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2004, 23 (07): -0 doi:
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STUDY OF EFFECT OF EXCAVATION SEQUENCE ON DEFORMATION MECHANISM OF CENTRAL PIER OF THIRD PERMANENT SHIPLOCK CHAMBER OF THREE GORGES PROJECT

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2004, 23 (07): -1061 doi:
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[PDF 214 KB] (875)

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There are different points of view about the deformation mechanism of the central pier of the permanent shiplock of the Three Gorges Project. The influences of different excavation sequences on the deformation of the pier are investigated，and parameter sensitivity analysis is made by using FLAC. The numerical results show that the main influential factor for the deformation is the excavation sequence，and the abnormal deformation is caused by asymmetrical excavation sequence at two sides of the pier. It is also found that the existence of the fault F215 cannot result in northward displacement of the south side，and the abnormal inclination cannot occur unless the rock mass of the pier has relatively high stiffness and strength. It may be concluded that the occurrence of the abnormal inclination doesn’t indicate the failure or collapse of the pier. On the contrary，it demonstrates that the pier has high stiffness and behaves elastically. The results provide a theoretical basis for a rational interpretation of the deformation mechanism of the central pier.

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STUDY ON SAFETY FACTOR OF 3# DAM FOUNDATION OF LEFT POWER HOUSE OF THREE GORGES PROJECT USING SLICE JOINT ELEMENT

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2004, 23 (07): -1066 doi:
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[PDF 301 KB] (947)

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A 3D finite element model including 41 large structures and 5 faults based on the real geometry is established. The model is used to study the stability of 3# dam foundation of the left power house of the Three Georges Project and the failure mode of power house. A rule for estimating safety factor of dam foundation in terms of strength reservation is proposed based on the results of the 3D finite element analyses. For 3# dam foundation，the suggested safety factor is about 3.5 based on the computation results，which also confirms the safety of power house.

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VARIATION OF MECHANICAL PROPERTY OF MARLITE IN PROCESS OF KARSTIFICATION AND WEATHERING IN THREE GORGES REGION

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2004, 23 (07): -1073 doi:
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The newly discovered karst problem of marlite in Three Gorges region is an important problem in engineering geology. Marlite is of both the properties of limestone in which CaCO3 can be dissolved and mudstone in which mud component can be weathered，which brings about the variation of the rock contents and textures. With the variation，the indexes of mechanical property of the rocks，such as uniaxial compressive strength (Rc)，deformation modulus (Eb)，elastic modulus (Et)，wave velocity (Vp and Vs)，dynamic elastic modulus (Ed) and dynamic shear modulus (Gd) drop gradually，so that some rocks belong to relatively soft rock by national standard. The loose soil layers brought about by dissolution and weathering，with the increase of montmorillonite content (S)，enlargement of specific surface area (B)，high liquid limit (wl)，high plastic limit (wp)，high plastic index (Ip)，strong pro-water property，expansive property and low shear strength (c，j)，are easy to be slided and deformed. As the foundation of project for population resettlement，there may occur geo-hazards，such as landslide，collapse，debris flow，uneven subsidence，fissure and cave-in by dissolution and weathering. So it is necessary to use flexible ideas to treat the stability of the foundation，and the key measure to control the geo-hazards is to keep the foundation from saturation.

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EXCAVATION-DISTURBED ZONE AND WEAKEN DEGREE OF MECHANICAL PROPERTIES FOR ROCKMASS OF TGP SHIPLOCK SLOPE

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2004, 23 (07): -1078 doi:
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[PDF 184 KB] (1044)

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By means of acoustic wave test and in-situ deformation test of rockmass，the excavation-disturbed zone and weaken degree of mechanical properties for the rockmass of the Three Gorge Project(TGP) shiplock slope are studied，and the mechanical parameters for disturbed zone rockmass are determined. The study results show that the weaken degree of strongly disturbed zone is 60% and that of weakly disturbed zone is 30%.

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BRITTLE ELASTOPLASTICITY MODEL OF ROCKMASSES DURING UNLOADING AND ITS APPLICATION TO HIGH SLOPE EXCAVATION

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2004, 23 (07): -1082 doi:
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Based on unloading characteristics of rockmasses during excavation，this paper presents a criterion for loaded and unloaded mechanisms，and establishes a brittle elastoplasticity model of rocks. The model and criterion are then applied to a stability analysis of excavated high slope of the Xiaowan hydropower station project. The combination of the model and criterion with a three-dimensional nonlinear finite element method provides a technique for the selection and optimization of reinforcement measures.

