To make a better understanding of the meso-mechanism of composing the long-term shear strength of fractured rocks, an experimental study of the micro-contact and damage evolution of fracture surfaces in rocks is carried out. Two types of fractured rocks are made by compressive shear and Brazilian tests respectively. Under a constant normal load, the fractured rock samples are tested by stepwise increasing creep shear forces. The fractured rocks are scanned using CT and laser scanner before, in the middle and after the creep shear test respectively. The meso-contact and the damage states in the fractured rocks are observed in different loading stages; and then the shear strength of the fractured rocks are obtained. The experimental results show that the long-term shear strength of fractured rocks is composed mainly by two mechanisms, one is the anti-shear ability of interlocked meso-asperities; the other is the anti-friction ability of contacted asperities. The tensile fractured rocks preset a relatively higher roughness and the shear strength is mainly from the first mechanism. The shear fractured rock gives rise to a relatively higher roughness; and the shear strength is mainly from the second mechanism. During creep shear, the two mechanisms are interacted and changed their roles with the development of time and shear displacement.

Foundation treatment and shield construction disturbance are the causes of squeezing soil which damages the initial structure and state, leads to the disturbance of soil, and changes the property of secondary consolidation. According to the squeezing disturbance of different levels caused by different preloads, a series of step-loading consolidation tests are conducted. The results indicate that, with the increase of preloads, the structure yield stress increases, compression index is almost the same when preload is less than structure yield stress, and decreases suddenly when preload is larger than structure yield stress; then it comes to a steady value. The secondary consolidation coefficient increases firstly, then decreases, finally gets to steady with the increase of pressure; and the secondary consolidation coefficient would decrease when disturbance increases; and a computational model for secondary consolidation coefficient is put forward; and the model coincides well according to the several testing data, and does well in predicting, which is useful for the prediction of post-load settlement.

Duncan-Chang nonlinear model has been widely used in numerical analysis of stress-strain in engineering. There exists insufficiency when Duncan-Chang model applied to complex stress conditions; this model is based on the axisymmetric stress conditions. We compared the model predictions with the experimental results of intact clay by true triaxial tests. The results demonstrate the applicability of Duncan-Chang model under complex stress condition. According to the analysis of the relationship between intermediate principal stress and the maximum principal strain under true triaxial stress conditions, and the maximum principal strain includes not only the maximum principal strain but also the strain, is caused by differences between the intermediate principal stress and the maximum principal stress. Based on Duncan-Chang E-B model, we proposed a method for determining Duncan-Chang E-B model parameter under different intermediate principal stress ratios and also established the modified Duncan-Chang model E-B model under complex stresses. The modified Duncan-Chang E-B model is reliable by comparison of the true triaxial test results of Xi'an intact clay; it is shown a way to use Duncan-Chang E-B model in complex stresses path.

There are phenomena of cut-off or truncation for Rayleigh wave dispersion curves when transfer matrix approach is used to calculate dispersion curves of some irregular horizontal layered profiles. But these can be avoided if the appendant layer method is adopted. In order to study the validity of this new method, phase velocities and the excited intensities are compared before and after appendant layer method used. The author calculates dispersion curves and the change of displacement components with the depth of three irregular profiles by the appendant layer method. According to the calculating results and comparative analysis, the appendant layer method can calculate not only the guided waves, but also the leaky mode waves. At a fixed frequency point, the error of the excited intensity between modified and original models decreases with the appendant layer’s burying depth increasing. And for an invariable burying depth of the appendant layer, the error is decreases with the frequency increasing. It is obvious that Rayleigh wave dispersion curves of some irregular profiles can be calculated by the appendant layer method on the basis of practical accuracy demand.

The problem of half-space nonhomogeneous foundation subjected to vertical and horizontal linear loads is studied. The linear transformative relation between the solutions of the nonhomogeneous foundation and the corresponding homogeneous foundation is analyzed. Based on deformation compatibility condition, the analytical expressions of stress and strain component are obtained. Through comparing solutions of nonhomogeneous foundation and the corresponding homogenous foundation, linearly correlation relation between the both is found. The solution of the nonhomogeneous foundation can be linearly expressed by that of homogenous foundation with the same conditions. The transformation factors between the solutions of two kinds of soil are derived in analytic forms, witch reflect the nonhomogeneous properties of the foundation. Therefore, solutions of the non-homogenous foundation can be reduced to that of a homogenous one and the calculation of the transition parameters, which simplifies the solution procedure. For the convenience of engineering application, analogous transformation coefficient is given by graphic form with different nonhomogeneous indices.

X-section cast-in-place pile (XCC pile) can save concrete usage under the same pile perimeter. However, there are little relative theoretical studies focusing on the lateral load reaction mechanism of the surrounding soil of XCC pile. The XCC pile holes are mapped on the unit circle using the conformal mapping of complex function method, and the plane strain solutions of stress and displacement distribution of surrounding soil of XCC pile under lateral load calculated by plane complex variable elasticity method are obtained. Then, the surrounding soil of pile are assumed as a series of independent springs, and the stiffness coefficients of the springs can be calculated by the plane strain solution in this paper. Pile deflection and internal force of XCC pile under lateral load can be calculated by using differential equations of the Euler-Bernoulli beam. The reliability of the theoretical calculated method built in this paper is verified by comparative analysis with the plane strain solution of the circular piles under lateral load obtained by Baguelin. Finally, one example is analyzed, and the results are compared with numerical calculated results. The results show that the reaction mechanism of the surrounding soil of XCC pile under lateral load can be simulated very well by this method, especially with small lateral load condition.

