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2009, 28 (11): -0 doi:
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PREDICTION AND MONITORING ANALYSIS OF IMMERSION EFFECTS OF CHAOZHOU CITY ZONE

CAO Hong1，SUN Zijun1，LI Jun2，FU Nengjiang3

2009, 28 (11): -2166 doi:
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[PDF 424 KB] (1053)

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During the design stage of Chaozhou water supply pivot project，the immersion problem is analyzed and the waterhead distribution is predicted. Groundwater monitoring network has been laid out to monitor the groundwater in the area that may be affected by immersion. Based on the previous numerical analysis results，combined with a more than two-year groundwater monitoring data and field investigation，the immersion is carefully analyzed and evaluated. The result shows that the primary design goal has been basically realized. According to impoundment and surge shaft influence degree of the groundwater monitoring points，the city zone is classified into three typical areas and Chaozhou main city zone is in the area affected both by impoundment and surge shaft. The immersion affected area is within 600–1 000 m behind the dike and the surge shaft works comparatively well.

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STABILITY ANALYSIS AND CONSIDERATIONS OF UNDERGROUND POWERHOUSE CAVERNS GROUP OF JINPING I HYDROPOWER STATION

LI Zhongkui1，ZHOU Zhong2，TANG Xuefeng2，LIAO Chenggang2，HOU Dongqi2，XING Xianglin2，
ZHANG Zhizeng1，LIU Zhonggang1，CHEN Qiuhong1

2009, 28 (11): -2175 doi:
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[PDF 889 KB] (2184)

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A brief introduction is given to the great challenge in the construction of Jinping I hydropower station，which is a key cascade underground hydropower project，located in the Southwest China，at the Yalong River. The challenge is caused by the following features. The project is very huge and the underground powerhouse system is very complicated，as well as the very high geostress and the complex geological conditions，including 3 large-scale faults and multiple sets of joints existing in the surrounding rock mass with poor quality combination. A detailed description is carried out to the extremely large deformations which is far beyond the deformation of other underground powerhouses with the same range of scale，and the time-related features of the deformation，the severe cracks of linings，the damaged zones develop continually，the over-loading of the rock- bolts and anchorages，during the excavation of the underground powerhouse caverns. All these phenomena happen frequently. Then，a preliminary analysis of those particular situations is given from the point of view of the relation of high stress level and the rheological feature of the rock mass. Finally，the feasibilities of several countermeasures are discussed，such as gradual support method，hierarchical controlling to the initial pre-stress of anchors，damage-zone consolidation and strengthening by the combination of bolting and grouting.

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DEVELOPMENT OF A DOUBLE LINKAGE TRIAXIAL TESTING MACHINE FOR HYDRO-MECHANICAL
COUPLING IN SOFT ROCK

CHEN Weizhong1，YU Hongdan1，WANG Xiaoquan2，JIA Shanpo3，HAO Qingze4，HUANG Sheng1

2009, 28 (11): -2183 doi:
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[PDF 453 KB] (1131)

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In order to study the long term mechanical properties，the double-linkage triaxial testing machine for hydro-mechanical coupling in soft rock is developed. This machine is particularly applicable to study the rheological characteristics of soft rock and hard soil under various stress conditions. Using the technology of servo-controlled，ball screw and hydraulic pressure，this machine can automatically stabilize voltage and record stress-strain variation curve and temperature duration curve. In addition to the function of ordinary triaxial device，because of the unique design form of this machine，it not only can implement the mechanical tests simultaneously of two samples with same axial pressure，different confining pressures and same water pressure but also execute confining pressure control，pore water pressure control and its survey，etc.. The service condition shows that it is a convenient machine with complete functions，simple structure，good stability and high precision.

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MATERIAL FORCE METHOD FOR SIMULATING SECONDARY STRUCTURES IN ROCK MASSES AND ITS FINITE ELEMENT IMPLEMENTATION AND APPLICATION

BAO Jinqing，YANG Qiang，LIU Yaoru

2009, 28 (11): -2192 doi:
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[PDF 493 KB] (847)

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Material force method for simulating secondary structures in rock mass is innovated based on composite material mechanics considering the disadvantages of existing equivalent methods and discrete methods. In this method，rock is regarded as matrix，and secondary structures are regarded as inclusions. The mechanical effects of secondary structures are embodied in material forces induced by eigen strain. Based on the essence of analysis and calculation of elastoplastic mechanics，material force method is planted into elastoplastic finite element method with the adoption of a dual-mesh system for quadrature. Compared with equivalent methods，material force method takes both the difference of deformation properties and the difference of strength properties between rock and secondary structures into consideration. Compared with discrete methods，the complication of pre-processor is reduced at great scale because its sub-meshes for quadrature are completely independent of the finite element meshes. In addition，calculating the material force induced by eigen strain step by step is the same essence of material force method and elastoplastic FEM. Therefore，the extra cost caused by material force method is minimized while keeping total degrees of freedom unaltered. The validity and effectiveness of material force method are shown by two examples.