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STUDY OF FAILURE CRITERION FOR BRITTLE
ROCKS BASED ON STRAINS

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2004, 23 (07): -1087 doi:
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When rock-like materials are tested under triaxial compression，two kinds of failure may happen，that is，ductile and brittle failures. The essential reason for rock failure is the relative displacement among mineral particles making up rock. Generally，rock failure can be either tensile or shear，which depends on the predominant mechanism when failure happen. The maximal tensile strain criterion can predict rock failure in tension，but is difficult to explain the effect of crack angle. Rocks are generally anisotropic. The principal strain axes are usually different from the loading axes. Therefore，the strains in the directions of loading axes may not be suitable to describe rock strength. The strain-based strength criterion considering tensile strains in three axes can describe rock strength. And it can describe the crack angle and its transformation. The theoretical analyses and laboratory tests presented in this paper validate this conclusion. With the increasing of the intermediate principal stress，the transformation of the strain failure criterion is of the same pattern as the transformation of the compressive strength and the maximum tensile strain criterion.

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NUMERICAL ANALYSIS OF STRAIN-RATE EFFECT OF STRENGTH ON SPALLATION OF ROCKS

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2004, 23 (07): -1091 doi:
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Strain rate affects the strength of rocks significantly，and therefore affects the fracture of rocks. In this paper the effect of strain rate on the spallation of rocks is studied. It is shown from the analysis that the increase of strength of rocks under intensive stress waves causes the decrease of plastic zone and the decrease of wave attenuation. This，in turn，causes the increment of magnitudes of reflection stress waves from free surface，and increases the potential of rock spallation when the tensile strength is mainly controlled by weak layers.

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ANALYSIS OF SIZE EFFECT，SHEAR DEFORMATION AND DILATION IN DIRECT SHEAR TEST BASED ON GRADIENT- DEPENDENT PLASTICITY

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2004, 23 (07): -1095 doi:
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The paper concerns the issue of size law，localized deformation and dilation or compaction due to shear localization. It is assumed that the shear localization initiates at the peak shear stress in the form of single shear band，and based on gradient-dependent plasticity，an analytical solution on size effect or snap-back is obtained. The results show that the post peak response becomes steeper and even exhibits snap-back with increasing of length. For small specimen，the relative shear displacement when specimen failure occurs is lower than that of larger specimen and the shear stress-relative displacement curve becomes steeper. The theoretical solution on non-uniformity of strains in shear band is obtained and evolution of the relative shear displacement is represented. By resorting to the linear relation between local plastic shear strain and local plastic volumetric strain，the dilation and compaction within shear band are analyzed. Relation between apparent shear strain and apparent normal strain and relation between shear displacement and vertical displacement are established.

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EFFECTIVE STRESS AND COLLAPSE PROCESS OF
UNSATURATED LOESS

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2004, 23 (07): -1100 doi:
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In this paper，the collapse test with increasing moisture for Weibei Zhangqiao unsaturated loess is studied. The curves of -p， -( － )， -q，as well as -( － ) are obtained respectively. The parameters defining effective stresses，xp and xq，are determined through curves of - and - . Using these results，the variation of effective stresses under collapse condition with increasing moisture for unsaturated intact loess can be estimated.

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DYNAMICALLY WEIGHTED GREY OPTIMIZATION MODEL FOR ROCKBURST RISK FORECASTING AND ITS APPLICATION TO WESTERN ROUTE OF SOUTH-NORTH WATER TRANSFER PROJECT

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2004, 23 (07): -1104 doi:
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[PDF 192 KB] (1119)

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Based on the principles of grey correlation analysis and fuzzy mode identity，a dynamically weighted grey optimization model for forecasting rockburst risk is established. In rockburst forecast，a new judging method is developed for composite judging index systems. This method overcomes the disadvantages of traditional methods and gives more reasonable results. The method was applied to prediction of rockburts in typical tunnel sections designed for the western route the South-North Water Transfer Project. The obtained results are compared with FEM analysis and show more accurate predictions .

