This paper describes a process of cutting blocks from statistically generated finite joint polygons in 3D space. If the ratio of joint length divided by joint spacing is less than 10，the rock mass is likely connected. If this joint length ratio is greater than 10，the rock is likely to be blocky. An algorithm is also presented for finding all removable blocks along any given moving direction. The rock mass boundary can be any excavated and natural free surfaces. The algorithm works for both joint sets and for any joint system where each joint has its own direction. This is an application of polygon cutting code DC of 3D DDA.

The Lianziya dangerous rock-body control engineering in Three Gorges Reservoir of Yangtze River lasted 51 months from beginning in May，1995 to finishing in Aug. of 1999. Engineering effect monitoring conducted for five years for Lianziya up to Dec. of 2004 and tested by water table 139 m of Three Gorges Reservoir after Jun. in 2003. Three factors，i.e. monitoring data about deformation in the surface of Lianziya，pressure in coal mined-out area and calculation results of stability，are united as a scientific criterion to access engineering control effects. It can be seen from deformation monitoring data that Lianziya becomes stable gradually because the horizontal displacement velocity is decreased from about 2.0 mm/a to less than 1.0 mm/a and vertical displacement velocity from about 1.5 mm/a to less than 0.75 mm/a before and after engineering control. Lianziya stability is extremely susceptible to response to constructing activity in coal mined-out area，where the horizontal velocity of surface monitoring points was about 8.0–18.8 mm/a and vertical velocity about 8.0–21.0 mm/a in engineering working period from May of 1995 to Aug. of 1999. It is proved that stress concentration and relaxation belt is existent resulting from the effect of cantilever plate with inclined pressure in coal mined-out area. In the lowest layer most of pressure data on the concrete key system for bearing pressure and anti-sliding are between 2.0 and 10.0 MPa，but the maximum and minimum values are 18.08 and －0.8 MPa，respectively. All the data are almost constant since Jan. of 2002. Displacement velocity change is not obvious and pressure values change is less than 0.01 MPa in Lianziya when water table rises to 139 m in Three Gorges Reservoir of Yangtze River after Jun. of 2003. Lianziya control engineering has achieved designing goal based on the stability coefficient greater than 1.15 in special loading condition and 1.30 in general. The large size(1 m×1 m) rockmass mechanics test was made in field to obtain the strength parameters for stability calculation of the engineering.

Detection on rock impaction with thermal infrared(TIR) imaging is not only a creative and prospective application of remote sensing technology，but also one of the important contents of the new inter-discipline called remote sensing rock mechanics(RSRM). The experimental technology of TIR imaging on rock impaction is analyzed；and the experimental exploration results at the early stage as well as recent research achievements are introduced. The main experiments conducted include the experimental exploratory to TIR imaging for detecting the transient process of solid impact，projectile impaction on rock by a Hopkinson compression bar(at different impacting angle or with water in rock body)，free-fall impaction between rocks，free-ball impaction on different types of rocks. Based on the results from the above experiments，two kinds of application foundations are researched，i.e. the back analysis of the impact-related quantities of rock impaction and the analysis of the possibilities for the disasters induced by rock impaction in mining area. It is shown that (1) the impact-related quantities can be back analyzed quantitatively/qualitatively by the TIR detection；for example，the impacting velocity or impacting energy can be back analyzed quantitatively；and the accuracy of the back analysis lies on the homogeneity of rocks，and the errors of back analysis based on the impaction on homogeneous marble are less than 12%；and (2) the increment of temperature due to rock impaction could probably ignite the gas in coal mine，therefore，it can be helpful to the analysis or the remote detecting/forecasting of disasters that may be induced by rock impaction. The mechanisms of the TIR radiation temperature variation due to rock impaction are discussed，including the rock fracturing，rock thermo-elastic effect and rock physics. It is pointed out that the future research directions include the radiation laws and physical mechanism，the quantitative analysis and remote sensing model，and the spectrum optimization and practical technology.

