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2010, 29 (03): -0 doi:
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ROCK MECHANICS COMPREHENSIVE STUDY OF BEARING CAPACITY CHARACTERISTICS OF TUNNEL ANCHORAGE FOR SUPER-LARGE SPAN SUSPENSION BRIDGE

WU Aiqing1，PENG Yuancheng2，HUANG Zhengjia1，ZHU Jiebing1

2010, 29 (03): -441 doi:
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According to bearing capacity problem of a tunnel anchorage at Yichang side for Siduhe super-span suspension bridge，to study systematically the deformation and failure mechanism，the rheological characteristics and overloading capacities of the tunnel anchorage and its surrounding rock mass by a comprehensive rock mechanics research method are proposed. The approach included in the research consists of in-situ geological investigation，rock mechanical tests in laboratory and in the field，the 1∶12 anchorage physical model test with the same rock mass at site of the actual schemed tunnel anchorage，and the numerical simulations related to physical model test and the engineering analysis of bearing capacity evaluations of the actual tunnel anchorage. Several conclusions have been drawn. Firstly，the mechanical properties and the relevant parameters of the surrounding rock mass are obtained comprehensively by rock mechanical tests；and the physical model tests are quite reasonable compared to the actual monitoring results. Secondly，the total deformation of the actual tunnel anchorage is in the grade of mm with the designing load which will be supplied by the suspension bridge. Thirdly，the design requirement for the safety factor of the tunnel anchorage，which is greater than 4.0，is evaluated to be satisfied by the 1∶12 in-situ physical model test where the maximum anti-pulling force is carried out in the physical test，and ultimate tensile bearing capacity is greater than 7.6 times of the design load. At last，the permanent safety factor of bridge anchorage is not less than 2.6 according to the rheological observations in the physical test. The rock mass deformation and some relevant results have been verified through monitoring in process of the bridge construction. In addition，the technological line is an example for bridge construction in some other similar mountain areas.

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STABILITY ANALYSIS AND REINFORCEMENT DESIGN OF HIGH AND STEEP SLOPES WITH COMPLEX GEOLOGY IN ABUTMENT OF JINPING I HYDROPOWER STATION

SONG Shengwu1，XIANG Baiyu1，2，YANG Jingxi1，FENG Xuemin1

2010, 29 (03): -458 doi:
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[PDF 1053 KB] (1954)

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The arch dam in Jinping I hydropower station is the highest arch dam under construction in the world；the height of excavated slopes at abutments is over 500 m. The power station is located in high mountains and narrow canyons in Southwest China，where natural slopes are very high and steep with high geostress，intensive rock mass unloading，developed faults，interlayer compressive belts and deep unloading fissures. Based on detailed geological investigation，models of the slope structure and the corresponding failure mode are determined，such as tensile rip rock body at left bank above elevation 1 800 m；zoning and analysis of slope stability are also implemented. According to the characteristics of slope structure，the excavation and harnessing principles are determined as follows：little excavation，slight blasting and strong reinforcement，reinforcing each zone and layer respectively，holistic control and covering local weak points with global measures，local and global，implementing shallow and deep reinforcement controlling systems of slope with prestressed cables and shearing-resistance tunnels as main measures and bolts and concrete grids as complement. Time sequence of construction and blasting technique are precisely designed and firmly controlled to guarantee the quality of excavated rock mass；and dynamic design schemes and reasonable management rules are implemented to ensure the safety of construction. Monitoring data from July 2006 to September 2009 indicate that maximum displacement in surface part of the slope is 79.5 mm，in direction perpendicular to the river；and maximum deformation in deep unloading fissures is 60 mm with the maximum rate of 0.1 mm/d. The displacement tends to converge；and it meets the designed safety standards. The successful implementation of high slopes in Jinping I hydropower station provides new practical experience and reference for future construction of projects，and it indicates a new stage of the research and design of rock mechanics and engineering in China.

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EXPERIMENTAL STUDY OF ROCK MECHANICAL PROPERTIES UNDER TRIAXIAL COMPRESSIVE AND FROZEN CONDITIONS

