2005-24期中英文目录

The finite-cover-based element-free method developed by the authors is briefly illustrated. The method takes the individual merits of both manifold method based on finite cover technique and the element-free method based on Galerkin weak form. In the method，the whole domain is overlaid by a series of overlapped mathematical covers. While being cut by joints，interfaces of different media，and physical boundaries，a mathematical cover may be divided into two or more completely disconnected physical covers. A cover weight function defined on each physical cover in conjunction with the multiple weighted moving least square approximation is used to determine shape function of a point under consideration. Afterwards，discrete equations of the boundary-value problem with discontinuity can be established by using variational principles. Then，the proposed method is extended to numerical simulation of fractural behavior and crack development process of rock masses with initial cracks. Two key techniques are used with the capability of automatically simulating crack propagation effectively：one is arbitrary small increment size of crack propagation and another is near-crack-tip stress releasing procedure. The proposed algorithm that is numerically implemented can be used for the evaluation of rock structures with stability of crack and automatic simulation of crack propagation，cutting-through and interaction of two adjacent cracks. Since a crack can propagate in a very small size of increment，the trajectory of the crack propagation is stable and does not manifest any sensitivity to choice of the increment size；and example analyses of fractural behavior of the rock mass with single crack are made. The numerical results are compared with the available theoretical or numerical solutions to verify the applicability of the method to fracture and discontinuous deformation analysis problems. Then，the stress intensity factor and crack propagation process of rock mass with multiple cracks are numerically simulated. It is shown that the proposed method is superior to the manifold method and the element-free Galerkin method.

As an example of a salt mining，the laws of deformation of salt rock in depth are investigated by the mechanics and creep experiment of salt rock. The 3D computational model of the deformation analysis of cavity for salt rock is proposed. The optimization of cavity，stability，and long-term stability are studied on the basis of the in-situ geological conditions；and the change laws of the volume of cavity are studied under different inside pressures. The results show that the scheme of energy storage in salt rock is acceptable in China.

After the excavation of the Three Gorges Project(TGP) shiplock slope，a larger tension stress area is seen because of unloading and stress redistribution，where the rockmass is shown on a tension-shear stress state. The laboratory rock tension-shear tests are carried out to study the strength criterion of the tension stress area. However，the in-situ rockmass test to analyze the criterion is seldom seen. Based on the in-situ tension-shear test with the size of 50 cm×50 cm in the TGP shiplock slope rockmass，the test results show that the tension-shear strength of rockmass is reduced continually as the tension stress increases；and the relationship between and has a obvious curve characteristic. The achieved conclusion of tension-shear strength criterion can be drawn that the rockmass tension-shear strength criterion should adopt the second-degree parabola model best；and the next preferable choice of criterion is hyperbola model. However，the beeline model applied to the tests will cause a considerably larger discrepancy. Consequently，when carrying on the deformation stability analysis to side slope，the strength criterion of beeline model to analyze the rockmass of tension-shear stress area should be avoided；and the beeline model relationship，which is obtained from the laboratory press-shear test of rock，can not be used to determinate the tension stress zone.

The burst potential of coal-bearing formation is the inherent attribution and necessary condition to induce a rockburst. There are many factors that can influence the burst potential of rock masses，but the rock composition and texture are the intrinsic factors to control its burst potential. Based on the microstructure of rock masses，the stress condition，the strength characters，and the deformation-fracture process of rock masses are discussed，which are used to establish the relationship model between the microstructure and macro-mechanical property of rock masses. The mechanism of energy accumulation and dissipation of rock masses during loading is analyzed to establish the qualitative and quantitative relations between the composition and texture and the burst potential of rock masses of coal-bearing formation. From the experimental researches and theoretical analysis，it is shown that the burst potential of rock mass has an intimate relationship with its composition. With the increasing of the detritus content of rock masses(from mud shale，siltstone，to fine and medium sand)，the compressive strength and elastic modulus of rock masses increase. The accumulated strain energy in rock masses during loading increases and the dissipated energy of plastic deformation decreases，which improves the possibility to induce the strain type rockburst. The texture characters of rock masses also have great influences on their burst potential，such as the grain diameter，agglutinate composition and type and so on. With the decrease of detritus grain diameter in rock masses，the contents of large grain mineral (quartz and feldspar) of rock masses decrease and the contents of fine grain flake mineral (mica，chlorite and smeciite) increase. Once being loaded by the concentrated stress，rock masses will dissipate more permanent deformation energy during the plastic deformation and accumulate less elastic strain energy during elastic deformation. The possibility of rock masses brittle failure becomes less；and the burst potential of rock masses decreases. Moreover，the rock masses with siliceous cements have higher strength than those with ferruginous，calcareous，and argillaceous cements. From the agglutination types of rock masses，rock masses with contact-agglutination are stronger than those with pore-agglutination and foundation-agglutination.