In most practical prestressed anchoring engineering，it is indicated that the distribution of lateral shear along anchorage length presents unimodal curve on the mortar-rock interface. The hypothetic model of thorough gluing bond along anchorage length is adopted in former theoretic analysis；and their results are not accordance with the practice. Slippage on the interface ought to be taken into account. Based on Mindlin¢s displacement solution of elastic semi-infinite body，one-dimensional mechanical model is established respectively for the semi-numerical calculation of the displacement of surrounding rock mass and axial displacement of grouting mortar. Slippage can be calculated by the difference of above displacements on the interface. By introducing the strength softening effect of the relationship between shear stress and slippage on the interface，semi-numerical calculation method of lateral shear distribution is put forward and further discussed. Compared with former models of thorough gluing bond，the slipping and strength softening effect model is more corresponding with practical projects. If slippage occurs in beginning anchorage segment after stretching force applied，lateral shear is reduced；and the stress redistribution forms a unimodal curve of lateral shear distribution.

Wushaoling long and deep-buried tunnel passes through the east foot of Qilian Mountain，with the length of 20 050 m and the maximum burial depth of 1 050 m. During the excavation of tunnel in the soft rock such as phyllite，plywood rock and tectonic breccia，the surrounding rock was deformed severely，with the maximum horizontal deformation magnitude of 1 034 mm and the arch top subsidence magnitude of 1 053 mm，which led to that not only supports lost their effects，but steel frames were distorted heavily. Moreover，the deformation lasted and could not converge. The testing results of original field stress show that these tunnel sections are under the action of clear modern tectonic stresses with the maximum principal stress of 20–22 MPa，and that the general feature of modern ground stress field is that sH≥sV＞sh. According to the analysis，it is considered that the strong deformation of surrounding rock of tunnel results from the joint actions of rather strong tectonic stress and vertical gravity stress；and that the tunnel has not be supported in time and soft surrounding rock can not bear such actions，which causes continuous large rheological deformation. Engineering practice indicates that the stress state of surrounding rock is the basis of support design；and that the timely support is very critical. However，proper deformation of surrounding rock is allowed，which can make the stress of surrounding rock release properly. Carrying out lining support construction in time when the large rheological deformation has not been formed and the surrounding rock has not lost its bearing capacity is of great significance to assure the stability of surrounding rock and the safety of supports.

In order to offer references for design of gob gas drainage with high-level long borehole，the laws of gob roof crack generation，fracture，fall and separation layer are analyzed with simulation experiment and key strata theory. Bending deformation of key strata undergoes the course of slowness→acuteness→slowness→fracture with the advance of working face，The bending and subsidence scopes of subordinate key strata are obviously smaller than those of major key strata. The elastic deformation of both side rock strata under key stratum will recover；and their subsidence will rebound after the fracture of key strata. Caving angles of roofs among key strata are different because of the differences of the load-bearing effect of key strata and mechanical characters of rock strata. The fracture of overlying key stratum results in decrease of the roof caving angle and the increase of periodic caving span and weighting intensity. The ultimate position and overlap distance of gas drainage boreholes can be determined based on fracture configuration of key strata，roof caving angle and periodic caving span，and gas drainage effect of boreholes can be also forecasted.

The reinforced shell structure is a new kind of forms in the supporting engineering for soft rock tunnel. The technique feature，structure characteristic and supporting theory are introduced；and the structure is analyzed theoretically. The calculation model and expressions of inner forces are deduced for this kind of structure. With its application to the Taoyuan Coal Mine，the construction technique requests and crafts are also set forth. Practice shows that the spatial bolted shotcrete supporting structure is of very high value and vast development foreground.

A time history analysis method for calculating the dynamic stability safety factor of high rock slope under excavation blasting is proposed. Based on the attenuation characteristic of the peak vibration velocity，and the time history curve of vibration velocity or acceleration，the inertia forces acting on the slices at given time can be calculated. The inertia forces would be acted on the slices according to their phases. Combined with Sarma method of limit equilibrium analysis，the stability safety factor at given time can be obtained. Analyzing the whole blasting vibration process at a certain time step，then the time history curve of the dynamic stability safety factor of the slope under blasting vibration could be got. In the proposed method，the attenuation of amplitude，the property of frequency spectrum，and phase of blasting vibration are included. The limitation of the conversion about blasting load by using a general coefficient in pseudo-static method is overcame. The time history of the safety factor of rock slope under blasting vibration is obtained，which well reflects the variation of the slope stability during excavation blasting，and can be a reference for the improvement and optimization on blasting design.

