontal anchor spring coefficient using the formula in code is smaller than the calculating result using the formula for whether soil-nail wall or pile-anchor retaining and protection structure. Therefore，the retaining and protection structure of excavation should be properly optimized for the purpose of controlling engineering cost.

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EXPERIMENTAL RESEARCH ON RIGID PILE COMPOSITE FOUNDATIONS

LI Xiping1，HE Chunbao2，TAO Longguang1，NI Guangle3，CHEN Cunen2，LIU Bo1

2009, 28 (S2): 3850-3856 doi:

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The settlement and stress ratio between pile and soil are the two most important parameters of composite foundation. But it is not easy to consider displacement coordination between piles and ground. Aiming at this problem，the equation of interaction is simplified. And three different static loading tests and in-situ measurement are carried out to analyze the load-bearing behavior and working mechanism of various types of rigid pile composite foundations in Guangdong Province. The settlement and rule of stress ratio between pile and ground are obtained. The measurement results show that proposed method coincides well with the practice condition. This method has better practical result than that of the method presented in technical code. And the results presented could be used for reference in rigid pile composite foundation design.

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RESEARCH ON BEARING BEHAVIOR MODEL OF LONG-SHORT PILE HIGH STRENGTH COMPOSITE FOUNDATION

LIN Benhai1，2，FANG Hui3

2009, 28 (S2): 3857-3862 doi:

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According to the deficiency of existing composite foundation research calculational model about the shear displacement method，rigid pile is divided into two sections at the depth of short pile length and the stress compatibility is considered. The shear displacement method calculation about different pile lengths and conformability to the actual soil layer distribution around the pile can be achieved. Through equivalent stiffness K of the contact soil body around the piles，the interaction when soil and pile simultaneously receive load can be considered，and the actual interaction between soil and pile can be taken into account. Through different stiffness influential coefficients b，the interaction of the difference among flexible short pile，rigid long pile and soil is considered. The calculational model and program are established through other existing research calculation model about the interaction and project example analysis，and the calculation model is proven to be reasonable and feasible.

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RESEARCH ON INFLUENCE FACTORS OF SIDE SOIL RESISTANCE OF PHC PIPE PILE

SONG Bing1，2，CAI Jian1

2009, 28 (S2): 3863-3869 doi:

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It is founded that the value of side soil resistance of pile will change distinctly in different situation，to determine it more accurately the influence factors of it need to be researched. Based on the mechanism analysis it can be concluded that the determinant influence factors of side soil resistance of pile are the strength of pile-soil interface，the strength of soil and the stress condition of soil. The stress condition of soil is the main reason which causes the variety of side soil resistance of pile，because it will change in different situations，influence the value of pile-soil interface strength，and make soil have different shearing-resistant abilities under a certain strength condition. An internal force test of three PHC pipe piles and its results are introduced. ADINA software is used to analyze the testing piles. The analysis includes possible destroy positions，pile-soil interface parameters and the changes of side soil pressure of pile in different depths of soil and under different loads. It is founded that damages all occur in the pile-soil interface of three testing piles，so the pile-soil interface parameters can be worked out using the testing value of side soil resistance. It is found that for silt soil adhesive force is the main interface force，but for sandy soil or residual soil，the friction is the main interface force. When friction is the main interface force，the change of side soil pressure of pile can cause the variation of side soil resistance of pile.

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THEORETICAL ANALYSIS OF DOUBLE-ROW PILES
RETAINING STRUCTURE DEFLECTION

HUANG Ping1，MO Haihong1，2，CHEN Junsheng1，2

2009, 28 (S2): 3870-3875 doi:

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A hypothetical shear slip surface will be used for piecewise analysis of double-row piles. Above the shear slip surface，the volume ratio method can be used for solving earth pressure，and the below used “m” method. Then，the differential deflection of each section can be established. According to the relationship of each section and the boundary conditions，the differential equations can be solutedsolved. After fetching each deflection equations，the situation of deformation and internal forces can be achieved.

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STUDIES ON DYNAMIC STRESS CHARACTERS OF LAYERED ROAD SYSTEM UNDER TRAFFIC LOADING

TANG Liansheng，XU Tong，LIN Peiyuan，YU Haitao

2009, 28 (S2): 3876-3884 doi:

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The data of field monitoring were used to analyze the affection of various factors. It concludes the dynamic stress distribution discipline in layered road system. Based on the existing elastic multilayer theories，using methods of transfer matrix and viscoelastic equation，the dynamic response of three-dimensional layered road system was obtained. Finally，the result，which was calculated by Matlab matrix numerical analysis software，was compared with the data of field monitoring test. Based on the above analysis，FLAC3D，the program was compiled for dynamic response of multi-layer road system under traffic loading. This program was used for three-dimensional numerical analysis of multi-layer road system，the distribution discipline of dynamic stress and dynamic displacement has been analyzed. At the end，the result was compared with the data of field monitoring to verify the effect of the program. the results indicate：(1) dynamic additional stress decreases quickly and the rate of attenuation tends to smooth as the depth increased；(2) dynamic additional stress is diffused effectively and significantly by the upper layers；(3) vehicle vibrating causes stronger dynamic additional stress than that without vibration；and (4) dynamic additional stress has accumulative effect.