A series of formulas about two-parameter parabolic Mohr strength criterion are derived. Based on the results of uniaxial tension test and uniaxial compression test，the parameters involved in the criterion can be determined，and the damage pattern is also discussed. After that，the formulas about the rupture angle and the friction angle are presented，and the formula of their relationship is also presented. Two-parameter parabolic Mohr strength criterion can describe both shear failure mode and tensile failure mode. In this criterion，the ratio of the uniaxial compression strength and the uniaxial tension strength can be set any value. The formulas of the rupture angle provide concrete theoretical foundation for the direction of crack face and damage pattern in the computation of macro crack propagation. At last，it is also pointed out that Griffith criterion is only an exceptional case of two-parameter parabolic Mohr strength criterion.

Numerical simulation of arbitrary discontinuities is a hot and difficult problem；especially for tracking the dynamic cracks，it has important practical meaning. A new numerical method，extended finite element method(XFEM)，which may conveniently simulate static and dynamic cracks，was introduced several years ago. The numerical method for modeling strong (displacement) as well as weak (strain localization) discontinuities with a standard finite element framework is presented. In the XFEM，in order to model the discontinuities of displacements，the jump function and asymptotic crack-tip displacement fields are added to the finite element approximation for the local enrichment by using the framework of partition of unity. Thus，the discontinuities are independent of the mesh. The principles of XFEM are given；and some formulas are derived. The integral scheme of discontinuous function is presented；and the evaluation of stress intensity factor is discussed. Numerical simulations illustrate that XFEM can effectively model the discontinuities；and it has wonderful practical merits.

Permeability is a key parameter in calculating and analyzing of geotechnical engineering；and its accuracy is very important. IFCO BAT system is a set of in-situ test system，which can gain the pore water pressure of ground and in-situ permeability of soil quickly and accurately. The theories for in-situ test of pore water pressure and permeability by IFCO BAT system were generally introduced. The applications to model test of dredger clay show that the theories are correct and the in-situ test results are accurate；and IFCO BAT system can be used in geotechnical engineering.

In response to the characteristic of rock masses and initial geostresses in Xiaowan Hydropower Station，elastic-brittle-plastic (EBP) constitutive model is employed to analyze the deformation and plastic zone of the rock mass surrounding the underground structures after the completion of excavation. Meanwhile，elastic-plastic (EP) model is also applied to analyse the problems. The results obtained by the two models are compared and the difference between them is obvious. Considering that several faults intersect the underground caverns，the effects of the faults on both deformation and the damage zone by the replacement of the infillings of them are presented. Numerical results show that faults exert much influence on the stabilities of the caverns when the faults are near the surfaces of the caverns.

The weight functions and the displacement functions of tetrahedron finite element covers are defined. The global equilibrium equations of three-dimensional numerical manifold method (3D NMM) based on finite element covers are established by minimizing the total potential energy. The stiffness matrix，initial stress matrix，loading matrix，inertia matrix，displacement resistance matrix，contact matrix and friction force matrix are derived and added to the global equations. The numerical results from several typical test cases indicate the proposed method is valid.