YANG Gengshe，XI Jiami，LI Huijun，CHENG Lei

2010, 29 (03): -464 doi:
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With the demands of fundamental construction in cold regions or special construction environment，it is more necessary to research the problems occurring in frozen rock mechanics. Taking the frozen shaft project of Hujia River coal mine in Shaanxi Bingchang coal mine area as the project background，sandstone and coal samples collected from the field，respectively，are tested under the triaxial compression at different confining pressures at the room temperature 20 ℃ and different freezing temperatures of －5 ℃，－10 ℃ and －20 ℃. Based on the experimental results，the influential law of confining pressure and freezing temperature on the triaxial strength properties of frozen rock is explored；and the strength properties of sandstone and coal samples under the same confining pressure at different temperatures and different confining pressures at different freezing temperatures are analyzed；and the identity and discrepancy of two rock samples on freezing temperature are comparatively studied. Due to the internal structural difference，the frozen effects of sandstone and coal exist obvious difference. Frozen water-rich sandstone is more sensitive to temperature than that of coal. Strength of the water-rich rocks increases with the decrease of temperature which is mainly due to the peak intensity of rocks greatly improved by mineral contraction and ice strength and frost heave force with temperature decreasing. The result provides some references for studying rock mechanics under cold environment and the construction and design for freezing shafts of coal mines.

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FINE TEST ON PROGRESSIVE FRACTURING PROCESS OF MULTI-CRACK ROCK SAMPLES UNDER UNIAXIAL COMPRESSION

ZHOU Huoming1，YANG Yu1，2，ZHANG Yihu1，FAN Lei1，ZUO Yongzhen1，WANG Xiang1

2010, 29 (03): -470 doi:
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[PDF 700 KB] (1650)

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By using integrally the sensitivity features of acoustic emission location technology and the computerized tomography(CT) technology，the fine test on progressive fracturing process of jointed rock under uniaxial compression is realized. By analyzing the positions of acoustic emission events，the CT slides and the change of CT number，the cracking propagation process is achieved. At the beginning of loading，although the whole jointed rock sample shows of crack compaction，the initial crack extension can be localized in the partial area. With the load increasing，both sides of the cracks extend gradually，and they will be destroyed progressively until to form a fracture plane finally. The results can lay the foundation for exploring micro-damage mechanism and the crack expansion discipline of rock，and it will also promote the development of visualization technology for rock mechanics test.

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RESEARCH ON DAMAGE MODEL OF ROCK UNDER COUPLING ACTION OF FREEZE-THAW AND LOAD

ZHANG Huimei1，YANG Gengshe2

2010, 29 (03): -476 doi:
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[PDF 291 KB] (1413)

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For freeze-thaw and loaded rock in engineering structures in cold regions，a damage variable is proposed with a new meaning，and three new conceptions are put forward，which are freeze-thaw damage，loaded damage and total damage. Defining the initial damage state as basic state，the damage model of freeze-thaw and loaded rock is established considering the heterogeneity of rock at mesoscopic level using damage mechanical theory and generalized principle of strain equality. The damage evolutions of meso-structure and macro-damage behaviors of rocks are described by damage variable and constitutive equation，which are in good agreement with the actual freeze-thaw breakage. It is shown that the mechanical properties of freeze-thaw and loaded rocks in engineering structures are determined by freeze-thaw，load and the coupling effects. The combined effect of freeze-thaw and load in the total damage of rock has obvious nonlinear properties，but the coupling effect will weaken the total damage. The weights of influence factors are determined by the lithology and initial damage states of the rocks，so the rock has different damage propagation characteristics. In comparison，sandstone is more sensitive to the freeze- thaw cycles，and load damage will lead to the destruction of shale eventually.

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PARTICLE FLOW MODELING MECHANICAL PROPERTIES OF SOIL AND ROCK MIXTURES BASED ON DIGITAL IMAGE

DING Xiuli1，LI Yaoxu2，WANG Xin1

2010, 29 (03): -484 doi:
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The basic process of digital image processing technique is described firstly. Based on the technique，a program is designed to directly set up particle flow model from digital image，which provides a new modeling method for particle flow simulation about mechanical behaviors of soil and rock mixtures(SRM). Then，using the proposed modeling method，a series of biaxial tests are simulated by the particle flow code in 2 dimensions(PFC2D). After that，the results of these biaxial tests for SRM are compared with those of homogeneous soils. The results show that the stress-strain curve of SRM has a feature of stepwise；and the differential value between principal stresses at the first step basically corresponds to the yield strength of soil；and the strength increase is due to strain hardening phenomenon caused by gravel，which is consistent with the field test result. Finally，the failure mode of SRM is studied；and the results show that there is a great difference comparing to that of homogeneous soils；and the failure zone is irregular for SRM；but when the homogeneous soil fails，there exists a banded shear zone.