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GREY RELATION ANALYSIS OF PARAMETER SENSITIVITY OF CAVERN STABILITY BASED ON 3D ELASTOPLASTIC FINITE ELEMENTS

NIE Weiping，XU Weiya，ZHOU Xianqi

2009, 28 (S2): 3885-3893 doi:

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Based on the comprehensive consideration of rock mass physical parameters and defects of conventional sensitivity analysis，grey relation analysis of parameters sensitivity of cavern stability based on 3D elastoplastic finite elements is put forward. Point safety factor is specified as examination index；and cohesion，angle of internal friction，elastic modulus，and Poisson¢s ratio are confirmed as sensitivity influential parameters. Taking Liangjiaren hydropower station on Jinsha River in China for example，the sensitivity analyses of many influential factors for point safety factor of excavated underground cavern typical sections have been conducted. Through the analyses，the influential effects for point safety factor of cavern stability are different when the influential factor has been changed. After excavation，the vault or sidewall of cavern is free and the constraint of cavity wall for inflection point is much larger，therefore，the safety factor of the inflection point is larger than that of vault or sidewall of cavern. Grey relation analysis shows that the scheduling of the influential degree of excavated underground cavern typical section on point safety factor is cohesion，angle of internal friction，elastic modulus，Poisson¢s ratio，therefore，the limitation of the conventional sensitivity analysis is overcome，and the sensitivity sequencing of the influential factors on key point safety factor are also unified，which verifies the mathematical and mechanical analytical results. Accordingly，clear direction for choice of support material of underground cavern stability is shown，and the requirements for cohesion and angle of internal friction must be paid more attentions.

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THIMBLE MULTICAST INSTRUMENT IN DRILL HOLE AND ITS APPLICATION TO TUNNELLING ENGINEERING

XU Jin1，2，ZHANG Zhilong1，2，WANG Lansheng3

2009, 28 (S2): 3894-3898 doi:

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According to the deep-buried long tunnels through mountains，such as the Erlangshan tunnel and the Xuefengshan tunnel，the thimble multicast instrument in drill hole and its installing and testing techniques，which are suitable for monitoring the loose deformation of surrounding rock in time during the construction，have been developed and invented. Practical engineering application shows that it has many merits，such as obtaining materials locally，manufacturing easily，being installed and testing quickly，powerful anti-interference capability and accurate testing result. The instruction will be used in tunnelling engineering and other underground engineering extensively.

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EVALUATION ON STRESS SENSIBILITY OF LOW PERMEABILITY ROCK UNDER RESERVOIR CONDITION

GAO Jian1，LU Jing2，WANG Jialu2

2009, 28 (S2): 3899-3902 doi:

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Two experimental methods are used respectively to evaluate a real reservoir¢s stress sensibility during the processes of production and water injection. It¢s shown that，compared with the conventional evaluation method，the loss rate of permeability is considerably lower during production process，and the rock¢s permeability loss caused mainly by elastic deformation is recoverable when the new method is used. However，the rock¢s deformation caused by both elastic and plastic deformations is irreversible in conventional experimental method. So serious stress sensibility does not exist in low permeability reservoir，which is significant for low permeability reservoir development.

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ASSESSMENT ON SAFETY OF LATTICE GIRDER REINFORCED SHOTCRETE SUPPORT FOR TUNNELS

LI Hongquan1，YANG Chengyong1，XU Mingxin1，LU Jinghui2

2009, 28 (S2): 3903-3908 doi:

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Based on the previous research，lattice girder reinforced shotcrete support is dealt with，and a method is set up to evaluate the safety of this kind of support for a tunnel in construction. Firstly，performance functions to a cross-section of the support are put forward according to the correlative formulae from Chinese codes. Then，parabola is employed to interpolate the central axis of an arch-like support segment，and the formulas to calculate internal forces of the support are derived through measured displacements under assumptions of linearly elastic material，small deformation，and plane cross-section etc.. After that，the uncertainty of the basic random variables，such as mechanical properties of rebars(compressive strength，tensile strength and modulus of elasticity)，the sectional area of rebars and thickness of shotcrete cover，is discussed. At last，case studies are conducted in two tunnels，Wushaoling Tunnel at the second line of Lanzhou—Xinjiang Railway and Huangzhuang Station at Line 4 in Beijing subway. Case studies show that the obtained results are consistent with in-situ situations and calculated reliability indices fall into the interval required by national codes. This work improves the so-called displacement- based method and addresses the very real need of assessing the safety of lattice girder shotcrete support during tunnel construction. This study is of both theoretical and practical significances.