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METHOD FOR CALCULATING SETTLEMENT OF RIGID-PILE COMPOSITE FOUNDATION

YANG Guanghua1，2，SU Bukun2，3，QIAO Youliang1

2009, 28 (11): -2200 doi:
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[PDF 257 KB] (1636)

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Based on undisturbed soil tangent modulus method，a new practical settlement calculation method for rigid- pile composite foundation is proposed. The load-settlement curve of soil under foundation and the load-settlement curve of rigid-pile are obtained by the undisturbed soil tangent modulus method. Considering that the settlement of pile and soil is equal when they support the foundation jointly，the load-settlement curve of the rigid-pile composite foundation is obtained based on the load-settlement curve of soil and the load-settlement curve of rigid-pile，then the settlement of rigid-pile composite foundation can be gotten from the load-settlement curve. For the composite foundation with loading test，the settlement of rigid-pile composite foundation can be calculated by the hyperbola tangent modulus equation which is put forward by directly using the test curve. The practical examples prove that the new method has more precision for settlement calculation.

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STABILITY ANALYSIS AND TREATMENT OF GUANGHUI OIL DEPOT SLOPE IN SHENZHEN

QIU Jianjin，WEN Jianpeng，GAO Wei

2009, 28 (11): -2207 doi:
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[PDF 316 KB] (979)

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A serious landslide occurred in a slope in Shenzhen due to the continuous rainstorms. The landslide generation mechanism is studied and the treatment scheme is discussed accordingly. Based on the investigation information，the slip surface is found in the contact interface between highly and medium- decomposed marble. The contact materials have become saturated due to rainwater infiltration. And most cohesive particles are washed away by the infiltrated rainwater flow. The serious lost of cohesion，thereby，has weakened strength of the entire slope body and caused a landslide. The numerical model is established for back analysis according to the slope characteristics and the compution values of strength parameters have also confirmed the cohesion reduction due to rainwater infiltration. In addition，discussions are conducted on the influence from different contact interface angles to evaluate the slope stability. The correlation between the contact interface angle and the calculated factor of safety do not tend to be monotonous，which would be an important factor affecting the slope stability. The slide-resistant piles with anchors are applied as the new reinforcement design to prevent the slope failure in consideration of the importance of oil tanks and power transmission tower adjacent to the slope. The information monitored after several heavy rainstorms shows that the slope deformation has been well controlled. It is approved that stability of slope has been improved and the landslide is well treated. Some experiences from this project can be referred for slopes stability analysis and treatment design under similar rainstorm conditions.

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ELASTIC CALCULATION MODEL FOR DYNAMIC ADDITIONAL STRESSES IN LAYERED SUBGRADE UNDER TRAFFIC LOAD

TANG Liansheng，LIN Peiyuan，WU Ke，XU Tong，YAN Bo

2009, 28 (11): -2214 doi:
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[PDF 203 KB] (1274)

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In light of the stratification of the subgrade and pavement system，evaluation of calculation model for dynamic additional stresses under cyclic dynamic loads is concerned by the theory of elastic layered system. On the assumption that layers of the subgrade and pavement system are elastic，stresses and displacements in the control equations of elastic dynamics are transformed to state vector under modal coordinate，and time factor is separated and eliminated. Then linear equations set with variable of integration are derived from dynamics partial differential equations through Laplace transform，and the transfer matrix for layered subgrade system in the transform domain is achieved by using matrix method. Boundary conditions of dynamic loads imposed on pavement are considered to establish the dynamic additional stresses quantification model for layered road system. Numerical analysis is applied by using Matlab program. Results indicate that errors generated by the suggested model，compared with measured value，are less than 12% in the pavement layers and 35% in the subgrade layers. However，the suggested model reveals that the distribution characteristics of dynamic additional stresses reasonably in the subgrade-pavement system and is significant to practice.

