The granular matter mechanics and the thermomechanical approach to establishing elastic/plastic constitutive model for geomaterials are introduced briefly. The form, mechanical behavior and energy dissipation of force chain and the corresponding strong and weak network are analyzed deeply. On the basis of thermomechanical model for soil, proposed by Collins, the stress and strain characteristic of strong and weak network is re-examined; and proper hypothesis is given. And then the idea and procedure of soil constitutive model with micro and macro incorporation is discussed.

Considering the heterogeneity of the rock, cohesion for elements throughout the rock is supposed to follow a Weibull distribution, and decreases to zero when element fails according to Mohr-Coulomb criterion. A damage evolution equation for rock undergoing compression is derived based on the statistic theory and shear force equilibrium equation on the shear failure plane. The derived damage evolution equation is reasonable because it considers the failed elements ability of resisting pressure and frictional shear force. A statistic damage constitutive model is then established and verified by comparing the simulated finite element method results with laboratory triaxial testing results. Numerical results show that the developed model simulates the peak and residual strength of triaxial tests very well.

Based on Biot's theory, the frequency domain fundamental solution for a vertical circular patch load applied to a layered poroelastic half-space is derived via the transmission and reflection matrices (TRM) method. Utilizing Muki and Sternberg’s method, the second kind of Fredholm integral equations describing the dynamic interaction between the pile rows and the layered poroelastic half-space subjected to a harmonic vertical load is constructed. The isolation effect of pile rows against the vibration due to the harmonic vertical load is investigated via numerical solution of the integral equations. Comparison of our results with an existing one shows that our results are in a good agreement with the existing solution. Numerical results of this study show that: a stiffer upper layer overlying a softer bottom half-space will worsen the vibration isolation effect of pile rows and vice versa. Also, pile rows with longer and stiffer piles or a smaller net spacing between neighboring piles in a pile rows are preferable for a better vibration isolation effect.

With the rapid development of large diameter slurry tunnels, the possibility of cutting different strata during tunneling becomes higher and higher. So the method used to control the face stability exceeds the normal static method’s cover. Based on mechanism of membrane formation, a filtration model is introduced to simulate the slurry membrane during slurry shield tunneling. In filtration model, the slurry is regarded as multiphase flow, while the stratum as porous medium. By control volume method, during the formation of membrane, it complies with mass and volume conservation. When it comes to the boundary condition, the output volume of filtration is equal to the compression of soil. This model reveals the dynamic formation process of slurry membrane and mechanism changes of the stratum, which is very important to the face stability during slurry shield tunneling.

The uncoupled state equation of three-dimensional transversely isotropic soils is deduced by constructing a decoupled transform in rectangular coordinate system; the transfer matrix of single soil layer is obtained through the double Fourier transform and Cayley-Hamilton theorem; in combination with the boundary conditions and the continuity conditions between layers, the transfer matrix solutions of three-dimensional transversely isotropic multilayered soils are obtained. Numerical calculation and analysis are carried out by the computer program. It is shown that the results agree well with the existing solutions; and the transversely isotropy and the characteristics of layered soils have remarkable influence on the vertical displacements and vertical normal stresses.

Aiming at different landslides movement behavior due to different inducement mechanisms, the total slopes and block coefficients of landslides were considered as evaluation indices to analyze the relationship between total slopes, block coefficients and landslide volumes, total energies; the total slopes and block coefficients of seismic and non-seismic induced landslides were studied contrastively. The results indicate that the volumes of seismic and non-seismic induced landslides are larger; the blocks of ground are smaller. The total slopes of seismic and non-seismic induced landslides decrease with the increase of volumes and energies; but the decrease ratios of seismic induced landslides are larger than non-seismic induced landslides. The average block coefficients of seismic induced landslides are about 0.4 to 0.5 and the average block coefficients of non-seismic induced landslides are about 40% to 50% of seismic induced landslides at the same volume. The results show that landslide movement behaviors are not only controlled by the volume and total energy, but also restricted by the landslide inducement mechanism and terrain block.

Generalized potential theory opens a broader mathematical background for constitutive models of geomaterial. Based on the generalized potential theory, constitutive models on strain space can be constructed as well as on stress space. By using the dual relationship it is convenient to transform the classical constitutive model, such as modified Cambridge model and Tsinghua model, etc., from stress space to strain space without changing the model itself. Furthermore, current constitutive model can also be amended to meet the test results based on the generalized potential theory. For example, Modified Cambridge model is amended to take account of triaxial test results, which is thought to be more reasonable than just utilizing compression test. In addition, the issue of extending constitutive models from 2D space to 3D space is also discussed. Since the extension involves too many variables, it is thought that the transformed stress method is more applicable.

Combined with Swipe loading method and fixed displacement ratio method, the bearing capacity of shallow skirted foundations subjected to inclined loading and eccentric loading is explored through plane strain finite element numerical studies. The effect of embedment and soil strength profiles on the V-H and V-M failure envelope of skirted foundations is investigated; and the soil deformation mechanism under various combinations of load components is illustrated. The results show that the embedment ratios and soil strength profiles significantly affects the failure mechanisms, but normalization of the failure envelope on the V-H and V-M load plane by the pure bearing capacities allowed it to be generalized for other varying conditions. The equation of failure envelope on the V-H and V-M loading plane is proposed respectively.

Silt soils have been encountered in most of the estuary of Qiantangjiang River. Drained and undrained triaxial tests have been made to study the dilatancy of the saturated silts. The test results show that one of the most significant properties of Qiantangjiang silts is their dilatant characteristics in shear. The amount of potential dilatancy is governed mainly by voids ratio and confining pressure. Conclusions from the consolidated-undrained(CU) tests are the undisturbed samples of the medium density tend to dilate during shear in the cell pressures range 600 kPa while the compacted samples of the small density tend to dilate under the cell pressure of less than 400 kPa during shear. Due to their dilatant nature, the undrained strength of many silts keeps increasing during shear, for this case there is no unique “undrained strength”. The compacted samples whose quality has been demonstrated in the consolidated-drained(CD) tests to be slightly dense tend to dilate under the cell pressure of less then 400 kPa during shear. The failure of Qiantangjiang silts usually goes through larger deformations. The stress-strain curve of drained tests can be divided into four stages. It is reasonable that the point where the strain can continue without further change of volume is chosen as a failure criterion to define the drained strength of silt.

There is an inherent relationship between deformation and stability of slope, so it is possible to identify the stability of slope by deformation field. Based on ideal elastoplastic model, the typical strength reduction method reduces strength of all elements of slope. Therefore, the deformation field by the typical method can not reflect real deformation when slope is close to instability. In fact, slope failure occurs when strengths of some regional soils are sufficiently weakened; so local strength reduction method is proposed here. According to local strength reduction method, only local soils strengths are reduced; and strength of the other soils keep unchanged. Moreover, this paper uses variable modulus elastoplastic model instead of ideal elastoplastic model. Actual engineering example shows that the slope stability analysis, which is based on local strength reduction method and variable modulus elastoplastic model, is feasible and rational.

A study of problem of ground vibration isolation by double row of piles as passive barriers in homogeneous saturated ground is introduced. The investigation is accomplished with the aid of the semi-analytical boundary element method(BEM) in cooperation with the basic solution of the thin layered method (TLM). Consequently, a 3D semi-analytical BEM model is put forward, where the TLM basic solution is employed, to use double row of piles as passive barriers taking into account the dynamical interaction of soil-structure. Effect of the model parameters on effectiveness of vibration isolation by double row of piles is investigated and discussed in detail. The results show that the double row of piles can isolate the ground vibrations due to the incident Rayleigh wave, of which the screening efficiency is better than that of a row of piles. Moreover, the net spacing between two rows has less effect on the screening efficiency, while the net spacing between two piles can affect the isolation effectiveness significantly.

Based on random mixed media (RMM) and combining with the characteristics of geotechnical material, a new method is proposed to calculate the thermal conductivity of geomaterials under low temperature considering phase change. According to the experimental data, RMM is adopted to calculate the thermal conductivity under the same experimental condition. The results of numerical calculation are compared with that of experiment; it is concluded that the results consist with each other; the maximum and mean deviations are 5.4% and 2.3%. Compared with other current three methods (exponential weighted average method, weighted harmonic mean method and weighted arithmetic mean method) on calculation of thermal conductivity, it is shown that: the popular exponential weighted average method is suitable for temperature above 0℃ but not for temperature below 0℃. The errors of results from weighted harmonic mean method and weighted arithmetic mean method are very great; and the effect of phase change on thermal conductivity can’t be reflected with this method. A reference is provided on determination of temperature field for geotechnicals under low temperature considering phase change.