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RESEARCH ON CENTRIFUGAL MODEL EXPERIMENT OF DEEP-BURIED COAL SEAM

LIU Deqian1，JIANG Zhenquan2，LI Jianshuo2，FENG Haiying1

2009, 28 (S2): 3909-3913 doi:

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Considering the geotechnical conditions of the Zhaolou coal mine，similitude material centrifugal experiment is done，and the stress variation at different positions in coal seam roof is found. The following results have been drawn. (1) Because of the excavation of coal，the pressure variation of coal pillar is evident，the influencing distance is about 35 m，10–15 m ahead the working face；and the maximum pressure concentration coefficient is produced，which reaches 2.8. (2) The pressure of immediate roof reaches its peak value，which is 1.74，immediately when the working face arrives；and it decreases firstly and then rises after the working face passes. (3) The peak value of the pressure of the basic roof occurs after 5–10 m excavation of coal，and the corresponding maximum pressure concentration coefficient reaches 3.91 on the condition of basic roof. Therefore special measures must be carried out. (4) The step of rupture on the basic roof is about 30 m. The research results are important to the design of coal channel，the excavation，and the prevention of geotechnical disaster.

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COUPLED BOLT-MESH-ANCHOR-TRUSS SUPPORTING TECHNOLOGY AND ITS ENGINEERING APPLICATION TO DEEP SOFT ROCK ROADWAY

GUO Zhibiao1，LI Qian2，WANG Jiong1

2009, 28 (S2): 3914-3919 doi:

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In deep soft rock roadway，supporting technologies and methods which have been adopted in shallow engineering are not applicable due to complex engineering geological conditions. The coupled bolt-mesh- anchor-truss supporting technology is suggested. The rationality and mechanism of the technology are studied by means of theoretical analysis and numerical simulation. Its technical characters and key points are analyzed. The results are applied to the deepest soft rock roadway in China. The rationality of the supporting scheme has been validated by field monitoring.

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RESEARCH ON EFFECT OF DRILLING FLUID ON KUQA SHALE STRENGTH BEHAVIOR AND ITS APPLICATIONS

LIU Xiangjun，LIU Hong，LUO Pingya，LIANG Dachuan，HUANG Jinjun

2009, 28 (S2): 3920-3925 doi:

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The effect of different drilling fluids on the strength behavior of Kuqa shale is studied based on triaxial rock mechanical test. Combined with existing drilling fluid performance evaluation methods，stress-strain curve shown by shale after immersion in different drilling fluids for 24 hours and the rock mechanical performance，rock deformation and failure laws，the existing drilling fluid is selected and optimized. One drilling fluid with better stabilization to this kind of shale formation is obtained. Besides，the formation collapse pressure change in different drilling fluids is also calculated and analyzed by testing rock strength before and after immersion in those systems. The findings achieve remarkable wellbore stabilization and speedup effect when they are applied to drilling field practice. Results show that present drilling fluid will remarkably decrease rock strength，and the shale strength performance can be regulated and changed by optimizing the drilling fluid. Rock strength performance research is applied to existing shale drilling fluid evaluation. It can not only induce the chemo-mechanical coupling between shale and drilling fluid initiatively into the optimization procedure of drilling fluid system，but also can establish theoretical and methodological basis to restrain the uncertain effect to shale wellbore caused by coupling chemo-mechanical radically. The research combines the optimization procedure of drilling fluid with wellbore stability. It establishes the basis to obtain collapse pressure of target shale formation and achieve safe，effective drilling with low density drilling fluid. Deformation failure law showed by shale after contacted with different drilling fluid is the important criteria to shale formation drilling fluid stabilization and wellbore performance optimization. The stress-strain curve of shale before and after being immersed by different drilling fluids can lead to achieve evaluation and optimization of drilling fluid performance. The shale strength behavior and collapse pressure are adjustable by optimizing drilling mud components.

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REGIONAL HORIZONTAL DISPLACEMENTS AND ITS EFFECT ON SHAFT IN MINING AREAS

LI Wenxiu1，WEN Lei1，LIU Xiaomin1，HOU Xiaobing2，LIU Lin1

2009, 28 (S2): 3926-3931 doi:

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In Xiaoguanzhuang iron mine，although the towers are outside the influential area of the conventional traveling angle，and only negligible vertical deformation has been observed as a result of mining，there has been widespread evidence of regional horizontal deformation of the land surface with large distances away from the mining area. Possible explanations of these movements include one or a combination of mechanisms such as pre-mining stress relaxation，regional joint patterns，movement toward active goaf areas. A case study of the regional horizontal displacements measured during mining and the possible explanations for these phenomena are presented. The causes of the displacement and the deformation of the shaft are analyzed. It is shown that the damage of the shaft relates to not only the size of the protective ore column but also the engineering geological condition，physico-mechanical properties of rock mass，horizontal stress field，hydrogeological effects and mining method.