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MODIFICATION OF JENNINGS STRENGTH CRITERION FOR INTERMITTENT JOINTS CONSIDERING ROCK BRIDGE WEAKENING AND JOINT SURFACE UNDULATING ANGLE

XIA Caichu1，2，XIAO Weimin1，2，DING Zengzhi3

2010, 29 (03): -492 doi:
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[PDF 387 KB] (1575)

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The shear strength of intermittent joints in rock masses has an important influence on the stability of blocky rock system. For a single rock joint，the surface roughness is of paramount importance to its mechanical property，such as shear strength. Many theoretical criterions have been proposed to predict the shear strength of intermittent joints，of which the Jennings criterion is the most widely used one. However，in Jennings criterion，the mechanical parameters of joint surface and rock bridge are simply averaged by a weight coefficient called connectivity rate to calculate equivalent mechanical parameters and the surface roughness isn¢t taken into account. So the direct shear tests are carried out on artificial coplanar intermittent joints with different surface undulating angles under different normal stresses to investigate the influence of undulating angle on the strength of intermittent joint and analyze the mechanism of the weakening of rock bridge mechanical parameters. Based on the direct shear test data，modifications are made to the Jennings criterion by considering the weakening of the mechanical parameters of rock bridge and the surface undulating angle during shear process. And comparisons between the results computed with modified Jennings criterion and the shear test data are made to evaluate the effect of modification；it is shown that the calculated results according to the modified Jennings criterion agree well with the experimental data；and the modified Jennings criterion is able to predict the shear strength of the intermittent joints with regular surface undulating angle well.

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STUDY OF BLASTING SEISMIC EFFECTS OF UNDERGROUND CHAMBER GROUP IN XILUODU HYDROPOWER STATION

LI Xinping1，2，CHEN Junhua2，LI Youhua3，DAI Yifei1

2010, 29 (03): -501 doi:
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Based on field testing of blasting vibration，the blasting seismic wave propagation laws in underground diversion tunnels under complicated construction conditions are studied. Regression analysis of testing data is conducted according to Sadaovsky empirical formula and the field testing results indicate that horizontal particle peak velocity of blasting vibration can be taken as safety criterion for underground chambers. The numerical simulation is carried out to study the influence of blasting vibration on adjacent diversion tunnels by software the fast Lagrangian analysis of continua in 3D(FLAC3D) and distributions of particle vibration velocity，stress and displacement of the adjacent diversion tunnel wall are obtained. The stability of adjacent chamber is assessed by considering the effect of static load and dynamic load separately. The result of numerical simulation shows that the blasting vibration responses predicted by numerical simulation agree well with field testing；and it is reasonable to use blasting vibration velocity as safety criterion. The near-blasting side of adjacent tunnel is the area where failure tends to occur under blasting load；and the tensile failure will appear possibly in adjacent tunnel straight wall facing blasting with the blasting impact load increasing. Finally，the critical vibration velocity of adjacent chamber under blasting vibration is proposed according to the statistical relationship between maximum tensile stress and maximum vibration velocity combined with the dynamic tensile strength criteria of rock for a project.

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PHYSICAL MODEL TEST ON DEFORMATION FAILURE AND CRACK PROPAGATION EVOLVEMENT OF FISSURED ROCKS UNDER UNLOADING

HUANG Da1，2，3，HUANG Runqiu2

2010, 29 (03): -512 doi:
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[PDF 750 KB] (1687)

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The excavation in rocks is mainly an unloading behavior. The characteristics of strength and deformation failure of rocks are researched；propagation evolvement and mechanical mechanism of cracks are discussed under two unloading stress paths based on physical model test of fissured rocks. The strength and deformation failure of rocks，propagation of cracks are obviously impacted by the included angle of cracks with unloading direction and combination between cracks. The magnitude of unloading velocity and initial stress mainly influence strength and amount of sub-cracks on fissured rocks，but little on the law of expanding mode and deformation. The propagation of cracks is made by tensile stress brought via different rebound deformations and shear stress increasing but resisting shear decreasing under unloading；and the influence of these stresses on the expanding evolvement is highly related with dip angle of cracks.

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STUDY OF METHODOLOGY FOR ASSESSMENT OF EXCAVATION DISTURBED ZONE OF UNDERGROUND CAVERNS

ZOU Hongying1，2，XIAO Ming1

2010, 29 (03): -519 doi:
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[PDF 383 KB] (1392)

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When conducting numerical analysis of plastic cracking zone of rock mass subjected to underground excavation，its results mainly depend on the adopted plastic flow criterion. Therefore，the discrepancy between numerical results and practical engineering is often considerable. The criterion for excavation disturbed zone(EDZ) is still not clear and only empirical，and the acoustic emission(AE) also lacks efficiency and accuracy in engineering practices. Based on the analysis of major influencing factors and a review of several experiments，the mathematical model for determining EDZ of underground caverns is put forward. The proposed model is based on analyzing AE data derived from construction process and statistical treatments. According to the abundant data，the underlying laws of EDZ development are analyzed by data mining. Some new concepts，such as major disturbed zone and percentage of spreading disturbed zone，are proposed by analyzing temporal and spatial characteristics of monitored displacements. The proposed method provides a new approach for determining general stability and disturbed degree of surrounding rock in underground caverns. Also，it provides an effective approach for analyzing monitoring data and assessing excavation quality of underground caverns. It can be referenced by other similar projects as well.

