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2010, 29 (07): -0 doi:
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FLOW CHARACTERISTICS OF JOINTS UNDER DIFFERENT CONTACT CONDITIONS

XIA Caichu1，2，WANG Wei1，2，3，CAO Shiding1，2，4

2010, 29 (07): -1306 doi:
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[PDF 494 KB] (1138)

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Seepage characteristics of rock joints under different contact conditions are studied. Artificial tension rock joints are made of white marble samples taken from construction site of the Yalong River(Jinping II Project)，using cleaving method. Surface topographies of rock joints are measured by a three-dimensional TJXW–3D-typed portable rock surface topography measuring instrument. A self-programmed software is used to calculate parameters for rock joints，including not only 2D fractal dimension of surface topography for each single joint surface，but also 3D fractal dimension of composed topography for vacuum formed by two coupled joint surfaces. Then seepage experiments of the artificial rock joints are carried out. During the experiment，contact condition of rock joints varied by offsetting the relative position of the joints from 1 mm to 6.5 mm. Deficiency of traditional empirical formulas，such as Darcy¢s law，cubic flow law and its modified formula，and seepage formula in turbulent flow，are exposed by comparing experimental results with calculating ones from those traditional empirical formulas. After a thorough study of experimental results，it is discovered that fractal dimensions of single joint surface topography and composed joint topography have great influences on the seepage characteristics of rock joint. By taking permeability and the topography coefficients of rock joint into consideration，a new empirical formula for seepage in rock joints that highly matches the test results is presented，which is much more reasonable in theory and accurate in practice than traditional formulas.

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STABILITY ANALYSIS OF LAYERED SURROUNDING ROCK MASS OF LARGE UNDERGROUND POWERHOUSE OF XIANGJIABA HYDROPOWER STATION

FAN Qixiang1，2，WANG Yifeng2

2010, 29 (07): -1313 doi:
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The underground powerhouse of Xiangjiaba hydropower station(33.4 m×85.2 m) is the largest underground powerhouse in the world. Excavation of large-span underground caverns in gently inclined stratum leads to significant stability problems of surrounding rock mass. Both 3D distinct element method and stress and displacement monitoring are used to study the surrounding rock mass stability，and two-ended anchor and systematic bolts are used to reinforce the surrounding rock mass. Then，based on the monitoring results，the stability of surrounding rock is analyzed. The research reveals the structure-controlled surrounding rock stability problem of shallow or middle buried cavern，and great attention should be paid to geology analysis and the survey of rock mass geometric features and discontinuity. It is appropriate to use the discontinuous medium mechanics method，and then to implement the corresponding optimal reinforcement measures.

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DEVELOPMENT OF MICRO UNIAXIAL COAL AND ROCK TESTING MACHINE AND EXPERIMENTAL STUDY

ZHAO Dong，FENG Zengchao，ZHAO Yangsheng

2010, 29 (07): -1322 doi:
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[PDF 327 KB] (1252)

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Because of the deficiency of uniaxial compression intensity testing and failure law on micro rock-samples，a testing machine for micro sample f 5 mm×10 mm has been designed in order to study fractures extending or breakage mechanism during the rock and coal samples under uniaxial compression. The machine is mostly composed of prestressing equipment，primary loading stress equipment，sample room and hydraulic pressure transmission equipment. There are several advantages compared with typical or ordinary testing machine：(1) During the loading process of rock and coal samples and coupling with three-dimension microscope CT，emergence and development of inner fractures and cracks have been observed. (2) Curves of complete stress-strain which are similar with ordinary curves have been drawn，using size-scale effects coefficient for calculating and obtaining the uniaxial compression intensity in others size of samples. Beyond these curves，four phases of micro samples under compression have been reflected faithfully during the whole testing course. (3) Compared with the former numerical simulation of rock testing，the same and different aspects have been analyzed；and the conclusion is used for deeper interrelated theories. In order to get more applications，in the future the machine¢s each part will be perfected：not only the operational characteristics will be enhanced，but also the loading values will be leveled up，so as to test the higher intensity rock-samples. The elementary testing results are proved that the experimental study is scientific and feasible. The development of this testing machine will improve the investigations on fracture law and the development of rock mechanics to which ordinary and large-scale machines could not implement.

