Based on two-dimensional Cosserat constitutive model for layered rockmass, a new three-dimensional expanded Cosserat medium constitutive model, in which the influence of meso bending was taken into account, was proposed for layered salt rock containing two alternate layers with mismatch mechanical properties. It was validated primarily by an experiment on laminated salt rock samples under uniaxial compression. By using this new model, it can be analyzed the influence on stiffness of layered salt rock of the presence of hard or soft interlayer and also the macroscopical isotropy of layered salt rock due to interlayer. Combined with conventional strength theories, this model can be utilized further through a routine way for the strength and failure analysis. The proposed model can be expanded to solve nonlinear problems directly, and can be embedded to numerical analytical software for analysis of the stability of complicated underground openings in laminated salt rock.

There are lots of discontinuities whose geometry exhibits a random behavior in rock excavated slopes, and the failure surface of the slope is normally consisted of the joints and rock-bridges. To determine the lowest shear strength of the slope failure surface becomes the most important subject in slope engineering. Based on field investigation and statistic of the joints and Monte-Carlo simulation method, the joint mapping of the slope rock mass was determined. Then, the sliding surface of the slope can be determined by using the simulated annealing method and the stability factor of the slope can be calculated via a new improved two dimensional Sarma’s limit equilibrium method. A practical example was given to verify this method.

The governing equations of coupled thermo-hydro-mechanical consolidation for a homogeneous isotropic saturated porous medium are given firstly. The physical meanings of every coupling term are analyzed. Based on both Biot’s consolidation theory under isothermal conditions and thermo-mechanical theory under isobaric conditions, the physical meanings of coupling coefficients and their expression equations are given. The studies show that some coupling coefficients are same in their function formations completely; and the governing equations can be simplified greatly. For this, some simplified governing equations for some typical condition in engineering are given. As an example, thermo-hydro-mechanical characteristics are discussed for the problem of infinite saturated porous medium subjected to a global heat source of variable strength with time. The effects of some coupling terms are analyzed comparatively.

The characters of FLAC3D are studied and compared with finite element method. FLAC3D method uses node motion equation and traces the medium motion process from being loaded to reaching equilibrium state. While the finite element method solves from mechanical equilibrium equation directly. The above is the basic difference between the two methods. Because FLAC3D does not use the real medium damping property and node mass, the real process experiencing by the medium is not given and the influence of medium motion process on result cannot be reflected rightly. So the physical meaning of stress and deformation given by FLAC3D is not very clear. The medium vibration during solving process is a noise rather than a more real simulation to medium mechanical behavior and could cause calculation error for elastoplastic medium. The study shows that FLAC3D has a very high precision in determining the stress and deformation of elastic medium at equilibrium state and the vibration in solving process almost does not affect the final result. The advantages of FLAC3D method are that its mathematical operation is simple, and the solving process is convergent, and it is convenient in treating cases of medium large deformation, elastoplastic property, non-associated flow rule, excavation and supporting, etc. compared with finite element method. The defects of FLAC3D are that its calculation time is long, and the efficiency is low, and in some cases the number of time steps is high amazingly which may result in accumulating error. Studies in four aspects are also made through examples. (1) Comparisons between Drucker-Prager yield criterion and Mohr-Coulomb yield criterion. (2) Influence of dilation angle value on calculation result. (3) Influence of large deformation mode and small deformation mode on calculation result. (4) Influence of calculation precision setting on result.

Based on the upper bound technique of limit plasticity and the shear strength reduction concept, the equation for expressing the critical limit equilibrium state is formulated and is employed to define the safety factor and its corresponding critical failure mechanism for a given anisotropic and nonhomogeneous slope in c-? soils. Through numerical analyses for typical examples, the solutions computed by the proposed approach are compared with the results available given by limit equilibrium methods and other analytical methods to verify the reasonability of the method. For the slopes of which the safety factor cannot fulfill the requirement of overall stability for the given loading condition, the stabilizing pile is considered for reinforcement of the anisotropic and nonhomogeneous slopes. As the key issue in this circumstance, the equivalent force and moment against sliding induced at the cross-section which intersects the potential slip surface are determined on the basis of the rational distribution mode of net lateral effective earth pressure acting on the stabilizing pile. Then the upper bound theorem of limit analysis is employed again for establishing the limit equilibrium equation of the slopes reinforced by stabilizing piles in which the mobilized strength parameters are given by the actual strength parameters with a reduction by the desirable overall safety factor. The net lateral effective earth pressure acting on the pile can be chosen as the objective function; mathematical programming method is utilized to define the critical state. The critical net overall lateral earth pressure acting on the pile will be used in the structural design of pile. Numerical computations are made to examine the optimum location of pile placement.