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TEST RESEARCH ON TYPICAL MECHANICAL CHARACTERISTICS
OF SOFT CLAY UNDER LATERAL UNLOADING CONDITION

ZHOU Qiujuan1，2，CHEN Xiaoping1

2009, 28 (11): -2221 doi:
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[PDF 238 KB] (990)

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The typical mechanical characteristics in deformation，strength and creep under lateral unloading condition of soft clay are investigated by laboratory triaxial tests. The specimens are black gray silty soft clay，which are taken from Pearl River Delta sediments. The results pointed that the stress-strain relationship shows the phenomenon of strain hardening，and can be normalized by average stress. The effective stress strength is lower than the total stress strength because minus pore water pressure is produced under the condition of lateral unloading，which is opposite to the stress law under the axial-loading condition. The initial unloading modulus under lateral unloading condition is smaller than that under the axial-loading condition，and there is a linear relationship with the average consolidation pressures. The unloading deformation modulus can be expressed as the tangent modulus at any time；and it can be obtained through the test results. Creep test shows that the creep deformation under lateral unloading condition is more significant than that under axial-loading condition. Even if the deviator stress is small，the creep deformation also occupied a large proportion of the total deformation. The logarithm of the strain rate decreases linearly with the increase of the logarithm of time. The development of the strain rate can be estimated at any loading condition from the linear experience formula considering the effect of shear stress on initial strain rate.

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EXPERIMENTAL RESEARCH ON SATURATED MUCKY FOUNDATION TREATMENT WITH WELL-POINT DEWATERING COMBINED WITH DYNAMIC COMPACTION METHOD

LIU Jia1，LUO Yan1，2，ZHANG Gongxin1，DONG Zhiliang1，WANG Youyuan1

2009, 28 (11): -2227 doi:
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[PDF 248 KB] (1220)

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Aiming at the insufficiency of traditional dynamic compaction method to saturated mucky with a high groundwater level，a new static-dynamic drainage consolidation technique，well-point dewatering combined with dynamic compaction method(WDDC) is developed. WDDC has been applied to Guangzhou Nansha harbor grain and universal terminal project soft foundation improvement test area research project where the in-situ monitoring (groundwater level，pore water pressure and settlement) and geotechnical laboratory tests are conducted to investigate the mechanism and qualification of WDDC. The ground treatment effect is confirmed by static cone penetration test，vane shear test，standard penetration test and static loading test. The specific penetration resistance can increase 200 to 300 kPa while the standard penetration test can be added 2 blows. The bearing capacity of foundation can reach 130 kPa. WDDC is an efficient soft foundation treatment method and the tests provide a new way for future industrial applications.

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EFFECT OF STRESS PATH ON SURROUNDING ROCK PRESSURE OF SUPER LARGE-SECTION TUNNEL

YAN Zongxue1，2，FANG Yingguang1，LIU Tingjin1

2009, 28 (11): -2234 doi:
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[PDF 339 KB] (1013)

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The construction of the situation of four-lane tunnel is introduced，and then its developments of design and construction at present are analyzed. Supported by Longtoushan bidirectional expressway tunnel with 8 lanes in Guangzhou，the effect of stress path of rock pressure on large-section tunnel is fully studied and discussed by making use of site measured data and numerical results of rock load with different excavations；meanwhile，the range of rock loose area of large-section tunnel with 4 lanes is verified. The load effect-coefficient of guide hole is modified by the coefficient of . After that，the results calculated by the formula compared with that calculated by M. M. Promojiyfakonov Theory，design specifications of highway tunnel and the formula proposed by H. F. QU，a new formula is proposed to calculate the process load of large section tunnel.

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EFFECT ANALYSIS OF PREVENTING SEEPAGE ENGINEERING IN SHIJIAO SEGMENT OF NORTH RIVER LEVEE

ZHANG Ting1，2，CAO Hong3，ZHAN Jiemin1，ZHOU Hongxing3

2009, 28 (11): -2241 doi:
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[PDF 563 KB] (886)

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Because the foundation of Shijiao segment of North River Levee is made up of the strong permeable layers, the dangers happened many times during historical flood periods. In order to raising the ability of preventing flood，many reinforcement measures are adopted，including constructing the high pressure-injected cut off walls，counterweight filling，building filtration and drainage structure，relief wells，etc. After the construction，the Shijiao segment stands the tests of floods many times. But the parts of effect of the measurements are arguable. The article is just right about the evaluation of these measurds by analyzing the data of field observations and simulating the seepage field，and a conclusion is drawn that the counterweight filling engineering is effective for this segment. The safety of preventing seepage is appraised. The conclusion is worthy of reference for the designers and managers.