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SHEAR CREEP EXPERIMENTS FOR ANCHORAGE INTERFACE MECHANICS AND NONLINEAR RHEOLOGICAL MODEL OF ROCKS

WU Guojun，CHEN Weizhong，JIA Shanpo，YANG Jianping

2010, 29 (03): -527 doi:
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[PDF 722 KB] (1321)

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Based on a large amount of tests and engineering practices，it is shown that the failure of anchorage system takes place at the interface between anchorage body and rock-soil；so it is necessary to carry out shear rheological experiments for interface mechanics of anchorage system in order to study the mechanism of grout-rock interface and the change characteristics of anchorage force during the rheological period. The results of experiments show that the shear rheological strain grows with time at the certain shear stress level，and grows sharply when shear stress level rises. Under the condition of low shear stress level，the initial rheological stage and steady-state creep stage occurs；however，the accelerating rheological stage will turn up when shear stress exceeds a certain value. With the increment of shear rheology，axial rheological strain of the anchor enhances a little and the anchorage force grows slowly. On the basis of experiment，a nonlinear empirical rheological constitutive model which has a continuous formulation is proposed，which is more reasonable because of its consideration of normal stress and its ability of describing the whole rheological process including primary rheological deformation，secondary rheological deformation and accelerating rheological deformation. For further research on feasibility of the anchorage interface rheological constitutive model，a numerical test is carried out to simulate a shear rheological experiment of sample 3 for 51 hours. It is shown that the results of numerical simulation test coincide very well with that of shear rheological experiment，so it is indicated that the proposed nonlinear rheological model is available.

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STUDY OF UNLOADING TRIAXIAL RHEOLOGICAL TESTS AND ITS NONLINEAR DAMAGE CONSTITUTIVE MODEL OF JINPING HYDROPOWER STATION GREEN SANDSTONE

ZHU Jiebing，WANG Bin，WU Aiqing

2010, 29 (03): -534 doi:
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[PDF 259 KB] (1367)

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Taking green sandstone samples from the diversion tunnel of Jinping II hydropower station as research objective，the unloading triaxial rheological tests by keeping axial stress and unloading lateral stress by steps are performed in laboratory. According to experimental results，the creep laws of axial and lateral deformations under unloading stress path are studied. Development of lateral plastic deformation is more rapid than that of the axial direction；and the response to failure in lateral direction is more obvious than that in axial direction. After detailed research and analysis of the test results，and considering damage effects of rock parameters，the damage evolution equation and nonlinear rheological Burgers model with various parameters are proposed. In the model，the creep parameters of sandstone are weakened with viscous strain gradually，so the deterioration process of the material can be reflected by unsteady creep parameters directly. By taking the sum square of survival difference as optimization objective，the least square embedded in Levenberg-Marquardt(LM) algorithm is adopted to optimize the fitting parameters of models. And then，nonlinear damage rheological constitutive model is established. By comparing with the test data，the fitting curves are well fitted with test data curves；it is shown that the rheological model can preferably present attenuating creep and steady rheological characteristics of Jinping green sandstone.

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RESEARCH ON LARGE-SCALE TRIAXIAL TESTS ON REINFORCED SOFT ROCK COMPOSED OF COARSE-GRAINED SOIL AS EMBANKMENT FILLINGS

XU Wangguo1，2，ZHANG Jiasheng1，HE Jianqing2

2010, 29 (03): -541 doi:
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[PDF 305 KB] (1112)

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In order to study the strength and deformation properties of soft rock composed of coarse-grained soil，as well as its reinforcement effect as fillings，large-scale consolidated drained and undrained triaxial tests are carried out for reinforced intense-weathered rock. The results show that the stress-strain relationship of geotextile-reinforced fillings is of strain hardening. The geotextile-reinforced fillings have little effect while the triaxial strain is less than 1%，and the reinforcing effect becomes more remarkable with the increase of triaxial strain. The pore water pressures of geotextile-reinforced soil samples are higher than those of pure coarse-grained soil samples；and they increase with the increase of geotextile layers. The coefficients of reinforcing effect are all more than 1.0，being 1.09–1.21 while with one layer of geotextile；1.30–1.71 with two layers of geotextile and 1.31–1.72 with three layers of geotextile. The internal friction angle j of fillings before and after reinforcements is nearly constant，while the cohesion force of the fillings increases with the increase of geotextile layers. The constitutive relation can be described with the Duncan-Chang model；and the parameters of Duncan-Chang model for geotextile-reinforced soil are obtained through tests.

