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2003, 22 (01): -0 doi:
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STUDY ON THE THREE-DIMENSIONAL COMPOSITE ELEMENT
MODEL OF BOLTED ROCK MASSES

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2003, 22 (01): -1 doi:
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[PDF 301 KB] (961)

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The general composite element concept is proposed firstly，then the principle of the model is used to establish a fully-grouted rock bolt element model which comprises rock material，grout material，bolt material，rock-grout interface and bolt-grout interface. The composite element can be incorporated into the conventional finite element analysis easily with hierarchical technique. On one hand，when one element contains no bolt segments，the composite element will be degenerated into the conventional finite element. On the other hand，if the number and direction of bolts are changed in the optimal reinforcement design，the FE grid will keep unchanged. In this way the mesh generation of the large scale reinforced rock structures becomes relatively convenient and feasible. The model has been implemented in the FEM software CORE3，and some numerical examples are presented.

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TRANSMISSION OF ELASTIC P-WAVES ACROSS SINGLE FRACTURE WITH NONLINEAR NORMAL DEFORMATION BEHAVIOR

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2003, 22 (01): -9 doi:
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[PDF 328 KB] (1369)

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A theoretical study is presented on normally incident elastic P-wave transmission across single dry fracture with nonlinear normal deformation behavior. The effects of nonlinear normal deformation on P-wave normal incidence are studied without the shear deformation considered. The linear displacement discontinuity model for wave propagation across fracture is extended to nonlinear model，the hyperbolic elastic model(BB model). Numeric solutions of transmission and reflecton coefficients for normally incident P-wave transmission across the nonlinear deformable fracture are obtained and related to the closure behavior of fracture. Parameter studies are conducted to get an insight into the effects of the nonlinear normal deformation of fracture on P-wave transmission，in terms of initial normal stiffness and the ratio of given closure to maximum allowable closure of the fracture，as well as the incident wave amplitude and frequency. Comparisons between the linear and nonlinear models are presented. It is shown that，the transmission and reflecton coefficients for the linear model are special solutions of those for the nonlinear model，when the incident wave amplitude is so low that the maximum closure of fracture incurred during the wave transmission is much smaller relative to the maximum allowable closure. In addition，the nonlinear behavior of fracture gives rise to the phenomenon of higher harmonics during the wave transmission across the fracture.

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EXPERIMENTAL AND NUMERICAL RESEARCH ON CRACK PROPAGATION IN ROCK UNDER COMPRESSION

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2003, 22 (01): -18 doi:
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[PDF 381 KB] (1445)

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The propagation and coalescence mechanism of closed joints under uniaxial and biaxial compressive stress is studied by rock-like material model tests. 8-node singular isoparametric element mode is applied to simulate the stress field near crack tip. Both the numerical and experimental results of crack propagation are in consistence. The new results are useful to study mechanical properties of jointed rock mass. Furthermore，based on the laboratory test results of KIC，the propagation area of fractures in surrounding rock mass of pump stations of Shanxi Yellow River Diversion Project during excavation and support is obtained.

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CONSTITUTIVE RELATIONSHIP OF MESOSCOPIC ELEMENTS USED IN RFPA2D AND ITS VALIDATIONS

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2003, 22 (01): -24 doi:
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[PDF 334 KB] (1837)

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Based on the heterogeneous characteristics of rock at mesoscopic level，the constitutive law of mesoscopic elements used in RFPA2D is described with elastic damage mechanics. The RFPA2D is used to simulate the strength and failure patterns of rock specimen subjected to uniaxial or biaxial loading. The numerical results are compared well with the corresponding experimental results，which proves that the constitutive law as well as the numerical system (RFPA2D) are reasonable and effective in simulating the failure of rock under various plane stress conditions.

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NEW STUDY OF DAMAGE VARIABLE
AND CONSTITUTIVE EQUATION OF ROCK

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2003, 22 (01): -30 doi:
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[PDF 229 KB] (1470)

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Firstly，based on CT number，a damage variable is proposed with more new meaning. Three new conceptions are put forward，which are positive damage，basic damage，negative damage. Secondly，the generalized theory of strain equality and damage constitutive equation of rock under uniaxial compression are given. Thirdly，the example of the equation is shown. Finally，compared to the traditional damage constitutive equation，the advantages of the one given are listed.