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RESEARCH ON ANCHORAGE OF DAM TOE OF
BAIHETAN HIGH ARCH DAM

GUAN Fuhai1，LIU Yaoru1，YANG Qiang1，XU Jianqiang2，YANG Ruoqiong1

2010, 29 (07): -1332 doi:
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High arch dam toe area is the focus of reinforcement design. In order to study its anchorage，anchorage mechanism of high arch dam toe，based on the deformation reinforcement theory，is farther illuminated. In this mechanism，the unbalance force of a load case is the corresponding minimal reinforcement for stability and unbalanced force direction is the optimal design of anchorage direction. Combined with this idea，the method of unbalanced force calculation and normal condition of anchorage of high arch dam toe area are presented. The mechanism is applied to numerical analysis of anchorage of Baihetan high arch dam toe，and the minimum reinforcement force and the optimal design of anchorage direction are obtained. The reasons of unbalanced force distribution law are analyzed. At the same time，geomechanical model experimental research，under large-scale (250∶1)，is carried out. From loading to failure，the displacement，strain and crack of high arch dam toe are monitored and analyzed；failure relationship between dam toe area and loading process is obtained. The experimental results and the numerical ones consistently show that left bank dam toe area of Baihetan arch dam is more vulnerable than the right ones. The research validates that deformation reinforcement theory provides scientific theoretical basis and practical analyzing method for anchorage of high arch dam toe.

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STUDY OF UNLOADING ROCK MASS DEFORMATION PARAMETERS FOR HIGH ARCH DAM FOUNDATION BASE OF GOUPITAN HYDROPOWER STATION

LI Weishu1，ZHOU Huoming1，CHEN Hua2，LIU Yang1，LING Wei2

2010, 29 (07): -1338 doi:
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[PDF 231 KB] (984)

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After the excavation and formation of high arch dam foundation base of Gupitan hydropower station in Wujiang River，a large amount of ultrasonic wave tests have been carried out on the foundation base. Through these tests with different elevations at different places，the unloading depth is determined according to the comprehensive relationship curve between wave speed and slope distance；and the wave speed distribution pattern and characteristics are also analyzed. In-situ deformation tests are made at 35 points in the unloading zone with conditions of loading path and the maximum pressure similar to that of the arch dam acting on the rock mass. According to dynamic and static comparative tests of the 35 deformation points，the relation curve between unloading rock mass deformation parameters and wave speed is established；and the rock mass deformation parameters in the unloading zone are evaluated based on results of large-scale acoustic tests. The weakening of rock mass deformation parameters in the unloading zone on the high arch dam foundation base is analyzed and studied in combination with the regularity for change of wave speed and deformation parameters before and after excavations. It is shown by experimental study that the foundation base unloading depth is 6 m；the wave speed of the unloading rock mass declines 7.0% on average；and the average deformation modulus reduces from 29.1 GPa to 16.2 GPa，down by 43.6% on average. Finally，the unloading rock mass deformation parameters and the calculating method are put forward.

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STABILITY ANAYSIS OF SURROUNDING ROCK MASS OF WATER-TIGHT OIL STORAGE USING BLOCK THEORY BASED ON STEREO-ANALYTICAL METHOD

ZHANG Zixin1，2，LIAO Yilei1，2

2010, 29 (07): -1347 doi:
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[PDF 281 KB] (1320)

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Based on the modified stereo-analytical method of block theory，a new software is developed，updated from Block V1.0 to Block V2.0. The new version added some strong functions，such as the choosing of discontinuity property and available excavation shape. An application to the stability analysis of the surrounding rock mass of the water-tight oil storage in Jinzhou is presented，considering the action of gravity，water and oil pressures comprehensively. The block identification results show：(1) the roof of the cavern is the most dangerous zone，and joint J1 and J2 are the dominant joints，which should be paid close attention during construction and running periods；(2) underground water greatly increased the sliding probability to a certain extent，however，the oil has a favourable effect on the cavern stability.

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VISCO-ELASTOPLASTIC CONSTITUTIVE MODEL FOR SEDIMENTARY SOFT ROCK AND ITS APPLICATION TO NUMERICAL CALCULATION

YE Guanlin1，ZHANG Feng2，SHENG Jiaren1，WANG Jianhua1

2010, 29 (07): -1354 doi:
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[PDF 559 KB] (1233)

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The sedimentary soft rock is a kind of geomaterial that exhibits the mechanical properties of strain softening，rheology，and influenced by the intermediate principal stress. In order to describe these properties as comprehensively as possible，a new visco-elastoplastic constitutive model is developed. Based on the tij concept and subloading surface，this model uses a state variable r which is a void ratio difference between the over- consolidated and normal consolidated states，and introduces a non-homogenous function as an evolution law for r. Compared to the Cam-clay model，only 4 new parameters are added to the new model，which have explicit physical meanings and can be determined from triaxial tests. A progressive failure of soft rock slope due to heavy rain is taken as background，and soil-water coupled FEM is conducted to investigate the influences of 2 kinds of groundwater table changes on the failure. The shear strain，displacement vector and propagation of the failure among the slope are analyzed carefully to clarify its failure.