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EXPERIMENTAL RESEARCH ON ELASTIC RESISTANT COEFFICIENT，DEFORMATION AND COMPRESSIVE MODULI OF SURROUNDING ROCK IN LARGE-SECTION LOESS TUNNEL

FANG Qianbao1，MA Jianlin2，YU Yu1，YANG Jianmin1，WANG Xindong3

2009, 28 (S2): 3932-3937 doi:

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Elastic resistant coefficient，deformation and compressive moduli of surrounding rock in large-section loess tunnel are very important for design of tunnel. Based on the project of large-section loess tunnels along the new passenger dedicated line(PDL) from Zhengzhou to Xi¢an，the elastic resistant coefficients，deformation and compressive moduli of surrounding rock in loess tunnels have been studied horizontally and vertically by plate loading tests. The formulas for these parameters mentioned above which are related to buried depth of tunnel are also provided.

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RESEARCH ON GENERALIZED LONGITUDINAL EQUIVALENT CONTINUOUS MODEL OF SHIELD TUNNELS

ZHANG Wenjie1，XU Xu1，LI Xianghong2，SHEN Yongdong2，ZHANG Mengxi1

2009, 28 (S2): 3938-3944 doi:

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Based on conventional longitudinal equivalent continuous model，a generalized longitudinal equivalent continuous model is proposed，in which transverse rigidity of the tunnel and the influential region of the longitudinal joints are considered. Yaohua local road tunnel for magnetic suspension train is selected as an example to investigate the variation of longitudinal effective rigidity ratio with the transverse rigidity and the influential region of the longitudinal joints. The analytical results show that，as the transverse rigidity decreases，the area of compressive region increases and the longitudinal effective rigidity ratio decreases. As the influential region of the longitudinal joints increases，the longitudinal effective rigidity ratio decreases. Both the conventional and the modified longitudinal equivalent continuous models can be regarded as special cases of the proposed model. The proposed model is more widely applicable and is of reference value for longitudinal stability analysis of shield tunnels.

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INFLUENCE OF SHIELD CONSTRUCTION OF ADJACENT LINE UPON EXISTING TUNNEL

YAO Jie1，YANG Guanghua1，2，ZHANG Yucheng1，2，ZHANG Youxiang1

2009, 28 (S2): 3945-3951 doi:

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Based on the transferring stiffness principle，a settlement difference method is put forward to evaluate the influence of each construction step on adjacent shield，and the total effect on the existing tunnel can be obtained by synthesizing single-step increment. Based on an urban metro，simulation analysis for the shield moving-forward process of the metro excavated afterward is carried out. It is found that the arch foot of the slumping arch induced by the tunnel excavated afterward acts on upper-right of the existing tunnel. The maximum circumferential tensile stress in the existing metro caused by single construction step of right line is 0.13 MPa，and the maximum additional tensile stress is 0.857 MPa. Combined with the analysis of original stress state of existing tunnel considering segment joints，the important internal causes of crack are found out. The research enriches the simulation methods of adjacent tunnels and can provide valuable reference for study of crack control and even for tunnel design and construction.

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FUZZY RANDOM FINITE ELEMENT RELIABILITY ANALYSIS OF SLOPE STABILITY WITH FUZZY BASIC VERIABLES AND FUZZY STATES

TAN Xiaohui1，HU Xiaojun2，WU Kunming3

2009, 28 (S2): 3952-3958 doi:

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Based on slip surface stress method of finite element analysis of slope stability，the fuzzy random reliability analysis method of slope stability is studied with consideration of both the fuzziness of basic variables and limit states. For the consideration of the fuzziness of basic variables，the method of equivalent transformation is used for the transforming from fuzzy variables to random variables. For the consideration of the fuzziness of limit states，the method of probabilistic integral is used for the calculation of fuzzy failure probability and fuzzy random reliability index. The proposed method can not only calculate the fuzzy random reliability index of each finite element，but also the minimum reliability index of the whole slope and the corresponding position of the critical slip surface. This method can consider the fuzziness of both the basic variables and the limit states，and it is an extension of the normally used stochastic finite element reliability analysis method. If the fuzziness of the basic variables and the limit states are not considered，the method will turn into the normally used stochastic finite element reliability analysis method of slope stability.

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STABILITY AND STRENGTHENING ANALYSES OF SLOPE ROCK MASS CONTAINING MULTI-WEAK INTERLAYERS

XU Baotian1，2，QIAN Qihu1，YAN Changhong2，XU Hongfa1

2009, 28 (S2): 3959-3964 doi:

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Three weak interlayers were found in the rock mass of Jiudingshan slope by outdoor investigation，which control the stability of the slope. The deformation characteristics of the slope rock mass are studied using numerical simulation. The results indicate that：(1) large relative slide will be induced by the direct excavation，and the maximum horizontal displacement，1.25 cm，happens on the slope surface where the weak interlayer P2 emerges；and (2) the relative deformation makes the strength of the weak interlayers reduce to be the residual one，which makes the slope more instable. The maximum shear stresses at the middle and front of the weak interlayers P1 and P2 are 239.0，172.4 kPa respectively. When the slope is strengthened by anchors，the axial force increases rapidly near the weak interlayers，which indicates that the anchors make the stability of the slope be improved. The stability coefficient of the slope after reinforcement calculated by strength reduction method is 1.65. It is shown that the numerical simulation can give the variation process of deformation and stress in the slope，and it is helpful for engineering optimization，informational design and construction.