Based on wavelet transform，a method of time domain for 3D dynamic finite element method (FEM) of tunnel entrance was introduced；and then a model of FEM was established. The dynamic response properties of tunnel¢s entrance with varying surrounding rock mass were analyzed under the vibration loading of the elevating train. The time-response laws for the entrance of tunnel were obtained. The obtained results have important significance for further analyzing dynamic stability of tunnel by reason of the speed-elevated train.

Three-dimensional finite element model of Lijiaxia Hydropower Station is established to monitor operation condition of the arch dam. Based on prototype observation data，an improved back propagation(BP) neural network is applied to calculate elastic modulus of arch concrete dam for Lijiaxia Hydropower Station and deformation modulus of its foundation. This method can provide precise parameters for the calculation of the model，and can make a precise evaluation on the safety condition of dam. It can also provide a new way to the back analysis of other physico-mechanical parameters.

The national key project，Yichang—Wanzhou Railway，passes through the limestone mountainous area in west Hubei；and many deep-seated tunnels are needed to construct. In order to optimize the design and guide construction，hydro-fracturing stress measurements have been conducted for many boreholes along Yichang—Wanzhou Railway tunnel line in west limestone mountainous area of Hubei Province. It can be concluded that the in-situ stress magnitude in this area is classified as middle to high level；and the direction of the maximal horizontal stress is near to East-West. Based on the in-situ stress results and four distinguish methods，which are engineering rock quality classification standard，Russenes method，Turchaninov method and Hoek method；rockbursts are predicted during tunnel construction in deep-seated and hard rock tunnel conditions；and large deformation are predicted during tunnel construction in deep-seated and soft rock tunnel condition. In order to avoid the disadvantage conditions，reasonable excavation method and safety precautions should be adopted during tunnel construction.

The mainly factors affecting overbreak in the tunnels include the geological characteristics of rock mass and geological constitution. The problems of overbreak are met during rock mass excavation. From the mechanism of rock rupture，the fractal dimension of tunnel perimeter is researched on the jointed rock mass. The generalized fractal dimension model of tunnel perimeter in jointed rock mass is put forward；and the relation between affecting parameters and generalized fractal dimension of tunnel perimeter is studied. According to the fractal theory，the relation between overbreak and generalized fractal dimension of tunnel perimeter is built. Based on the geological mechanics mechanism，the relation between overbreak and generalized fractal dimension is built. Finally，an engineering case is used to testify the adaptive of this model. The achieved results show that：(1) the magnitude of generalized fractal dimension model is decided by the characteristics of discontinuity plane during tunnel excavation；(2) it probably produces biggish overbreak due to the biggish fractal dimension；and (3) the quantity of overbreak presents nonlinear increase for many times with relative fractal dimension.

The stress-strain curve of rock with a given size is only a kind of macroscopical manifestation，which can not be applied directly to the design of geotechnical engineering and the analysis of numerical computation，i.e.，there is an indiscerptible relation between constitutive model and size of rock，which is not clearly understood. Based on the strain strength theory and the random statistical distribution hypothesis of rock strength，a statistical constitutive model for rock damage under uniaxial compression，which considers the nonlinear relation of unit volume failure or elastic modulus and the size，is established by adopting the damage constitutive theory of continuous medium. With the servo-controlled testing machine，uniaxial compressive experiment is performed on the marble specimens with different ratios of length to diameter. On the basis of experimental results of marble specimens with different sizes，the relation between mechanical parameters of rock material and size is discussed；and then the parameters for statistical damage constitutive model of rock considering scale effect are confirmed. The achieved theoretical curves by the damage model of rock with different ratios of length to diameter ratios are in good agreement with the experimental results. Finally，the evolution law of rock scale on the damage properties is discussed.

It is common to use the nonlinear load-transfer method (p-y curve method) or Poulos¢s elastic theory to calculate piles subjected to lateral soil movements at present. The characteristics of the two methods are discussed and a new coupling analytical solution based on the two methods is developed. In the new method，the soil moduli along pile length are calculated by the p-y curve method according to the soil elements¢ stresses level and lateral displacements between the pile elements and soil elements. Then，the elastic theory is used to account for the soil-pile interaction between different elements by using the above soil moduli. The results of the proposed coupling method are reasonable as shown by comparing lateral behavior of the pile under horizontal soil movements with those of the above two methods.