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DETERMINATION OF MULTICORRELATION FOR PROPERTY PARAMETERS OF GEOTECHNICAL ENGNIEERING MATERIALS

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2004, 23 (07): -1109 doi:
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[PDF 190 KB] (1235)

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The material parameters of rock and soil masses are often variables with uncertainty. They are mutually dependent as pairs of causes and effects，because of their cross influence. For cases of multi-variations，the correlation coefficients among these variables are not simple because of such interactions. The method of partial coefficient of correlation presented in this article can distinquish these interactive relations quantitatively. It has been shown that there is a significant difference between partial and simple coefficients of correlation from engineering application examples，and that the former is more accurate and realistic. The interactive relations among the variables that have large correlation coefficients must be taken into account during estimation on the reliability and risk of engineering works.

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MASS TRANSFER MODELING METHOD FOR EVOLUTION EVALUATION OF SLOPES

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2004, 23 (07): -1114 doi:
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[PDF 1317 KB] (916)

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In general，most slopes undergo a long evolution process before they fail. It is therefore important to monitor and evaluate the evolution process of slopes. By means of mass transfer modeling with variations of chemical and isotope composition along the groundwater flow paths，the mineral forms，quantity，rate and trend of the mass exchange between rock-soil materials and groundwater can be determined and the modeling results may provide scientific bases for slope reinforcement and landslide prediction. Taking a roadbed slope as an example，the application of the method to evolution evaluation of slopes is introduced.

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NUMERICAL SIMULATION OF DYNAMIC FALLING OF OVERLYING ROCKS AND ABUTMENT PRESSURE IN SURROUNDING ROCKS FOR FULLY-MECHANIZED TOP-COAL CAVING STOPE

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2004, 23 (07): -1122 doi:
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[PDF 234 KB] (1157)

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Based on the key layer theory，the falling process of the overlying rocks in fully-mechanized top-coal caving stope is simulated using the RFPA¢2000 software. The dynamic distribution patterns of the caving of the overlaying rocks and the abutment pressure in surrounding rocks are analyzed. The distribution of the abutment pressure in the goaf is obtained by numerical simulation for the first time. According to the calculated results，the cracked rocks in the goaf can be divided into three areas，namely，natural accumulation area，structure supporting area and steady compaction area. The findings are of important value for describing the compaction state and analyzing the seepage features of the cracked rock in the goaf.

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ABUTMENT PRESSURE DISTRIBUTION AND ITS TRANSFER LAW IN FLOOR OF DEEP ISOLATED FULLY-MECHANIZED MINING FACES USING SUBLEVEL CAVING

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2004, 23 (07): -1127 doi:
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Based on the mining condition of No.4403 isolated fully-mechanized mining face with the sublevel caving in Dongtan Coalmine，the transfer of the abutment pressure in the floor is studied. The results provide a basis for controlling additional roadway deformation efficiently and ensure the regular production of the mine.

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IMPROVEMENT AND APPLICATION OF ANN METHOD IN STRESS AND DEFORMATION PREDICTIONS DURING TUNNEL EXCAVATION

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2004, 23 (07): -1132 doi:
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[PDF 185 KB] (1036)

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The stresses and deformations of rocks during tunnel excavation are predicted using an ANN approach based on results of FEM simulation. The algorithm of the BP network technique is improved appropriately. Several new improving methods are developed and lead to good results. The approach proposed in this paper can obtain more accurate and more suitable results for practical applications.

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THREE DIMENSIONAL ELEMENT-FREE METHOD
AND ITS APPLICATION

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2004, 23 (07): -1136 doi:
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[PDF 285 KB] (999)

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Using the theory and implementation technology of two dimensional element-free method as a reference，this paper presents a three dimensional element-free method using moving least squares approach based on orthogonal basis functions. The treatment of the essential boundary conditions，derivation of governing equations and implementation algorithms are also discussed. A program of three dimensional element-free method is developed and is applied to analyze the deformation of a pillar under the action of dead weight. Comparison bewteen the calculated numerical results and the exact solution shows that the method and program presented in this paper are reliable.