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STUDY ON PRESTRESS LOSS LAW OF ANCHOR CABLES IN DEEP UNLOADING DEFORMED RIPPED BLOCKS

ZHANG Jinlong1，2，XU Weiya1，2，XU Fei1，2，CAI Dewen3

2009, 28 (S2): 3965-3970 doi:

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According to the construction process of prestressed anchor cable，the total prestress loss is divided into three parts，that is，tensioning prestress loss，locking prestress loss and time-dependent prestress loss. The definition and calculation formula of each part are specified. The monitoring data of prestressed anchor cables of left bank excavation slope in Jinping first stage hydropower station are analyzed systematically，and the distribution features of prestress loss are obtained. The analysis result shows that the tensioning prestress loss is the maximum component of total prestress loss of anchor cable，and the time-dependent prestress loss is the intermediate one and the locking prestress loss is the minimum one. A comparison is made between the law of cable prestress loss of left bank excavation slope in Jinping first stage hydropower station and those of some other hydropower engineering slopes. The result shows that the tensioning prestress losses of anchor cables of left bank excavation slope in Jinping first stage hydropower station are greater than those of some other hydropower engineering slopes remarkably. Based on the engineering geology of left bank excavation slope of Jinping first stage hydropower station，the factors resulting in large tensioning prestress loss are analyzed，and some measures to reduce the tensioning prestress loss are put forward. At last，the present load of anchor cables is evaluated. It is shown that the present load of anchor cables can meet the requirement of design. This result can provide references to other similar engineering.

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STUDY ON SLOPE STABILITY AND OPTIMIZATION OF BOUNDARY PARAMETERS UNDER CONDITION OF COMBINED OPEN-UNDERGROUND MINING

ZHU Jianming1，LIU Xianquan2，FENG Jinyan1，WU Jianping1

2009, 28 (S2): 3971-3977 doi:

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3D numerical program is used to analyze the stability of the slope affected by underground excavation. Research show that the open-off cut position plays a key role in the slope stability. The numerical simulation is conducted to optimize this boundary parameter，and the results shows that the slope stability is improved to ensure the safe production when the horizontal distance between open-off cut and slope increases to 20 m based on the original data. At the same time，the material simulation method is used to make sure of the scheme. The slope is stable when the scheme is adopted in field.

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GIS-BASED LANDSLIDE SUSCEPTIBILITY ASSESSMENT USING ANALYTICAL HIERARCHY PROCESS IN WENCHUAN
EARTHQUAKE REGION

XU Chong1，DAI Fuchu1，YAO Xin2，3，CHEN Jian1，TU Xinbin1，SUN Yu4，WANG Zhiyi5

2009, 28 (S2): 3978-3985 doi:

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On 12 May 2008，a catastrophic earthquake with surface wave magnitude of 8.0 struck the Sichuan Province of China. Tens of thousand of landslides were triggered by this earthquake over a broad area. 48 007 landslides were interpreted from aerial photographs and multi-source remote sensing imageries，verified by field check. A spatial database，including landslides and associated controlling parameters which may have influence on the occurrence of landslides，was developed and analyzed using geographical information system(GIS) technology. The correlations of landslide distribution with controlling parameters，including faults，lithology，elevation，slope angle，slope aspect，drainages and roads are firstly analyzed，and landslide area-ratio was calculated for each group of the above parameters. An analytical hierarchy process(AHP) was then applied to determine the significance of controlling parameters in triggering the landslides. The resulting susceptibility map showed five classes of landslide susceptibility，i.e. extremely high，high，moderate，low，and extremely low. The area with extremely high and high susceptibility accounts for about 8 211 km2，16.9% of the study area. This indicates that the result is reasonable in 60.5% of the landslides occurred in high or extremely high susceptibility region.

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NUMERICAL SIMULATION OF DYNAMIC STABILITY OF SLOPE ROCK MASS UNDER SEISMIC LOADING

TAN Rujiao1，LI Mingsheng1，XU Pengxiao1，HU Ruilin2，SU Yan1

2009, 28 (S2): 3986-3992 doi:

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Taking the deformed rock mass of Longpan slope along Jinsha River for example，the dynamic response and failure mechanism of slope rock mass under seismic loading are simulated by distinct element method. The time-history curve of artificially synthetic acceleration is used，and the effect of excess static pore water pressure is taken into account. The following results are obtained. The seismic inertia force results in accumulation of shear stress. The discontinuous structures are crucial to wave transmission. The ultimate dynamic response of slope system takes place at the initial period of seismic loading. Essentially the main mechanism of deformation and failure of rock mass induced by earthquake is the coupling effect of shear stress and excess static pore water pressure accumulation. At the same time，the results show that the deformed rock mass of Longpan slope is unlikely to form a long-distance landslide. This conclusion has important application value for the choice of dale dam site along Jinsha River.