Due to the merits of strength reduction method, it has been broadly used in nonlinear numerical analysis of the slope stability. In general, the rock and soil are regarded as to be an idealized elastoplastic model; and Mises yield criterion is used. The stability analysis of densely jointed rock slopes using ubiquitous-joint model , the joint property can be considered as well as the rock, thus fitting better with the practical engineering. It is assumed that failure might occur first either in rock or along joint or in both during the rock strength reduction. According to a real engineering project and based on strength reduction method with ubiquitous-joint model, the calculation results show that the potential slip surface appears in style of a polygonal plane; and the dip angle of the potential slip near slope foot is similar to the equivalent friction angle of joint, while the potential slip near the top slope is related to tension failure of rock. The results also show that the dip angle of the joint determines the slope safety factor and the potential slip range. The steeper joint sets affect less the slope stability. Throughout the investigation of the slope failure criteria and the slip surface, it is recognized that the case of the force or displacement becoming not convergent can be properly used as the failure criteria of slope. The shear strain rate in slope can also be used as the criteria for confirming the potential slip of slope because its physical meaning is very explicit.

Considering characteristics of Grotto Relics, the influence factors and dynamic finite element analysis methods on deformation stability grotto country rock are discussed. Focusing on two sections of Mogao Grottoes in Dunhuang of Gansu Province, the dynamic response and variation regularity of rock mass and its adjuncts are revealed through numerical simulation of displacement and stress field under dynamic loads with different PGA, spectra and durations. The results indicate weak points for seismic retrofitting. It also shows that the displacement and stress increase, range of stress concentration expands and the damages probability of country rock increases with the increase of peak ground acceleration (PGA), characteristic period and duration of dynamic loads. The distribution of stress is closely related to the quantity, combination feature, geometry shape and size of caves. This paper provides theoretical basis and practical reference for the preservation of grotto relics and seismic retrofit and seismic hazard mitigation for the rock mass.

The stability of the slurry-supported trench excavations during the construction of a diaphragm wall panel has always been a matter of considerable concern. Some methods of the global stability analysis have been derived from either the force equilibrium analysis or the stress limit state analysis based on various types of slipping surfaces or sliding wedges assumed. In order to discriminate the applicability of these methods, a comparative study of their theoretical bases, parametric sensitivity and practical application effectiveness is carried out. It has been found that the trench stability analysis methods established based on the prismatic and apsidal sliding wedge assumption can estimate reasonably the stability of the trench.

Based on the dynamic consolidation theory of saturated soil, the behavior of a caisson dyke under ocean waves was predicted using finite element analysis codes- SWANDYNE II. The cyclic stress-strain behavior of seabed soil was modeled by a generalized plastic model, Pastor-Zienkiwicz Mark III model, and cyclic triaxial tests were performed to calibrate the main model parameters. Only the action of ocean waves directly on the structure was considered, while the action of traveling waves on the surface of seabed was neglected in the analysis. The result of the dynamic response analysis was the same in nature as that of pseudo-dynamic limit equilibrium analysis. The dynamic response analysis also provided with the distribution of the displacement, stress and excess pore water pressure of the system, as well as the cumulative process of the structure displacement with wave duration time. The broad prospect was presented of application of dynamic consolidation finite element analysis in offshore and coastal geotechnical engineering field.