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ELEMENT-FREE GALERKIN METHOD FOR SOVING BIOT CONSOLIDATION PROBLEM

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2004, 23 (07): -1141 doi:
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[PDF 233 KB] (1056)

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The system equation for 2D soil consolidation is given and the corresponding program is developed with element-free Galerkin method based on the equilibrium differential equation and the continuous equation of soil，combined with the initial and boundary conditions. In addition，the essential boundary conditions are enforced with penalty method. This method forms the shape functions using the moving least-squares(MLS) polynomial interpolation grounded on a set of arbitrarily distributed points in an influencing domain. Time discretization adopts the Crank-Nicolson integral scheme. The accuracy and feasibility of the EFG method for consolidation problem are verified by comparing the calculation results of a numerical example with those from the analytical method and FEM.

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BACK ANALYSIS METHOD BASED ON FINITE ELEMENT METHOD OF LINES AND ITS APPLICATION TO GEO-ENGINEERING

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2004, 23 (07): -1146 doi:
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[PDF 180 KB] (1126)

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Finite element method of lines (FEMOL) is combined with back-analysis method for geo-engineering problem. The back analysis method based on FEMOL is put forward for the first time in this paper，which not only sheds new lights on the more effective application of FEMOL，but also enriches the techniques of back analysis. This method is verified in a practical engineering example with satisfactory results.

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FORWARD AND INVERSE ANALYSES OF WATER FLOW INTO TUNNELS

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2004, 23 (07): -1150 doi:
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[PDF 191 KB] (1521)

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Dynamic design and information-based construction are often adopted in deep buried tunnels in rocks abounding with in groundwater. The most important information collected in the course is the flowrate of groundwater. The flowrate from the surrounding rocks is calculated by forward and inverse methods，with practical examples. The calculation results show that the forward and inverse analyses of water flow into tunnels are essentially different from each ofter. At the pre-design stage，the flowrate can be obtained by the forward method，engineering judgement，and numerical or analytical calculations. During the dynamic design-construction stage，the flowrate can be obtained with the inverse approach based on the measured data to improve the prediction and design.

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DEM ANALYSIS ON STABILITY OF UNSUPPORTED TUNNELS IN JOINTED ROCK MASSES AT DIFFERENT DEPTHS

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2004, 23 (07): -1154 doi:
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[PDF 278 KB] (1151)

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The stability of unsupported tunnels in jointed rock masses at different depths is analyzed using the distinct element method. The analysis of an autobahn tunnel shows that the unsupported shallow tunnels (for example，at a 5 m depth) are not as stable as those at a larger depth (for example，at 50 m) if the joints are steep and there exist more joint sets，and vice versa. The pressure-arch effect on the stability of jointed rock mass surrounding a shallow tunnel proves to be important.

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FINITE ELEMENT ANALYSIS OF INFLUENCE OF PIPE-JACKING CONSTRUCTION ON ENVIRONMENTS

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2004, 23 (07): -1158 doi:
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The deformation and stresses of soil by pipe-jacking are calculated with 2D and 3D finite element methods. The calculations considere three factors independently，that is，the soil press on the head of pipe-jacking，friction in soil and deviation of pipe-jacking head. Their influence on earth surface deformation are examined and some useful conclusoions are drawn.

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DYNAMIC ANALYSIS ON RESPONSE OF TRANSVERSELY ISOTROPIC
STRATIFIED MEDIA TO INCIDENT P-SV WAVES

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2004, 23 (07): -1163 doi:
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[PDF 207 KB] (816)

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The dynamic response of soil to incident plane P-SV waves is studied in this paper. Since the horizontal elastic moduli are often different from the vertical ones，a model of transversely isotropic(TI) stratified media，which takes into account the polarization angles，is used to simulate the soil ground situated on a half space. The dynamic stiffness matrix of the media and the formula of their response to P-SV waves are derived. Some examples are given and the numerical results are taken to illustrate resonant characteristics of the ground and the effects of the anisotropic parameters on field responses.

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STUDY ON WAVE MOTION INPUT AND ARTIFICIAL BOUNDARY FOR PROBLEM OF NONLINEAR WAVE MOTION IN LAYERED SOIL

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2004, 23 (07): -1169 doi:
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[PDF 196 KB] (1206)

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Wave motion input method and artificial boundary conditions in simulation of nonlinear wave motion in infinite layered soils are proposed. One dimensional artificial boundary equations of a linear damping material are derived first. Approximate two dimensional artificial boundary equations are then generalized. The artificial boundary conditions for simulating nonlinear effects of the far-field layered soils are developed by means of equivalent linearization method. Finally，the method of wave motion input is established. Numerical examples prove good accuracy of the artificial boundary conditions and wave motion input method，which can be easily used in study of problems of nonlinear wave motion in layered soils.