When a cool fluid such as water is injected into a hot reservoir，a growing region of cooled rock is established around the injection well. The results in change of in-situ temperature field and the influences of induced stress due to thermal stress field on the initial fracture condition are analyzed. The achieved results show that the thermal induction stress should be considered. The example illustrates that the initial stress due to the effect of thermal induced stress can be decreased about 16%.

The seismic activities in China are chiefly concentrated in the West Region. The study of seismic mechanism and geostress measurement in West China becomes very important while the construction investment increases rapidly in recent years. The relation between seismic activity，geostress，and their present situation of study have been recounted. The geostress measurements in deep boreholes should be strengthened；and the technique and method of geostress measurement by hollow inclusion triaxial strain gauge have been emphatically described. Meanwhile，the geostress measured results at the Xiabandi Hydraulic Project in Xinjiang Autonomous Region have been presented.

Based on initial data of axial-symmetrically triaxial compression test of silty and sandy clays with temperatures of －4 ℃ and －6 ℃，respectively，two methods are adopted with/without considering the cross-section area change of specimens. The relationships among the cross-section area change of specimens，axial strain and confining pressure are discussed. According to the results，it is found that the specimens increase nonlinearly with the axial strain increase. However，it is also seen that the cross-section area increases when the confining pressure increases to about 3.0 MPa below which the area change basically keeps constant；and it was not varied with the soil type and temperature. Moreover，the patterns of stress-strain curves and compressive strength values，when the revised area is considered，are obviously different from the corresponding ones without considering the revised area.

In the dynamic analysis of underground structure，the constraint to structures caused by the surrounding soil is often simulated by the virtual parameters，such as virtual mass，stiffness and damping parameters. Because of these virtual parameters，the model of underground structure is different from that of ground structure，which will cause traditional methods to fail in solving underground structure. Therefore，two approaches are presented—one method is applied to shear-type underground structure which can identify the structural parameters and virtual parameters at one step；and the other method which can be used to estimate common system with multi-degree freedoms by two step. In the first step，the structural parameters are identified；and in the second step，the virtual parameters can be estimated by using the structural parameters identified before. At last，a numerical example of shear-type building is applied；the results show the feasibility and efficiency of the method.

The soil classification is very important in geotechnical engineering；and the flat dilatometer test(DMT) is a very useful in-situ test. Based on 17 600 measured data of 157 flat dilatometer tests in Shanghai，the ranges of ID for different kinds of soils are analyzed and summarized for the clay，silt and silty sand；and the basis for soil classification with material index ID is provided. At the same time，the influences of over-consolidation are discussed.

With six tests of expansive soils for the roadbeds，which come from Ningming section of Nanning—Youyiguan Highway in Guangxi Autonomous Region，and Cili section of Changde—Zhangjiajie Highway in Hunan Province，respectively，are analyzed under different weather conditions such as dewatering，overcast，sunshine and precipitation. The different dewatering boundaries，the densities of roadbed，the accumulated water contents are considered for the roadbed. The moisture contents variation，water permeation and evaporation in the expansive soils roadbed are also researched. The achieved results can provide some useful references for the design and construction of expansive soils roadbed.

Based on Biot¢s theory and the concept of homogeneous porous fluid，the function of vertical vibration amplification is described as a function of degree of saturation，soil properties，layer thickness and loading frequency. Numerical examples are given to illustrate the influence of saturation，soil properties，layer thickness，coefficient of viscoelasticity，and frequency on the motion amplification. The achieved results indicate that the influence of saturation，coefficient of viscoelasticity and layer thickness on the vertical vibration amplification are different. Some valuable conclusions are drawn.