The slope protection with vegetation is to stabilize slope and protect slope surfaces according to the mechanisms of conservation of both moisture and soil with vegetation. Research shows that the mechanisms of the slope protection with vegetation include that (1) root system of woody plant can anchor rock and soil slope bodies；(2) root system of herbaceous plant has reinforcement action for rock and soil slope bodies；and (3) vegetation can prevent the erosion caused by slope surfaces. The chief characters of the slope protection with vegetation can be described as follows：(1) the effort of the slope protection with vegetation is very weak in initial stage，but will increase as vegetation growing；(2) the action range and effort of root system is limited；and (3) relatively stable slope is demanded for the slope protection with vegetation. Based on these，environmental compatibility and routine of the slope protection with vegetation are discussed. Combining the technologies of traditional slope protection and slope protection with vegetation，the respective merit of each method can be displayed，with this method slope stability can be guaranteed，reinforcement measure is durably effective，and immediate revegetation on the slope surfaces and the ecological environment protection are realized.

Landslides caused by twin-arch tunnel not only threaten the safety of construction but also damage the integrality of tunnel linings and reduce tunnel life，even destroy the whole tunnel structure，which will induce large economic and social losses. Taking Xiaomansa River Tunnel along Yuanjiang—Mohei Expressway in Yunnan Province for example，12 tunnel slope monitoring points and several monitoring items in tunnel are arranged. In the monitoring course，3D deformation mode of the tunnel slope is determined through monitoring. Monitoring results indicate that (1) the deformation of tunnel slope presents 3D characters，and the slide face is under the tunnel and presented arch shape；and (2) the deformation in the outside direction of mountain(Y-direction) along tunnel is the maximum one，the primary deformation trend of the monitoring points is inside mountain and crossed with tunnel；and Y direction is the mainly sliding direction. 3D deformation monitoring results provide displacement mode of the tunnel slope，and is applied to the slope anti-slide design，which is significant for both stability analysis and control measurement of twin-arch tunnel slope.

Sandstone is a typical sedimentary rock with bedding stratum as a result of weathering，transportation and sedimentation of clastic substances，which possess strong inherent anisotropy in deformation，energy dissipation and wave propagation. The effects of bedding inclination on elastic modulus，Poisson¢s ratio and attenuation of bedding sandstone are investigated by uniaxial cyclic loading tests. The data of 10 specimens in which the bedding inclinations are from 0° to 90° with increment of 10° are gained，and used to compute the anisotropy of the sandstone instead of the data in the directions parallel and perpendicular to the bedding stratum. Experiments demonstrate that the elastic modulus and Poisson¢s ratio of sandstone subjected to cyclic loading parallel to bedding are smaller than those of sandstone subjected to cyclic loading perpendicular to bedding，whereas the attenuation of the sandstone subjected to cyclic loading parallel to bedding is larger than that of sandstone subjected to cyclic loading perpendicular to bedding. Elastic modulus，Poisson¢s ratio and attenuation at any inclination bedding are between those in the directions parallel and perpendicular to bedding. By a transformation of the coordinate system，the equations linking the oriented elastic modulus and Poisson¢s ratio to the elastic parameters in the directions parallel and perpendicular to bedding of sandstone are obtained. The over-determined set of equations is solved by a least-square method to compute the elastic parameters by which the degree of anisotropy of elastic properties is discussed. This treatment can reduce the errors of computed anisotropic parameters；and even with large error of computed Poisson¢s ratio，its degree of anisotropy can also be estimated. The anisotropy of elastic modulus，Poisson¢s ratio and attenuation of Wuhan sandstone are 5.6%，5.7% and 5.5%，respectively. The anisotropy of Poisson¢s ratio is larger than that of elastic modulus for Wuhan sandstone.

Rock bolting is a support method widely used in slope engineering，tunnel and large cave support，as well as reinforcement of building structure. As the main part of the support structure，the bolt must have enough reliability and durability. However，steel is easily eroded by the environment，so the durability of commonly used steel bolt should be paid more attention to. The glass fiber reinforced polymer(GFRP) bolt，which has better mechanical properties and corrosion resistances is a new kind of reinforcement material compounded with resin and glass fiber. The durability problem in slope engineering can be solved if the GFRP bolt takes the place of steel bars. The bolt stressometer and BOTDR monitoring technique are introduced；and the relationship between stress and strain of the GFRP bolt under cyclic tensile load is studied. The test result shows that BOTDR technique is a feasible method；and the monitoring effect is reliable. The stress of the GFRP bolt increases with the load increasing and decreases with the depth of the anchor increasing. The stress depth curve of the GFRP bolt agrees with regular hyperbolic pattern in the superficial part. With the length increasing，the distribution curve of the GFRP bolt transits in a lineal pattern. The stress transfer depth of the GFRP bolt increases with the cyclic tensile load and cyclic times；and the maximum stress depth of the GFRP bolt is less than 1.70 m under the test condition. The field test is undamaged one，and the maximum load of the test is 100 kN and does not reach the failure load of the GFRP bolt. So the damage course of the GFRP bolt must be further studied.