The seepage problem with a free surface is solved by combining the hybrid boundary node method (HBNM) and iterative method. The HBNM is based on a hybrid displacement variational principle and moving least square(MLS) approximation. The domain variables are interpolated by fundamental solution, while the boundary variables are approximated by MLS. Therefore, the HBNM is a truly boundary-type meshless method. Only nodes on the boundary are required and any mesh is not required. At first, the initial position of free surface is assumed; then the solution is obtained by the iterative method. The numerical example indicates that this method has high precision, little computation work; and it is suitable for solving various seepage problems with free surfaces.

Based on the unified strength theory, analytical elastoplastic solutions for cylindrical cavity expansion are deduced considering seepage, anisotropy, shear dilation and intermediate principal stress. Case study results indicate that it is necessary to consider the effect of volumetric force of seepage on the expansion pressure under rich water condition; and the expansion pressure without considering the seepage is smaller than the engineering practice. The radius of plastic zone would be smaller with the increase of seepage volumetric force. In addition, the traditional analytical solutions of cavity expansion which are based on the isotropic initial stress state supposition overestimate the ultimate expansion pressure and underestimate the plastic zone field around the cavity; and this would result in lower engineering safe class. The results provide some reference value for engineering design and a theory base for the elastoplastic analysis of subsea circular tunnel and other underground horizontal construction under seepage condition.

Heat transfer in surrounding rock of metro tunnel is a large proportion of the entire metro tunnel heat system. To get the accurate heat load of surrounding rock, the heat transfer in metro tunnel is simulated and the temperature distribution is studied through model test. And the inverse calculation of rock thermal conductivity is also given. It is indicated that the temperature decreases with the distance from metro tunnel wall, and follows the exponential law at the same time. And the influencing area of heat fluid in metro tunnel extends with time. The temperature at a distance from metro tunnel wall increases with time. At the closer distance the temperature is higher and the rate of temperature rise decreases with time; and the change rule of farther distance is opposite. Gradually the temperature growth tends to a certain value when heat transfer for more than a certain time. Finally, the precise rock thermal conductivity is also given.

The triaxial test apparatus which works together with the CT system was enhanced, including a triaxial pressure pot with ±0.1 ℃ temperature control precision and loading device. Then, a series of CT scanning tests were performed on frozen Lanzhou loess at different temperatures under uniaxial loading condition. And then some conclusions are drawn as follows. When the strain changes in the range of 0-0.7%, the CT number increases lightly. When the strain changes from 0.7% to 6.5%, the CT number is almost unchanged, and plastic strain begin occurs. When the strain exceeds 6.5%, the CT number decrease obviously; and damage begins occurring. When the strain reaches 10%, CT number decreases speedily, and failure in samples occurs. So, as for frozen Lanzhou loess, the yield strain is 0.7%; damage strain critical value is 6.5%; and failure strain critical value is 10%. In addition, temperature also has influence on the CT number. When the temperature changes in the range of -0.6 ℃- -1.7 ℃, lower the temperature is, smaller the CT number will be. The CT number changes little at temperature range of -1.7 ℃ and -5 ℃.

Reproducing kernel particle method (RKPM) is a typical meshless method based on kernel function (spline function) simulation. The first and second derivatives of RKPM shape function are deduced completely; with Kirchhoff thin plate theory, the meshless method RKPM governing equations for deflection solution of thin plate on Winkler foundation are established; numerical analysis results indicate that the above method and corresponding program are feasible and effective.

Anisotropic initial stress is described by the coefficient K0 of earth pressure at rest. A two-dimensional elastoplastic numerical stimulation is performed to analyze the pressure-controlled cylindrical cavity expansion with anisotropic initial stress. The results indicate that the radial displacements around the cavity are unequal in different directions and the cylindrical cavity expansion is asymmetrical ellipse due to anisotropic initial stress. The largest range of plastic zone develops in the direction of the maximum principal initial stress and the plastic zone has devious directivity. The results also demonstrate that the undrained shear strength and initial stress level have significant effect on the pressure-controlled cavity expansion process with anisotropic initial stress. With the undrained shear strength increasing, both the largest range of plastic zone and the effect degree of anisotropic initial stress on the anisotropic plastic zone distribution decrease under the same expansive pressure. With the increasing of initial stress, not only the largest range of plastic zone but also the effect degree of anisotropic initial stress on the anisotropic plastic zone distribution increase.

The computational model and wave equation of dynamic responses of large diameter pipe pile in low strain integrity testing are established based on radial invariability assumption. Combined the initial conditions and boundary conditions, the analytical solution of wave equation in frequency domain is obtained by Laplace transformation method. The dynamic responses in time domain are obtained by Fourier inverse transformation. The comparison of the analytical solution in this paper with results of three-dimensional(3D) frequency domain solution indicates that the time difference between incident and reflected waves has little distinction. The radial invariability assumption has little effect on two-dimensional (2D) frequency domain solution for a large diameter thin wall pipe pile; so it is reasonable to analyze waveform of low strain testing by 2D theory. The comparison of the 2D frequency domain solution in this paper with 2D time domain solution indicates that the results of two methods can match well each other. The circumferential displacement has little effect on numerical results; so the horizontal displacement need not be considered in waveform analysis of large diameter pipe pile.

Based on the field test results of dry density for a project, the influences of the maximum grain size, coarse material content (percentage of coarse material diameter above 5 mm) and gradation on compaction properties of soil-aggregate mixture are discussed. The results indicate that dry density increases gradually when coarse material content increases; dispersion of dry density is greater when it is about 90%. The reasonable coarse material content which is 60% - 80% is suggested. Dry density increases gradually while maximum grain size increases. Dry density decreases and the dispersion is greater, when the maximum grain size over a certain value. So the maximum grain size which is about 30% of the loose thickness (800 mm) is suggested. There is no obvious correlation between gradation and compaction properties, but the gradation should be continual. This study may have a certain significance to similar projects.

In view of the long-term dynamic stability of red clay cutting bed under ballastless track of Wuhan-Guangzhou high-speed railway, the reformed stress controlled dynamic triaxial test apparatus is utilized to measure fatigue dynamic shear strain threshold firstly, replacing the shear strain controlled resonant column test apparatus not existing at home now. A complete set of test program and data processing method are put forward, which open up a new test way of measuring fatigue dynamic shear strain threshold. The values of fatigue dynamic shear strain threshold of red clay are obtained through fatigue dynamic triaxial tests under 9 kinds test conditions. According to curves trend features, - curves of red clay (where is dynamic modulus, N is number of vibration) can be classified as three types: the stable type, critical type and destructive type; and the same type curves have similar trend characteristics under different test conditions. Influences of water content ratio and confining pressure on fatigue dynamic shear strain threshold of red clay are discussed; and a simple and practical empirical formula for estimating fatigue dynamic shear strain threshold is also given. Based on results of laboratory test and field dynamic response test, the long-term dynamic stability of red clay cutting bed under ballastless track of Wuhan-Guangzhou high-speed railway is preliminary evaluated; and the corresponding minimal replacement thicknesses of red clay under different physical conditions are also given. A new train of thought is put forward for evaluating long-term dynamic stability and ensuring replacement thickness of cutting bed under ballastless track of high-speed railway in China. Valuable first hand data for the further study of fatigue characteristics of red clay are provided.

Considering the effect of atmosphere, field test on simulating single anchor and frame anchor is carried out in Guangxi. The test results are as follows. Firstly, the swelling-shrinkage characteristics of expansive soil influences the working state of anchor deeply; so a free part of anchor should be set up in the drastic atmosphere influencing depth. Secondly, in rainy season, the anchoring action to frame beam restricts the swelling deformation and keeps the dry soil density in a certain range, which can prevent the strength weakening tendency of expansive soil and the shallow damage of the slope. Finally, because the frame anchor system is semi-rigid structure, the swelling stress may be released partly with the compatible deformation process when the soil is wetting and swelling, which keeps the soil additional stress under the beam to a constant value and show a distribution form of a big one in the center and a smaller one on each side. The results of field test can optimize the design of frame anchor system.