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EXPERIMENTAL VALIDATION OF NONLINEAR STRENGTH PROPERTY OF ROCK UNDER HIGH GEOSTRESS

WANG Bin1，ZHU Jiebing1，WU Aiqing1，LIU Xiaohong1，2

2010, 29 (03): -548 doi:
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[PDF 323 KB] (1286)

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The strength characteristics of deep rock mass exhibit distinctly nonlinear response to excavation. Based on triaxial compressive tests and unloading confining pressure tests results under high stress in laboratory，the behaving nonlinear strength property is validated. Moreover，the nonlinear strength parameters¢ change laws by loading and unloading paths of rock failure are brought into research. The quadratic parabola，hypobola，and power types of envelope functions are employed to present nonlinear strength characteristics；and the results reveal that the power type of Mohr criterion can favourably describe the strength property of rock under high geostress in loading path as well as unloading path. The triaxial unloading failure strength is usually less than that under triaxial compressive strength at low stress level，and reversed at higher stress level. According to relationship of internal friction angle with equivalent normal stress，the intrinsic friction angle is not constant，which takes on power functional type of nonlinear characteristics and attenuates gradually to angle of π/4.

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MONITORING ANALYSIS OF SURROUNDING ROCK DISPLACEMENT OF COMPLEX STRUCTURE TUNNEL

QIN Weimin1，LI Qi2，REN Weizhong1，LIANG Chao3，YANG Yu3

2010, 29 (03): -557 doi:
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[PDF 382 KB] (1212)

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Wucun tunnel is a two-way and six-lane tunnel with complex structure in Xiamen City，which is composed of double-arch tunnel，small-distance tunnel，initially supported multi-arch tunnel and split tunnel. Vault settlement and convergence of surrounding rock are the main in-situ monitoring work，and the monitoring results are comprehensively analyzed combined with the measures and procedures of tunnel excavation. Research results show that vault settlement in main tunnel is less than half of that in guide hole in three-hole method construction area；and it is shown that the double-arch structure is applicable to the tunnel with higher settlement control requirement. Vault settlement derived from CRD1 can exceed half of the total value settlement during the excavation period. If the measuring point is embedded after excavation of core soil，the lost settlement will be approximately 37.5% of the total. Surrounding rock can be reinforced by full-face curtain grouting，which achieves better control in vault settlement than in convergence of surrounding rock. Under the influence of dead weight and larger cross-section of pipe roof chamber，larger vault settlement appears in pipe roof area. The removal of temporary support has less impact on the displacement of surrounding rock. Construction factors such as excavation mainly lead to larger convergence deformation as well as grouting；the latter produces a greater impact. Excavation in right tunnel has a certain impact on secondary lining in left tunnel.

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STUDY OF STATIC ANALYSIS OF 3D HIGH-ORDER DDA

ZHANG Yang1，WU Aiqing2，LIN Shaozhong3

2010, 29 (03): -564 doi:
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[PDF 263 KB] (1181)

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Applying three-dimensional high order discontinuous deformation analysis(DDA) with the volume- oriented advantage to structure static analysis gets rid of the limit of compatible mesh，which helps to simplify the preprocessing. Furthermore，by introducing high-order displacement mode，higher precision can be gained when the three-dimensional structure is simply divided into only one or few blocks. Based on above idea，the concepts of connecting face and connecting point pair is defined；and the deformation compatibility conditions of high-order DDA block in continuous structure computation are presented；then the principal formulas of three- dimensional high-order DDA are deduced，including elastic sub-matrix，initial stress load matrix，point load matrix，volume load matrix，fixed point matrix and the connecting matrix of adjacent blocks. The whole balance equations are established at last. Above thought is realized by program. Comparative analysis of some typical samples is applied between the method，analytic solution and finite element results. It shows the feasibility and advantage of DDA method in the static computation of continuous structure.