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DAMAGE ANALYSIS OF FLOOR STRATA

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2003, 22 (01): -35 doi:
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[PDF 205 KB] (994)

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The key to mining with pressure is to understand the floor failure mechanism by mining and water pressure. The failure of the floor rock mass depends on floor stress field and distributions of the primary discon- tinuities. First，based on the rock engineering failure criteria，the definition of the floor failure is discussed. Then，according to the in-situ comprehensive observation data，by using two damage variables of the isotropic elastic damage model to describe the primary discontinuities of the floor，the mesoscopic mechanism of the floor failure is studied with displacement back analysis. The presented study provides the foundation to evaluate the floor safety.

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STUDY ON INFLUENCE OF PERFORATION ON FORMATION FRACTURING PRESSURE

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2003, 22 (01): -40 doi:
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[PDF 259 KB] (1261)

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Hydraulic fracturing treatments of oil wells in petroleum industry are affected greatly by the perforation parameters selected. A three-dimensional finite element model together with the tensile criterion of rock materials is employed to investigate systematically the influences of perforation in vertical wells on formation fracturing pressure，including perforation density，perforation orientation，perforation diameter and perforation length. Based on a six-month simulation research in University of Petroleum，China，several conclusions are drawn. Perforation density and orientation angles are the most important factors of all to affect formation fracturing pressure. However，as for perforation diameter and perforation length，their influences are much slight. The conclusions reached provide valuable guidance to the designers of hydraulic fracturing treatment and engineers of oil fields.

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BROKEN FEATURE OF KEY STRATA AND ITS INFLUENCE ON ROCK PRESSURE IN SUPER-LENGTH FULLY-MECHANIZED COAL FACE

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2003, 22 (01): -45 doi:
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[PDF 253 KB] (1122)

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It is found by model experiment and field measurement that with the length of fully-mechanized coal face，the size of the broken blocks of key strata in the coal face will decrease correspondingly，and thus the rock pressure in the face is much welldistributed. This is good for the top coal broken and caving conveniently. However，the overlying rock pressure of the main key strata will happen accordingly. Furthermore，the relevant measurements must be taken efficiently to control the key strata for coal mining safely.

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DETERMINATION OF RATIONAL STAGGERED DISTANCE
IN DOUBLE-LONGWALL FACES IN MINING ON CONFINED AQUIFER

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2003, 22 (01): -48 doi:
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[PDF 212 KB] (947)

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The influence of staggered distance on the failure of floor strata in double-longwall mining on the confined aquifer is local and temporary. After longwall mining having reached a certain scale，the failure depth in floor strata depends on macroscopic parameters of mining technology and geological conditions. The current and ultimate failure depth of the floor strata does not change due to the magnitude of mining staggered distance (5～30 m). Based on the mining geological conditions of a practical double longwall mining panel，a rational staggered distance of double-longwall faces is proposed to be within 10 m，by means of observing the changes of in-situ abutment pressure and 3D coupled numerical modeling of fracture in floor strata.

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EFFECT OF CONFINING PRESSURE ON THE YOUNG’S
MODULUS OF ROCK SPECIMEN

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2003, 22 (01): -53 doi:
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[PDF 307 KB] (3508)

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Rocks are different in their structure，mineral particles and deforming history，and the effect of confining pressure on Young’s modulus is not understood clearly. The Young’s modulus is various with the definition method as the stress-strain curve is not a direct line. The secant modulus from zero stress can not describe the deforming property of the practical rock mass. But the average modulus，which is determined from the average slope of the more-or-less straight-line portion of the axial stress-strain curve，is less influenced by the experimental conditions. Experimental results from servo-controlled testing machine and public references are used to study the relation between confining pressure and Young’s modulus for various rocks. Confining pressure does not influence Young’s modulus of rock with homogeneous material in macrostructure or with local flaw only. But specimen from weathered rock or drilled in weak rock strata usually has distributed fissures. The friction in the fissures will increase with confining pressure，which reduces the shear slide between fissures and makes Young’s modulus higher as well. The relation between Young’s modulus and confining pressure shows the state of rock damage.

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EXPERIMENTAL DATA INTERPRETATION AND PROBABILITY ANALYSIS OF PULLED ROCK BOLTS

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2003, 22 (01): -61 doi:
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[PDF 210 KB] (1199)

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In-situ experimental data of anchoring strength of bolts in complex rock are interpreted by application of fuzzy-random theory. A new effective method is presented to solve the fuzzy-random probability model. And the fuzzy-random method is proved to be useful by case study. Probability of pulled rock bolt is computed when correct distribution of shear stress on bolt surface is taken into account.