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DESIGN AND MONITORING OF STEEL SHEET PILE COFFERDAMS OF LIEDE BRIDGE IN GUANGZHOU

PAN Hong1，CAO Hong1，YIN Yiming2

2009, 28 (11): -2248 doi:
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[PDF 241 KB] (1313)

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The cofferdams of Liede bridge pier are retained by steel sheet pile and steel struts structure. Steel pipe piles are used to support the bottom of steel sheet pile to avoid excessive bottom displacement and cofferdams unstability due to less embedment length of steel sheet pile cofferdams. The method to ensure safety of cofferdams not only assists the achieving of the project successfully，but also offers the experience for the application of steel sheet pile on the similar geologic conditions. To find out excessive displacement of bottom of cofferdams，relative displacement of steel sheet piles locating two ends of steel struts is monitored. Technique of design and monitoring is effective.

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TEST AND THEORETICAL RESEARCH ON PERMEABILITY CHARACTERISTICS OF SHEAR FRACTURE IN ROCK MASS

XU Lihua1，2，XIE Ni1，2

2009, 28 (11): -2257 doi:
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[PDF 309 KB] (1059)

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Under the triaxial stress state，a shear fracture of the diabase samples from Danjiangkou reservoir is obtained by shear failure. Permeability tests under different confining pressures and fracture water pressures(i.e. permeability pressure gradients) are carried out to study the permeability characteristics of the shear fracture. The test results show that overwhelming majority of the rock samples produces a single running-through fracture after shear failure，of which the permeability coefficient decreases with the increase of net confining pressure，following the law of exponential function. The effect of axial strain on the permeability coefficient of rock samples is relatively weak，while the circumferential strain has strong influence on it，as well as the fracture water pressure. The permeability coefficient of fracture increases with the increase of fracture water pressure while the net confining pressure is the same，which is mainly for the additional compressive deformation of the rock matrix caused by the comparatively big fracture water pressure that leads to the widening of fracture aperture. Based on test data，theoretical analysis and the displacement model of fracture and rock under three-dimensional stress condition，a formula for permeability calculating is obtained with the effect of fracture water pressure taken into consideration. The formula corresponds with the changing trend of permeability coefficient under different confining pressures and fracture water pressures fairly well；and all the parameters can be obtained by triaxial compression test simply. The calculated and measured values of permeability coefficient of fracture match with well each other.

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TEST STUDY OF DEFORMATION AND DAMAGE MECHANISM OF HORSESHOE-SHAPED TUNNEL CROSSING GROUND FISSURE WITH 40°

PENG Jianbing1，2，HU Zhiping3，MEN Yuming1，2，JI Yongshang1，ZHAO Zhenrong3

2009, 28 (11): -2265 doi:
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[PDF 332 KB] (932)

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Based on the engineering background of Xi¢an metro tunnel and the geological environment of Xi¢an ground fissure，the physical modeling experiment for horseshoe-shaped tunnel lining structure crossing the ground fissure with 40° is designed according to the similarity theory. The strains of concrete，longitudinal and circumferential reinforced bars，the peripheral soil pressure，convergence displacement of lining structure model，the soil deformation on the top of model and other macroscopical phenomena of deformation and damage are studied. It is shown that the deformation and damage style of monolithic horseshoe-shaped tunnel lining structure crossing the ground fissure with 40° is asymmetric with distortion，bending and shearing. The concrete circumferential crack range is 0.83D(D = 1.80 m) in the hanging side region，and 1.11D in the lying side region. The concrete longitudinal crack range is 1.11D in the hanging side region，and(1.94–2.22)D in the lying side region. The damage degree of structure in the lying side region is more serious than that in the hanging side region. The segmentation of lining structure shoud be used to fit the distortion，bending and shearing in the horseshoe-shaped tunnel crossing the ground fissure with 40°. Antitorque means should be used in the structure design，and the enlargered cross-section and high-performace concrete should be used to resist the shearing deformation.