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RESEARCH ON CHARACTERISTICS OF ROCK DEFORMATION CAUSED BY EXCAVATION DISDURBANCE BASED ON HOEK-BROWN CRITERION

SHEN Yanjun1，2，XU Guangli1，2，ZHANG Lu1，ZHU Kejun3

2010, 29 (07): -1362 doi:
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[PDF 364 KB] (1560)

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Considering the deterioration effect on rock mass parameters caused by construction disturbance，the disturbance factor D is proposed in the Hoek-Brown empirical criterion(2002 edition)，but it is only a rough qualitative description. The wave velocity drop l obtained from sonic wave testing is employed to optimize the disturbance factor D；and the optimized Hoek-Brown empirical criterion can be used to get the solution to the characteristic formula of rock mass elastoplastic deformation caused by excavation disturbance. Thus，the radius of plastic ring can be represented more accurately. In order to verify the rationality of that theory，various monitoring methods，such as sonic wave testing and displacement monitoring methods，etc.，have been applied and the finite element numerical simulation method is used to compare with the monitoring methods as well. In addition，taking into account the site effect of deformation characteristics induced by excavation disturbance，an empirical formula of deformation and excavation disturbance fitted with different lithologies and excavation methods is put forward. The calculation results of an engineering example indicate that the optimization of disturbance factor D from the Hoek-Brown empirical criterion(2002 edition) is reasonable；and it can calculate the eigenvalue of rock mass elastoplastic deformation caused by excavation disturbance and accurately obtain the radius of plastic ring. Furthermore，the empirical formula of deformation and excavation disturbance obtained by fitting can satisfy different engineering demands with certain rationality. This study can provide a methodological reference for researching the Hoek-Brown empirical criterion and the characteristics of rock mass elastoplastic deformation caused by excavation disturbance in underground caverns.

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HYDRAULIC FAILURE MECHANISM OF KARST TUNNEL SURROUNDING ROCK

WANG Jianxiu1，2，FENG Bo2，ZHANG Xingsheng2，TANG Yiqun1，2，YANG Ping1，2

2010, 29 (07): -1370 doi:
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[PDF 406 KB] (1084)

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According to surrounding rock structure，the hydraulic failure of karst tunnel is divided into the extension of non-transfixion cracks，the extension of transfixion cracks(grouted transfixion cracks)，the rock fall of isolated rock blocks and the collapse of rock wall between tunnel and karst cave. The hydraulic failure mechanisms of non-transfixion cracks and transfixion cracks(grouted transfixion cracks) are analyzed with fracture mechanics method，and the non-transfixion crack is treated as a sheet crack in infinite body. Its extension is calculated with Green and Sneddon¢s solutions，and the transfixion crack is treated as a crack in plate，and its extension is calculated with function of complex variable of Westergaard. The hydraulic failure mechanism of isolated rock blocks is analyzed with stereographic projection and limit equilibrium method，and the calculation formula of limit equilibrium considering water pressure is presented. The hydraulic failure mechanism of rock wall between tunnel and karst cave is analyzed with strength reduction method，and an instance is presented with finite element method. Corresponding control measures are suggested for different failure modes，so as to provide reference to similar projects.

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RESEARCH ON BLASTING STABILITY CONTROL TECHNOLOGY OF LARGE-SPAN HIGHWAY TUNNEL WITH SUPER-SMALL CLEAR SPACING AT HIGHWAY EXPANSION PROJECT

LIN Congmou1，CHEN Libiao2，JIANG Lili3，ZHENG Hongli4

2010, 29 (07): -1378 doi:
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[PDF 405 KB] (1175)

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Based on the uncommon tunnel—Damaoshan tunnel，the stability control technology of tunnel is studied when blasting construction on new-built tunnel，combining with the current study results and codes. According to the modern information construction theory，and the field monitoring technique is used to obtain the blasting vibration velocity and regression analysis result，the critical value of particle vibration velocity of existing tunnel is defined as 20 cm/s，then the blasting parameters are optimized. The final monitoring result indicates that the operation of the railway is not influenced by the construction of tunnels obviously. At the same time，the numerical simulation is employed to get the law of vibration velocity in disturbanced rock and exiting tunnel wall rock variation with time. The largest blasting velocity of rock can be proved to be accordance with the criterion，which validates that this kind of control technique about blasting stabilization is reasonable. Through data analysis，some results are obtained：vibration velocity at tunnel shoulder is that at the bottom 1.19–3.99 times，vibration velocity at tunnel waist is that at bottom 1.10–3.11 times，vibration at head-burst side is that at back side 5–10 times. The research result offers the theoretical and methodological experiences to the similar engineering.