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SEISMIC DAMAGE ANALYSIS OF ROAD SLOPES IN
WENCHUAN EARTHQUAKE

ZHOU Depei，ZHANG Jianjing，TANG Yong

2010, 29 (03): -576 doi:
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[PDF 1671 KB] (1798)

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Seismic damages of road slopes in mountainous areas have different characteristics in mechanism and types from those in flain. Based on cases of damaged road slopes in the Wenchuan earthquake，failure mechanisms and types of the road slopes for cutting and embankment slope and slopes around bridge and tunnel，as well as retaining structures，are analyzed. Slopes stabilized by using anchored foundation beams or lateral loaded piles with prestressed anchors have better performance in the earthquake. The reason is that these structures make both structures and soils become integral，and so deformation between structures and soil is consistent. Geogrid or other reinforced embankment slopes have better performance in the earthquake；but the aseismic performance of embankments without reinforcement，particularly high embankments，is poor. Based on the cases of liquefaction or soft soil layer-induced settlement，it is suggested that engineers in aseismic design should pay attention to liquefaction-induced settlement at the toe of the slopes constructed on sandy soil layers and take measures to prevent from pavement failure caused by the settlement on soft soil layers and slope instability caused by the settlement at the toe of the slope. At tunnel portals and portal slopes，engineers should strengthen aseismic design of retaining structures. Safety and stabilization of bridge abutment，foundation and transition between abutment and embankment constructed on slopes are dependent of the slope stability；and so aseismic design of the slope，on which those structures are constructed，should be strengthened. For bridges constructed along the bank of river，unstable slope can damage the bridges，some measures in aseismic design should，therefore，be taken into consideration. At present，codes for aseismic design of roads and railway have few contents for how to design slope and retaining structures；and so the achievements obtained will be helpful to revision and supplementary of the codes.

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STUDY OF RHEOLOGICAL MECHANICAL MODEL OF PILLAR-ROOF SYSTEM IN MINED-OUT AREA

WANG Jin¢an，LI Dazhong，MA Haitao

2010, 29 (03): -582 doi:
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[PDF 207 KB] (1236)

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Based on the mining with pillar supporting in the mined-out area，a rheological mechanical model of pillars and roof plate system for mined-out area is established，which brings out the displacement control function of the roof stratum supported by pillars under rheological effect；and the fracture stages in roof stratum are analyzed regarding to the time-dependent behavior. The result indicates that the roof stratum supported by pillars in the mined-out area will gradually fail and till collapse by taking into account of the rheological feature of pillars. Based on a case study，the proposed mechanical model could be used to estimate the stable time of the roof stratum in pillar-roof system of mined-out area by considering the rheological behavior of pillars.

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ANALYSIS OF IMPACT OF TUNNEL CONSTRUCTION ON MASONRY BUILDINGS IN XIAMEN AIRPORT ROAD

XU Lihua1，2，AI Xinying1，2，YU Jiali1，2，LI Qi3，HE Yabo1，2

2010, 29 (03): -592 doi:
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[PDF 634 KB] (1518)

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Tunnel construction will cause surface deformation inevitably，which has a negative effect on the surface buildings. According to the construction practice of Wucunshan Tunnel in Xiamen Airport Road，the effect of tunnel construction on the surface masonry buildings is analyzed through field monitoring and finite element simulation. The results show that the excavations of tunnel face CRD1–4 have the most important influence on building settlement. Tunnel excavation has little influence on the building under compact construction，and vice versa. The grouting pressure and grouting amount must be strictly controlled in the construction process. It is better to grouting slowly rather than fast，which can ensure the uniform uplift of the whole building. The most obvious response of building under uneven settlement occurs at the bottom story；and its ability to resist down concave deformation is stronger than that to upper convex deformation. The cracks are mainly distributed around the door and window openings in the longitudinal wall at first floor，developing slantwise along the side of smaller settlement to the side of larger settlement. Moreover，the development of the cracks aggravates with the increase of the differential settlement，and vice versa.

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TEST AND NUMERICAL ANALYSIS OF EFFECT OF NOTCHED
SILL OF GRAVITY ANCHORAGE ON SOFT ROCK GROUND OF SUSPENSION BRIDGE

LAI Yunjin1，2，WU Changjiang1，2，ZHANG Zixin1，2

2010, 29 (03): -602 doi:
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[PDF 405 KB] (1129)

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Based on the rigid calculation model，the formation mechanism of notched sill effect of gravity anchorage is analyzed for suspension bridge on soft rock ground. It reveals that the mode and performance of notched sill effect mainly depend on the centroid position of anchorage. Taking the anchorage project，Ganjiang suspension bridge on Ganjiang River for example，field model test for anchorage is conducted to investigate notched sill effect by studying the stress distribution of each step of notched sill subjected to different cable tension levels. The results from test validate the formation mechanism of notched sill effect. Additionally，three-dimensional numerical simulation is performed to disclose the mechanical characteristics of gravity anchorage with notched sill by means of the fast Lagrangian analysis of continua in 3 dimensions(FLAC3D). The interaction between surrounding soft rock and anchorage both with and without notched sill is studied. It is concluded that the existing notched sill obviously influences the stress distribution on the bottom of foundation，decreases the horizontal displacement，greatly improves the anti-sliding capacity，and changes the instability mode of anchorage. The results from numerical simulation are in good agreement with ones from the field test. Moreover，the analyses of factors of notched sill effect，including the centroid position of anchorage，the height of notched sill and the parameters of interface and surrounding ground，are implemented for structural optimization design. Finally，some principles for designing anchorage structure with notched sill are suggested.