The existing of voids is the character of the porous media, which determine the constitution relation of porous media will be more complicated. A model of ideal porous media is presented. The apparent stress and apparent strain, actual stress and actual strain of skeleton for porous medium are defined. A discussion of the stress-strain relationship of the ideal porous medium suggests that although skeleton structure could be satisfied with the hypothesis of stress-strain linear elastic, the relationship between apparent stress and apparent strains remains nonlinear character. The nonlinear relation of stress and strain is the character of porous media.

Based on Mononobe-Okabe’s postulation and the reasonable consideration for the restricted pore water, a first-order differential equation of the dynamic active earth pressure on rigid retaining walls with submerged backfills in the translational movement mode under earthquake loads is set up by using the method of level-layer analysis. And the theoretical answers to the nonlinear distribution of the dynamic active earth pressures are obtained. The analytical results indicate that some parameters such as the groundwater level, the content of restricted pore water, the internal friction angle of backfills, the angle of wall friction and the earthquake coefficient have influence on the distribution of the dynamic earth pressure, the application point of the resultant earth pressure and the overturning moment. The present procedure incorporates the effect of the porosity and the permeability of backfills and the period of ground vibration.

In the numerical analysis for the soil-dam interaction, the bi-material model (on the interface, two materials possess the same lateral deformation ) is usually used, that causes error between analytical result and practice. In order to discuss the error and set the correct analytical model, the bi-material model and the bi-body model (relative lateral deformation is considered) are proposed. Besides, their samples were tested under axial compression. It is shown that the ratio of strengths ? between two materials is an important parameter for both models, but its effect and the mechanism on each model is different.

Facing to the problem that the influence of expansion fracture fillings on fracture seepage is rarely studied at present, based on the test results of the hydrated properties of fracture fillings and the mechanical parameters of altered rock mass of Daye Iron Mine, the influence of the mechanical response of fillings on fracture seepage is discussed on the basis of the comparison of expansion stress of fracture fillings with mechanical parameter of altered rock mass. It is showed that the expansion effect of fracture fillings has an important influence on the deformational of altered rock mass. Both tensile effect and shear effect produced by fracture fillings can greatly increase the permeability of the fracture. What’s more, the plasticizing effect and liquefaction effect of fracture fillings can also improve the permeability of the fracture.

The interaction characteristics of geosynthetics with fill materials are the key factors for geosynthetic reinforcement projects; hence, it is essential to study interaction characteristics by pull out tests. The comprehensive investigation into the interaction characteristics of 5 kinds of domestic geosynthetics with sand and lime fly ash was presented by pull out tests. Experimental results show: (1) Lime fly ash is light in unit weight, high in shear strength and its pull out coefficient (Cpo); therefore, it is ideal fill material; (2) Geosynthetics are arranged in Cpo from high to low: polyester (PET)warp knitting geogrids, uniaxial/biaxial oriented geogrids, geonets and geotextiles; (3) The variation of Cpo for various geosynthetics and fill materials is larger, hence Cpo should be determined through pull out tests for concrete projects. These conclusions can be used to guide choosing geosynthetic type and to make research on geosynthetic reinforcement mechanism.

Fundamental theories of slope stability analysis by finite element method are introduced systematically. Safety index and judging criterion are discussed in detail; and related visual analysis software AFEAS is developed by object-oriented technique. An engineering example of slope stability analysis is given; related finite element analysis results are compared with results of rigid body limit equilibrium method. Analytical results verify safety index and judging criterion feasible and show advantages of analyzing slope stability by finite element method.

Because the prediction accuracy of gray theory, GA and ANN algorithm is insufficiency for tunnel rock surrounding stability, the method of ?-support vector machines was applied to researching of evolution law for tunnel rock surrounding displacement; and in order to enhance the learning efficiency of ?- support vector machines and the capability of forecasting, the accelerated hybrid genetic algorithm (GA) is used for optimizing parameters of ?-support vector machines. Comparison the forecasting results of gray theory, GA and ANN and monitoring results for tunnel rock surrounding displacement, the results show the learning efficiency and prediction accuracy of ?-support vector machines is superior to gray theory, GA and ANN obviously.