The research on failure criterion and evolution process of deformation instability of tunnels is one of the hot issues and difficulties in underground engineering field. Based on dissipative structure theory, energy dissipation process and evolution characteristics of tunnel are analyzed from excavation to unstable failure. The energy dissipation mechanism of whole tunnel system is analyzed by thermodynamics basic laws. An energy evolution model is also established. By combining the established model with the length of time sequence for general deformation monitoring data as well as the effective analysis of nonlinear dynamics, the energy criterion of the stability evolution process of the tunnel system is built separately under different data conditions (more than 3 000 and less than 3 000). According to unstable and failure features of every evolution stage of the tunnel system, the energy criterion is proposed. By applying this criterion to give a stability judgment of an overlapped tunnel in Guangzhou metro, its reasonability and reliability are verified. This research has a great significance for the stability judgment of tunnels.

To analyze the stability of an ellipsoidal cavity in soil foundation, the exact stress solutions for the extremum key points on the surface of ellipsoidal cavity in linear elasticity and isotropy infinite body under far field triaxial stresses are obtained based on principle of superposition. The limit of exact stress solution for an ellipsoidal cavity is degenerated to the counterpart solution for a spherical cavity when the shape ratio s is equal to 1 by Matlab program. Then Mohr-Coulumn criterion is used to estimate the stability of ellipsoidal cavity under triaxial compressive stresses. The results indicate that the ellipsoidal cavity is less easy to lose stability than the corresponding elliptical hole under the same far field stress condition. It is concluded that three dimensional ellipsoidal cavity model is more practical than either the corresponding two dimensional elliptical hole model or the spherical cavity model.

Qualitative analysis of microcosmic mechanism of limestone dissolution driven by different temperatures and hydrodynamic pressure in CO2-H2O solutions are scanned by the environmental scanning electron microscope (SEM) before and after the mercury injection test. First, the limestone dissolution is influenced by temperature and water pressure besides lithology and structure, dissolution of micrite small than oolitic limestone under the same conditions. Secondly, the sample produced different magnitude irregular figure crystal under high hydrodynamic pressure, the increase and extension of pores and fissures. And that produced great magnitude regular figure crystal by rising temperature that the dissolution and deposition are increased. The dissolution not only affects on the surface of the rock produce secondary pore and secondary mineral, but also influences the inner pore structure; the pore structure became inhomogeneous and discontinuous, decreases the permeability and connection among the structural planes of rocks. These microscopic characters are also well documented the information and results of the dissolution process.

Based on the low strength piles composite foundation settlement model, a group of settlement calculating equations for the low strength piles composite foundation are put forward. During the equations derivation, the interaction between the pile-soil-cushion is considered, and the stress-strain compatible equations are constructed. At the same time, the pile-soil stress ratio and the analytical solution of equal settlement surface are also received. Further more, the piles and their surround soil stress distributing regulation, compression deformation, the up sticking deformation of the cushion and the lower sticking deformation of the underlying soil are all obtained. Through the summary of underlying soil and the piles surround soil compression deformations, a formula for calculating the whole settlement of the low strength piles composite foundation is received. The settlement calculating method presented above can be a significant reference for later research and design of the low strength piles composite foundation.

Based on the upper bound theorem of limit analysis, admissible velocity field of strip anchor is constructed by using a combination of several rotational block sets. Upper bound solutions of pull-out capacities of deep and shallow strip anchors in undrained clay are analyzed. Pull-out capacity and failure surface characteristics under different embedment inclinations and depths are studied. The results are compared with results of existing methods. It is shown that the bearing capacity of deep strip anchor is independent of the incline angle of anchor embedment and the roughness of anchor surface. The failure surface radius of deep strip anchor under completely smooth condition is half of the radius under completely rough. The failure surface of shallow strip anchor enlarges rapidly with embedment ratio increasing; and the pull-out capacity of shallow strip anchor also increases with the increasing of embedment ratio. Comparison of the upper bound solutions with the existing solutions shows good agreement. Failure surface derived from rotational block set is explicit. It can be a reference for the practical design.

A number of different in-situ soil tests, such as plate loading test and pressuremeter test, have been carried out to get the regularity of bearing capacities and deformation parameters on horizontal and vertical variations of the laterite ground. The experimental results indicate that the horizontal and vertical foundation bearing capacity and deformation modulus of the laterite ground variate with the changes of depth, thickness, topography, water content and other factors; and vertical bearing capacity and deformation modulus were increased first and then decreased. The bearing capacities measured by pressuremeter test and by the plate loading test had shown some differences. The pressuremeter modulus and the deformation modulus could be associated with soil structural coefficient; and they were consistent with the Menard’s conclusion which based on a large number of clay test data.

In order to reveal the mechanism of permeability variation of the aquifer in the process of the saline water energy storage with recharging in Tianjin coastal area, laboratory column experiments were conducted to investigate the capability and rate of colloid release at different temperatures, the effect of colloid release on the permeability of the aquifer, and the change characteristics of Ca2+ during colloid release. The research results show that the colloid release from saline aquifer water-bearing media is pulse type, and presents to increase suddenly and decrease slowly with the period of 20 pore volumes in the saline water energy storage recharging process. The cumulative release capacity of colloids from saline aquifer increases with increasing pore volumes; and the release dynamic curve of colloid is segmental straight-line, and release rate and growth range of colloid is decreased. The permeability of the aquifer varies in the process of colloid release. The permeability coefficient of the saline aquifer shows a curve of “S” type with increasing pore volumes. In the condition of 0℃,10℃ and 20℃, the permeability coefficient increass by 4.02, 12.21 and 6.63 times respectively. Although the initial permeability coefficients of the saline aquifer vary at different temperatures, and increases gradually to reach about 15 cm/d after 60 pore volumes. Ion exchange reactions of Ca2+ with K+, Na+ exist in the process of colloid release; but the dynamic features of the reactions change with temperatures.

The mechanical characters of expansive soil structure reinforced with geogrids are directly affected by the water content, whereas the mechanism is rarely studied before. So, the filling with dimension of 600 mm×600 mm×600 mm laminated shear test apparatus is adopted to carry out a series of pull-out tests to investigate the effect of water content on pull-out behavior of the interface between geogrid and compacted expansive soil. The results show that the water content has a notable effect on the pull-out force and geogrid’s displacement, the characteristics of the interface stress and strain, and the strength parameters of the interface. When the water content is higher, the rigid motion of geogrid occurs earlier, and the pull-out force per width when rigid motion more approaches the peak value; and relation of friction and relative displacement of the interface tends to be more ideal rigid-plastic. The interface quasi-cohesion increases with decrease of water content, whereas water content has little effect on the quasi-friction angle of the interface.

The process of reservoir water level fluctuation will cause the changes of the slope body in the pore water pressure distribution, which has influences on slope stability. By improving critical slip field of slope, the numerical simulation method of critical slip field of slope, considering the process of water level changes, is proposed. Thus, slope local safety factor and slope safety factor of the whole in the process of changes in water level course are calculated conveniently and rapidly. By means of stability analysis of a typical slope in the process of rise and fall in water level and comparing with other methods., the results show that the critical slip field method can search for any shape of the most dangerous slip surface; and the safety factor is reasonable.

The load distribution of anchoring section for rock bolt is one of the key problems in rock-soil anchoring technology. Firstly, the strain of measuring points in the body produced in tension test is acquired. Then the data is fitted into curve with composite power function and Gauss function. Finally the axial and shear stress distribution of anchoring section under critical failure state is obtained. The experiment results show that the shear stress is distributed in the front part of bolts; the axial stress distribution is better described by Gauss function for anchoring section under critical failure state; and the damage emerges in the plane where shear strength is much larger than bond strength. The study results provide a theoretical basis for the design of bolt in rock-soil anchoring.

The stress-strain relationship, shear strength behavior and the influence of water on strength and deformation under low confining pressures are analyzed detailedly via large-scale triaxial test. Test results indicate that under low confining pressures over coarse-grained soils are characterized by weak strain softening or strain hardening. The form rests with the value of confining pressure. At the same time, volume shrink happens first and cubic dilation develops gradually with the increase of axial strain. The sample varies from dilation to volume shrink with the increase of confining pressure. But the shrinkage degree decreases little by little till stability. The shear strength of over coarse-grained soils shows nonlinear characters with the stress level. It decreases generally with the increase of confining pressure. Water has important effect on the compression characters and the shear characters of over coarse-grained soil. It mostly makes the compression coefficient degree increase and the parameter of shear strength decrease.