Taking second shaped coal samples as research object, the coupling relationship between characteristics of gas flow and lateral strain of coal containing gas under triaxial loading is studied by self-developed triaxial servo-controlled seepage equipment for thermo- fluid-solid coupling of coal containing gas. The results show: Poisson ratio defined by elastic mechanics can not accurately express the characteristics of axial strain and lateral strain of coal containing gas; the relationship can be properly expressed by quadratic function. Characteristics of gas flow velocity is showed by the law that firstly rapid decreased then slowly increased in restoration stage of lateral strain caused by preloading. Gas flow velocity can be showed by the law of monotonic slowly increased in transformable stage from lateral compressive strain to dilated strain; and there is a special internal structure critical state point where the gas flow velocity is the smallest. The gas flow velocity of coal containing gas at initial state of lateral compressive strain is larger than it at end state of lateral dilated strain.

Soil structure and anisotropy were generated during the depositional process for natural sedimentary soils, which made them different form that of the remolded soils. Since natural soils may generally undergo different stress paths during external loads in the engineering practice; it is necessary to carry out stress path tests on natural soils both considering the effects of soil structure and anisotropy. Analysis of mechanical behavior under different stress path tests can be the basis for set up reasonable constitutive model for natural soils. In this study, different K0 consolidation drained stress path triaxial tests were performed by GDS triaxial apparatus on undisturbed Zhangjiagang silty clays, which were taken by large diameter PVC samplers from depths of 2.5m underground. Test results show that stress paths exert significant influence on volumetric and shear deformation. Global stress and deviator stress have cross effects on the volumetric strain and shear strain. Obvious yielding behavior can be observed in stress-strain relations, whatever the stress paths are controlled by volume or shear deformation. Yielding curve obtained by connecting the yield points under different stress paths shows an incline elliptical shape, which agrees better with the yield curve in the constitutive model proposed by Wheeler et al. than that of the model presented by Nakano et al..

In the process of deep excavation and tunnel design, soils of different sites may undergo different static stress paths. Under different stress paths, soils may behave different static characteristics. At the same time, in engineering practice, the work strain of soils is in the range of small strain; and in the range of small strain, the static characteristics of soils behave more nonlinear and depending the stress paths. In this paper, based on the soft clays which spread widely in the Eastern China and behave many bad engineering properties, a series of static stress paths tests were conducted under undrained condition and drained condition. Test results show that: under both undrained and drained conditions, the stress paths make great influences on the static strength; the stress paths with increasing confining pressure increase the static strength; while the stress paths with decreasing confining pressure decrease the static strength. Meanwhile, the stress paths make greater influences on the degradation of secant Young’s modulus; the stress paths with increasing confining pressure decrease the secant modulus; while the stress paths with decreasing confining pressure increase the secant modulus. The influence of stress paths on the secant modulus is more significant in the range of small strain; and it is due to the anisotropy induced by the change of stress path directions.

In order to make full use of terrain, geological structure and material characteristics of concrete, and optimize unfavorable forced state of linear interval cantilever row piles and improve the global stability, a new spatial anti-slide structure of arc interval row piles with arc beam on the top of piles is proposed; that is according to the terrain and geological conditions of slope, to set piles in arc shaped with coupling beam on the top of piles and set resistance piles at the two ends of coupling beam, namely compose a new spatial anti-slide structure to resist landslide thrust. According to force method, the restraint force between the piles and the coupling beam can be regarded as the redundant force, then the calculation model of the anti-slide pile and the coupling beam are built, respectively; and to analyze theoretically the internal force of the coupling beam and the displacement of the anti-slide pile. Then according to the displacement coordination condition between anti-slide pile and coupling beam, to establish the typical equation to solve the redundant force. Finally, the theoretical calculation formula of the bending moment, shear and axial force of the coupling beam and the displacement and internal force of the anti-slide pile are obtained. By analyzing the calculation example and comparing with the cantilever row piles and the linear interval row piles with beam on the top of piles, the results show that the internal force distribution of arc coupling beams of spatial anti-slide structure is more reasonable; and the arc coupling beam can constrain displacement of piles and the effect is obvious.

Soluble salts is a critical disease for Yungang grottoes of Datong city in Shanxi province, which leading to the surface weathering strengthen reduction and structure damage. An experiment of deterioration simulation with sodium sulfate has been carried out for the sandstone taken from the sculptures distribution layers. The deformations of samples have been real time monitored and the mass loss, strength decrease and pore character change, and etc. have been tested during the salt crystallization cycles. Following conclusions have been obtained. Firstly, the injury of the soluble salts is the main reason for the powdered form on the sand rock surface, which cause the historical value is fading away. Secondly, the inner structure has been changed and the glue materials have been destroyed by the crystalline of the salts inside the rock, the consequence is the porosity ratio increase and stiffness and strength decrease. Lastly, in the dry season, the deterioration effect of soluble salt on rock should higher than other time from the comparative of two phases simulation tests, thenardite (Na2SO4) and mirabilite (Na2SO4•10H2O). For long term prediction of the deterioration action of salts, a logarithm model has been used for porosity increase and an exponent model for strength decrease.