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EXPERIMENTAL RESEARCH ON MECHANO-HYDRO-CHEMICAL COUPLING OF GRANITE WITH SINGLE FRACTURE

SHEN Linfang，FENG Xiating，PAN Pengzhi，ZHOU Hui

2010, 29 (07): -1388 doi:
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[PDF 557 KB] (1410)

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Experiments of granite with single fracture under constant triaxial stress and chemical solution seepage are conducted，and the response mechanisms of single fracture rock to mechanico-hydro-chemical coupled condition are studied. Experimental results show that when triaxial stress and hydraulic stress are applied to the fracture spontaneously，the lateral creep deformation always increases at a constant rate. These phenomena indicate the softening effect is induced by water，which is different from the volume expansion of intact rock. Obvious dissolution between fracture surface mineral and permeant is observed，for that concentrations of Al3+and SiO2 of outlet solution increase with time. Meanwhile，according to the SEM graphs，distinct etch holes can be found at feldspar and quartz surface，and muscovite leaves uncompleted cleavage. Aperture changes with the development of water-rock interaction. Under the acid solution seepage，aperture decreases and then becomes stable. While as for distilled water seepage，aperture increases firstly，and then keeps stable. The cause for such difference is the effect competition between chemical reaction and cutting through of permeability channels. Tests of 3D laser scan of fracture surfaces denote that JRC of after-test fracture are smaller than those before test，and surfaces become smooth. Such results show the preferential dissolution occurs at mineral interface.

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TIME EFFECT AND MAIN INFLUENCE FACTORS OF UNLOADING SPLITTING OF DEEP-SEATED ROCK WITH NONUNIFORMITIES

FAN Pengxian1，2，WANG Mingyang1，QIAN Qihu1

2010, 29 (07): -1396 doi:
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[PDF 255 KB] (1105)

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The splitting of stressed rock in the neighborhood of underground openings is a common phenomenon that is not well explained theoretically up to the present. The stress concentration at nonuniformities is believed to be the crucial one among the factors influencing the tensile failure process under pressure conditions. Based on the model of rock with nonuniformities，three main factors of the splitting fracture of rock，including unloading duration(or deviator strain rate)，scale of nonuniformities and initial geostress，are detailed investigated in order to reveal the mechanism behind the phenomenon of splitting. The results of theoretical analysis show that：(1) The excess tension stress of nonuniformities is affected by deviator strain rate significantly；and it increases nonlinearly as the unloading duration shrinks. (2) There is a nonlinear corresponding relationship between the scale of nonuniformities and the magnitude of deviator strain rate；and higher deviator strain rate tends to excite smaller nonuniformities. (3) If there exist nonuniformities with big scale enough，the maximum excess tension stress is proportional to the initial geostress. Therefore，the possibility of unloading splitting is determined by the relation among the three parameters：initial geostress，stress concentration coefficient and tensile strength. Results of an unloading test，in which the axial stress of hydraulic stressed rock samples is unloaded with different control modes，and data of in-situ core disking observation，are cited to verify the analytical analysis results. The main phenomena and critical stress condition of core disking predicted by the theoretical model coincide well with the results of the cited experiments and in-situ observation data.

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ANISOTROPY OF STRENGTH OF ROCK MASS UNDER COMPLICATED STRESS STATE

LI Hangzhou1，LIAO Hongjian1，2

2010, 29 (07): -1403 doi:
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[PDF 393 KB] (1047)

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Discontinuities are ubiquitous in rock masses. The discontinuities significantly affect the strength of rock masses，which cause the failure of the rock mass along the discontinuities. Based on the analysis of the effect of the intermediate principal stress on the strength of rock mass，a twin shear unified strength theory is illustrated. The unified cohesion and friction angle，which are dependent upon the Lode parameter and the intermediate principal stress parameter b，are established. The stress distribution on the discontinuities in rock mass is investigated. The anisotropic strength criterion of rock mass is proposed. For the specific case，the proposed strength criterion is simplified. The application condition of the criterion is also analyzed. The polyaxial test results of jointed rock mass are used to verify the proposed criterion. The results indicate that the proposed criterion can well predict the strength of the jointed rock mass. The effects of the intermediate principal stress，inclination and azimuth of the discontinuities on the strength of rock mass are also investigated.