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饶伟锋1 张若京2

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2004, 23 (07): -1174 doi:
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[PDF 197 KB] (949)

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The investigations on hydraulic fracturing suggeste that the small openings distributed in the rock influence the process of fracturing. In this paper，the small openings of rock are treated as the regularly distributed holes，and the asymptotic homogenization method is employed to establish the relation between the equivalent elastic constants and porosity of the rock. The comparisons show that the equivalent elastic constants provided by this model are similar with the Budiansky¢s，and can be applied to predict the result of hydraulic fracturing.

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VISUAL SIMULATION ON COUPLING MODEL OF SOLID DEFORMATION AND GAS LEAK FLOW

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2004, 23 (07): -1179 doi:
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Based on the new viewpoint of the interaction between solid deformation and gas leak flow，the mechanism of gas leakage in double deformable coal seam can be understood. Under the action of geophysical fields，the methane gas flowing in double deformable coal seam can be essentially considered the compressionable gas flowing with time-dependent mixed permeation and diffusion through a pore-cleat deformable medium of the heterogeneous anisotropic coal seam. Then based on this new viewpoint，the coupling mathematical model for coal-seam deformation and gas leakage flow in double coal-seam is formulated and the practical numerical simulations for gas emission from area close to up (down) coal seam is successfully achieved. Therefore the conclusion can be drawn from this study that the coupling models might be closer to actual situation. Meanwhile it is effective for SIP(strong implicit procedure) analysis on the coupling models for coal-seam deformation and gas leakage flow. At the same time，applying three-dimensional computer simulation technology，the macroscopic feature of the effective coupled gas leak flow and coal-rock mass deformation can be reappeared visually，and a feasible new method is offered for control of the underground coal gas leak flow and prediction of coal gas gushing from the near layer.

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COLLAPSE MECHANISM ANALYSIS OF STEEP-HIGH ROCK SLOPE OF SHIQUAN HYDROPOWER STATION AND REINFORCEMENT DESIGN

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2004, 23 (07): -1186 doi:
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[PDF 313 KB] (1157)

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The powerhouse of the Shiquan hydropower station is located near the river bank. The turbine pit excavation depth is about 42 m. During excavation，collapse of surface layers of the rock slope happened twice，and a crescent open space was formed between the powerhouse and the rock slope. According to geological structure characteristics of the collapse exposure，the collapse mechanism of the high slope was analyzed. On this basis，a reinforcement scheme was designed. Required force for the pre-stressed cable bolt was optimized by the limit equilibrium computation. Interactions between the slope and concrete frame were analyzed by a 2D contact-nonlinear FEM. Based on the numerical simulation results，a comprehensive treatment and reinforcement scheme of building concrete frame in the crescent open space was worked out. The idea is to utilize the elastic resistance generated from the moderate distortion of the concrete frame to increase the stability of the slope foot. The practical cases show that this scheme not only increases the safety degree of the slope，but also provides favorable economical benefit.

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SAFETY ASSESSMENT AND INDICATORS OF GEOLOGICAL DISPOSAL SYSTEM OF HIGH-LEVEL RADIAOACTIVE WASTE

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2004, 23 (07): -1193 doi:
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Safety assessment for geological disposal systems of HLW differs from other engineering systems in the following aspects. (1) Extremely long time scales must be taken into account. (2) Natural environments，which are heterogenous and cover large areas，must be evaluated. Therefore，the safety assessment has difficulties in dealing with uncertainties associated with the far future state of the biosphere and the conditions in near-surface zone. This paper describes the feature，methodology and safety indicators of safety assessment for geological disposal systems of HLW.

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CURRENT RESEARCH STATE OF PROBLEMS ASSOCIATED WITH MINED-OUT REGIONS UNDER EXPRESSWAY AND FUTURE DEVELOPMENT

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2004, 23 (07): -1198 doi:
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The current research state of problems associated with mined-out regions is reviewed systematically，including the exploration technology，prediction of stability，treatment and inspecting techniques. Some important points needed to researched in future are also pointed out.