In order to study viscoplastic properties of clay，uniaxial compression tests are performed with computer-controlled triaxial apparatus on saturated，wet，air-dried，and oven-dried Japanese Pleistocene clay (Fujinomori clay：specific gravity Gs = 2.69，D50 = 0.017 mm，coefficient of uniformity Cu = 10，plastic limit IP = 33%，liquid limit IL = 62%). In the tests，axial (vertical) strain rate was changed stepwise for many times，and drained creep tests were performed for several times during monotonic loading at constant strain rate. Global unloading and reloading were also applied. Results of the tests on the Japanese Pleistocene clay with different water contents(different saturations) were presented. The results show that viscous properties of the Japanese Pleistocene clay with different water contents are significant in all the tests. Load rate effect (i.e.，the stress changes immediately after change in the strain rate occurred in the stress-strain curve) and creep deformation can be seen clearly in all the tests. The analytical test results show that：(1) viscous behaviour of Japanese Pleistocene clay does not appear due to the delayed dissipation of excess pore water pressure(not only saturated and wet but also air-dried and oven-dried specimens show significant viscous behaviour)；(2) viscous properties of specimens with different saturations are similar (load rate effect and creep deformation were observed in all the specimens with different saturations)；and (3) the stiffness of specimen with different saturations increases significantly after creep. In addition，a nonlinear three-component model is proposed，which can simulate well the viscous properties of clay.

Data mining (DM) is a new information technology and a key knowledge discovery in database mining. It can process knowledge and information from a lot of practical data with incompletion，noise，fuzzy and uncertainty. Based on DM theory，the loess mechanical data mining system(LMDMS) was developed；and LMDMS was applied to the classification loess mechanical properties. The classification and regression trees (CART) decision trees and probabilistic neural network(PNN) in the LMDMS were applied to mining the loess classification rules and the principal component analysis was applied to compressing data to reach reducing dimension. After data were processed by the principal component analysis，the new variables could be obtained from mined objectives. Through the analysis of engineering application，the results indicate that：(1) the loess mechanical properties can be thoroughly seen by using the LMDMS based on a lot of loess mechanical basis physical indexes in practical engineering；(2) through comparing an algorithm of CART decision trees with an algorithm of probabilistic neural network in loess classification，an algorithm of CART decision trees is simpler in computation method，faster in computation velocity，and higher in computation precision；(3) CART decision trees method and probabilistic neural network are applied to mining loess classification rules and to constructing PNN model for loess classification，respectively，Meanwhile，coupling CART decision trees method and probabilistic neural network model can intelligently classify loess strata for loess engineering application；and (4) the principal component analysis can compress data，reduce data dimension，and simplify model. Meanwhile，it can improve computation velocity and precision and PNN model. The achieved results show that proposed model and rules are effective in engineering practices.

After the metro was put into operation，there has been increasing longitudinal nonuniform settlements of shield tunnel due to various causes including the vibration load of train，leakage of tunnel，different soil properties，etc.. This kind of nonuniform settlement will greatly endanger the safety of the train. Based on the measured data for longitudinal settlements of a tunnel in soft soil， the security of the tunnel caused by settlements is studied. Firstly，the longitudinal settlement was simulated by polynomial part by part and the relative longitudinal curvature was gained. Secondly，the equivalent axial stiffness model of shield tunnel initiated by a Japanese scholar is introduced. Finally，the relationship between longitudinal curvature and crack of shield tunnel segment joint was found based on the equivalent axial stiffness model of shield tunnel. The results not only can help us to learn the current situation of the longitudinal settlement of shield tunnel and the longitudinal crack of shield tunnel segment joint，but also provide the guidance for tunnel protection，waterproof design and construction technique of shield tunnel.

Studies on silty clay subjected to triaxial loading by using real-time computed tomography(CT) scanning experiment are carried out. Based on the CT-number and CT images，it is shown that the stress-strain curve of soil can be divided into four stages¾micro-defects closing stage，initial damage stage，rapid damage development stage，and softening failure stage. Silty clay is a typically nonuniform and original damaged material. During loading process，local deformation is formed；and the failure of soil is caused by local deformation and formation of shear band. Macro-fissure will be completely generated at the peak and post-peak of strength.