Aiming at the shortcomings of traditional constitutive theory failure to describe the non-coaxial deformation of soil for simple shear test, a constitutive model amended with non-coaxial plasticity theory is employed to improve it. Based on the critical state and state-dependent theories, with the method of macro-meso-incorporation, a novel anisotropy state variable is introduced in the model to describe the anisotropy of sand. In view of the geometric relationship of meso-fabric and stress state, the state of sand changes in the principal stress axes rotation condition, and the dilatancy and hardening law of model is the function of sand state, so the model can describe the effect of inherently anisotropy on deformation of sand in this condition. The non-coaxial plasticity theory employed to amend the constitutive model, a three-dimensional non-coaxial model for anisotropic sand is presented. The loading conditions of simple shear test causes the rotation of principal stress axis relative to the soil deposition direction; the amended constitutive model can describe the effect of inherently anisotropy and stress-induced anisotropy on deformation characters under the principal stress rotation conditions; so the amended model can describe the whole characters of simple shear test with clear physical meaning. The verification with simple shear test results of rod mass and Toyoura sand shows that the amended model can well simulate deformation properties.

In order to analyze the role of vertical additional force on the shaft wall under deep alluvium when considering temperature effect, the temperature stress analytical formula of shaft wall is established，included the temperature self stress produced by temperature difference between inside and outside wall and the temperature stress produced by radial expansion hindered. Based on the fact that the rupture of shaft wall in the deep alluvium is due to the vertical stress of the shaft wall exceeding the limit of the reinforced concrete strength, the vertical stress components in the shaft wall are analyzed, which are produced by the temperature load, dead weight, horizontal lateral pressure and vertical additional force. The results show that the vertical additional force is the most important factor to lead to shaft wall fracture and the temperature stress is also an important factor of shaft wall fracture. Considering the rupture characteristics of shaft wall, the maximum value of vertical additional force which is caused by the settlement of the strata drainage is gotten through inverse analysis based on shaft lining structure design theory. And the reference is provided for the design and safety assessment of shaft walls in future.

Using large-scale shearing device, consolidation-drained triaxial test and isotropic consolidation-drained triaxial test under different confining pressures are performed for three relative densities (0.9, 0.8, 0.7) overburden material of ShuangJiangKou earth dam. The difference between dilatancy behaviours of coarse-grained soil under -consolidation and isotropic consolidation is investigated. Meanwhile, applicability of the modified Rowe dilatancy equation for coarse-grained soils under -consolidation is tested. The test results show that the dilatancy under -consolidation is more remarkable than that under isotropic consolidation; and this difference is more obvious for coarse-grained soils with lower density. By means of the nonlinear fitting of the results of triaxial tests, a relationship formula for coarse-grained soils under -consolidation and isotropic consolidation among dilatancy factor and relative density and confining pressure is obtained, according to which, the dilatancy’ strength of coarse-grained soil under different consolidations can be judged. For the coarse-grained materials under -consolidation, of which dilatancy characteristics can be reflected well by the modified Rowe dilatancy equation.

The knee-shaped deflection fractured zone located in the dam-foundation of a hydropower station is a main engineering geological problem of the project. The lithology is soft sandstone with poor integrity and pore cementation contact, which composed by cataclastic rock and clastic rock. The engineering mechanical properties of sandstone may have a significant impact on the deformation and stability of the dam. Based on the characteristics of loose organizational structure, high moisture content and poor physical mechanical properties, the basic physical properties tests are carried out to fractured zone sandstone first. It's considered the sandstone which is extremely complex microstructure and good permeability as small porosity sandstone. Secondly, the conventional and field tests are carried out to study mechanical properties. Finally, the influences of the fractured zone are discussed based on a certain macromechanical parameter. The results show that, the internal structure of sandstone is damage seriously; and main mineral compositions are quartz, feldspar, sericite and so on; the main chemical constituent is SiO2; but the chemical erosion is not significant. The shear curve shows the characteristics of four distinct stages. The failure mechanism of triaxial compression test is plastic shearing; and the curve shows a low strength, significantly ductility dilatancy; and yield platform is formed. Also the cataclastic rock strength is slightly higher than clastic rock. The field tests show that the deformation of rock mass is uniform, but the deformation modulus is low of which the range is 60-630 MPa. And the foundation bearing capacity ranges from 0.8-2.3 MPa. The research results provide greatly referential value for dam foundation of hydropower station.

Adopting the step loading method on combined structure of spatial truss micro-pile system as supporting structure , the changing law of internal force of micro-pile system is studied by new geological mechanics model test. According to the test methods and the state of force of the space truss micro-pile system, the structural analysis solution which is under the conditions of step cyclic loading and based on the elastic foundation beam constrained laterally is deduced. The test results show that, under the conditions of the broken-rock soil, the link beam can effectively limit the micro displacement of pile top; and the moment of pile body reduced; the soil pressure distribution in front of the pile is relatively uniform in sliding body; the distribution of the moment of each row of micro-piles is relatively close to each other; the maximum moment is close to the sliding face. The structural analysis solution based on the elastic foundation beam constrained laterally deformation can describe the changing law of internal force and distribution rule of micro-pile system after step cyclic loading better. The research results have a good reference value for correct analysis of anti-sliding mechanism and anti-sliding design of the micro-pile.