Discontinuous deformation analysis(DDA) and discrete element method(DEM) are two important numerical methods that analyze large-scale opening，sliding，and complete detachment of elements or blocks of discontinuous media such as fractured blocky rock masses. These methods have been widely used in codes and applied to two-dimensional analysis of discontinuous deformation. However，the methods have scarcely ever been applied to three-dimensional analysis of practical rock engineering problems. Until recently，spheres，bonded spheres and ellipsoids are used as elements or blocks in 3D codes，but they can not reveal the real behavior of more angular block system such as fractured rock masses in which joints，fissures and faults are intersected. During modeling the 3D rock block system，DDA and DEM confront a great difficulty in contact detecting between two blocks because the existing detection methods cannot get the exact contact relationship sometimes between two 3D blocks that contact each other. The common-plane(C-P) method introduced by Cundall can detect the correct contact relationship between two 3D blocks provided that the common-plane position could be located correctly. Unfortunately，the algorithm to position the common-plane can¢t always get the correct position because it can¢t reveal exactly the influence of variation of a block geometrical shape upon the common-plane position. The limitations and advantages of three contact detection schemes，especially two main schemes used in codes，are discussed. The principle only according to which the correct detection method can be brought out is represented. Based on advantages of the existing methods，a new approach called incision body is put forward. The simulation examples of block movement are also given. The simulation result shows that the incision body method is capable of overcoming indeed limitations of the existing methods，detecting 3D block contacts correctly and hence simulating the interactive detachment and sliding between two blocks.

Experiments performed on split Hopkinson pressure bar(SHPB) with a large diameter of 75 mm show that the dynamic stress-strain curve of anthracite of Yunjialing coal mine is of distinct plastic yield characteristics；and the initial elastic modulus，yield strength，as well as the ultimate strength go up with strain rate；but there is the best correlation between yield strength and the strain rate. Based on the characteristics of measured dynamic stress-strain curves and analysis of existing dynamic constitutive models of rock，as well as preparatory simulation，a new viscoelastic damage model has been introduced. A linear spring is put to parallel to two Maxwell units with different relaxing time to express distinct plastic flow，and the damage D is equal to the ratio of Eb－E(ei) to Eb，where Eb is the initial elastic modulus and E(ei) is the slope of the line between the origin point and any other point on the tested dynamic stress-strain curve. In the new constitutive model，one Maxwell unit with low relaxing time j1 is used to describe the low strain rate response of anthracite；and the other one with high relaxing time j2 to describe high strain rate response of anthracite. Simulated stress-strain curves using the new model is of good consistency with measured curves；and the simulated parameters indicate that the response of the low strain rate of anthracite is just as same as that of concrete；but the response of the high strain rate of anthracite is much more violent than that of concrete.

By the site investigation and exploration of engineering geology，physico-mechanical tests in laboratory and field，adopting the analytic mathematic statistics and unbalanced-thrust method，with the concrete engineering practice of debris landslide，the general physico-mechanical characteristic and permeability of debris landslide，the influence of its groundwater pipe network drainage system(GPNDS) on its stability，and the action mechanisms of its instability and failure are researched and analyzed. The research results are as follows. First，the influences of the contents of block and broken stone grain-grade，and fine earth mainly made up of silt and clay grain on debris permeability coefficient are the biggest and most remarkable. Second，debris permeability coefficient increases and decreases in natural exponent，respectively，with its grain-grade contents of block，broken stone and gravel，and the fine earth with grain size less than 0.1 mm. Third，the GPNDS of the debris landslide takes crucial action on natural slope stability. Fourth，when the GPNDS of the debris landslide is destroyed and blocked，groundwater level will obviously rise to make the pore water pressure of potential slide plane and down-sliding force clearly increase，which will make the slope stability coefficient descend obviously，even result in slope instability，disintegration and failure to some extent.