It has been proved by tests that post-peak strength of rock enhances with the increment of confining pressure. How to model the effect of confining pressure on strain softening of post-peak strength rock is a key issue. The degradation index of post-peak strength presented by FANG Z[1] is presented to model the effect of confining pressure on the post-peak strength and the secant modulus of rock. In combination with Mohr–Coulomb model, the strain softening model of rock with confining pressure is presented. Fish function method within FLAC is used to perform the model. In case study, the strain softening processes under variable confining pressures for Tennessee marble are modeled. The results show that the modeling results accord with experimental data; and the model presented is effective method to model the strain softening processes of post-peak strength rock.

Expanded polystyrene(EPS) composite soil is a new kind of lightweight fill material. Compared with well-known EPS geofoam, EPS composite soil will be widely used in the future. The fundamental physico-mechanical properties of EPS composite soil have been studied by many researchers. However, the creep properties of EPS composite soil have not been published in the literatures according to our best knowledge. Firstly, the triaxial undrained creep tests were conducted on EPS composite soil with various confining pressures. Secondly, three well-known empirical creep models were used to simulate the creep behavior of EPS composite soil including Singh & Mitchell model, Mesri model, and Findley model. Singh & Mithcell model and Mesri model were able to predict the long-term deformation of EPS composite soil, however, they could not describe the initial sharp rising deformation. It was observed that Findley model which was firstly used to predict the creep behavior of EPS geofoam had the best fitting results under higher deviator stress level. To some extent, the creep property of EPS composite soil was similar to that of EPS geofoam. Finally, a new creep model was proposed for EPS composite soil, in which the element models were used to describe the elastic strain and empirical models to describe the plastic strain. It was shown that whatever the stress levels were, the proposed new creep model could not only describe the initial sharp rising deformation but also predict the long-term deformation, i.e. creep deformation.

Jiangjiagou ravine is one of the most world-famous rainfall-induced debris flow or flow-like landslides gully in Southwest China. The surface layers of the slopes are covered by unsaturated weak-cohesion gravelly soil which can be classified as a porous non-plastic soil. Broadly graded gravelly soils have uniformity coefficients much greater than 20, and the grain size distribution curves are up concave or double peak, and they can be as internally unstable soils. The main clay mineral composition of fine fraction (<1 mm) of gravelly soil is chlorite and illite by X-ray diffraction analysis. The microstructure was investigated by environmental scanning electron microscopy; and a particular bonding was found. The bonding of the soil is easily broken by rainfall infiltration, which not only can decrease the soil cohesion, but also detach free particles from the bonding, the diameters of these particles were tens of microns. This is due to high dispersion of the clay part of gravelly soil. In addition, these free particles can be transported and will clog at pore throats during the process of self-filtration in soil. This process will decrease the permeability of gravelly soil, and be favorable to the formation of transient perched water zones in slopes during rainfall; thus can be as pre-failure of the slopes. The results indicate that the characteristics of gravelly soils and the particle detachment, transport and clogging play an important role in the stability of slopes.

Starting from the governing equations of axisymmetric consolidation, together with the technique of Laplace-Hankel transform with respect to time t, coordinate r, and Laplace transform to coordinate z, respectively, a set of linear equations in the transform domain is obtained. After solving these linear equations, the transfer matrix for a single layer rock with anisotropic permeability and compressible constituents is acquired. Based on the continuity and the boundary conditions, the transfer matrix method is utilized to derive the solution of the multilayer rock with anisotropic permeability and compressible constituents in the transform domain. By the inversion of the Laplace-Hankel transform, the solution of consolidation problems for the multilayer rock with anisotropic permeability and compressible constituents in the physical domain is obtained. Numerical calculation and analysis are carried out by the computer program; and the effects of the compressibility of pore fluid and anisotropic permeability on the process of consolidation is discussed. The results show that growing compressible constituents will cause larger immediate settlement of the rock; and the influence of anisotropic permeability on consolidation process is obvious, but minute on initial and immediate settlement.

Based on the deep foundation pit of Tianjin Transfer Junction Station, the settlements of diaphragm walls, deformations of upright post piles and plates due to excavation unloading of deep foundation pit by top-down method are analyzed through the contrast between measured data and numerical simulation results. The results show that the upright post piles and the diaphragm walls have some upheavals in the vertical direction; and the middle piles upheavals are bigger overall. The differential deformations of pile-pile and pile-wall increase with the increasing of the excavating depth, and the latter exceeds the warning value of design control. The horizontal deformation curves of the diaphragm walls are similar to "bow"; and there is lateral deformation towards the outside at the pithead. The maximum of the horizontal displacement is smaller than the normal construction method; and it occurs at about 1/3-1/2 of the pit depth away from the excavation surface. It is obviously different from the maximum at bottom of the excavation surface by normal construction method. Most of vertical deformations of horizontal plate are upheavals. The maximum of vertical displacement lies near the supporting column in the middle zone of top plate. Discussions on design control standards of the deformation of upright post pile are also made.

Engineering geology and hydrogeological conditions of Yushu earthquake damaged zone in 27 towns of 4 counties are studied. Four factors such as topography, lithology, hydrogeological condition, seismic intensity are selected as the evaluation indices; and evaluation criterion for single factor index is presented. Then a hierarchical model is established; and weight of each factor is identified. On this basis, evaluation results based on natural unit, town and the construction site of each town particularly the heaviest damaged zone Jiegu town are given with fuzzy mathematical method. Evaluation results indicate that except the construction site of Benda town, Zhenda town, Luoxu town, Zhengke town and Gaduo town, where the engineering geology and hydrogeology are in poor and extremely poor conditions don’t meet the reconstruction need; the construction sites of all other towns are all located in area with relatively good and good engineering geology and hydrogeology conditions, and can meet the reconstruction need. The eighty five percent (85%) of the original construction sites of Jiegu town are located in the area with relatively good and good engineering geology and hydrogeology conditions; and only sporadic construction sites are located in the area with poor and extremely poor engineering geology and hydrogeology conditions, in which active faults develop, the geological hazard is prone to occur, and should be excluded from the potential construction sites.

The influence on the deformation behavior of existing pipes induced by tunneling is a problem highly concerned by the geotechnical engineers during the urban subway construction. However, previous solutions are usually based on the assumption that the ground is homogeneous. There has very little investigation into the problem of tunneling in multilayered soils and coupling effects between existing municipal pipes and surrounding soil. The elastic layered half space soil model is combined with the analysis to consider the soil nonhomogeneous characters, and the nonuniform convergence soil deformation model is imposed to the tunnel opening boundary, the coupling method and two-stage method are presented for response analysis for existing pipes traversed vertically by tunneling in layered soil. The results indicate that the accuracy of the proposed coupling method is better than the two-stage method based on the closed form solution by Loganathan and Poulos (1998). And the soil nonhomogeneity, neglected in previous solutions, has a significant influence on the deformation behavior of existing pipes induced by tunneling in multilayered soils. It may provide certain basis to draw up correctly protective measurements of environmental effects influenced by adjacent tunneling.

Taking the shield tunnel segment as a section curved beam, the segment was articulated each other and contacted nonlineariy with the rock stratum. Infinite element was used to absorb the reflection and refraction of seisminc waves in boundary; the Mohr-Coulomb elastoplastic constitutive model and EI Centro seismic wave were used; an implicit dynamic finite element analysis of axial force and bending moment distributions under seismic loads was conducted by stratum structure method. According to the finite element analysis results, the reinforcement of the segment is checked combining with structural mechanics approach. Comparing with the load-structure method, the proposed method can simulate the relationships between the segments, segment and surrounding rock; the supporting structure such as bolt can also be considered; so the method can give more accurate results. The research provides a method of checking calculation and design basis for the optimization design of the shield tunnel and reduces the cost of the support.