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RESEARCH ON TWO ARCHES OF TRUSS SUPPORTING LOOSE ROOF

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2003, 22 (01): -65 doi:
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[PDF 209 KB] (1073)

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The mechanism of the truss supporting loose roof is studied through physical simulation tests. Two arches named the first arch and the second arch are found in loose roof in simulation tests. The simplified mechanics model of the truss supporting loose roof is set up according to test results and in virtue of some theory. The two arches of truss supporting loose roof are studied thoroughly in theory. The deduced calculation formula provides calculation methods and theoretical references for parameters designs of truss supporting loose roof and is of important maturational meaning to practice.

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JOINT INTERACTION MODELS FOR SHIELD TUNNEL SEGMENT REINFORCED BY SECONDARY LININGS

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2003, 22 (01): -70 doi:
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[PDF 313 KB] (960)

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The principle and results of load test on double-layer linging joint are discussed simply. Based on the above results，three joint interaction models are proposed according to the different structural forms of joint between the primary and the secondary linings. The linging fracture created by tensile force is simulated，and the calculational result is compared with the test data. It is shown that reducing the stiffness of lining in the case of occurrence of fracture is reasonable，and the model result is in good accordance with the test data.

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EXPLICIT FINITE ELEMENT SCHEME FOR DYNAMIC ANALYSES
OF WAVE PROPAGATION IN MULTI-LAYERED MEDIA

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2003, 22 (01): -75 doi:
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[PDF 240 KB] (1100)

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Based on the explicit finite element schemes for analyzing dynamic response of solid，fluid-saturated porous media，fluid，a procedure using those schemes for dynamic analyses of wave propagation in multi-layered media is presented considering the boundary condition at the interfaces and the artificial transmitting boundary for simulation of the far field. The procedure and its computer program have been verified by examples. The results obtained by the proposed procedure agree well with the corresponding analytical solutions. In addition，the results obtained considering the radiation damping by the artificial transmitting boundary show that the accuracy of the procedure can be assured for the proposed scheme.

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ANALYSIS ON HARMFULNESS OF EMBEDDED
CRACK IN SPILLWAY PIER AND ITS TREATMENTS

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2003, 22 (01): -81 doi:
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[PDF 297 KB] (1095)

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A numerical analysis of cracks in the pier of spillway in a water conservancy work is carried out with the unique crack elements to simulate the cracks and the special bolts crossing crack element. The results of the numerical analysis show that the deformation of the cracks under the external loads may be unstable if the cracks are not treated. The treatment parameters of chemical grouting are also given by the simulation analysis.

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NUMERICAL COMPUTATION AND ANALYSIS OF INFLUENCE OF PLUNGE POOL CONSTRUCTION ON UPLIFT PRESSURE OF DAM FOUNDATION

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2003, 22 (01): -86 doi:
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[PDF 219 KB] (865)

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Based upon the observed data of uplift pressure and prior information of pouring water test in Baishan hydraulic power station，the permeability coefficients of rock and concrete are identified by making use of neural networks. According to the inversion results of permeability coefficients，the changes of the uplift pressure are researched by three-dimensional FEM under the four different loading cases after the plunge pool excavation. The computation results testify that the construction of plunge pool will not increase the uplift pressure while the drainage system of plunge pool is effective. The construction of plunge pool will increase the uplift pressure while the drainage system of plunge pool is invalid. The technological measures of reducing uplift pressure have been taken for the dam foundation with high uplift pressure based on the calculation result.

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ANALYSIS ON SEISMIC EFFECT FOR SATURATED SOIL
USING B SPLINE FUNCTION FINITE ELEMENT

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2003, 22 (01): -90 doi:
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[PDF 406 KB] (734)

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Applying principle of effective stress，the numerical analysis is made on the seismic effect，such as the vibration pore water pressure，displacement and stress，for saturated soil under the influence of earthquake with B spline function on the basis of Biot’ consolidation theory. The calculation is made for a real example and the result is good in accordance with the usual law obtained from normal FEM.

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STUDY ON DYNAMIC STEADY STATE STRENGTH OF
SAND SOIL LIQUEFACTION

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2003, 22 (01): -96 doi:
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[PDF 434 KB] (1122)

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According to the dynamic triaxial test of sand，there is a steady state at the last phase of the development of strain and stress path. In different cycle of this phase，the stress paths superpose with each other，but the axial
strain tends to a steady rate. The strength of the sand in this phase is studied because it is an important parameter to evaluate the stability of sand soil liquefaction. Considering the strength developed with stress path，the mechanism of saturated sand liquefaction seems more clear.