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IMPROVED METHOD FOR CALCULATING NONLINEAR SETTLEMENTS OF STRIP FOUNDATION

CAO Wengui，TIAN Xiaojuan，LIU Haitao，ZHANG Yongjie

2009, 28 (11): -2272 doi:
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[PDF 201 KB] (1029)

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According to the variation characteristics of deformation parameters caused by the interstitial compressibility of foundation soils，the nonlinear settlement calculation method of strip foundation is improved. Through further studying the mechanism about the effect of additional stress and stress history on foundation soil modulus，the analytical models that reflect the mechanical deformation parameters of foundation soils which change with additional stress and stress history are established. Then，a new computational method for nonlinear settlement of strip foundation is put forward based on the traditional layer-wise summation method for calculating foundation settlement，in which the nonlinear characteristic of ground settlement calculation and an idea for stepwise loading are incorporated. Consequently，this method not only reflects the characteristics in which the deformation parameters of foundation soils change with additional loads，but also the effect of different soil moduli induced by different initial stress levels or different stress histories on foundation settlement computation. Moreover，the using of the compression test curves in foundation settlement calculation is avoided efficiently. Finally，by comparing the computation and analysis of an engineering example with actually measured and calculated settlements and results by other methods，it is shown that the proposed method is reasonable and feasible.

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EXPERIMENTAL ANALYSIS OF INFLUENCE OF CREEP ON PERMEABILITY OF GAS-BERING COAL

XU Jiang1，PENG Shoujian1，TAO Yunqi1，2，YANG Hongwei1

2009, 28 (11): -2279 doi:
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[PDF 281 KB] (1181)

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Taking briquette made from raw coal as an object of study，which is from Shihao mine of Songzao Gas and Electric Company in Chongqing，the method and steps of triaxial test of creep and seepage for coal specimens containing gas are designed. By means of experimental equipments of coal seepage，under different temperatures and effective stress situations，the seepage test before and after coal creep are performed and a large number of test data are obtained；the effect law of creep on coal permeability is investigated based on the experimental results. The results show that，with the same temperature and average effective stress，permeability decreases 38.7% to 25.2% after the creep of coal sample；under the triaxial stresses condition，the higher the temperature and the greater the average effective stress are，the lower the coal gas permeability tends to be；meanwhile，the mechanism of their effects of the two factors on permeability has been discussed；the permeability loss caused by creep can not be partly recoveried；with a certain temperature，the permeability of damage and effective stresses conforms to the linear relationship；the permeability of damage increases with an increase in effective stress，and the higher the temperature is，the greater the rate of increase tends to be；with different temperatures and effective stress coupling，the influence of creep on coal permeability is different. The results have a reference value for further exploring the law of gas seepage in coal.

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STUDY OF DEFORMATION AND FAILURE LAWS OF DEEP ROADWAY AND COUNTERMEASURES IN JINING COAL MINE NO.2

YANG Jun1，2，SUN Xiaoming1，2，WANG Shuren3

2009, 28 (11): -2285 doi:
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[PDF 361 KB] (1020)

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With the deterioration of geological environment，serious disasters increase in deep mining，and many failure phenomena occur in the roadway support，such as caving，floor heave，roof crush and so on. Taking roadway 93up06 in the 9th mining area in Jining coal mine No.2 for example，numerical simulation is used to represent the process of deformation and failure；and four conditions including roof crush，floor heave，axial wedge failure and caving along the structural planes are analyzed. Based on these failure characteristics，an optimized roadway support design is provided. The practice shows that the floor heave can be controlled effectively by changing the cross-section of the roadway，digging out the mudstone in the bottom and using bolts in floor；and then the roof crush and caving can be controlled effectively by modulating the support parameters.

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GEOSTRESS CHARACTERISTIC AND SIMULATION EXPERIMENT OF ROCKBURST OF A DEEP-BURIED TUNNEL IN GAOLIGONG
MOUNTAIN

ZHANG Yongshuang1，XIONG Tanyu1，DU Yuben2，LI Dejian3，GUO Qiliang4，DENG Hongke2，
ZHANG Chunshan1

2009, 28 (11): -2294 doi:
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[PDF 575 KB] (1198)

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Taking a deep-buried tunnel in Gaoligong mountain in Southwest China where the geological action is most complex for example，on the basis of tunnel engineering geological condition analysis，the true triaxial compression tests have been performed on granophyre samples because rockburst most probably occurs. According to the in-situ geostress data，the triaxial stress values and loading or unloading styles of rockburst experiment are determined under different working conditions. The experimental results reveal that both unloading and loading-unloading styles can lead to rockburst，but the rockburst intensity of the latter is higher than that of the former，which indicates that the geostress centralization caused by secondary stress distribution has important influence on the rockburst. The process of rockburst usually has a character of gradual rupture，showing that debris flaked off from the sample surface at first，sometimes accompanying with crack propagation，and the block shooting occurs finally. Most test samples show obviously lagging，which means that rockburst always retards after a period of time when loading or unloading. But the rockburst process only lasts for very short time(about 1 s)，showing obvious instantaneous character. The sound radiation monitoring data show that the granophyre samples have extensive sound radiation under outer loading process，which can be a useful factor for rockbust prediction. All above simulation test results and relevant realizations have important significance for deep-buried tunnel construction in the orogen with complicated geological condition.