Rock quality designation (RQD) is a quantitative parameter that used to reflect the degree of integrality of engineering rock mass. And it has been applied to assess the stability of rock slope in the field of water resources and hydropower engineering, mining, underground engineering, transportation engineering. However, the traditional RQD definition isn’t able to take into account the anisotropy of the engineering rock mass. Aiming at the structural properties of the arch dam of Qianzhong Hydraulic Project in Guizhou Province, and based on the joint network of rock mass simulated by the computer with Monte-Carlo method, a method of deciding RQDt under different threshold values is proposed. Many engineering practices have validated that this method is able to reflect the engineering rock mass quality objectively.

The model of feed-forward neural networks trained by differential evolution (DE) algorithm is presented to overcome the shortcoming of traditional regression model widely used in monitoring the safety and deformation of dams. DE algorithm is a population-based one in global optimization, with the merits of being easy to use and fast convergence. The neural networks trained by DE can effectively avoid the problem of being stuck in any local minimum that often happens in classical BP neural networks model. The case study of deformation monitoring of an arch dam shows that the DE neural networks model proposed results in a better precision, comparing with traditional regression model and BP neural networks model.

Analyses of the distribution of rockmass discontinuities and their association characteristics are prerequisites for studying stability of rock mass. According to the discontinuity network stochastic simulation method, based on the surveying data of the discontinuities which are on the rock mass’s surface, a numerical model of probability statistics for distribution of discontinuities of rock mass can be established; and a network structural model of discontinuities of rock mass is determined. With the model, 3D geometrical forms of free blocks are analyzed; and the possible destruction forms of the blocks are to be pointed out. Meanwhile, the integral stability of block system is to be forecast in macroscopic perspective.

Anchor frame beam is a method for strengthening the expansive soil roadcut slope. It can effectively prevent cracks and fissures of expansive soil slope from expanding. Thus it can preclude the slope from being destroyed. FLAC3D software is used for simulating anchor frame beam strengthening expansive soil roadcut slope. Main parameters such as length, range interval and angle of anchor frame beam, are investigatedimplored so as to acquire how to influence slope deformation. The results show that the ratio of slope has an impact on slope deformation; and that the angle and the range interval of anchors influence slope deformation. The pertinent proposal for design of main parameters of anchor frame beam is put forward so as to offer reference for engineering optimum design.

A total stress-based bounding surface visco-elastoplastic model for soft clays is developed to accommodate multiaxial stress reversals. The model is constructed based on the dynamic triaxial tests of the model soil for the metro station structure shaking table model test, taking into account that the clays yield under very low stress level and present energy dissipation even the strain tending to zero under cyclic loading. The numerical simulation of the free field model test is performed based on the visco-elastoplastic model; and it is shown that the acceleration history of model soil is consistent with the results of the model test.

The compression properties of naturally and artificially structured soils under one-dimensional compression or isotropic compression are described comprehensively. The reconstituted soil samples or the elastoplastic element of breakage mechanics for geological materials are regarded as the reference state; then by introducing a structured state parameter ? reflecting the influence of soil structure, the formula of the compression curve of structured soils is established. Finally, the proposed model has been verified for two different structured soils under confining stress conditions and under isotropic stress conditions respectively; and it is seen that the proposal describes well the behavior of these two soils. The formula suggested reflecting the nonlinearity of compression curve for structured soils has some theoretical meaning for the settlement calculation of structured soils.

Based on bearing capacity and settlement control design methods for composite foundation improved by flexible piles, as well as the system reliability analysis theory, the system of reliability analysis for composite foundation can be divided into three sub-systems; that are bearing capacity sub-system, settlement sub-system and settlement difference sub-system. The system probability of failure for composite foundation can be obtained by calculating that of three sub-systems respectively. It provides a method of system reliability analysis for composite foundations.