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NON-LINEAR PERTURBATION STOCHASTIC FINITE ELEMENT METHOD FOR ANALYZING THE RELIABILITY
OF VERTICAL LOADED PILE

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2003, 22 (01): -103 doi:
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[PDF 384 KB] (1057)

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The algorithm of second-moment non-linear perturbation stochastic finite element method is studied and presented for the reliability analysis with the Duncan-Chang non-linear constitutive law of geotechnical engineering taken account into，and a corresponding computer program is also developed. The spatial soil properties are modeled as three-dimensional homogeneous random fields，and the criteria of modeled some soil properties as random fields. The technique of axisymmetric random fields’ discretization by local average approaches is studied. The algorithm and the assembly method of covariance matrix are proposed. The first and second order partial derivatives of the elasticity matrix of axisymmetric case，and the assembly method of partial derivatives of the global stiffness matrix are obtained. The analytical model for estimating the first two probabilistic moments of pile’s bearing capacity by stochastic finite element method is proposed. Both the uncertainty attached to the spatial soil properties and the uncertainty associated with load are considered for the influence of the reliability index. Application to a practical pile is given to demonstrate the suggested method. The results show that the non-linear stochastic finite element method is effective for analyzing the reliability of vertical loaded piling.

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MEASUREMENT AND ANALYSIS ON SHEAR STRENGTH
PARAMETERS OF MUNICIPAL SOLID WASTE

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2003, 22 (01): -110 doi:
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[PDF 363 KB] (1132)

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On the basis of undisturbed samples obtained from the municipal solid waste landfill，the laboratory measurements are performed using the large direct shear tests. According to the results，some factors that effect on shear strength parameters are analyzed preliminary. The field measurements are also been performed using the pressuremeter tests. The method used to calculate shear strength parameters of the solid waste by pressuremeter curves are presented.

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TREFFTZ DIRECT METHOD AND ITS RELATIVE PROBLEMS

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2003, 22 (01): -115 doi:
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[PDF 239 KB] (862)

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This paper attempts to further extend the so-called Trefftz direct method(TDM)，which has been developed and applied to a wide variety of boundary value problems in recent years. In this approach，the complete system of solutions of the partial differential equations is used as weighting functions and a non-singular boundary integral equation is used as the starting formulation. Several relative problems are discussed here. They are the problems of necessary and sufficient conditions for Trefftz-type boundary integral equations；the relationship between the Trefftz method and the variational principle and the infrequently encountered but possible singular problems in the Trefftz method and the treatment in practice. Numerical results are presented to illustrate the computational efficiency of the approach and to demonstrate its advantages.

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TECHNIQUE OF ACOUSTIC TOMOGRAPHY

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2003, 22 (01): -122 doi:
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[PDF 187 KB] (1332)

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Along with the economy development，all kinds of infrastructure are being built in a great quantity，which brings forward higher request on studying of rock and soil engineering properties and testing method of quality and strength of concrete member. Acoustic tomography technique has a vast field for application in studying rock and soil mechanics and testing concrete quality. Its principle and method are introduced in detail，and its characteristics and effects are illuminated through modeling experiment and application examples.

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SUBGRADE TREATMENT PRACTICE OF THE PLATEAU
SLOPE ON SOFT CLAY

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2003, 22 (01): -126 doi:
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[PDF 221 KB] (1180)

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The effects of subgrade treatment of the plateau slope on soft clay by the compacted stone column are analyzed. It is shown in practice that the stability of the plateau slope soft clay can be increased by combining the compacted stone column and the deep infiltration ditch. So the treatment method of combining the compacted stone column，the deep infiltration ditch and the anti-slide pile can be used if the slope angle of plateau soft clay is large，and in this way the stability of the slope will be ensured.

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EXPERIMENTAL STUDY ON EXCESS PORE WATER PRESSURE OF SOILS COVERED BY CLAY LAYER

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2003, 22 (01): -131 doi:
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[PDF 296 KB] (1189)

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Experimental study is made on soil-structure interaction by shaking table tests. The development of excess pore water pressure in sandy silt and medium sand covered by clay layer under simulated earthquake excitations，and their consolidation behavior shortly after the simulated earthquake excitations are studied. The development mechanism of excess pore water pressure in saturated sandy silt covered by clay layer is analyzed. In the end，some main factors are pointed out to affect liquefaction potential of the soil covered by clay layer.