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EXPERIMENTAL STUDY OF NON-DARCY WATER FLOW
THROUGH A SINGLE SMOOTH FRACTURE

WANG Yuan1，2，GU Zhigang1，2，NI Xiaodong1，2，LI Dongtian1，2，ZONG Guoqing1，2

2010, 29 (07): -1408 doi:
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[PDF 273 KB] (1459)

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An experimental apparatus is designed for studying the behavior of high velocity non-Darcy water flow through a single fracture. The fracture is constructed by two smooth parallel plates with variable apertures ranging from 0.5 mm to 6 mm. Circle water flow system and high hydraulic gradient are applied. The experiment is carried out and the behavior of non-Darcy water flow with high velocity is studied. A nonlinear relation between velocity of water flow and hydraulic gradient is fitted. Experimental results are compared with Lomize¢s formula and Su¢s formula；and it is found that they are similar when hydraulic gradient is low，but there are big differences when hydraulic gradient is high. Finally，the theoretical analysis of non-Darcy water flow through a single fracture and the related criterion are discussed. The relation between velocity and fracture aperture of non-Darcy water flow is also developed in order to apply conveniently in the engineering.

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SEEPAGE STABILITY ANALYSIS AND DAM-BREAKING MODE OF
TANGJIASHAN BARRIER DAM

HU Xiewen1，LUO Gang1，WANG Junqiao1，LIU Juan1，HU Hengyang2

2010, 29 (07): -1417 doi:
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[PDF 638 KB] (1242)

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Based on accurately obtained data of Tangjiashan barrier dam on geological structure(three-layer structures from top to bottom：gravel soil，blocks and gravels，stratoid cataclastic rocks) and the relevant parameters，using the Visual Modflow，which is a three-dimensional visualization software，seepage field of the dam under four conditions of water levels(710，720，730 and 740 m) of the dammed lake are simulated. According to the results of simulated calculation，each soil layer¢s seepage velocity and seepage gradient are calculated，and the analytical results show that the first and the second layers have the characteristics of coarse particles and high permeability，so the overall performance is of a stable flow，with the characteristics of seepage and stable change of overall gradient，and it will not have turbulent conditions of low-permeability clay，inflexion of seepage gradient and the characteristics of piping. The maximum seepage gradient in gravel soil of the first layer is more than allowed gradient in the transition between the first layer and the third layer，so it will cause sporadic or partial seepage destruction on downstream of barrier dam. And simulated results show that gravel soil of the first layer will experience seepage failure when the water level of dammed lake is more than 726 m. With the uplift of water level，the dam-breaking mode of overall barrier dam is that gravel soil of the first layer will be eroded and washed away by the seepage failure and head erosion，also by the down-cutting caused by overflow. The blocks and gravels of the second layer are gradually washed away and down-cut because the first layer is washed and water velocity increased，but it will not happen overall breaking. The stratoid cataclastic rocks of the third layer will remain stable，and the depth of erosion and down-cutting is the top of the third layer.

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STUDY OF DISTRIBUTING CHARACTERISTICS OF STRESS IN SURROUNDING ROCK MASSES AND IN-SITU STRESS MEASUREMENT FOR DEEPLY BURIED TUNNELS

LUO Chaowen，LI Haibo，LIU Yaqun

2010, 29 (07): -1423 doi:
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[PDF 323 KB] (1338)

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The following preliminary results are obtained based on the study of in-situ stress measurements using hydraulic fracturing(HF) method and distributing characteristics of stress in surrounding rock masses in the region of Panyi Mine：(1) The dominative stress of the tunnel for Gangue adhesive tape machine at elevation －790 m is tectonic stress and the maximum horizontal principal stress is larger than 28.33 MPa. The ratio of saturated uniaxial compressive stress to maximum horizontal principal stress is 5.82，which means that the stress level in this region belongs to high stress are. (2) The plastic zone of surrounding rock to the ratio of maximum horizontal principal stress for the tunnel extends from the periphery to depth；at the same time，the stress of surrounding rock gradually increases and reaches the maximum value at a location of about 2 times of tunnel diameter，then gradually decreases and is finally equal to in-situ stress in some location. (3) The influence range of the floor track tunnel on the stress of surrounding rock of the top tunnel is greater than 6 times of tunnel diameter，which far exceeds the influence range of 3 times of that obtained by traditional elastic mechanics. The above results indicate that the distributing characteristics of stress in surrounding rock masses for deep-buried tunnels are different from that for shallow-buried tunnels，and it can provide references for similar projects.