Based on the monitoring data from two short-distance parallel highway tunnels with 11.36 m of external diameter and 4.0 to 5.7 m of spacing, effect of latter-constructing tunnel on former-constructed tunnel was analyzed. The results show that the soil between two tunnels moves simultaneously along parallel and perpendicular tunneling direction. The maximum lateral displacements along depths locate around 0.2 time external diameter above the depth of tunnel circle center. The lateral displacements of the soils between two tunnels and waist segment of former-constructed tunnel reach the maximum values at the stages of shield tail passing and subsequent segment installation. Convergence measurements indicate the segments of former-constructed tunnel move inward at the upper part while move outward at the lower part.

In order to reduce the uneven settlement of the dam construction period and improve the stress and deformation state of the slab during the operation phase, the basic ideas of dam deformation control are proposed based on Shuibuya high concrete faced rockfill dam(CFRD) design lessons, including the three-dimensional finite element simulation analysis, engineering analogy, dam zone, compacted standards of rockfill materials, procedures for the construction filling, concrete slab pouring time, the height difference between the top of the slab and temporary dam crest when pouring the slab.

Based on the block theory and Newmark sliding block method, seismic response and stability of key block in large underground opening group are studied. It is found that inertia force of the key block which acting with short time and large force leads to generation of permanent displacement under three-direction seismic loads, and seismic loads with different intensities cause the key block not only quantitative change of seismic response but also motion regularity and patterns. The result also shows that seismic response characteristics is related to the depth and volume of key blocks through statistic analysis; and seismic stability evaluation method considering multiple factor and indexes is established according to key blocks in large underground opening group. Finally, seismic response of the key block is studied considering cyclic degradation of structure plane strength; and some beneficial conclusions are drawn.

Recently, cases of excavation tunnel close to pile foundations have significantly increased. Problems are arising with its difficult construction controlling and high costs. In this paper, the safety factors of interaction between the tunnel and pile foundation are computed by using the strength reduction FEM in a variety of different cases based on the Mohr-Coulomb strength criterion. Those cases include the level distant between the pile and the tunnel, the imbedded depth of pile and the loads of pile. Practical rules of the variation of the safety factors are summarized from the computed results. It is shown that the critical level distance of pile away from the side wall of tunnel is one time width of tunnel. The influences of the pile-tunnel interaction can be ignored while the level distant of the pile-tunnel is more than one time width of tunnel. The loads on the pile foundation have important influences on the safety factor of the tunnel. The safety factor will decreased about 1/4 while the loads on the pile is increased about one time. The conclusions provide strong references for constructions of excavation tunnel close to piles.

The pile foundations of full containment LNG storage tanks have usually two kinds of forms: the low cap pile foundations and the high cap pile foundations. Based on elastic vibration theory and considering the shell liquid coupled vibrations effect, the aseismic properties are analyzed for the storage tanks of high and low cap pile foundations. The vibration characteristics of the full containment LNG storage tanks of the two forms of pile foundations are given, including the structural natural period, the horizontal seismic force of single pile, resistive overturning capability, the uplift force of unit length around tank bottom, and the sloshing period and sloshing wave height of the liquid and so on. Analysis results have shown that the horizontal seismic response of the high cap pile foundation is 8.69% more than the low cap; and vertical seismic response is 6.34 % more than the low cap; the resistive overturning capacity of the low cap pile foundation is more 12.11% than the high cap; and the uplift force is 11.42% more than the high cap; the structural natural period of the high cap is more than that of the low cap. Generally, the aseismic properties of the low cap pile foundation structure is preferable to the high cap pile foundation structure. The given conclusions have certain reference value to the design and the construction of the full containment LNG storage tank pile foundations.

Swelling tests of Mengzi remolded expansive soil immersed with water are carried out by simple consolidometer; and shrinkage tests are made by contractometer. The characteristics of expansion and contraction and break-down mechanism for expansive soil under different initial conditions are studied systematically. Does Response model is used to fit quantitatively the rules of swelling and shrinkage time interval for expansive soil. The results show that the difference between swelling and shrinkage for expansive soil is remarkable. Generally speaking, swelling ratio of samples immersed with water is larger than shrinkage ratio. The larger the expansion coefficients of samples under the same conditions are, the larger the contraction coefficients are. The anisotropy of samples is stronger. The internal and essence of shrinkage deformation disaster of expansive soil is that there are a lot of small clay particles, montmorillonite mineral crystal and significant microstructural characteristics. And the external cause is the development of micropore, fracture structure and the initial state.

This paper has explored karst spatial prognosis by logistic regression model so as to offer evidence of karst surface collapse in Shenzhen Universiade Center. The lithological feature, groundwater depth and geological structure have been chosen based on influencing karst developing factors and acquired data on site. The site karst development has been classified into five depth groups, namely, <10m, 10-22m, 22-30m, 30-36m and ≥36m, according to soil (karst) cave depth frequency hierarchical cluster analysis from drill display. The site has been classified into 6843 grids by 10m×10m in plane. The 3 factors logistic models of each depth group have been established when borehole information has been taken as samples of karst development based on GIS technology. The logistic PL value of each grid in five depth groups has been calculated by individual logistic model of boreholes. The weight is set by different depth karst frequency. The integrated evaluating P of each grid has been calculated by PL of each depth group by accumulating weights on the same position in different depth groups. After carrying out hierarchical cluster analysis of P, the site has been plotted into karst development area, karst development—non development area, karst non-development area. The results show that this model is reliable and can provide evidence for karst surface collapse assessment.

A construction method that a running tunnel with two tracks is constructed by large diameter shield machine and moreover a station is built by shallow mining method to enlarge large diameter shield tunnel can be regarded as a new approach to construct metro engineering fast, efficiently, safely and economically; in more and more complicated environment which would lead to difficult layout of metro lines, increasing construction risk and making still stricter demands on construction methods of metro engineering. Taking Gaojiayuan station of Beijing metro line 14 as an engineering background, two schemes for the metro station construction by the CRD (cross diaphragm) shallow mining method to enlarge a large-size shield tunnel with an outer diameter of 10 m are introduced. Two-dimensional finite element models are used to simulate the metro station construction on the basis of the ground-structure interaction. The mechanical performance of the structure of the metro station is obtained. The numerical results show that the structural stress state varies frequently in the process of enlarged excavation. The position of maximum axial stress shifts from the shield segments to the primary lining; and the position of maximum shear stress gradually appears at the key segment. The stress state of the segments shifts from the dominative axial compression to the predominant shear. The primary lining, temporary diaphragms, top and bottom beams and temporary struts are mainly in the compressive status. Compared with other structures, the key segment and top flanges of the top beam are subjected to greater stresses during the construction; furthermore, it is suggested that they should be reinforced.

The deformation of karst cave and its roof are the audio-visual qualification to evaluate the stability of karst cave foundation. The thickness of karst cave roof more than 8.0 m was determined which can ensure stability of karst cave roof under roof rock weight and pile foundation loading. It breaks the survey and design code about that the ratio of thickness to span of karst cave should be larger than 0.8. Based on finite element analysis, the deformation characteristic of the karst cave and its roof were forecasted. The multiple-point borehole extensometer was inbuilted in karst rock, so deformation of karst cave and cave roof rock mass under construction loading were monitored on-site. The results of monitoring show that 8.0 m thickness of karst cave roof is safe, and rationality of comprehensive evaluation was confirmed. The monitoring results show that the deformation of the karst cave and its roof are faster at the begin of construction loading application. The strain of the karst cave is larger than that of the superficial rock, and the strain of the cave roof rock mass is the smallest.

Using an effective stress dynamic analysis module which is compiled from secondary development of ANSYS on the basis of partitioned solution procedures of Biot equation coupled mechanical systems, analysis on liquefaction shock settlement of the embankment foundation of a reservoir is performed. In the calculation, two-dimensional finite element model of representative embankment section is set up; and input ground motion is artificially composed seismic accelerations with a 10% transcendental probability for 50 years in Shanghai. Distribution of ratios of pore water pressure and effective stress of embankment foundation of reservoir and distribution of seismic subsidence of the embankment are obtained by calculation. As demonstrated by the analysis, ratio of pore water pressure of central part of the embankment foundation is smaller than that of both sides of the embankment foundation; and foundation treatment is not necessary for the central part of the embankment foundation. The method can provide references for design and construction of other similar projects.