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CASE STUDY OF REINFORCEMENT OF A TYPICAL ROCK LANDSLIDE ALONG HIGHWAY S212 IN QINGDAO CITY

LIU Xiaoli1，TAN Changwei2，DONG Taiwen2

2009, 28 (S2): 3993-3998 doi:

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The characteristics and failure mechanism of the Shilaoren Scenery Garden rock landslide along highway S212 in Qingdao city are investigated. On the basis of the rock landslide properties and the control requirement，a new kind of composite anti-sliding pile is used in the reinforcement engineering. The composite anti-sliding pile is composed of the general anti-sliding pile and the assembled drilled micro-steel tube piles，that is，the general anti-sliding pile is adopted in the seriously weathered rock layer of the sliding mass in view of the easy excavation，while the assembled drilled micro-steel tube piles are adopted in the moderate or slightly weathered rock layers in view of the hard excavation. The composite anti-sliding structure combines the general anti-sliding pile and the drilled mirco-steel tube piles to form an integrated structure，which is applicable to reinforcement of such similar rock landslide for the convenient construction and the large stiffness. The rock landslide reinforcement engineering has been proved successful in practice，and the application of the new kind of composite anti-sliding pile to the engineering has built up a successful example for control of the similar rock landslide.

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ESTIMATION OF CUT-FILL VOLUMES IN ROCK SLOPE ENGINEERING BASED ON FRACTAL INTERPOLATION

MENG Yongdong1，2，XU Weiya1，TIAN Bin2，LIU Dawen 3

2009, 28 (S2): 3999-4005 doi:

[PDF] 464 KB (909)

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The traditional interpolation algorithm is mainly based on smoothing mechanism，the result of interpolation cannot truly reflect the natural rock slope surface morphology，and the volume cannot be estimated through these results. In view of the natural terrain of rock slope engineering with random dithering and self- similar characteristics，by acquiring the surface characteristics and using interpolation algorithm based on the fractional Brownian motion(fBm)，more intensive dataset of rock slope with natural terrain can be obtained through the samples of mapping data，and the geomorphic feature of rock slope can be accurately restored. Therefore，the TIN model of excavation mass will be constructed by constraint Delaunay triangulation algorithm according to the dataset points and constraint lines of natural terrain. This method can accurately estimate cut-fill volumes of rock slope engineering. Under the prerequisite that a regional dataset of surface control points is regarded as the actual landscape，and the results of error analysis show that the error percentage of calculating cut-fill volumes with fBm fractal interpolation method is 0.14%，and that using Nurbs interpolation method is 1.5%，and fBm fractal interpolation method has much higher accuracy than traditional methods. In addition，a case study of the left bank high slope excavation of Jinping first stage hydropower station is given. It is shown that this research can provide references for excavation calculation and 3D visualization analysis of slope engineering.

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MODEL TEST OF SANDY SOIL SLOPE REINFORCED BY SOILBAGS AND UPPER-BOUND SOLUTION

WANG Yanqiao1，LIU Sihong1，YANG Junjie2，LIU Qiang2

2009, 28 (S2): 4006-4013 doi:

[PDF] 377 KB (861)

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A series of model tests are carried out on sandy soil slopes with and without reinforcement by soilbags. The reinforcement effect of soilbag is validated by comparing the slope failure modes and ultimate bearing capacities. Based on the test results，an allowable slope failure mode and the velocity field are established. Meanwhile，the ultimate failure heights of the reinforced slopes are obtained by using the upper-bound solution theory，which agrees well with those from the model tests. Both the model tests and the upper-bound calculations show that，after reinforcement with soilbags，the steeper the soil slope is，the more the increases of the ultimate failure height and the bearing capacity of the soil slope are，indicating a better reinforcement effect of soilbags.