In order to analyze the mechanical mechanism of fracture grouting during the early phase by using the theory of large-deformation and plastic mechanics, the early phase of fracture grouting is regarded as the question of cavity expansion in infinite soil. The stress distribution due to the cavity expansion in soil is considered as three zones. The deformation following little deformation in elastic zone and large-deformation in plastic zone is taken into consideration. On the bases of the stress equilibrium equation and continuous boundary condition of stress and deformation, the stress distribution in three zones, the terminal radius and grouting pressure are obtained. According to the compassion, the results of the present theory is very near to the outcome of the engineering practice.

Contraposing the concrete project, a geomechanical model is established based on the analysis of engineering geology and theory of similarity; and it is used for research on distortion and breakage mechanism of inverve-dip layered slops rock mass. The design of experimentation is described; and the stability of inverse-dip layered slope is analyzed. At the same time, it is researched that the stability of inverse-dip layered slope when terrane obliquity, terrane thickness and intensity of terrane interface are transformed. The results show that the distortion is collapse; and the brakage is disjunction; the breakage firstly come into being at the tip of slope; the accelerated distortion is late forexcavation, the terrane obliquity is bigger and the duration is longer; the terrane thickness and intensity of terrane interface are bigger and the size of the rock mass distortion is smaller.

Development of the design and calculation module of foundations based on GIS platform is one of the important contents of information management system of major projects. It can use the time-depended renewed dynamic data from the database efficiently to improve the efficiency of design and calculation and can provide a technical support for the design and construction of projects. On the basis of rock and soil mechanics and the designing standard of related specialty, by taking the MAPGIS as a developed platform, the main point is focused on some key problems and their visualization technologies such as designs of piles, composite foundations of soft clay, supporting of surrounding rocks of tunnels as well as slope reinforcement by combining with database technology and C＋＋ program technology etc.. The module which is built up by these technologies can automatically transfer the data from the database to calculate and design for piles, composite foundation and supporting of tunnels, and also to give an analysis of slope stability; furthermore, to provide a function of memory and inquiring of data. By associating with the development of underground environmental information system in a major project, Water Supply Reconstruction Project from Dongguan to Shenzhen of Guangdong Province in China, this paper is focused on the details of function design and realization methods as well as their application to the major project. The research results show that developed module in the GIS is proved to be effective.

The construction and excavation process of underground powerhouse of Fuziling Pumped Storage Hydropower Station are simulated by three-dimensional fast Lagrangian method(FLAC3D). The pattern of deformation caused by excavation and stress state in surrounding rock mass are studied. The stabilities of surrounding rock mass of the powerhouse and the high slope of the surge chamber are analyzed. The bolting supports are performed on the region of the underground powerhouse caverns; and the mechanical properties of the reinforced surrounding rock mass are analyzed. By using the Ubiquitous model of FLAC3D program, we introduce a major joint cranny to surrounding rock mass and analyze the excavation deformation and the integral stability of the underground powerhouse caverns. Compared the numerical simulation results with no joint cranny around the surrounding rock mass, the effects of joint cranny on the stability of surrounding rock mass are evaluated comprehensively.

Lots of long and large fissures with slight slope and few with medium slope towards the downstream in the bedrock of the foundation of No.1-5 dam units of the left powerhouse of the Yangtze Three Gorges Project constitute the problems of the deep layer slide and stability by the joints of the high slope. The modes of sliding of various monoliths are generalized based on the distribution of the measured long and large gentle inclination structural faces. In addition, two kinds of hypothetical and extreme sliding models were proposed. This paper researches the slide and stability of the No.1-5 units dam from the aspects of engineering structural measures, analysis of deep stability against sliding, analysis for observed data. The rigid limit equilibrium is used for analysis of deep stability against sliding in the No.1-5 monoliths of the left intake dam section, which is accompanied by FEM numerical analyses and geo-mechanical model tests. The results above show that the Kc′ values derived from the rigid limit equilibrium of the No.1-5 monoliths of the left bank intake dam section meet the requirements for stability safety. The values by other analysis methods are: 3.0－4.5 or above for FEM analysis, 3.5－4.2 for geo-mechanical model test. The stability analysis of the sliding modes dominated by rigid limit equilibrium and supplemented by various other analysis methods indicates that after engineering structural measures taken for the No.1-5 monoliths of the left bank intake dam section, guarantee has been provided for the stability against sliding of the dam and its foundation rocks. Analysis of observations shows that for the foundations of No.1-5 monoliths of the left bank intake dam section, horizontal deformation is little; vertical deformation is undersized; asymmetric settlement does not appear. The dam foundation is stable.