Cellulose organic matter and hummus will affect the mechanical properties of soft soil. The higher of the Organic matter content, the worse of the mechanical properties. To study the consolidation characteristics of high organic soft clay, the formation mechanisms of permeability、consolidation and structural characteristics are analyzed by the test of decomposition degree after the tests of permeability、consolidation、micro-meso structural characteristics at different depths. The results indicate that permeability coefficients have larger difference at different depths; and permeability and consolidation speed are faster. The value of permeability coefficient is during silt to silty clay magnitude; The vertical permeability coefficients are smaller than horizontal permeability coefficients at depths from 0.5m to 1.8m. and others are lagger than horizontal coefficients. The decomposition degree studies have shown that decomposition degree will affect the consolidation characteristics directly; and lower decomposition degree will easer lead to plastic deformation. Also the structure changes from flocculated structure to laminatted structure according to different depths, and transforms into massive structure finally. It proved that the characteristics of permeability、consolidation and structure have been direct effected by the degree of decomposition after the decomposition degree is analyzed.

The mechanical property of interface between geomembrane and sand is a critical problem in stability analysis of landfill liner system. Based on basic theories of elastic mechanics and soil mechanics, the analytical solution of additional stress is given. The additional stress distribution of sandy soil near the interface is analyzed. The results show that there are three kinds of distribution form of additional stress isolines, which are hyperbolic type arch, enlarge shoulder arch type and circular arc arch. The additional stress distribution patterns are only related with the length of reinforcement and the distance from the reinforcement surface. There are no relation to the bearing stress of reinforcement. Under the same conditions, the effect of strip reinforced geomembrane is larger than that of lump reinforced geomembrane. So the strip reinforced geomembrane can improve the interface shear performance more effectively. The farther the sandy soil from the interface, the weaker the additional stress. When the distance from the reinforcement surface is up to 12 mm, the additional stress is close to zero. That is to say, the range of influence of reinforcement is about 12 mm.

Mass fraction and waste rock proportion are main influence factors which affect flow characteristics of backfill paste mixed by unclassified tailings and waste rock. To study of the influence law of these factors about paste flow characteristics may have important significance about controlling paste flow characteristics. Shear test of mixed backfilling is conducted with the improved small direct shear device and then get the change law of mixed backfilling. The test results show that paste presents approximate elastic at prophase of force-deformation and the stepladder trend in displacement-shear stress curve increases with the increase of waste rock proportion. Cohesion of paste depends on mass fraction and internal fraction angle is affected by mass fraction and waste rock proportion almost the same, and that is combined effect. When mass fraction in the range of 80%-88%, cohesion pretends as nonlinear growth with the increase of mass fraction, internal fraction angle and mass fraction presents S-type trend, shear strength increases with the increase of mass fraction and varies significantly when in the range of 82%-84%; at the same time, flow characteristics is mutation.

Sand is a kind of typical granular material. Its mechanical and deformation characteristics are macro phenomenons of its meso-particles under loading. In view of the sand with graininess and fragmentation, the meso-structure level research on sand is necessary. In this research, the soil particles are simplified as ellipsoids. The direction angles of the soil particles obey normal distribution. The friction characteristics and failure mechanism of sand material are studied at meso-particles level based on meso-statistics. The friction characteristic of sand is composed of the resistance caused by the rise of the sand particles around the plane which is normal to the shear plane. The angle between the particle movement direction and the shear plane is considered as the friction angle of a single particle. The friction angle and direction angle meet the same normal distribution law. The shear failure process of sand composes of particle rearrangement and internal stress redistribution. During this process, some particles friction angles gradually become weak and the number of particles sustaining load increases. Moreover, the distribution of sand internal stress gradually become uniform. With the increases of the vertical load, the internal friction angle of the sand decreases. The relationship between the internal friction angle and the applied load can be therefore quantitative calculated.

Gradation, one of the most important physical characters of soils, has significant influence on the stress strain response of coarse aggregate. Accurate prediction of the gradation evolution during loading procedure is an essential part for efficient analysis of strength and deformation characteristics of soil structures. Following Einav’s fractal breakage theory, the energy dissipated from particle breakage during loading is assumed to be in direct proportion to the increment of fractal breakage ratio. Method of measuring the gradation evolution during loading as well as a novel yielding model considering gradation evolution of coarse aggregate is then established by employing a well-known energy equation. Investigation of the gradation evolution of coarse aggregates is thus conducted by employing corresponding experimental data from relevant literatures. After that, preliminary discussion of the newly proposed yielding function is also conducted. It is observed that each yield surface during loading corresponds to a specific gradation of coarse aggregate. Moreover, the yield surface is suggested to be a shear strain-based isosurface, of which the shape is mostly determined by shear strain.