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STRENGTH REDUCTION METHOD TO STUDY STABILITY OF GOAF OVERLAPPING ROOF BASED ON CATASTROPHE THEORY

ZHAO Yanlin1，2，WU Qihong3，WANG Wenjun1，2，WAN Wen1，2，ZHAO Fujun1，2

2010, 29 (07): -1434 doi:
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[PDF 966 KB] (1348)

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Strength reduction method which is used to study stability of goaf overlapping roof based on catastrophe theory is established. The concepts of safety factor of overlapping roof are proposed. With the reduction of strength parameters，a cusp catastrophe model of vertical displacement of the midpoint of roof and reduction coefficient is built. The mutability of overlapping roof failure process can be reflected when this model is employed as the failure criterion. Taking double cuboid goafs for example，fitting logarithm function between safety factor of roof and thickness to span ratio is drawn. Fitting function shows that safety factor of roof is effected by the thickness to span ratio and span of roof. Using strength reduction method to study stability of multilayer goafs overlapping roof based on catastrophe theory，it is obtained that the upper goaf overlapping roof instability can induce instability evolution of the lower goaf overlapping roof. Studying the stability of multilayer goafs overlapping roofs in No.105 tin orebody of Gaofeng mining area，as result，except for goafs No.1 and No.2，the rest overlapping roofs are stable in the main，whose safety factors are over 1.5. Strength reduction method based on catastrophe theory provides a new research approach for stability analysis of goafs.

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APPLICATION OF EQUIVALENT ROCK MASS TECHNIQUE TO ROCK MASS ENGINEERING

WU Shunchuan1，2，ZHOU Yu1，GAO Lili1，ZHANG Xiaoping3

2010, 29 (07): -1441 doi:
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[PDF 445 KB] (1241)

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On the background of an open-pit rock masses，some rock mechanics laboratory and field tests are implemented. Based on the particle flow theory and PFC3D(particle flow code in 3 dimensions)，equivalent rock mass(ERM) technique is used to construct ERM model，which reflects the distribution feature of the joints and meso-scale fracture effect. A load-unload code is developed by Fish language in PFC3D to study the strength and mechanical effect of the rock mass. Some study results are drawn as follows：(1) Under the condition of uniaxial compression，the axial stress-strain curve of ERM is divided into three stages，which includes elastic deformation，plastic deformation of unsteady fracture and deformation of post-failure. Compared with standard rock samples，compressive strength and elastic modulus of the ERM are significantly decreased. (2) With increase of confining pressure，compressive strength，residual strength and plasticity of ERM are enhanced. (3) The ERM technique efficiently can describe rock mass anisotropy induced by joints distribution. (4) Microcrack in ERM is distributed and extends along strike direction of joints. Therefore rock mass failures are controlled by properties of the dominant joints.

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INFLUENCE OF DIFFERENT THICKNESSES OF MARBLE LAYERS ON TBM EXCAVATION

GONG Qiuming1，SHE Qirui1，WANG Jimin2，HOU Zhesheng3，WU Shiyong2

2010, 29 (07): -1449 doi:
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[PDF 604 KB] (1246)

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The tunnel boring machine(TBM) performance is influenced by the joint spacing in a large extent. TBM penetration rate increases with decreasing joint spacing. But，too small joint spacing makes the tunnel face in stable that is not favorable to TBM excavation. The rock masses along the headrace tunnel of Jinping II hydropower station are composed of marble with different thicknesses of the layers. The thickness varies largely along the tunnel alignment from several centimeters to several meters. The layer surface is the main non-continuous face in these rock masses and the intersection angle between the tunnel axis and the layer is from 60°to 80°. The rock breakage process in the tunnel is influenced by the high in-situ stress and the layer thickness. TBM performance is analyzed in thin layer，thin to middle layers and thick layer marble rock masses under the high in-situ stress from the point view of rock breakage mechanism by TBM，respectively. The influence of the layer thickness on TBM penetration is studied.

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PREDICTION MODEL OF LOCALIZATION DEFORMATION OF
ROCKS CONSIDERING THE THIRD DEVIATIORIC
STRESS INVARIANT

LI Yunzhen1，2，HUANG Tao1，DAI Benlin3，CAI Chen1

2010, 29 (07): -1456 doi:
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[PDF 233 KB] (793)

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Comparing with some other constitutive relations，which only consider the influence of two stress invariants，about the deformation behaviour of rocks，a model is proposed considering the influence of the third deviatoric stress invariant through a similar angle on the basis of Rudnicki and Rice(RR) single yield surface model and Issen two yield surface model. The model is used to obtain the determinant condition of the three types of deformation bands and band angles. The axisymmetric stress state data are chosen of Mogi¢s experiment on Dunham-Dolomite and Haimson¢s on Westly granite as boundary condition to deduce the elastoplastic parameters in the model，and then to predict the band angle of the other stress states. The results are compared with the data of Mogi¢s true trixial test on Dunham-Dolomite，and it is found that the predictions are in reasonable agreement with the experiment data more than the two stress invariants model.