Deep mixed (DM) column is installed in field through mixing the injected chemical binder with in-situ soft soil using rotating blades. The injection of chemical binder and rotating mixing disturb the surrounding clay, change the stress state, and cause excess pore water pressure in the surrounding ground. The excess pore water pressure was measured during installation of DM columns in sensitive Ariake clay, Japan. Field measured results showed that significant excess pore water pressure was generated in the surrounding clay and its value was greater than its effective overburden stress to make the surrounding clay under tension state. However, at the initial stage (5 minutes), the excess pore water pressure dissipated very fast. The interaction mechanism between deep mixing column and the surrounding clay during installation can be simulated by using shearing-expanding process of cylindrical cavity. An approach is presented for the calculation of excess pore water pressure around DM column. The proposed method considers the effect of shearing force caused by the rotation of blades during mixing. In the proposed approach, the excess pore water pressure is determined in terms of undrained strength of clay, shearing force, injection pressure and pore water pressure parameter. The proposed method is verified by the laboratory test and field measured data.

Taking a large project for example, the dynamic compaction tests are carried out to treat its saturated soft foundation The pore water pressure is monitored; the working parameters and intermission cycle are defined. The results show that the stabilization is well acquired according to checking. At the same time, the success is acquired in the application of the project.

Earth pressure is the main load on the retaining structure of foundation pit. The really earth pressure is very different from that of theoretic one due to many factors. The reliability of earth pressure controls their safety and stability in support structure designing. By analyzing the monitoring data of earth pressure on the diaphragm wall, which using as retaining structure for deep foundation pit of north anchor for Run-Yang Bridge, it is found that the earth pressure diagram is different in every excavation stage, that is, it changes with excavation and supporting. This will be very important to reliability design for resemblance engineerings. Moreover, it will be a base for soil and structure interaction study.

ABAQUS is adopted to simulate the mechanical behavior and deformation for retaining structure of foundation pit with excavating process. In order to reaveal the deformation and internal force of surport structure, spatial nonlinear finite element analysis is carried out in which the excavation process is considered. Ciritical parameters are discussed in detail. The analytical results show that the investigation of simulation of excavation process is necessary in such complex problem.

Aiming at open problems in the design and construction of double span arch-connecting tunnel, a research on three-dimensional stress characteristics of two types midboard is carried out by means of finite difference method FLAC3D2.0; and their merits and demerits, as well as applicable conditions are analyzed. The result shows that stress of separated type curved wall is more proper than integral type stalk on shallow depth double span arch-connecting tunnel in the condition of II type rock; inner force of midboard has been in stabilization when left cavern heading face drives to three times diameter from researched cross-section; while right and left cavern heading face drives to (–1–1)D time diameter from reseached cross-section, inner force of midboard greatly changes, and these constructions are key processes.

A series of in-situ simulated tests and geotechnical tests are completed in big trough and medium trough under the condition of controlling the relative density and moisture of the Taklamaka desert sand in laboratory. Then some data and indexes such as static point resistance qc of cone penetration test, allowable bearing capacity pa , angle of internal friction ? , relative density Dr , modulus of deformation E0.01 etc. are got. On the basis of these data, some correlations including qc vs. pa , qc vs.? , qc vs. Dr , qc vs.E0.01 and digital forms applied for desert are given. All these are accumulated experience for application of cone penetration test on desert foundation investigation.

Large-scale model tests on vertical deformation of cement-soil pile composite foundation under cyclic loading are performed through a new load-applying system designed by ourselves. It is shown that the critical cyclic stress ratio of cement-soil pile composite foundation is bigger than that of saturated soft foundation and is not affected by cement mixing ratio basically. In addition, cyclic stress ratio and number of cyclics have remarkable effects on vertical deformation of cement-soil pile composite foundation.