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RESEARCH ON CHARACTERISTICS OF POROUS FOUNDATION SUBJECTED TO MOVING LOADS BASED ON GENERALIZED THERMOELASTIC THEORY

LU Zheng1，YAO Hailin1，LIU Ganbin2，LUO Xingwen1

2009, 28 (S2): 4014-4020 doi:

[PDF] 289 KB (997)

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The characteristics of porous elastic medium subjected to harmonic strip moving load are investigated analytically in the context of generalized thermoelastic theory by introducing relaxation time. The material of foundation，obeying Biot¢s dynamic poroelastic theory，is idealized as a uniform，fully saturated poroelastic half- space stratum. The coupled thermo-hydro-mechanical governing equations are derived by modifying Biot¢s dynamic poroelastic theory. The general solutions of temperature increment，stress，displacement and pore water pressure are obtained by employing Fourier transform. Considering the heat source acted on the surface of foundation and mixed boundary condition，analytical solutions in the form of integral are derived using the inverse method. Numerical results are obtained by using inverse Fourier transform and adaptive quadrature algorithm. The calculating results can be degenerated to the corresponding classical Flamant solution of static problem. Furthermore，the influence of the different heat source conditions on the temperature increment，stress，displacement and pore water pressure is discussed. Computing results show that the temperature increment is slightly affected by the heat source condition；and the distributions of stress，displacement and pore water pressure are obviously influenced by the heat source.

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IMPROVEMENT OF STACKED SHEAR MODEL BOX

GAO Bo，ZHANG Hongru

2009, 28 (S2): 4021-4026 doi:

[PDF] 223 KB (906)

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Technical improvement has been made to existing laminar shear model box. The main idea of the technical improvement is using shafting bearing and the rigid restriction system in one side to replace ball bearing and lateral rigidity restriction system which are normally used respectively. The way of the technical improvement is changing laminar square steel frame into the one with H-formed steel and square steel stacking alternately. External diameter of the interlaminar shafting bearing has been changed from 16 mm to 72 mm，the force mechanism of the model box has been changed from “drawer” to “stack”，and the lateral rigidity restriction system has been replaced by riveted elastic thin steel plate in non-main vibration direction. The software ANSYS has been used to verify the effect of the riveted elastic thin steel plate on the dynamic characters of model box and soil. It is shown that there is a little effect on model box riveted by thin steel plate. After improvement the deadweight of the model box decreases，the interlaminar spacing is smaller than before and also can be adjusted to the needed sizes，and the force mechanism of the model box is more close to the actual one of soil. Equipment can be reused，and its operation capability is better than before. By using the improved test equipment，it can be achieved to simulate the soil performance under dynamic load.

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TEST STUDY ON DYNAMIC DEFORMATION BEHAVIOR OF REINFORCED GABION RETAINING WALL UNDER CYCLIC LOAD

LIN Yuliang1，YANG Guolin1，LI Yun1，HUANG Xiangjing1，2

2009, 28 (S2): 4027-4033 doi:

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In order to study the deformation behavior of reinforced gabion retaining wall，model test is carried out. The cyclic loads with five frequencies(2，4，6，8， 10 Hz) and three amplitudes(40–80，50–100，60–120 kPa) are imposed. According to the test，the dynamic deformation behavior(both lateral and vertical deformations) of wall face，the main influential factors and their significance，and the deformation behavior of retaining wall when unloading are obtained. Test results show that：(1) the dynamic deformation is affected by amplitude of cyclic load，vibrations，filling ratio of gabion cage and so on，and not significantly affected by vibration frequency；(2) large lateral deformation occurs in the third，the fourth and the fifth layers of wall face；(3) with the increase of amplitude，vibration time to stable deformation increases，and the deformation also increases；(4) dynamic deformation increases during vibration quickly first and then tends to be slowly；and (5) the lateral deformation of the wall face shows almost no elastic recovery when unloading.

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EXPERIMENTAL STUDY ON TWO-DIMENSIONAL
ELECTRO-OSMOTIC CONSOLIDATION OF SOFT CLAY

LI Ying，GONG Xiaonan，JIAO Dan，LIU Zhen

2009, 28 (S2): 4034-4039 doi:

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A laboratory test program on electro-osmotic consolidation was conducted on saturated soft clay in the axisymmetric condition using an newly developed apparatus. Voltage，current，water discharge were observed during the test，and settlement and water content were measured after the test. Then consolidation characteristics of remolded soil were studied from the point of view of electro-osmotic mechanism and energy consumption on the basis of the measured data. The following conclusions are drawn. (1) Voltage at a certain point in the soil relies on both the distance to cathode and the working time. For axisymmetric model，electric potential is distributed in the form of a broken line，and the turning point is adjacent to cathode. (2) Electric field intensity in the soil is not constant but decreases with the working time when the interface resistance is not considered. (3) In the final stage of this test，soil resistance and the consumed energy may increase greatly close to a mutation point after a certain time. The test shows that the energy consumption curve can be used to control the electro-osmotic time and to reduce the energy consumption for a high efficiency of electro-osmosis.