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IN-SITU TEST OF FRACTURED ROCK MASS WITH HIGH PRESSURE SEEPAGE IN DAM FOUNDATION

ZHAO Haibin1，2，JIAN Bo2，WANG Sijing1，JIANG Zhongming3

2009, 28 (11): -2300 doi:
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[PDF 296 KB] (886)

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To acquire the seepage characteristics of fractured rock mass under the dam foundation of Xiangjiaba hydropower station，high pressure seepage test system and experimental method are researched based on spatial distribution of fractured rock mass. An in-situ high pressure seepage test method for the seepage of dam foundation fractured rock mass is proposed. The focus of this study is that the in-situ seepage deformation is researched by method of comparative analysis of water quality and video in measured borehole. Basic criterion is put forward to determine critical hydraulic gradient. Study results indicate that the critical hydraulic gradient obtained from in-situ seepage test is more reasonable than that of indoor test because in-situ high pressure seepage test method can reflect the actual environment state of fractured rock mass better.

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TEST STUDY OF INFLUENCE OF BRINE ON TENSILE STRENGTH OF MUDDY INTERCALATION

SHI Xilin1，LI Yinping1，YANG Chunhe1，2，QU Dan¢an2，3

2009, 28 (11): -2308 doi:
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[PDF 446 KB] (966)

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The existence of indissolvable muddy intercalation leads to many adverse effects for building salt cavern storages by solution mining. It is an urgent technical problem that how to forecast and control the collapse of indissolvable intercalation. Taking the problem as research background，the laws of tensile strength weakening of intercalation samples soaked in different brine concentrations are studied. The test results show that the lower of brine concentration is or the longer of soaked time is，the more obvious the weakening degree will be；the two factors，namely solution of salt and water-uptake soften of clay mineral，promote each other during weakening process. The test results also show that the weakening laws are not the same among samples with different salt content rates. Soaked in brine whose concentration is close to field brine concentration，the tensile strength of muddy intercalation samples with low salt content rate are weakened lightly and slowly；the samples with middle salt content rates are weakened obviously when soaked in middle concentration brine，and the solution of salt grains and water-uptake of clay mineral play a controlling role in weakening of intercalation；soaked in unsaturated brine，the samples with high salt content rate are weakened quickly，and the primary reason is the damage of framework caused by solution of salt grains.

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A MESO-MECHANICAL COUPLING CONSTITUTIVE MODEL OF DAMAGE AND PERMEABILITY IN ROCK-LIKE MATERIALS UNDER TRIAXIAL COMPRESSION

CAO Linwei1，PENG Xianghe1，YANG Chunhe2，REN Zhongjun3

2009, 28 (11): -2319 doi:
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[PDF 527 KB] (1183)

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Microcracks and microvoids are the main microdefects in rock-like materials. When water infiltrates into microcracks，an additional opening stress will be caused on the surface of microcrack. Based on superposition principle，the response characteristics of these rock-like materials which need to consider the water pressure in microcracks under triaxial compression are separated. Considering the deformation，extension and kink of elliptical microcracks in infinite deep buried rock under the condition far field 3D compressive stress，the additional flexibility tensor caused by single closure elliptical microcracks and kink microcracks on any space orientation in a RVE(representative volume element) is obtained. With the assumption that the permeability of the RVE is mainly up to the variation of kink microcrack extension on normal direction under triaxial compression，and making use of the Darcy¢s law and cubic law of laminar flow，the expression of additional permeability tensor of single kink microcrack is derived. Considering the effect of microcrack system on the deformation and permeability of RVE by Taylor¢s scheme，a 3D meso-mechanical coupling constitutive model of damage and permeability in rock-like materials under triaxial compression is obtained by probability density function. The numerical calculation shows that the calculations of this model agrees well with that of test.