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PREDICTION MODEL OF LOCALIZATION DEFORMATION OF
ROCKS CONSIDERING THE THIRD DEVIATIORIC
STRESS INVARIANT

LI Yunzhen1，2，HUANG Tao1，DAI Benlin3，CAI Chen1

2010, 29 (07): -1456 doi:
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[PDF 233 KB] (700)

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Comparing with some other constitutive relations，which only consider the influence of two stress invariants，about the deformation behaviour of rocks，a model is proposed considering the influence of the third deviatoric stress invariant through a similar angle on the basis of Rudnicki and Rice(RR) single yield surface model and Issen two yield surface model. The model is used to obtain the determinant condition of the three types of deformation bands and band angles. The axisymmetric stress state data are chosen of Mogi¢s experiment on Dunham-Dolomite and Haimson¢s on Westly granite as boundary condition to deduce the elastoplastic parameters in the model，and then to predict the band angle of the other stress states. The results are compared with the data of Mogi¢s true trixial test on Dunham-Dolomite，and it is found that the predictions are in reasonable agreement with the experiment data more than the two stress invariants model.

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REINFORCEMENT STRATEGIES OF CONSTRUCTION IN SHALLOW-HURIED TUNNEL ENTRANCE USING PIPE-ROOFING METHOD IN VALLEY

WANG Shihhui1，2，WANG Cheinlee1，HSIEH Chitai1

2010, 29 (07): -1466 doi:
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[PDF 934 KB] (1435)

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The growth of environmental protection awareness in Taiwan has made it necessary for tunnel engineers to consider altering the natural surroundings as little as possible when undertaking tunnel design and construction in practice. Tunnel projects in Taiwan have progressively evolved into using the method of direct excavation to replace the traditional method of cut and cover excavation when dealing with tunnel entrances. Even when both the geological and topographical conditions are unfavorable，the method of direct excavation is still adopted because it leads to the lowest environmental impact. The applicability of various methods of direct excavation for tunnel entrances is discussed. These methods include the fore-poling method，the pipe roofing method，the plate shield method，and ground improvement method. The site of a twin road tunnel under construction in northern Taiwan is given as an example. Engineering difficulties and landslide failures at the site are encountered during construction；and remediation technologies are adopted and evaluated after each failure. The observations and suggestions provide dependable references for future tunnel projects facing similar problems in Taiwan.

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RESEARCH ON ROCK MASS CONTAINING DISCONTINUOUS JOINTS BY DIRECT SHEAR TEST BASED ON WEAKENING MECHANISM OF ROCK BRIDGE MECHANICAL PROPERTIES

LIU Yuanming1，XIA Caichu2，3

2010, 29 (07): -1472 doi:
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[PDF 222 KB] (1158)

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Based on weakening mechanism for rock bridge mechanical properties，at five different normal stress levels，three different rock mass samples containing discontinuous joints which are tooth-shaped asperities have been studied by laboratory shear test. The tests are conducted with electro-hydraulic servo-controlled shear system. The tests are to study both failure mechanism and strength behavior，displacement behavior of rock mass containing discontinuous joints. At lower angle of tooth-shaped asperities and under lower normal stress，the failure model I is found，which is always in tension failure model. However，at higher angle of tooth-shaped asperities and under higher normal stress，the failure model II is found，which is in first tension but final shear failure. Under the same joint appearance，with the normal stress increasing，both the shear strength and the displacement for peak shear strength raised. However，at the same normal stress，with the joint appearance increasing，the displacement for peak shear strength decreased but the shear strength raised. Moreover，all of cohesion calculated based on Jennings¢ theory is higher than the experimental results. Some of angles of friction calculated based on Jennings¢ theory are more than the experimental ones.

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A THREE-DIMENSIONAL SLOPE STABILITY ANALYSIS PROCEDURE BASED ON MORGENSTERN-PRICE METHOD

CHEN Changfu1，ZHU Jianfeng1，2

2010, 29 (07): -1480 doi:
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In most cases，the slip surface is a 3D surface in practical engineering. Therefore，it is not in accord with the practical condition to study the slope stability by using the traditional 2D analysis method. The Morgenstern-Price limit equilibrium method，which is the most rigorous method of 2D slope stability analysis，is developed and introduced to the 3D slope stability analysis. Through the assumptions similar to Morgenstern-Price method on slice forces，a new approach to three-dimensional slope stability analysis，the three-dimensional limit equilibrium method based on Morgenstern-Price method，is established. Two examples are given to verify the proposed method. Comparing with several other 3D slope stability analysis methods，the proposed method is more reliable and the proposed mechanical model is more rigorous. Furthermore，the proposed calculation formula is simple and easily to be programmed. The proposed 3D slope stability analysis method can be widely used by geotechnical engineers in the design of slopes and treatment of landsides.