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STUDY OF IMPACT OF SHIELD TUNNELING SIDE-CROSSING ON ADJACENT HIGH BUILDINGS

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

2010, 29 (03): -608 doi:
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[PDF 257 KB] (1459)

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Based on a certain constructing running shield tunnel of Beijing metro side-crossing close to a high-rise building，using the finite element method calculation model and site monitoring method，the foundation characteristics of the high-rise building affected by the constructing shield tunnel are studied. In different construction stages，the variations of the foundation settlement and inclination of the high building are analyzed. The simulation results show that stratum vertical displacement has a sudden change near the high-rise building. Away from the building in an enough distance，the displacement curve becomes flat. From site monitoring results，the high-rise building inclined to the direction away from the tunnel prior to the shield closing to the building，while the building inclined towards the tunnel during shield crossing. The settlements of the monitoring points reach the maximum value when the shield is 10.0 m away from the monitoring surface. However，the settlements declined significantly when the shield is more than 60.0 m from the monitoring surface，and finally becomes stable. The simulation and the site monitoring results agree well. The conclusion would be helpful for the future similar shield tunneling projects.

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INVERSION ANALYSIS OF INITIAL SEEPAGE FIELD OF DALIAN UNDERGROUND OIL STORAGE CAVERN

YU Chong1，LI Haibo1，LI Guowen2，XIA Xiang1，XIE Bing1

2010, 29 (03): -616 doi:
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[PDF 1329 KB] (1260)

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The initial seepage field analysis is prerequisite and important content for the water-tight underground oil cavern design. Although the field water pressure test can provide a more accurate isotropic permeability coefficient，which does not reflect the anisotropy permeability of jointed rock mass. In initial seepage field analysis of Dalian underground oil storage cavern，based on joins network simulation technique，a new method for calculating the anisotropy permeability is proposed. Firstly，different sizes of three-dimensional random joint networks are generated with the programming language Fish embedded within 3DEC. The values of joint geometric characters and number of random joints in each group are decided through the derivable formulas. Different sizes of rock permeability tensor are calculated based on fractured rock permeability tensor theory；meantime，with the size of three-dimensional random joint networks increasing，representative elementary volume is also determined until rock permeability tensor is not changed obviously. As the difficulty of fracture width measurement，some fracture fillings and the presence of non-connected，as well as the impact of fracture roughness，the calculated permeability tensor have a certain degree of error in value. It is necessary to amend according to field water pressure test. Principal value and characteristic vector of permeability tensor are easily calculated with Matlab software. Finally，considering the space orthotropic permeability coefficient，the initial seepage inversion is completed with the fl_anisotropic model within FLAC3D，the Fl_anisotropic model parameters are obtained from principal value and characteristic vector of permeability tensor. The inversion analysis provides initial seepage field for water-tight underground oil cavern water curtain design and stability analysis.

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STUDY OF TIANSHAN SLOPE ROCK MASS RATING(TSMR) SYSTEM

ZHANG Yuancai1，HUANG Runqiu1，ZHAO Lidong2，FU Ronghua1，PEI Xiangjun1

2010, 29 (03): -623 doi:
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[PDF 309 KB] (1839)

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Tianshan highway is located in high altitudes and cold region where freeze-thaw action is very strong，so it is important to take the influence of freeze thaw action into account when evaluating the side slope stability along the Tianshan highway. On the basis of statistical analysis of more than 100 slopes in Tianshan highway，a new rock mass rating system—TSMR，which is suitable for the slope stability evaluation of Tianshan highway，is established. With the RMR，SMR and CSMR rock mass rating systems，the correction coefficient x of slope height and condition coefficient l of structure plane are adjusted by using mathematical statistics tools；and freeze-thaw coefficient d is also introduced. At the same time，several pertinent supporting recommendations are proposed in TSMR system according to slope stability levels. Application results show that misjudgment rate of TSMR system is lower than that of the RMR-SMR system，thus the results are acceptable for slope stability evaluation in high altitudes and cold region.