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DEVELOPMENT OF CONTACT MODEL IN PARTICLE DISCRETE ELEMENT METHOD

WANG Tao1，2，LU Qing1，LI Yang1，LI Hongming1

2009, 28 (S2): 4040-4045 doi:

[PDF] 233 KB (2402)

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Generalized Kelvin model for calculation of contact force between particles is deduced based on the research of theoretical background of particle discrete element method. With the object-oriented programming technique and the redeveloped interface of PFC，the generalized Kelvin contact model is developed and used in a verification example. In the example，two particles are bonded together and the relaxation is calculated by PFC and theoretical method. The result shows that the contact force exponentially decreases as time increases，which coincides with the analytical solution. Based on the researches，taking a deep-buried tunnel for example，the cracking and failure of rock are analyzed under conditions of different contact constitutive models. Results show that the generalized Kelvin contact model is better than linear elastic contact model，and the former is more consistent with the calculation chart from Hoek-Brown strength criterion.

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NUMERICAL ANALYSIS OF FREE FIELD SYSTEM IN LIQUEFIABLE SITE AND VALIDATION OF SHAKING TABLE TESTS

LU Xilin1，REN Hongmei1，LI Peizhen1，PENG Gongsheng2

2009, 28 (S2): 4046-4053 doi:

[PDF] 494 KB (1004)

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3D fully nonlinear analysis of seismic response of free field in liquefiable site is carried out using the general finite difference program FLAC3D. Compared with the equivalent-linear method，the permanent and irreversible displacements can be modeled automatically in the fully nonlinear method. A proper plastic formulation is used in the soil nonlinear constitutive relation，whereby plastic strain increments are related to stresses. Combined with the pore water pressure model，soil liquefaction under the seismic excitation can be modeled. Soil nonlinearity，pore water pressure build-up process and boundary condition of the model are taken into account in the calculation model. A comparison between the results from the finite difference analysis and those from the shaking table tests is made to validate the effectiveness of the computational model. Numerical results demonstrate that the liquefied soil can filter and isolate vibration. The phenomena of transient minus pore pressure occurr in the test. Pore water pressure does not always dissipate in short time immediately after the excitations，but it may keep on increasing.

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RESEARCH ON RELATIONSHIPS BETWEEN WATER CONTENT AND RESISTIVITY OF EARTHEN RUIN WALLS

ZHOU Zhonghua1，2，ZHENG Long1，2，SUN Bo1，2

2009, 28 (S2): 4054-4058 doi:

[PDF] 287 KB (1230)

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Porous media resistivity is affected by a number of factors. In the specific structure of the soil wall sites，changes in resistivity depend on the moisture and temperature changes. By the resistivity model analysis of rammed earth wall in Ruins of Jiaohe，combining with the improved Archie model，a resistivity model for the wall in a specific structure is established by the tests to find out the relation between water content and resistivity，and to determine the structural parameters and soil parameters in the model formula. According to the established formula by the moisture inversion with the resistivity，using high-density resistivity chromatography，the field wall in Ruins of Jiaohe is tested. The results demonstrate the practicality of the model formula in relics sites，which lays foundation for practical application of monitoring water translocation in relics sites.

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INFLUENCE OF WATER CONTENT ON PULLOUT BEHAVIOR OF GEOGRID IN RED CLAY

FENG Xiaojing1，2，YANG Qing1，2，LI Shoulong1，2，LUAN Maotian1，2

2009, 28 (S2): 4059-4064 doi:

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The pullout behavior of geogrid in red clay is studied. An experimental investigation is conducted using geogrid in eight groups of red clays with different water contents. The results indicate that the geogrid embedded in red clay mainly represents pullout failure，and the ultimate pullout force is sensitive to water content. It decreases with the increase of the water content firstly. Then it tends to be constant around the plastic limit. Moreover，the ultimate pullout force is independent of the normal load in this zone. The distribution character of geogrid strains proves that the decrease of the ultimate pullout force is due to the reduction of the friction resistance between soil and geogrid. Besides，the water content influences the process of the pullout behavior. The increase of water content leads to the ultimate pullout force soon after the geogrid strain increases linearly.

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EXPERIMENTAL STUDY ON STRUCTURE RESPONSE IN TWO-PHASE SATURATED SOIL UNDER BLASTING LOAD

XIN Kai1，2，JIANG Xinliang1，WU Xiangyun2

2009, 28 (S2): 4065-4070 doi:

[PDF] 259 KB (982)

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The two-phase saturated soil with air content less than 99.99% and structural response are investigated by experiments，and explosion experiments are conducted by cylindrical simulating explosion device with sizes of f 2.5m×5 m. Mass charges of TNT are adopted and buried in the saturated soil to carry out contact explosion with unified proportional buried depth. Square large-span structures are set in the saturated soil，and overall damage appears for these structures. At the same time，limit structures of complete immobility wall are investigated. By the comparison with large-span structures，reflection factors of different types of structures are systematically researched. Experimental investigation indicates that，if the pressure in the two-phase saturated soil is more than 2 MPa，the dynamic liquefaction appears in the saturated soil，and stress waves are changed into shock waves. The pressure has little relation with specific particle properties of saturated soil. By means of research on two kinds of structural responses at limit state，the result shows that the reflection factor of the structures with different spans in saturated soil is 0.5–2.0，and its value is decided by structural forms.