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STUDY OF CONTROL CAVING METHODS AND REASONABLE HANGING ROOF LENGTH ON HARD ROOF

WANG Kai1，KANG Tianhe1，LI Haitao1，2，HAN Wenmei1，2

2009, 28 (11): -2327 doi:
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[PDF 222 KB] (1164)

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Based on the characteristic of large primary bestraddle distance，long periodic fracture hanging roof and serious threaten to mine safety in hard roof long working face，three control caving methods of the primary fracture and the reasonable hanging roof length of periodic fracture are studied systematically. Three caving methods controlled by blast such as cycle shallow kerve，middle kerve and tip kerve are used to shorten the primary fracture distance of hard roof working face，of which the kerve depth and blasting quantities are analyzed and contrasted by establishing mechanical model of rock embedded beam at both ends. The results show that side kerve is the least，middle kerve is followed and cycle shallow kerve is the largest on the part of blasting quantities. By establishing and analyzing the model of cantilever rock beam，the reasonable overhanging length and face support strength are ascertained on the basis of designed resistance of face support. Additionally，the relation between overlying strata load and the working face controlling roof distance is deduced. This study has a successful application to working face 15102 of Qiling mine in Jincheng；and it can provide theoretical support and application guidance to control caving in hard roof under the corresponding conditions.

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MODEL TEST STUDY OF DEEP-HOLE INDUCED CAVING IN MINING ENVIRONMENT REGENERATION

ZHOU Keping1，2，XIA Ming1，2，XIAO Xiong1，2，LIU Zezhou1，2，DENG Huanyu1，2，LEI Tao1，2

2009, 28 (11): -2335 doi:
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[PDF 446 KB] (837)

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Based on the prototype of the Kalatongke Copper-nickel Mine in Chian¢s Xinjiang Autonomous Region，the geological mechanics modeling test is made to deeply analyze the artificial roof，upper and lower surrounding rock evolution rules of mechanical induced by deep-hole induced caving excavation. The model test in the simulation test system of rocks excavation under bidirectional loading is carried out. The process of mining environment regeneration with deep-hole induced caving and filling in 8 excavation steps is simulated. The test results show that：(1) when #1 and #2 drilling chamber and under drilling driftway are excavated，the stress and deformation of upper and lower surrounding rocks increase slowly，but the stress of middle part of artificial roof gradually decreases，it is in tension. When the V-shaped trench are excavated，the stresses of upper and lower surrounding rock increase quickly. The stress of upper surrounding rocks bottom，lower surrounding rocks bottom and left part of artificial roof reaches 2.2，2.14 and 2.53 times of the in-situ stress，respectively. Stress concentrates in these parts；(2) After the final excavation，the maximum subsidence of upper and lower surrounding rocks and artificial roof reaches 6.5，2.8 and 8.6 cm respectively，which can meet the requirements of mine safety. The upper surrounding rock has the phenomenon of whole deformation；(3) The 9 m thickness of artificial roof does not break during the whole model test，it achieves the mining environment regeneration，and ensures the safety and stability of the whole test stope.

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STUDY OF IN-SITU DATA OF PILE-SUPPORTED EMBANKMENT WITH PILE PARTIALLY PENETRATED IN SOFT SOILS

XU Zhengzhong1，2，CHEN Renpeng1，2，CHEN Yunmin1，2

2009, 28 (11): -2341 doi:
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[PDF 205 KB] (1016)

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Taking Shen-Su-Zhe-Wan(SJZA) highway as engineering background，in-situ study of pile-supported embankment with pile partially penetrated in soft soils is carried out. Soil pressure acting on the pile splint and soil surfaces，settlements of embankment and subjacent bed are monitored in two tubular pile sections during and after land filling. The results are compared with those in-situ data when pile penetrates soft soils. It can be found that the load share ratio decreases as the pile spacing increases. The measured load-bearing ratios are 61.4%–75.5% when pile partially penetrates soft soils，which are smaller than those measured when pile is penetrated in soft soils. Both soil arching heights are 1.0–1.4 times as large as the clear pile spacing. The measured differential settlements when pile is partially penetrated in soft soils are larger than those measured when pile penetrates soft soils. The settlements of embankment after land filling make up about 30.0% in total settlement. The settlements of subjacent bed make up about 60.0% in total settlement. Applicability of each method is evaluated by comparing in-situ test results and computing results of four theoretical methods.