Kaolin and bentonite, two clay minerals are mixed with sand respectively, and then mixed with lead nitrate to produce artificial lead-contaminated soils. Cement and lime are used to solidify the artificial lead-contaminated soils respectively. The samples are made using the compaction method. The relative mass loss, cumulative mass loss rate and unconfined compression strength (UCS) of samples after wetting-drying cycle tests are recorded, in order to evaluate the wetting-drying cycles durability of the solidified lead-contaminated soil. The results show that the wetting-drying cycles durability of samples in this study all meet the requirement; wetting-drying cycles durability of bentonite mixed soil is worse than kaolin mixed soil; cement solidified soil performs better than lime solidified soil in terms of wetting-drying cycles durability; admixing 8 000 mg/kg lead slightly leads to an enhancement of wetting-drying durability of stabilized soils. Water content is a key parameter to immobilize heavy metal in cement or lime, and enough water should be available for hydration, hydrolysis, pozzolanic and carbonization reactions of cement or lime.

By modified DRS-I high pressure direct shear test apparatus, interface shear tests of gravel and different structural planes under medium and high pressures are carried out. With different structural planes having different peak-valley distances H, relative scale R is defined as the ratio of H to average particle size ( ). Effects of relative scale R on mechanical and deformation characteristics of interface shear process under medium and high pressures are studied. The test results show that the relative scale R affects the interface shear energy consumption and shear volume deformation directly; and influential rules are different between medium pressure and high pressure. Whether under medium or high pressure, there exist limited and critical R respectively described as and Before , the increase of R results in monotonous change of interface shear energy consumption and shear volume deformation. After , the increase of R will cause shear energy consumption and shear volume deformation meeting a critical state, and the corresponding relative scale is . For above rules closely relate to particle displacement and grain breakage, the limited and critical values of R give new thoughts to research the roughness which affected by relative scale of particles and structural planes under different pressures; and it also has some significance for describing the mechanics and deformation mechanism of interface under different pressures.

In order to investigate the dynamic tensile strength of rock after high temperature under impact loading, the dynamic flattened Brazilian disc experiments of marble after different temperatures subjected to radial impact compression are carried out by using split Hopkinson pressure bar (SHPB). The temperature and impact loading rate effects on the dynamic tensile strength and dynamic tensile failure form of marble under impact loading after high temperatures are analyzed. It is demonstrated that after different high temperatures the dynamic tensile strength of marble is substantially higher than the static tensile strength and has an obvious impact loading rate strengthening effect. As temperature increases, the dynamic tensile strength of marble under the same impact loading rate increases first and then decreases. Meanwhile, the temperature and impact loading rate both have strong influence on the dynamic tensile failure form of marble under impact loading after high temperature.

For level pillar stoping under loose medium, determining the critical thickness of roof is difficult. In order to solve the problem, using elastic beam theory, the level pillar is simplified as a mechanical model of a beam fixed at both ends under uniform load; and is considered to be the main failure stress according to the elastic stress solution of beam. Theoretical analysis shows: in level pillar stoping process, the main influence factors of critical thickness of roof is loose medium load, stoping span and tensile strength of rocks. Through using FLAC3D and combining with orthogonal experiment result of numerical simulation, the relationship between single influence factor and critical thickness of roof is revealed. Based on multiple nonlinear regression analysis method, the mathematical forecasting formula of critical thickness of roof under multifactor influence is established. Finally, The critical thickness of the roof is predicted accurately; and applicability of the mathematical forecasting formula is verified by the engineering practice of level pillar stoping in Fenghuangshan Mine.

Thermal effect of brittle failure for hard rock tunnel under high geostress and high ground temperature need to be studied urgently; and the calculation analysis related to brittle failure rarely considers thermal effect. Based on the method of thermal-brittle-fine mechanical calculation, the thermal effect of excavation unloading for hard rock tunnel is calculated by using a new constitutive model reflecting the brittle failure of hard rock; and the energy release rate index is also analyzed. Taking the rock pillars of APSE tunnel in Sweden for example, the mechanical response of tunnel excavation is analyzed under different ground temperatures. Then the damage degree of surrounding rock is analyzed under the action of temperature loading. The failure zone, energy release value and stress index are compared under different ground temperatures. The result shows that increased temperature will strengthen the brittle failure because temperature will make rock mass to generate additional thermal stress. The method of thermal-brittle-fine mechanical calculation can reasonably describe the progressive failure process of hard rock. The proposed method reveals the thermal effect of brittle failure for deep hard rock tunnel, and could benefit the stability evaluation for deep hard rock tunnel under high ground temperature.

To study the shear property of weathered schist residual soil, in-situ direct shear tests was carried out at a slope project in northwest mountain area of Hubei province; and the structural composition, fracture characteristics, relationship of stone ratio and waviness and so on were analyzed. The results show that: The stress and strain curves show strain hardening features, and no obvious peak. The lonely stone and cluster stones are rolling and gnawing fracture in shear surface. There is an approximate linear relationship between waviness of shear surface and stone ratio; and the value of waviness increases with the increase of stone ratio. The climbing effect may cause shear dilation and increase of shear stress and normal stress. With increase of normal stress, the failure mechanism in shear surface turns sliding into gnawing fracture; and the ratio of shear-normal stress is in decrease. The results can be referenced for deformation and stability analysis of slope projects.