It is difficult to tunnelling in soft sandy stratum. To explore the key construction technology and study the mechanical effect of tunnelling in sandy stratum, numerical simulation and field experiments were carried out in sandy stratum section of Guanjiao tunnel. There existed about 450m long shallow-buried sandy stratum in the entry section of Guanjiao tunnel in the 2nd line between Xining and Golmud. Collapse had occurred during tunnelling using the initial three bench method; so four bench method was put forward. The excavation and support process of four bench method were simulated by means of FLAC3D numerical model, the deformation of surrounding rocks, ground settlement and stress distribution of primary support were analysed. And the superiority of the new method was proved by comparing the construction effect of three bench method. It was confirmed by actual construction and deformation measure that big arch-foot section, four bench excavation, long horizontal lead pipe-shed support, temporary transverse steel-support and shortening the distance of inverted arch closure were the key technologies of tunnelling in sandy stratum of Guanjiao tunnel. These methods could assure the safety of shallow-buried sandy stratum tunnel with big section. These could offer valuable experience to similar engineerings.

Based on the characteristics of half-hard and half-soft at outlet section of latter excavated left hole of Leigongpu tunnel with small clear-distance, the monitoring programs including ground settlement of the tunnel, vault settlement, horizontal convergence, the displacement of the middle pillar, axial force of the anchor, surrounding rock pressure and the stress of steel frame, and so on are conducted in the excavation process of the tunnel according to the new Austrian tunneling method. The monitoring results show that: the reservation soil core method can better control the deformation and stress of the surrounding rock; the vault settlement of the latter hole is greater than that of the foregoing hole, and the settlement on the side of the soft rock is much greater; the middle pillar is relatively weak, which moves to the foregoing hole in the initial excavation; rainfall greatly influences the deformation and pressure of surrounding rocks, which should be paid much attention in the construction process. The experiences and conclusions presented can be adopted in the design, construction and research of similar tunnels.

The urban rail transit and other municipal construction projects may inevitably lead the surrounding buildings and structures to deform. The deformation controlling index is the foundation of safety monitoring and controlling. The various types of deformation parameters and its quantitative research results are summarized. According to large information of deformation monitoring data, the damage grade is determined. The regular monitoring items of settlement, differential settlement and tilt are analyzed; and the relationship between building size, deformation value and damage grade is studied. The result shows that the buildings with independent plinth on sand soil are easy to deform and damage. The excessive settlement should be limited to keep building safe from damage caused by other deformations. The buildings are safe under angular variable of 0.002. The building size affects the deformation; and the easily damaged multistory and high-rise buildings should be paid more attentions.

The Metro Line 3 is the main framework line from southwest to northeast of Xi’an City Rail Transit Network. Due to the special geological environment, construction will encounter land subsidence, ground fissures, and other adverse geological problems. So it is very necessary to make clear of the cause of formation, location and development tendency of ground fissures and land subsidence along the Metro Line 3. Through site investigation and analysis of previous research results, the authors think that the Metro Line 3 will pass through five old subsidence centers (Xinjia Temple, Hujia Temple, Jinhua South Road, Guanyin Temple, Xiaozhai) and two new subsidence centers (High-tech Zone and Qujiang New District). At present, the settlement rate of the old subsidence centers and Qujiang subsiding center are lower; and their danger is low. But the settlement rate of the Yuhuazhai section of the new subsiding center is high; and its danger is medium. The Metro Line 3 intersects the seven ground fissures at twelve locations. Six locations have great risk, five locations have medium risk and one location has small risk. And special attention should be paid to the intersection segment of the Metro Line 3 and ground fissure f7 (from Jixiang village to Xiaozhai). Corresponding countermeasure are put forward based on the effect of the subsidence and earth fissures on subway. This researth has great helpful to the construction of Xi’an Metro.

In order to analyze the sliding mechanism of Longdong slope reinforced with piles, by making use of the developed strength reduction finite element codes, the both local and global stability of unsaturated soil slope are analyzed. Four kinds of reinforced measures are combined according to the installed position of stabilizing piles and matric suction. The comparison of results not only evaluate the influence of matric suction losses on the stability of slope, but also analyze that the two local sliding surfaces in upper and down slope may result in local instability if without the proper reinforced position of piles. In addition, the recommended design which could control the two local sliding surfaces works more effective than the other reinforced measures.

Based on the existing landslide field, a stability analysis of high slope along the loess plateau of Guanzhong Basin is presented. The format of explicit finite difference of twin shear unified elastoplastic constitutive model is developed which is based on the elastoplastic theory, non-associated flow rule and twin shear unified strength theory. According to the site surveys and laboratory tests, the terrain features before and after sliding and scale of the slope are analyzed; and the three-dimensional model is created from the sketch of terrain before the landslide event. With the influence of intermediate principal stress, stability analysis of high slope is processed with FLAC3D; ground water level variation and seepage flow are taken into account. The results show that the horizontal displacement at top of slope increases with the rising of ground water level with the consideration of intermediate principal stress. The result of no seepage flow calculation shows that the slope reaches a steady state under a certain displacement yielded on the top of slope. However, the displacement increases continually and then sudden failure may occur when the seepage flow is taken into account. This study may provide a reference for the research of failure mechanism of high soil slope.

It’s an increasingly serious problem that the influences of vibration and environmental changes on the stability of railroad embankment in permafrost regions. The maintenance of the railroad and assessment for the influence of the railway on the permafrost requires investigation and monitoring the changes of the embankment and the permafrost layer. We firstly applied a field experiment on applicability of transient surface wave survey on natural ground and railroad embankment together with permafrost investigation. The experiment data were good and the dispersion characteristics distinct. The Vs profiles of the natural ground, embankment, and their permafrost layers underground were obtained through dispersion analysis and inversion. Moreover, the result gave very clear boundary of the table and bottom of the permafrost layer underground at the Beilu River test segment of the Qinghai-Tibet Railroad. The table of permafrost is around 2m in deep; the thick of permafrost layer is about 20m; and their average Vs are above 600m/s, which is coincident with the borehole data and wave velocity test in this area. It demonstrates that the transient surface wave survey is effective for permafrost investigation in Qinghai-Tibet plateau.

Property risk assessment for single landslide is the foundation of prevention and mitigation measures. Since we can not evaluate the vulnerability of elements at risk quantitatively, property risk assessment of single landslide becomes hard to achieve accuracy. In light of the typical elements at risk, a quantitative assessment model for property risk caused by single landslide is presented, which defined by probability of slope fall, reliability of structure and the value of elements at risk. Avoiding the vulnerability evaluation, assesses the property risk from a new point of view. Through the research, it is shown that the model can reflect the influence of landslide factors exactly, and provides a new way to assess property risk quantitatively for single landslide. A new conception of safety zone that based on this model is introduced. For each one of elements at risk, the impact area of single landslide can be divided into dangerous zone, relatively dangerous zone and safety zone.

Cores were taken from hanging wall of the Ⅲ-1 ore body at Kangjiawan Lead，Zink and Gold Mine. 50 samples for compression tests and 50 samples for tension tests were fabricated. And 50 compressive strength values and 50 tensile strength values were obtained by using the electro-hydraulic and servo-controlled testing system RMT-150B. The probability distributions for the compressive strength and tensile strength were tested by using the obtained compressive strength values and tensile strength values and the hypothesis test method. It is shown that the uniaxial compressive strength follows normal distribution; and uniaxial tensile strength follows the lognormal distribution. It composes of 50 groups of , , , by random sampling to 50 , and 50 , without replacement. The stress of surrounding rock was calculated by using FLAC and 50 maximum values and 50 minimum values were respectively gained. The results show the former follows lognormal distribution and the latter follows normal distribution. The reliability of surrounding rock without tensile and compression failure was calculated under uniaxial compressive, tensile strength and probability density function of maximum and minor principal stress. Shear strength and the stability of surrounding rock were checked.

Based on known equations for predicting skin friction force, a new equation is presented with consolidated-quick shear strength parameters, in which three coefficients will be determined. According to the results of tested frictional piles in 19 projects in Shanghai and the least squares method , coefficients in new equation for different soft clayey strata is determined. Ultimate unit frictional force in different strata is calculated for different tested piles. Results indicate that unit frictional forces in same stratum for different tested piles are distributed in narrow range. Ultimate unit frictional forces obtained by statistical method are located between up and below limitation of which are calculated with up and below values of consolidated-quick shear strength parameters for different soft clayey strata. The effect of depth on unit frictional forces appears undistinguished，but the effect of stratum of pile tip is obvious.