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STUDY ON SOFT SOIL PROPERTIES OF THE PEARL RIVER DELTA

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2003, 22 (01): -137 doi:
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[PDF 245 KB] (1476)

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Based on the test results of a large number of samples ingathered in the Pearl River Delta，the statistics and analysis about physical and mechanical indexes of soft soil are made. The characters of nonlinearity and creep of soft soil are analyzed，according to the data obtained in field and laboratory tests. Through the calculation by nonlinear viscoelastic model，the quantitative influence of creep property on deformation of ground and variation of pore pressure are studied.

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PRELIMINARY STUDY ON CONSTRUCTION DISTURBANCE OF VERTICAL DRAINAGE BODIES IN THE PEARL RIVER DELTA

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2003, 22 (01): -142 doi:
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[PDF 274 KB] (976)

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The construction of vertical drainage bodies causes compacting effect. The stress change in soft clay and the range of construction disturbance zone due to construction of vertical drainage bodies are analyzed using the column cavity expansion theorem in the light of a plane stress problem. The increment of pore water pressure and the stress change in soft clay are prominent. The plastic zone around a vertical drainage body is like a bottle. Within the depth of Z0，the radius of plastic zone depends on the initial stress and undrained shear strength of the soft clay，and increases with the depth. Below Z0，the radius of plastic zone is invariable，and its value depends on the initial stress，undrained shear strength，secant modulus of soft clay，the types of vertical drainage bodies and the guide tube，length of and distance between vertical drainage bodies，etc. The construction disturbance mainly occurs within the plastic zone with the heave of ground surface as a byproduct. In-situ soil test reveals that in comparison with the untreated soft clay ground，the shear strength of the soft clay in the ground treated with vertical drainage bodies decreases greatly in the Pearl River Delta and the settlement of treated soft clay ground increases. Theoretical analysis shows that the radius of construction disturbance zone in the soft clay ground is about 1.2 times of that of the plastic zone and 9 times of that of the guide tube of vertical drainage bodies.

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APPLICATION OF SOIL SUBTITUTION TECHNIQUE IN INCLINATION CORRECTION OF HAZARDOUS BUILDING ON HETEROGENEOUS FOUNDATION

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2003, 22 (01): -148 doi:
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[PDF 284 KB] (1065)

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The soil substitution technique is used to correct the inclination of hazardous building，in which one side of the building is bolted with static piles to limit the settlement and the other side is forced to reverse the inclination by horizontal soil removal. The correction is successful due to the application of various methods on the heterogeneous foundation.

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COMBINED REINFORCED TECHNOLOGY FOR SLOPE AND BUILDING BASE NEAR FOUNDATION PIT

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2003, 22 (01): -153 doi:
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[PDF 237 KB] (1253)

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The combined reinforced technology with static bolt-pile and grouting is adopted in the reinforcement for the old building with large settlement near foundation pit，and the soil nail wall is applied to support the slope while excavating. The presented methods of design and construction are of reference significance for other similar projects.

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屠毓敏1 吉建兴2

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2003, 22 (01): -157 doi:
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[PDF 304 KB] (1090)

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By field sliding resistance test of the retaining structure both with and without key wall in the soft clay ground，the effect of key wall on the retaining structure is studied. The field test results are analyzed by means of non-linear FEM. The conclusions are as follows. The effect of the key wall on sliding resistance is quite great in spite of shorter key wall length，and the sliding resistance is in direct proportion to the key wall length in the range of testing key wall length. The earth pressure in front of the key wall reaches the passive pressure and the earth pressure behind the key wall is close to zero while the retaining structure is in limit equilibrium condition. The FEM predictions are in good agreement with the experimental results. Finally，the critical length of the key wall is studied by means of FEM.

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NEW KNOWLEDGE ON LAW OF GROUND SINKING IN MINING AREA

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2003, 22 (01): -162 doi:
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[PDF 189 KB] (1209)

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According to the practical observation data of ground sinking in many mining areas，a new ground sinking calculation formula is obtained. The relationship is expounded among the ground sinking value with the mean height of slope，the mean ratio of length to width of slope，the layout of protected ore pillar，the plane area of slope，the mean height from slope top to ground，the mean elastic modulus of covered rock stratum，the shape factor of slope，the mean angle of slope cutting rock stratum and distance from slope center.

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PROBLEMS AND THOUGHTS OF DEVELOPMENT OF SLOPE
STABILITY ANALYSIS SOFTWARE IN CHINA

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2003, 22 (01): -166 doi:
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[PDF 189 KB] (2146)

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