The influences of slope angle and rainfall intensity on infiltration process of landslides are not considered in the traditional rainfall infiltration model. In order to describe the rainfall infiltration process of Huangtupo landslide better, an improved infiltration model considering the influence of slope angle and light rainfall intensity is deduced based on the Green-Ampt infiltration model. In order to obtain the parameters of the improved infiltration model, double rings infiltration tests, rainfall monitoring, water content and matric suction monitoring are conducted on the No. 1 slide of Huangtupo landslide. The results show that the saturated hydraulic conductivity of the rock falls of No. 1 slide of Huangtupo landslide is about 4.81×10-5 m/s; water content increases under continuous rainfall and decreases under the cessation of rainfall, and the effect of hysteresis occurs in the deeper soil; on the contrary, the matric suction decreases under continuous rainfall and increases under the cessation of rainfall. The parameters of the improved infiltration model of Huangtupo landslide are get. The results calculated from the improved infiltration model are very close to the data obtained from monitoring. Therefore, the improved infiltration model can be used to rainfall infiltration analysis on Huangtupo landslide.

Through comparative study of two different geo-models of Liangshuijing landslide, it concluded that Liangshuijing landslide is in fact a paleo-falling and sliding rock accumulation without forming a whole and continuous “sliding belt”, and the landslide is divided into two parts named as the main sliding part at middle-below and the towed part at the up in terms of the landslide structure and the accumulation sequences. Also, the deformation mechanism has been researched, coming out the conclusion that the landslide initial deformation is due to the coupling process of reservoir water softening, uplifting and the river bank slumping; while in the condition of the reservoir operation, the main influencing factor of the landslide stability is rain fall, especially storm and long-time rainfall. It is also concluded from stability study that from May 2009 the landslide has entered the state of creeping by a slow process of stress releasing. Furthermore, from the prediction analysis of stability and failure mode, there comes the results that in the condition of reservoir operation, by coupling of strong and long-time precipitation and reservoir triggered bank slumping, the surface part of the main sliding body will be sliding firstly(sliding model 1), and the sliding of the whole landslide is also possible (sliding model 2).

In order to study the deformation characteristics of embankment with deep permafrost table and degenerative permafrost, based on the permafrost temperature and settlement monitoring data of Qinghai-Tibet Highway, the change process of permafrost table and embankment settlement characteristics were analyzed by analyzing the soil of permafrost, ice content of permafrost, permafrost temperature and embankment settlement deformation data in Xidatan, Tanggula North Slope and Tanggula South Slope. The layered settlement test data monitored from permafrost embankment in Tuotuohe and Qingshuihe area were also analyzed. The results show that the soil and ice content of permafrost have great effect on the degenerative permafrost embankment settlement; while deep permafrost melting has less effect on the embankment settlement. The settlement comes form degenerative permafrost layer and the consolidation of degenerative permafrost layer take a long time to complete in freezing and thawing cycle. In stable road section with permafrost of ice-poor and icy frozen soil, the degenerative embankment settlement rate is 3.9-5.6 mm/a approximately; and the degree of embankment settlement is very small. The embankment settlement has characteristics of persistence and no-slowing with soil of high ice content and powder clay; permafrost embankment deformation shows uniform settlement with less transverse differential settlement.

Based on weights back analysis and efficiency coefficient method, a new surrounding rock classification model of underground oil storage caverns is put forward. And rock compressive strength, integrated coefficient, character of discontinuity, groundwater, the angle between tunnel axis and soft surface are selected as key factors of surrounding rock stability. Then using weights back analysis method to determine the weights of factors, after which the model of the surrounding rock classification can be established based on weights back analysis method and efficacy coefficient method. Finally, the established classification of surrounding rocks model is used in practice; and the results show that the outcomes of stability analysis match the actual surrounding rock classification. It proves that the method used in surrounding rock classification of underground oil storage caverns is rational and effective, so as to provide a new idea to predict surrounding rock criterion for underground oil storage caverns stability.

The interfaces in bedding rock slopes are regarded as weak planes, which are equivalent to equal-interval collinear multi-joint mechanical model. The anchorage model of the slope reinforced by prestressed anchor cable is equivalent to plane problem of the rock mass joints with finite width. The original stresses and additional dynamic stresses caused by seismic loads are regarded as far field effect, and the force of the anchored slopes is the superposition of far field effect and effect of concentrated force of joint surface. The stress intensity factor of crack tip subjected to seismic loads is calculated based on superposition principle. It is found that the prestressed anchor cable whose anchor point located close to the crack tip can greatly reduce the stress intensity factor of the mode I crack. The reinforcement mechanism of bedding rock slopes reinforced by prestressed anchor cable subjected to seismic loads is interpreted using stress intensity factor as an important parameter of compression and shear failure criterion of rock mass, which can well explain the failure features of slopes in Wenchuan earthquake.

For a low embankment road, the reasonable prediction of vehicular load-induced plastic deformation plays an important role in the road design. According to the mechanism of vehicular load-induced plastic strain, the plastic strain comprises two parts: plastic volumetric strain and plastic shear strain. In the calculation of plastic volumetric strain, the dissipation equation with a source term, which couples Terzaghi’s consolidation theory with the experimentally-achieved cumulative pore pressure model under undrained condition is adopted. While in the calculation of plastic shear strain, the hardening factor of plastic volumetric strain is taken into consideration. The validity of the model is verified by the dynamic triaxial test results of saturated clay under undrained and drained condition. For practical problems, the vehicular load-induced stress is calculated by the numerical method firstly; then the plastic strain can be calculated by the proposed model. Finally, the plastic deformation is obtained by the layer summation method. The calculation example of the point NO.1 on Saga Airport access road is analyzed to illustrate the validitity of the model in a pratical boundary value problem.