As a large underground water-blocking structure, anti-seepage curtain is usually very crucial to the success of a hydraulic project, because its enshrouded construction condition, complex techniques, high cost of construction. Based on a large-scale project of anti-seepage curtain located in a complicate karst condition, the author mainly expounds the key techniques of the plan demonstration, optimizing comparison, node path, and also the post-evaluation of the underground curtain construction quality. Throughout the project, from feasibility study, construction work to the final function phase, nothing but accurate and precise work was done, which contributed to a total success. The results have certain application value, and can be for reference of other similar projects.

A study of the bearing mechanism of single pile in sand under vertical load is presented based on two dimensional discrete element method (DEM) by regarding single pile as a plane problem. Firstly, DEM simulations of formations of ground and boring cast-in-place pile are made; as well as the biaxial compression tests on the ground soil are taken. Secondly，DEM simulation of the static load test of single pile is carried out to study its bearing mechanism. The numerical results by DEM show that: the tip resistance increases straight as the settlement of pile increasing; while the shaft resistance inceases at first and then reaches a constant value; the shaft resistance of unit pile length increases unlinearly from top to tip of the pile; when the load reaches the ultimate bearing capacity of the pile, the pile tip penetrates into soil; this penetration leads to high gradients of rotation field and stress field around the pile and the soils near the pile, as well as the large rotation of principal stress.

This paper ascertains the reasons for the numerical non-convergence problem when the yield vertex non-coaxial model is implemented in the finite element analysis to predict the behaviour of a complicated geotechnical engineering problem, shallow foundation behaviour. It is found that a large non-coaxial influence at the start of elastoplastic loading, which causes the predominance of non-coaxial plastic strain rate over the coaxial plastic strain rate in stress-strain responses, is the reason for the numerical problem. The original yield vertex non-coaxial model is modified to overcome the numerical problem. It is shown that the modified non-coaxial model retains the functions of the original non-coaxial model. Meanwhile, it overcomes the non-convergence problem when a larger non-coaxial influence is considered.

Applying gas-solid two-phase flow of the Fluent, using turbulence model, we could research the wind erosion and failure pattern of the desert roadbed. After analyzing the sand process that includes disturbance slowing, growth recovery for the different cross-sections of the sand subgrade, the weakened and restore area that result from the existence of the sand roadbed as obstacles, we can summarize the regular pattern of the wind change for the feature point section of the roadbed. Through comparing the data, both on-site test data and simulated data have good uniformity. Research results show that under different roadbed cross-sections the distribution of the weakened and restored area is highly sensitive to the changes of different roadbed height and smaller influence on the slope gradient. The different slope gradient along the road winds is obviously different from all kind of height and roadbed cross-sections. When the slope gradient is fixed，with the increase of roadbed height the flow disturbances is enhanced significantly around the roadbed and the wind speed of windward slopes increases obviously on the top and the wind speed of wind slope dropped significantly near the bottom. The height of the subgrade is certain: the smaller the slope is, the gentler the wind along the road changes. The slope gradient of 1/3 shows: when the embankment height increased to 3m by 1m, the wind speed on the top increase 12% and the wind speed of wind slope reduces 20% near the bottom. In order to avoid the wind erosion damage of desert roadbed, we suggest that the height of the roadbed should not be too tall and the smaller slope gradient is advisable.

Unsaturated flow problem in a porous medium is closely related to the characteristics of porous medium, soil moisture state and its drying/wetting history. Based on capillary cyclic hysteresis model which considers the effect of the history of water content on the relation of soil water characteristics, a modified U-DYSAC2 finite element program is developed to simulate the unsaturated seepage problems. Unsaturated flow analysis is done under experimental conditions. Compared the simulated results with experimental data from the literature, the results with hysteresis effect are much nearer to the data from the tests undergoing repeating changes of pressure boundary conditions. Hence the applicability and necessity of the numerical model is verified being capable for modeling the intial boundary problems of unsaturated seepage. Subsequently, an example is shown for flow analysis in a soil column subjected to complicated infiltration redistribution history. The results show that the discrepancy of water content, pore water pressure and movement rate of wetting front in the column is large during redistribution process considering hysteresis effect and non-hysteresis effect respectively. It is shown that rate of drying in uppper layer and rate of wetting in lower layer considering hysteresis effect than that of nonhysteresis analysis. The simulated results confirm that soil moisture state in unsaturated porous media is not only dependent on water content, but also related to hydraulic path in porous medium. Hence, under cyclic change of boundary conditions, it is necessary to consider hysteresis effect in modeling unsaturated seepage problems.

The formation and development of geological disasters in rock area are dependant on the kinematic behaviors of rocks, especially of grains, fissures, and fillings in the rocks. In the conventional studies, rocks are generally treated as entireties and few concerns are concentrated on the individual meso-compositions in these rocks. Taking a limestone for example, macromechanical properties were obtained for the rock specimens of laboratory tests; and particle flow code in two-dimensions (PFC2D) was used for simulating the macromechanical properties of the rock material. In the simulation, the material was discretized as an assembly of rigid particles. The mesomechanical parameters, such as contact forces, contact modulus, normal contact strengths, and stiffness ratio, were obtained; and the mesostructural model was established for the limestone; connecting meso-level changes in particles with macromechanical properties. Because the individual compositions were taken as the direct objectives, reflecting the intrinsic features of rock materials or rock masses, the techniques presented herein may be of great significance in studying the constitutive law of fissured rocks, engineering properties of rock masses, and mechanism of geological disasters

A method of slope displacement back analysis considering excavation unloading effect is presented. In the stability analysis of section 1-1 of left bank of Longtan hydropower station, the geology generalization, excavation step and disturbing zone are analyzed to establish the computing model of finite element method. The mechanical parameters of rock masses are solved by using finite element method with neural network-genetic algorithm. The results of forward analysis with these parameters show that the displacements are reasonable and very agreement with the monitoring results. The maximum compressive stress is 1.0MPa and no tension stress at the excavation zone. The plastic zones are distributed at the slope top, excavation zone and near the big fault.

Three-dimensional particle flow model test for coarse-grained soil is conducted with the mean principal stress and the intermediate principal stress parameter being invariant. The stress-strain and strength behaviors of coarse-grained soil are presented under the different mean principal stresses and the different intermediate principal stress parameters. Three-dimensional particle flow model test can well simulate three-dimensional mechanical behaviors based on comparisons between the particle flow model test results and laboratory test results. The unified failure criterion can well capture the particle flow model test results and laboratory test results by adjusting the material parameter.

To study the relevance existing in the factors which influence the collapsibility of loess, an analytical model is established by using the cluster analysis and factor analysis. The natural specific gravity, dry bulk density, void ratio, moisture and plasticity index are chosen as the evaluation factors; and the collapsible index of loess is selected as the evaluation index. It is shown that the natural specific gravity, dry bulk density and void ratio can be considered as the same class of factors due to their same contribution to the collapsibility of loess. In addition, the moisture and the plasticity are considered as an independent class respectively, which makes the relevant origin factors independent. The cluster analysis and factor analysis are used to evaluate the collapsible level of loess, not only retains the information of origin factors, but also eliminates the influence caused by the multicollinearity; thus makes the analytical results more accurate. Finally, it is demonstrated through an engineering example that the calculation results by the presented model have good agreement with the practical results; and it is significant in engineering practice.

According to the characteristic of small spacing tunnels, the finite element models with various tunnel sections have been established. The comparative analyses of their surrounding rock stabilities during construction were made; and the basic mechanical characteristics of large-section twin tunnels with small spacing have been pointed out, which differs from that of two-lane twin tunnels. Analytical results show that the influence of tunnel spacing and rock grade on surrounding rock stability is dramatically different corresponding to various tunnel sections. Under the same condition of tunnel spacing, the mechanical state in three-lane twin tunnels is much more inferior to that of two-lane twin tunnels. Accordingly, the smaller the tunnel spacing, the worse the surrounding rock grade, and the more significant the difference. In addition, the worst position of mechanical state in large-section twin tunnels and small-section twin tunnels are the upper part and middle part of inter-space rock in weak surrounding rock, respectively. The results can be for reference in the design and construction of large-section twin tunnels with small spacing.

soil is naturally non-homogeneous as the result of deposits, but the investigation is only a few about the face stability of tunnel which is excavated in non-homogeneous ground, so they was treated as homogeneous ground in actually geotechnical projects. the beneficial effect of non-homogeneous ground on the minimum support pressure which maintain the stability of the head face, and the impact of non-homogeneous ground on failure mode are not taken into account. So the elastoplastic finite element method based on Tresca criterion is used to study the stability of the plane strain tunnel face which is in pure clay ground with the condition that the cohesive force varies linearly along the depth. The whole progressive failure process of soil instability is simulated. Finally, the effectiveness of dimensionless is verified; the smallest support pressures in different conditions are obtained; and the effect of non-homogeneity on failure mode is found. So as to provide a deep understandings for theoretical analysis and project practices.