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EXPERIMENTAL STUDIES OF MECHANICAL PROPERTIES OF TWO ROCKS UNDER DIRECT COMPRESSION AND TENSION

LI Diyuan1，2，LI Xibing1，LI C CHARLIE2

2010, 29 (03): -632 doi:
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[PDF 676 KB] (1168)

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Uniaxial tests are carried out on two types of hard and soft rocks by using Instron 1342 hydro-servo- controlled machine，including uniaxial compression tests and direct tensile tests. The mechanical properties of these two rocks are obtained. The uniaxial compression strength(UCS) and the uniaxial tensile strength of the two rocks are compared. Both the axial strain and the lateral strain of the specimens are logged during the tests；and the acoustic emission(AE) of the specimens is monitored by the AE sensor. The stress-strain curves and the AE counts rate curves of the two rocks are obtained under direct compression and tension. The AE characteristics of the two rocks are studied. It is found that under direct tension there are almost none of AE events during the loading process until close to the final failure. The variations of elastic modulus and the Poisson¢s ratio with the applied loads are compared between the two rocks. It shows that under compression，the initial elastic modulus of hard rock is relatively small at the beginning stage and then increases to a stable value when the stress is within its 80% of UCS；and then it decreases until the final failure. By contrast，under tension，the elastic modulus of hard rock is relatively large at the beginning stage and then decreases with loading. The Poisson¢s ratios of the two rocks are both ranged from 0.2 to 0.3 under compression；but it becomes very small and can be neglected under tension. The fracture angles，the internal friction angles and the cohesions of the two rocks are compared；and the failure modes of the rock specimens are discussed. Finally，the tensile fractures of typical rock specimens are measured by a 3D surface measurement machine. The microstructure and the roughness profile of the tensile fractures are obtained.

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STUDY OF PREDICTION MODEL FOR TRIANGULAR WAVE LOADING SECTION DEFORMATION RATE OF YICHANG SANDSTONE

LIU Jie1，LI Jianlin1，2，DENG Huafeng1，ZHANG Chaofeng3，LI Yingxia1

2010, 29 (03): -639 doi:
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[PDF 281 KB] (1018)

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By taking Yichang sandstone as the research object and RMT–150C rock and soil mechanics test system as the test platform，a prediction model of deformation rate in triangular wave loading section is studied. Loading process is divided into lag time segment and non-lag time segment；and then classification standard is established. Given in the lag time，it may occur the phenomenon of or ，so the concept of apparent modulus is proposed. By analyzing the axial loading test results of the same rock samples without damaging under different waveforms and different frequencies，the linear relationship between apparent elastic modulus and instant vertical force by experiment is found；and then the physical meanings of related parameters are given. On this basis，first，a predicting model of deformation rate in triangular wave loading section with non-lag time segment is established；then some examples are given by combinating load patterns and related parameters. At the same time，a prediction model of lag time segment is given according to experimental data. The prediction model is reasonable by comparative studies，because prediction deformation rate and stress-strain curve anastomose exactly with measured values.

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POST-PEAK STRAIN SOFTENING MECHANICAL PROPERTIES
OF WEAK ROCK

LU Yinlong1，2，WANG Lianguo1，2，YANG Feng1，2，LI Yujie1，2，CHEN Haimin1，2

2010, 29 (03): -648 doi:
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[PDF 413 KB] (1732)

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Weak rock brings about a series of difficult issues to tunnel support and maintenance in mining engineering. Further study of the mechanism and law of weak rock deformation and breakage has great significance to the safety and stability of the tunnel wall rock. Based on the conventional triaxial compression test of weak mudstone，complete stress-strain curves under different confining pressures are obtained. Then based on the assumption that the stress state at a point satisfies Mohr-Coulomb critical failure criterion，building the weak rock subsequent yielding plane model characterized by generalized cohesion and generalized internal friction angle using the test data，several Mohr¢s stress circles of post-peak rock at different softening conditions are drawn；then using tangent method to build the fitting equation of Mohr¢s strength envelope curve， and under different confining pressures could be determined. And by means of Matlab software，the relationship between generalized cohesion ，generalized internal friction angle ，equivalent plastic shear strain and confining pressure are fitted by using least square surface. Through the relationship，the post-peak mechanical parameters softening law of weak rock can be obtained. The results show that with the increase of confining pressure，generalized cohesion shows a rapid increase trend；but generalized internal friction angle decreases significantly；and the influence that the softening condition brings to the generalized cohesion is evident；the generalized cohesion has a rapid decrease when the stress state changes from the peak value state to the residual state；the average of the decrease is 53.88%，while generalized internal friction angle almost maintains stable during the change of the softening condition. At last，the fitting equations of generalized cohesion and generalized internal friction angle are embedded into the strain softening constitutive relation of the fast Lagrangian analysis of continua in 3 dimensions(FLAC3D)；and using FLAC3D software，numerical verification is made to the model. The results show that the numerical simulation curves agree well with the test curves comparatively.

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2010, 29 (03): -649 doi:
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[PDF 104 KB] (907)

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