According to the results of mine test and lab experiment，non-Darcy seepage flow will occur during the exploitation of reservoirs with low permeability and extra-low permeability，especially the crude oil seepage flow，which will have a obvious startup pressure gradient. Considering that the seepage flows of the oil and water have startup pressure gradients and that rock has stress sensibility，the three-dimensional oil-water two-phase mathematical model is built，and combined with the characteristics of the low permeability reservoir¢s water injection exploitation. The finite difference schemes of the seepage mathematical model are obtained by the finite difference method；and the numerical simulation software is developed. The numerical simulation results of the production history of Yuan 121–3 block of Zhaoyuan Oil Field in Daqing are compared and successively verified with the field production data. Based on the five-point injection-production well network，a square injection-production unit is designed. Under the condition of keeping bottom pressures of producer and injector wells constant，the space between the injection and the production well is changed；and the formation fluid pressure，fluid pressure gradient，formation absolute permeability，and the spatial distribution of the startup pressure gradient are obtained by using the numerical simulation software when oil well begins to produce water. At last，the effective space between the injection well and the production well is achieved to provide references to the network arrangement of the injection and production wells for the extra-low permeability reservoir.

The determination of parameters in viscoelastic constitutive equations of soft rocks is very important to analyze the time-dependent behaviors of embankments，foundations and mines in soft rocks. The complex viscoelastic model equations can be transformed into unified linear equations，and the parameters of the model can be got by back analysis method. But the general back analysis method doesn¢t take the randomicity and fuzziness of the parameters into account，therefore，it does not be in accordance with the fact. In the general back analysis method，the membership function is introduced. The methods of fuzzy back analysis and viscoelastic model identification with fuzzy correlation degree are proposed. The method can identify the models such as Kelvin model，H/M model，H-K model，M-K model and Mechant model，and can also get their parameters. On the basis of the creep experiments of two groups of salt rock from a mine factory，the method is used. The results show that the samples of group I are Mechant bodies and the samples of group II are H-K bodies. The parameters of the two models got by back analysis method coincide with the test results very well.

In-situ stress is critical to well instability in silt formations during drilling. Based on the analysis of in-situ stress measurement methods such as hydraulic fracturing method，Kaiser effect method，differential strain analysis(DSA) method and multi-pole logging method，it is difficult to acquire in-situ stress of complex silt formations through any method mentioned above. The best way is the combination of the advantages of these methods. Two methods to determine the in-situ stress are presented in this paper. The in-situ stress ratio can be measured by DSA method if there are drilling cores in the fracturing test，while the in-situ stress difference can be measured by multi-pole logging method if there is no drilling core in the fracturing test. Combined the acquired in-situ stress relative value with the fracture pressure mode for fracturing test，the horizontal in-situ stress can be determined. These two combined methods，in which one is the combination of formation fracturing test with DSA method and the other is the combination of formation fracturing test with multi-pole logging method，are feasible in field application.

Fast and efficient contact detection algorithm is one of the most important key techniques to control computational efficiency in 3D discontinuous analysis such as the distinct element method. Based on direct contact detection method，field-decomposition，circumscribed-sphere detection，visibility and post-round are induced to develop a new contact detection algorithm for 3D convex polyhedron：Herein，the fundamental principle of the contact detection algorithm is described；and the methods to identify the neighboring block and to define the contact types and contact direction are analyzed. The algorithm is then applied to analyze the colliding process of a pair of columns subjected to impact loading. The result demonstrates that the contact detection algorithm is less cost，robust and apt to be realized.

First of all，according to the research on the transverse sections of the stable nature slope in the engineering area，the slope shape data of the sand-slate and marble slopes are gained. Secondly，in combination with data acquired from some slopes of the being built or built hydropower stations and natural slopes，the excavation angle is recommended for the dam abutment slope from perspective of geology. Thirdly，based on the characters research of the deep fracture at the left abutment slope in detail，the failure mode of the abutment slope and boundary condition of the potential failure block after excavation are analysed. During the analyses，3D rigid limit equilibrium method is used to analyze the stability of the potential failure block in abutment slope in the nature and excavated stages individually. What is more，the computation model can be established massively or sectionally according to the assumption of different boundary conditions of the potential failure block. Finally，through comprehensive analysis，the conclusion that the sectional computation model is accordance with the dam abutment slope engineering is drawn. Reinforcement measures are put forward for the high slopes. The results can not only solve the practical engineering problems but also provide some referential experiences for similar projects.