Regarding a cutting slope of express highway in the mountains of northern Guangdong as the research object, through centrifugal model test and finite element analysis, the deformation characteristics and the mechanism of slope stability during the construction process were revealed; the effect of anchor bolt on slope stability was discussed. Results show that: the excavation caused slack deformation, and the value of deformation increased gradually from top to toe and reduced gradually from free surface to interior. The maximum displacement and plastic zone appeared near the toe. After anchor bolt support, the strength of the supported soil was improved; the slack deformation caused by the lower stage excavation was reduced; and the development of the plastic zone in the toe was restricted. The axial forces distributed differently along the anchor, which was concerned with its length; and generally the axial force of lower anchor bolt was greater than the upper one. The anchor bolt not only improved the stability of slope during construction, but also effectively weakened strain softening on the adverse effects of long-term slope stability and improved the safety factor of slope stability. The results obtained have some guidance meaning for the design and construction of cutting slopes.

Based on CT test of concrete meso-damage, segmentation equation of damage evolution is established based on the density damage (CT number changes) variable; then, the meso-damage of concrete specimen is numerically simulated under unaxial compression. The results of numerical simulation and CT test is compared and analyzed in failure chart of concrete and curve chart of load-displacement. The results shows that the crack propagation is similar to the result of CT; the concrete meso-damage associate with the degradation of macro- mechanical properties is accomplished. So the study provides mechanical basis to improve test design. At the same time, it make possible that the numerical method replaces of some test in a reliable and effective promise.

The failure process of horseshoe-shaped tunnel under different lateral pressure coefficients is numerically simulated, based on which, the effect of the lateral pressure coefficient on the initiator damage, displacement at roof, stress distribution, and the failure modes around the tunnel are examined. The numerical results indicate: Damage mechanism is mainly controlled by the lateral pressure coefficient , i.e. when ≤1, the position of damage initiation is largely discrete, especially at arch foot, spandrel and tunnel roof; when >1, however, spandrel is seriously damaged, vertical displacement of vault increases with the decreasing and increasing depth. The stress σ1 and σ3 increase with , even though the stress concentration at different parts of tunnel is quite different. Within a certain distance, the mechanism of the tunnel shape has more intensive influences than the distance from free tunnel perimeter. For the failure mode, when is relatively small, the main cracks spread in the vertical direction, while with the increase of , cracks gradually spread in the horizontal direction.

A new kind of quay wall structure with geosynthetics has been proposed for renewing existing sheet-pile quay wall structures to increase their earthquake resistance capability. The proposed structure (SG-WALL) is the combination of stabilization technique (S) of dredged soil and geogrid (G) for quay wall (Wall).The effectiveness of SG-WALL structure has been verified by a series shaking table tests. Dynamic numerical simulation of the shaking table tests are made trying to reproduce the experiment and find the key factors that will influence the seismic performance of SG-WALL structure. It is proved that the simulation can reproduce the main characteristics of SG-WALL structure during shaking. It is found that the length of stabilized soil plays a significant role in restricting the displacement of the quay wall during shaking. The maximal tensile strain of the geogrid occurs near the connection point with the sheet-pile; and the strain decreases along the geogrid.

The seepage field relates to canal lining and canal slope stability for the Middle Route Project of the South-to-North Water Transfer, especially for stretches of deep canal on confined aquifer. In order to analyse the distribution of seepage field and rationality of seepage control measures comprehensively, a typical canal model is established with the 3D finite element technology suitable for the simulation of phreatic surface and dense drainage holes. The seepage field is simulated and the effects of seepage control measures are analyzed. The results show that water pressure under the canal lining plate will be reduced significantly by the measures integrated by canal slope drainage holes and drainage cushion with drainage holes which open just when the ground water head in the cushion is higher than the water level in the canal, so as to ensure the project safety.

A few integrative variables can substitute for original multidimensional variables by principal component analysis with little data information lost; and the data organizations are relatively simple by this method. In order to get the main factors that reflect the quality of rock, the principal component analysis is put into use. Five indirect factors on rock quality such as dry density, distortion module, saturation drink rate, dry resistance strength and longitudinal wave velocity are chosen to test in laboratory. The main parameters have been found after processing those indirect factors by principal component analysis; and the evaluation model for rock quality has been got. The quality of rock is evaluated by the model base on principal component analysis, and the quality sort of sixteen groups of rock samples is given. It is shown that the evaluation results by the model and the actual quality of rock samples are well coherent. The model has good reliability on the evaluation of the quality of rock. It can evaluate the quality of rock quickly, impersonally and truly.

Based on some urban subway station foundation-pit project, retaining structure of the foundation pit and its deformation monitoring program are designed; in-situ monitoring data of the retaining structure deformation in the foundation pit are analyzed. The laws of the horizontal deformation of the retaining structure changing with the excavation depth and time are studied. Elastoplastic finite element model is built to do construction simulation calculation of the station foundation pit; FEM results and in-situ monitoring results of retaining structure deformation are compared; and sensitivity factors analyses of the foundation pit deformation are done with a variety of retaining structure form. The results showed that: the retaining form with steel support and supporting pile has good limit to the lateral deformation of the foundation pit soil. The results calculated by FEM are consistent with the in-situ monitor results; it is shown that the results of finite element analysis is credible; it plays an important role in limiting lateral deformation by change the position of steel support; with the increase of supporting pile insertion depth; the soil deformation trending to the foundation pit inside is slowed down somewhat.

In the design of soft ground treatment, the soft soil indices are the basic design parameter, and their changes have a strong geographical feature and significant uncertainty. Today, the soft soil indices statistical analysis content is mainly in the correlation and distribution regularity of physico-mechanical indices, which lack systematic study in different regions for different types of soft soils, and the statistical samples are from indoor tests and in-situ tests, without considering the impact of different test methods. In this paper, taking the soft soil in Tianjin as an independent statistical unit body, based on studying the change confines, variability, correlation, probabilistical distribution model of soil indices, some statistical relationship empirical formulas and probabilistical distribution models for physical indices, compression index, strength index were obtained; moreover, the correlation of shear strength results by straight shear test, triaxial test, vane shear test are analyzed; and a method for using random factor to evaluate the uncertainty involved in different test methods of soft soil parameters is proposed. The study results provide a basis and reference for defining the values of geotechnical parameters for soft soil.

Xiangshui offshore wind power station is located in shore water near Chengang of Jiangsu province. As the pile groups of the wind turbines have complicated engineering characteristics, their design is one of the technical difficulties of the project. Deformation behaviors of the piles foundation of Xiangshui 2MW wind turbine generator system are computed and analyzed under static loads and cyclic wind loads. The results show that deformations of the foundation are allowable; and the deformations due to static loads are comparatively smaller than that under the containing cyclic wind loads condition. With the depth increasing, the horizontal displacement and its influence range decrease; while the maximal vertical settlement is steady and vertical influence range increases. Deformation characteristics of pile-soil system depend not only on the loads combination of the subject, but also on the soil conditions.

A kind of direct shear model test apparatus is introduced, which can be used for laboratory model tests of anti-sliding structures for slopes (landslides). The model test apparatus consists of shearing system, loading system and data collecting system. The shearing system is composed of an upper direct shear box, a lower direct shear box and two straight steel rails. The upper and the lower direct shear boxes are connected by the straight steel rails. The loading system is composed of load transducer, hydraulic jack and reaction rack. The shearing system and the loading system are connected by steel base. The apparatus has been successfully used in anti-sliding model test of single row grouting micro-piles based on detailed analysis of its structure design and characteristics. Application results of the apparatus indicate that this kind of direct shear model test apparatus possesses great practicability; and it can be used further in other similar model tests.