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PERMEABILITY CHARACTERISTICS OF ROCK AND SOIL AGGREGATE OF BACKFILLING OPEN-PIT AND PARTICLE ELEMENT NUMERICAL ANALYSIS

GAO Qian1，LIU Zenghui1，2，LI Xin1，LI Junhua3

2009, 28 (11): -2348 doi:
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Combining with the backfilling(RSA) engineering in stope III of Sijiaying open-pit to underground iron mining of Hebei Iron and Steel Group Mining Co.，Ltd.，the permeability of rock and soil aggregate(RSA) is studied systematically by laboratory test，in-situ experiment and numerical simulation. The results show that there is an approximation linear relationship between the permeability coefficient of RSA and its non-uniform degree，and the permeability coefficient of RSA is directly proportional to the void ratio. The permeability of RSA can be reduced effectively by controlling the gradation of particle size of waste rock backfilled and reducing the average particle size and non-uniformity reasonably. The influence order to the seepage discharge of RSA is determined by particle element numerical orthogonal tests. The relationship formulas of the effects of four factors(thickness of back-packing，head pressure，porosity，particle diameter) on the seepage are obtained by quadratic stepwise regression analysis，and it can provide a calculation tool for impermeability of RSA.

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STUDY OF STABILITY OF REMNANT MOUNTAIN BODY IN BACK SCARP OF TANGJIASHAN LANDSLIDE AFTER “5.12” WENCHUAN EARTHQUAKE

HU Xiewen1，2，LUO Gang1，Huang Runqiu2，ZHENG Yong3，LU Xiaoping1，WANG Xuerui1，CHEN Shiyong4，SHI Yubing4

2009, 28 (11): -2359 doi:
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Based on the field geological investigations of remnant slope as well as the distribution，scale and penetration depth of crack in slope surface，combined with the mechanism of Tangjiashan high-speed landslide，it is presumed there is still the possibility of that the large-scale landslide except for the sprinkling rockfall occurs on the surface of remnant mountain body. The large-scale landslide failure mode is：tension cracks of slope crest penetrate through bedrock，bedding landslides take place on the middle slope and shear oblique layer on the bottom，and the characteristics can be expressed with tension-sliding-shearing model. According to the failure mode，considering different conditions of natural，continuous rainstorm as well as earthquake，the stability calculation and analysis of remnant mountain body by two-dimensional and three-dimensional broken line potential sliding surfaces are carried out. The results show that the remnant mountain body is stable wholly，but the shallow surface stability is unfavorable，and the control measures to remnant mountain body are proposed.

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STUDY OF FORMATION CONDITIONS AND TOSS MOTION PROGRAM OF HIGH LANDSLIDES INDUCED BY EARTHQUAKE

WANG Yunsheng，XU Hongbiao，LUO Yonghong，WU Junfeng

2009, 28 (11): -2368 doi:
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Based on structural features and earthquake-induced slope response，the genetic mechanism of the typical earthquake high slope landslides can be concluded as follows：the structural plane of rock mass cut by cranny is apart from the lower limit of strong unloading zones，and is made run through to lose the bonding force with underneath rock mess by upper throwing force of P-wave and horizontal shear force of S-wave；the surface wave with huge acceleration(more than 2 g normally) arrives last and is enlarged by terrain，by which the upper surface layer of the slope is thrown out approximately horizontally or decumbent；and the earthquake-induced high slope landslide is formed.

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ANALYSIS OF LANDSLIDE INDUCED BY WENCHUAN EARTHQUAKE BY STRONG MOTION RECORDS

WANG Xiuying1，NIE Gaozhong2，WANG Dengwei3

2009, 28 (11): -2376 doi:
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Based on the Newmark analysis，a method is introduced to deduce critical acceleration with the data of strong motion records and landslides. With this method，critical accelerations are calculated with the data of earthquake-induced landslide and strong motion records obtained from 3 stations in Lixian County during Wenchuan earthquake. The estimated critical accelerations of Shaba，Taoping and Muka stations are 40，50 and 70 gal respectively. The results are in accord with the vulnerable geologic situations in the earthquake-hit area. The critical acceleration can be regarded as a quantitative criterion for judging the failure strain of a slope under earthquake excitations by ground motion parameters. It provides a new way to study earthquake-induced landslides with quantitative method. With the recommended method and the large number of strong motion records obtained from Wenchuan earthquake，critical accelerations in the Longmenshan region can be estimated；and it can provide quantitative reference information for the reconstruction work such as the engineering application，earthquake-induced landslides forecasting and localization in the earthquake-hit region. The research method and its results are helpful to promote the quantitative research on earthquake-induced landslides in China.

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2009, 28 (11): -2377 doi:
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2009, 28 (11): -2378 doi:
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2009, 28 (11): -2379 doi:
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