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WATERPROOF AND DRAINAGE TECHNOLOGIES FOR LINING OF SUBSEA TUNNEL IN WEATHERED TROUGH

GUO Xiaohong1，2，CHEN Weizhong3，4，CAO Junjie4，LIANG Wei2，YU Hongdan4

2010, 29 (07): -1488 doi:
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[PDF 793 KB] (935)

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Effective measures should be adopted to avoid geologic hazard such as collapse，water gushing and debris flow，when the drill and blast method is used to construct subsea tunnel. In the drill and blast method，the technical difficulty for engineering design and construction is how to ensure the safety of project when the tunnel passes through the fault zone. Combined with the characteristics of surrounding rock in Xiamen subsea tunnel，the grouting reinforcement，waterproof and drainage techniques are studied；and the related design schemes are proposed for tunnel passing through the fault zone with drill and blast method. According to the laboratory triaxial test results，the permeability of highly weathered granite is obtained. And the mechanical parameters of surrounding rock are obtained by back analysis. The distribution of external water pressure on lining of tunnel in weathered trough is obtained by numerical simulation. The achievements obtained in the research will benefit other subsea tunnels in practical engineering.

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RESEARCH ON CONSTITUTIVE MODEL OF MARBLE OF
JINPING HYDROPOWER STATION UNDER LOADING AND
UNLOADING CONDITIONS

LI Hongzhe1，2，3，XIA Caichu1，2，XIAO Weimin1，2

2010, 29 (07): -1495 doi:
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[PDF 280 KB] (1153)

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A series of loading and unloading tests of marble from deep-buried diversion tunnel of Jinping hydropower station are carried out，which reveal that marble specimens have remarkable volumetric dilatancy before failure in both loading and unloading conditions. To describe the law of volumetric deformation of marble in the tests，a new constitutive model is presented based on modifying Weng¢s model[13] of rock mass. Comparison between theoretical and test results indicated that the proposed model can describe the characteristics of marble volumetric deformation well. This model can consider the discrepancy of rock strength under loading and unloading conditions；and it can be used to describe unloading process from uniaxial compression stage；the proposed model is of high applicability.

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ANALYSIS OF ACOUSTIC WAVE FREQUENCY SPECTRUM CHARACTERS OF ROCK MASS UNDER BLASTING DAMAGE BASED ON WAVELET(PACKET) TRANSFORMATION

YAN Changbin1，WANG Guijun1，SHI Shouliang1，XU Guoyuan2

2010, 29 (07): -1502 doi:
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[PDF 221 KB] (1130)

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The blasting damage of rock mass results in the change of energy attenuation and its frequency spectrum，besides influences on the acoustic velocity. In order to make the best of the plentiful information taken by the acoustic signals of rock mass and remedy the shortage of simple acoustic velocity analysis，the research on the rock mass damage under simulative blasting with little charge for ten times by acoustic measurement in the surrounding rock of some underground engineering is carried out. And the acoustic wave frequency spectrum characters are decomposed to be analyzed with the wavelet(packet) transformation methods，in view of the deficiency of Fourier analysis. Research results show that the variety law of rock mass acoustic wave frequency spectrum obtained by wavelet(packet) transformation is more obvious after blasting. The amplitudes and power spectral density of wavelet components with 2–4，2–5 and 2–6 scale are far higher than those with other scales；and these wavelet components are more sensitive to the blasting damage of rock mass. The acoustic signals of frequency corresponding to the energy concentration area and the distribution percentage of most energy turn to lower as the result of the blasting damage of rock mass. The obtained research results will provide an important reference to reveal the internal relations of the blasting damage of rock mass and the acoustic signals frequency spectrum characters.

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INFLUENCE OF STRUCTURAL DAMAGE ON YIELDING CHARACTERISTICS OF EXPANSIVE SOILS

YAO Zhihua1，CHEN Zhenghan1，2，HUANG Xuefeng1，MIAO Qiangqiang1

2010, 29 (07): -1512 doi:
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[PDF 573 KB] (1014)

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By using CT-triaxial apparatus for unsaturated soils，compression tests under confined suction are carried out with remolded expansive soils which are suffered from multi-drying-wetting cycles. The yielding characteristics of expansive soils influenced by structural damage are researched from the viewpoint of meso-scale. The results indicate that，yielding stress would drop off gradually while the level of structural damage increases. Compression index before yielding stress appearing would increase slowly while damage level would increase gradually. Based on the test data，the quantitative equations of structural parameters along with yielding stress and macrovariable are employed for the Barcelona expansive model with structural damage.

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2010, 29 (07): -1513 doi:
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[PDF 100 KB] (699)

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2010, 29 (07): -1514 doi:
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[PDF 102 KB] (662)

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