A new earth pressure expression is derived to calculate the earth pressure on the shotcrete of flexible retaining method with prestressed anchor in order to solve the computation model of earth pressure on the shotcrete in the anchor shotcrete support design on the base of two-dimensional soil arch. And the distribution of earth pressure on the shotcrete along the depth is established. The values of earth pressure from this paper are compared with those calculated by silo method from the Specifications of design for geological hazard stabilization for different soil parameters, such as soil cohesion , soil internal friction angle , soil-shotcrete friction angle and horizontal distance between the adjacent anchors. The results show that the earth pressure on the shotcrete increases with decreasing ; and values are greater than those calculated by silo method for a small . The maximum earth pressure is proportional to while has no effect on the maximum earth pressure. Variation in parameter has a significant effect on the earth pressure and should not be neglected for engineering design because of the contribution for decreasing the earth pressure on the shotcrete. Finally, a simplified expression for calculating earth pressure on shotcrete is provided.

In order to study seismic stability of soil walls reinforced with different materials, the two simplified failure surfaces are considered. Then, due to the limitations of pseudo-static method and the layering features of reinforced soil walls, the formula of the total reinforcement tensile force and critical angle of rupture is obtained by the combination of pseudo-dynamic method and horizontal slice method, considering both horizontal and vertical seismic force. The example analysis results show that the total reinforcement tensile force increases with the increase of seismic acceleration coefficient and unit weight of backfill or surcharge load; while it decreases with the increase of soil internal friction angle or cohesion. Furthermore, the total pullout reinforcement tensile force for flexible reinforcement material is larger than the total breakage reinforcement tensile force for rigid reinforcement material under the same conditions. Compared with the pseudo-static method and the method in the specification, the design of reinforced soil walls is more economic by using pseudo-dynamic method.

During the excavation of deep caverns, the strain energy accumulation and release of surrounding rock are the most important incentives to cause the catastrophe damage. Aiming at the excavation of circular tunnel, the energy transient adjustment process of surrounding rock under the different unloading ways of initial in-situ stress (static and dynamic unloading) is analysed and compared, and based on energy point of view the damage scale of surrounding rock is calculated. The results show that, energy transmits from far and near in the surrounding rock by the radial stress working under the unloading of initial in-situ stress, and causes the strain energy of the near parts of surrounding rock gathering, with the excavation of underground caverns and tunnels. The strain energy of the near parts of surrounding rock decreases firstly and then increases, this caused by the dynamic unloading of initial in-situ stress; firstly the rock releases its own strain energy by radial stress working on the adjacent rock mass near the excavation surface, with the continuous transmission of the unloading stress wave, its own strain energy gathers by the working of adjacent rock mass away from the excavation surface. Comparing with the static unloading of initial in-situ stress, the high strain energy accumulation degree caused by the dynamic unloading of initial in-situ stress leads the larger extent of damage zone.

The retrogressive landslide occupies a considerable proportion among expressway landslides in the mountain area. The reinforcement projects often cost enormously and the environment around is usually damaged severely. Taking a certain expressway retrogressive landslide for example, through approaches of geological survey, deformation investigation, stress-strain behavior analysis and numerical modeling, the failure mechanism is confirmed as follows: (1) the loss of resisting key block is caused by slope foot excavation, shear strain softening is induced by stress concentration; (2) physico-mechanical properties alternation of the rock and soil mass are remolded by the surface rainfall and groundwater; (3) tensile cracks are fromed deformation incompatibility and its expanding backward. The monitoring results show that the applied combined reinforcement measures work well. The geological characteristics of excavation-induced retrogressive landslides are discussed. A principle that “the safety factor should be calculated by section should use to evaluate retrogressive landslide; the reinforcement of the whole landslide should be controlled by the predetermined safety factor; while the reinforcement of landslide rear should be controlled by displacement.

In soft ground, the lateral displacement of piled foundation and the additional bending moment of the bridge pile caused by the surcharge load is an extremely negative impact on the safety of the bridge. Through the introduction of specific project, the influences of the unilateral and bilateral surcharge load on the lateral displacement and the internal force of the bridge piled foundation are analyzed in-depth using the finite element analysis; and the calculation results and the measured results are compared. According to above analyses, the change rules of the lateral displacement and the internal force of the bridge piled foundation are further understood. By the impact of unilateral surcharge, the lateral offset and bending moment on the pile is much more significant. The inflection point of the pile is occurred at the interface between the soft soil and hard soil. While the additional bending moment of the pile is significant, it will result in pile cracking. By the impact of bilateral surcharge, the lateral offset of the piled foundation is determined by both sides of the load. Unloading both sides at the same time is less impact on the lateral offset of the piled foundation; but it plays an important role in reducing additional moment of the pile.