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STUDY ON SHRINKAGE AND RECOVERY OF THICK LAYER
BASE MATERIAL SPRAYING FOR BIO-SLOPE-ENGINEERING

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2004, 23 (07): -1203 doi:
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[PDF 311 KB] (993)

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Shrinkage and recovery of base material mixtures are one of the important indices for evaluating thick layer base material spraying for bio-slope-engineering. Based on spraying experiments on simulated rock slopes，the effects of differently proportioned base material mixtures on their shrinkage and recovery are studied. The study result is of some significance for selection of base material mixture composition and proportion.

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TUNNEL STARTING SCHEME OF RIGHT LINE OF WANWU TUNNEL

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2004, 23 (07): -1209 doi:
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[PDF 169 KB] (1117)

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Safe starting of tunneling is the premise of smooth tunnel construction. In general，tunnel starting is difficult when the geological condition of the surrounding rocks is not good enough. This paper discusses the tunnel starting scheme of the right line of the Wanwu Tunnel of the Fuding-Ningde Expressway. Based on tunnel support mechanism，the general and specific tunnel starting schemes，tunnel starting construction procedure and technical measures and parameters are introduced. The scheme described in the paper has been proved to be very successful in practice，and provides a good reference to similar works.

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STUDY ON MECHANICAL BEHAVIOUR OF TRANSVERSLY ISOTROPIC FOUNDATION UNDER HORIZONTAL LOADS

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2004, 23 (07): -1212 doi:
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[PDF 241 KB] (809)

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Based on the constitutive equation of a transversely isotropic foundation with horizontal isotropic symmetric planes，the constitutive equation for a transversely isotropic foundation with inclined isotropic symmetric planes is derived. In addition，the methods of computing earth stress of a transversely isotropic foundation under the above two conditions and the analytical solutions of additional stress caused by horizontal loads are developed. From practical examples，the differences in the mechanical behaviour between a transversely isotropic foundation and an isotropic foundation are found. The study result can also be applied to explain the phenomena of larger horizontal stresses compared with the vertical ones and anisotropic horizontal stresses as observed in practice.

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NUMERICAL ANALYSIS OF EXCAVATION SUPPORT SYSTEM
OF JINHUA BUILDING

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2004, 23 (07): -1219 doi:
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[PDF 199 KB] (998)

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The paper sets up the calculating model of stresses in the support structures according to the character of excavation engineering，using the MARC program. Based on the model，the practical excavation project with support design changed for several times is analyzed. The rational and scientific treatment on the engineering decision is discussed.

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DESIGN AND OPTIMIZATION OF
DRY DOCK OF IMMERSED CHANGHONG TUNNEL IN NINGBO

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2004, 23 (07): -1223 doi:
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[PDF 319 KB] (1021)

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The location selection is described for dry dock of the immersed Changhong tunnel in Ningbo. Comparison is made for the designs of dock pier，bank，and dock slope. The treatment of dock base is discussed. The stability of dock slope and the deformation of dock base are calculated. The method and experience of dry dock design are also summarized.

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STUDY ON EARTHQUAKE-RESISTANCE OF SIMPLY-SUPPORTED GIRDER BRIDGE WITH EXAMPLE OF SUQIAN BRIDGE IN JIANGSU

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2004, 23 (07): -1229 doi:
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[PDF 172 KB] (1135)

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A calculation method of earthquake-resistance design of simply-supported girder bridge using rubber branch seats is proposed. With the example of the Suqian Bridge， the earthquake induced stresses in both vertical and horizontal directions are analyzed. The results show that the lower part of the bridge is controlled by earthquake induced stresses，with large vertical and horizontal stresses. It can be concluded that good bridge design can only be achieved through a combination of scientific design methods and effective earthquake-resistance measures.

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SIGNIFICANCE OF STRENGTH AND STRUCTURE OF SLIDING BODY IN TREATMENT OF LANDSLIDES OF SOIL AND LOOSE MATERIAL

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2004, 23 (07): -1233 doi:
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[PDF 187 KB] (1153)

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During remediation for the landslides of soil and loose material，the three problems are often neglected，such as the extrusion of soil above top of pile，the extrusion of soil between piles，and the decay of anchoring forces in cable bolts. The three problems are discussed based on analyses of typical engineering examples，and the principles are put forward for the investigations and reinforcement designs of the landslides of soil and loose material.