The widely accepted and relations are used for deducing the analytical equations of one-dimensional nonlinear consolidation coefficient of saturated clay，where the effective stress and void ratio are considered. The advanced GDS consolidation system，which can measure the bottom pore pressure during the consolidation process and where the following permeability test can be taken under the same consolidation pres- sure，is used to investigate the behavior of consolidation coefficient of Xiaoshan saturated clay. The compression index and permeability index can be obtained to calculate the nonlinear consolidation coefficient. Compared with the results from one-dimensional consolidation tests，the nonlinearity of consolidation coefficient is obtained.

Deep landfill of nuclear waste has become a key issue for the safe use of nuclear energy in the world. As a key sealing material for separating the nuclear waste from outside world at a deep underground point，the properties of swelling clay have attracted more and more attentions from geotechnical engineers. The volume change characteristics of densely compacted expansive bentonite under different hydration controlling suctions are studied by using mercury intrusion porosimetry(MIP) and scanning electron microscope(SEM) techniques in a comparison way. The osmotic technique was used for controlling suction. Tests on different densities of MX80 clay were carried out. The achieved results show that：(1) swelling potential of compacted bentonite during hydration depends on the initial compaction density；(2) the denser the clay is compacted，the higher the potential of expansion is；and (3) the volumetric swelling of the compacted clay is mainly derived from the expansion of the pores inter-aggregations.

The dynamic displacement response of an infinite strip resting on a viscoelastic foundation，where horizontal resistance exists at its bottom，has been investigated when the system is subjected to an impact loading. A linear hysteretic nature for the foundation was considered. By using the triangular series method and Fourier integral transformation method，the analytical solutions are achieved. Analyses were performed to investigate the effects of various parameters such as the loading duration，strip thickness，damping，and stiffness of foundation，and to examine how the horizontal resistance at the plate bottom affects the vibration. The results presented herein can provide the theoretical foundation for the pavement engineering design and roadway evaluation.

The true three-dimensional strata modeling is a common issue for geology，three-dimensional GIS，scientific visualization and engineering application. After introducing and summarizing the theory and method of three-dimensional geology modeling，a true three-dimensional tetrahedron network(TEN) model of strata is proposed. The model represents three-dimensional stratum with a series of tetrahedrons，which can provide the best flexibility to fill regions defined by simplified boundary elements(i.e.，edges in two-dimensional，triangle in three-dimensional). Geological exploration hole is the main information for engineers to know the soil strata. Geological exploration hole are abstracted as scattered point data. Each point is the demarcation point between two different strata and a topologic dimidiate datum structure is designed. Based on these scattered points abstracted from geological exploration hole information，the three-dimensional TEN stratum model is reconstructed by Delaunay triangulation algorithm. The modeling method can disposal broken mutation such as failure and dwindle. At last，some assumed classic strata and strata of a practice project are constructed by the method. The model has the advantage of convenient for storing and fast visualization. The characteristic of construction method is taking advantage of computer more effectively. Because the model strata are represented by tetrahedron，the strata model can also be used as the FEM mesh and convenient for special analysis，such as settlement or seepage of soil.

It is necessary to adopt safe monitoring and measuring in tunnel construction. The construction measured results of marked tunnel section 57–61 of drainage system of the tender CQWW2.01 in Chongqing City are presented. Based on the analysis of the measured results，the basic methods of supervisory measurements on tunnel construction under the complex conditions that surrounding rocks are mainly sandy clay are introduced；and the basic deformation regularity of similar tunnel and ground are also summarized. The achieved experience and data can be for reference to the construction and research of similar tunnels.

The important significance for the research on fluid-solid coupling seepage in porous media is introduced. Developments of the fluid-solid flow in the porous media are reviewed；and the further research directions are also presented. Particularly，studies on the fluid-solid coupling multiphase flow and its application and studies on various coupling methods in the last ten years are discussed. The fluid-solid coupling flow is concerned chiefly with flow of oil and gas through porous media. It is considered that the establishment and development of interaction cupling for multiphase fluids and multifield models and its numerical method have great meanings of the fluid-solid coupling mechanics.