Initial geostress is one of the most important factors in the design and construction of the geotechnical engineering. According to the measured geostress data，there are many methods of calculating initial geostress field with different advantages. According to the measured geostress data from Xiluodu Hydropower Project，through 3D FEM combined with the linear multivariate regression analysis principle，the neural network as well as the genetic algorithms，the geostress field back analysis are conducted. It is shown that the back analysis results by the three kinds of methods are very close，and all the methods can simulate the real geostress field. The further analysis shows that，since the yield zone in the rock mass is small，and nonlinear character of the initial geostress field of dam site is faint；the linear multivariate regression analysis results are acceptable. The results also show that，under the condition of accurate results，the linear multivariate regression analysis is of more merits，that is，more convenient，rapider，easier，only solution，compared with the neural network method and the genetic algorithms.

The existing state of structural studies is discussed. Load is applied on disturbed saturated loess samples with the same dry density in order to destroy the structure of intact loess. Based on the stress-strain curves obtained by triaxial compression tests of intact loess and disturbed saturated loess，the quantitative comprehensive structural parameter is used，which can reflect not only the arrangement but also the coherent structure of soil particles. The effects of water content and confining pressure on the structural parameter are investigated during the shear course. The study indicates that (1) structural parameter can not only reveal the influences of water content and confining pressure on the structure of the intact loess under shear，but also is of rationality，sensitivity and stability；(2) structural parameter decreases with the increase of water content，and this change tendency decreases with the increase of strain；and (3) when initial loading is applied and failure of sample occurs，structural parameter decreases with increase of confining pressure，and when strain reaches 15%，structural parameter firstly increases and then decreases with the increase of confining pressure.

The relationship between principal stresses in the plane strain state is the stress-strain relationship of soil with a certain strain path. The characteristics of deformation and strength of soils under the plane strain condition can be simplified as a two-dimensional problem. How to easily and reasonably determine the value of principal stress in the direction of plane strain is the key point. Based on the elastoplastic theory and test data under the plane strain condition，it is assumed that the relationships between the principal stresses in plane strain direction and those in the other directions are bilinear. The parameters of bilinear function are determined by one-dimensional consolidation and failure state. The principal stress in the plane strain direction is expressed as a function of stress states and material properties. Substantially，the proposed relationship of the principal stresses embodies the characteristics of deformation of soils in plane strain state. The function of this relationship passes three key points，that is the original point(1，1)，the state point of one-dimensional consolidation(bc，Rc) and failure point(bPS，RPS). Compared with test results，the validity and practicality of the proposed bilinear principal stress function are testified.

Geogrid reinforced soil retaining wall is composed of panel，geogrid and soil. Its structural characteristics are emphasized in practice at all times. Based on the self-consistent theory and concept of strain consistency，a mechanical model for soil-reinforced composite material is put forward to simulate the grogrid and soil around grogrid with a definite thickness. The structural characteristics of stepped geogrid reinforced soil retaining wall are hereby numerically analyzed with finite element method. Compared with model experiment，it can be seen that the results calculated by the present method are commendably consistent with those obtained by model experiment.

An efficient numerical method by using 2.5D finite element combined with thin-layer element has been developed to study the dynamic responses of track structure and surrounding ground due to train moving loadings and wave propagation phenomena in three-dimensional ground. In the numerical model，the track and the attached sleepers are simplified as Euler beams resting on infinite half-space，while the ground in near field with complicated geometries and physical properties is modeled by finite elements. The infinitely extended layered half-space in far field is represented by thin-layer elements to let the outcome waves dissipate without reflection into near field. The wave-number transform has been applied in the track direction to reduce the three-dimensional problem to a plane strain problem in which three degrees of freedom are considered for each node. The dynamic problem is solved in a section perpendicular to track direction，and the three-dimensional responses of the track and the ground are obtained from the inverse wave-number expansion. Both single moving load and multi-wheel axle train loading are considered here to study the track and ground vibrations；and the computation results have been verified with the field measured data from X2000 high-speed train on west line in Sweden Ledsgard. Also，the ground response characteristics under train moving loadings have been studied to determine the critical moving speed of train for the specific site.

Complementarities to modified computation procedure of Sarma method which is proposed by the authors recently are given. The iterative scheme which ensures the convergence of the safety factor is also given. The effectiveness of the procedure is illustrated with an example.

Gravity-type retaining wall is one of the most common structures in civil engineering；and the lateral earth pressure due to the backfill is generally a major factor for the design of this type of structure. The earth pressure can be calculated using limit analysis method based on upper bound limit theorem in plasticity. Besides the traditional methods discretizing the backfill into thin slices or using rigid finite element method，upper bound limit analysis can be also numerically performed by element integration method，which is induced in this paper. In the present method，small triangle elements are used to discretize the soil behind the retaining wall. A kinematically admissiable velocity field is supposed by mathematical equations containing two or three parameters. It is independent with the element mesh. The work done by the body forces，surface loads as well as internal energy dissipations within an element are convenient to be obtained under such a failure mechanism. The whole energy can be calculated from the energy integration among all the elements. The limit external load can therefore be solved from the upper bound limit theorem；and its minimum value can be obtained from optimization method. For single block mechanism，such as plane and log-spiral slip surface，the validity of this method has been verified by a typical two- dimensional example.

The bridge pile foundation in high-steep rock slope has double function，i. e. bearing vertical and horizontal loads from superstructure and counteracting landslide-thrust from pile foundation side；and the mechanical behavior in the pile in high-steep rock slope is much more complex than that of antislide pile and simplex inclined-loading pile. Considering the landslide-thrust of the high-steep rock slope，the law that the landslide-thrust of the high-steep rock slope has parabolic type is found from in-situ test；and the parabolic distribution loads of the landslide is put forward. The finite difference method is introduced to calculate the displacement and inner-force of the bridge pile foundation in high rock slope under inclined loads. The result from the bridge pile foundation in K83+745 of Shaoyang—Huaihua Expressway in Hunan Province shows a good agreement with measured result. This indicates that the presented approach is feasible and applicable in engineering practice.

Multigrid method solver is of high numerical efficiency when used in solving linear equations derived from boundary-value problems of partial differential equations. There are some shortages in geometrical multigrid method which restricts its application area. The algebraic multigrid method is used to solve finite element linear equations which are derived from three-dimensional finite element analysis of rock mechanics and engineering. The three-dimensional coarse-grid selection method based on element agglomeration and the three-dimensional interpolation operator are briefly introduced. By using the newly developed three-dimensional finite element program based on algebraic multigrid method，four different numerical experiments are designed，and carried out to validate its convergence character，numerical efficiency and practical application to modeling excavation problem of rock engineering. The numerical experiments show that the algebraic multigrid method is of better stability，good convergence character and better adaptability，with much higher numerical efficiency with increasing of the number of linear equations and much less computer memory compared with direct method. Increasing. The algebraic multigrid method has much better numerical efficiency. The algebraic multigrid method is suitable and efficient for three-dimensional finite element modelling of large-scale geomechanical engineering.

Water diffusion ratio of unsaturated loess considering the influence of density is studied by test. The test data show that the variation of soil density，for loess with higher water content，can result in great change of diffusion ratio. For the loess with lower volumetric water content，the variation of soil density can result in less change of diffusion ratio. Furthermore，for loess samples with different densities，the matrix suction of the unsaturated loess with different volumetric water contents is tested. On the basis of analysis of test data，the relationship between water diffusion ratio and density of unsaturated loess is explored，and the specific water volume of loess is given. The formula is got to define the seepage coefficient of unsaturated loess considering the influence of density. After analyzing the change law of permeability coefficient resulting from the change of soil volumetric water content and density，it is pointed out that the permeability coefficient of the unsaturated dense loess is sensitive to soil density change compared with loose loess.

During fracture propagation driven by detonation gas in oil well，dynamic response of crack surface under the gas pressure results in fast fracturing. In order to simulate the dynamic fracture process，kinetic energy is introduced into the equation of energy balance to describe the energy relationship during fracture propagation driven by gas pressure. Here，an approximate formula educed by dimensional analysis is presented，which involves fracture velocity and loading rate，to calculate kinetic energy increment. Thus fracture velocity and length can be obtained by iterative solution of energy balance equation in every time step when loading rate is given. In the case study，the results show that when gas pressure rising rate becomes slow，the dynamic response of crack tip to crack development will become weak. So it is obvious that dynamic response greatly influences the ultimate fracture length.