Creep damage and fracture of rock are the main forms of rock creep effect. But the internal damage evolution process of rock is difficult to be observed directly. So, the particle flow code (PFC2D) is used to analyze the mesomechanism of creep damage and fracture for Jingping marble. Based on the laboratory test data, the particle flow stress corrosion model (PSC) is used to establish the numerical model of Jinping marble. The model can simulate the short-term and long-term strength characteristics of Jinping marble. The numerical simulation result shows that the creep damage evolution process is significant different from the process in transient state. In the creep damage evolution process, the microcracks almost dehisce along the load direction; and the distribution of them is even. The number of microcracks in rock specimen increases rapidly firstly, and then increases stably. Finally, the microcracks evolution unstably till the rock sample fracture. When the load is lower, the rock specimens present the splitting failure state. However, when the load is higher, the rock specimens present the shear failure state. In the initial damage stage and prophase of stable evolution stage, the load magnitude has a little effect on the creep damage process of rock specimens. In the later stage of stable evolution stage and the failure stage, the damage of rock specimens under lower load increases faster than the specimens under higher load.

Mining technology gob key to the success depends on a stable overlying strata gob of time and location. Mining stope surrounding rock stress redistribution exercise-induced dynamic stresses acting on the rock pit and make state disaster is the root cause of mine disaster occurred. Layered thick seam fully mechanized roadway layout (including internal fault, external fault and vertical), reasonably determine the coal pillar size, roadway methods and parameters to the greatest possible self-supporting ability to play rock, is to improve the stability of the important roadway guaranteed. Stable internal stress field in the range of small pillar supporting roadway layout, can significantly improve the surrounding rock stress state, greatly improving the recovery rate. Through theoretical analysis, numerical simulation and field measurement methods such as, for layering under thick seam gob roadway layout small pillar of different designs, through analyzing and comparing the stress and strain and displacement of pillars to determine the thick coal seam under the sub-layer along gob roadway reasonable position and pillar dimensions and overlying strata control techniques, and get engineering validation is accurate and reliable, Thus little thick seam mining technology provides an important scientific basis.

A fully implicit integration scheme in the bounding-surface plasticity model for cyclic behaviors of saturated clay is presented by modifying the conventional implicit return mapping algorithm. Within the critical state framework, based on the concept of shrinking the elastic region to a point, combining isotropic with kinematic hardening rule and a rotated bounding surface, and introducing a damage parameter representing the remolding of the soil fabric, the model can reflect the initial anisotropy, the cyclic stiffness degradation and strength softening of saturated clay under cyclic loading. Firstly, the numerical simulations of the undrained triaxial tests both for isotropic ( ) and anisotropic ( ) consolidated kaolin clay are carried out with variable strain increments. By comparing with the test data, the rationality, robustness and the accuracy of the new fully implicit integration for the bounding surface plasticity model are verified. Furthermore, the prediction for an undrained cyclic triaxial test on a saturated clay is given, and the cyclic degradation of the stiffness and strength is obtained, which indicates the validity of the computational results.

From the perspective of microstructure of rocks, based on reasonably simplifying the actual tunneling condition, and by employing particle flow code (PFC2D), two-dimensional numerical simulation of rock fragmentation of shield machine cutters is put forward. The mechanism of rock fragmentation under the situation of sequential cutting by two shield cutters is studied; its influential factors and corresponding experiments are carried out to verify the mechanical properties of rock fragmentation. Studies show that: first, it is the cutter's tip that is of the most destructive effect; second, the force of cutters fluctuates constantly along with the cutting process; and the horizontal cutting force is greater than the vertical cutting force; third, it is different between the single-pole cutting and sequential cutting since in the process of sequential cutting, the former cutter leaves many residual cracks, which decrease the cutting force of the following cutter; forth, from the aspect of cutting performance, rock cracks become bigger and cutting force become greater as cutters go deeper; so we can conclude that the cutting depth and the cutting force are closely related; last, the experimental situation of the accumulation of cracks and chips at the front of cutters and the wave phenomenon of cutting force in the experiment show great agreement with the results of numerical simulation.

In order to grasp the nonlinear response characteristics of soil pressure transducer in high-modulus soil, based on the interaction of model of transducer with soil, the reasonable modulus ratio of transducer and soil medium was studied with FEM. And the main factors about nonlinear response of transducer was studied by monomer transducer calibration test and transducer calibration in graded broken stone medium. Based on the results of FEM and calibration test, some conclusions are drawn as follows. The modulus of domestic mainstream transducer is too low to satisfy the reasonable modulus ratio at present when used in high-modulus soil meadium, which leads to the significant nonlinear characteristics of calibration test curve. The monomer test curve is highly linear and the modulus of transducer is stable, which shows that the nonlinear characteristics of calibration test curve is mainly caused by the soil modulus’s change. The test precision can be significantly increased by calibrating the transducer in the same state soil as field test and correcting the calibration results nonlinearly.

Using combined load-displacement searching method, the stability of skirted bucket foundations in saturated soft clay subjected to horizontal load (H), moment (M) and torque (T) non-coplanar combined loading is studied through three-dimensional finite element numerical analysis. The soft soil is assumed to be undrained and obeys elasto-perfectly plastic constitutive relationship following the Tresca failure criterion. The failure locus of bucket foundations in various loading spaces is investigated. The results show that the shape of failure envelopes of bucket foundations subjected to non-coplanar combined loading varies considerably from that under planar combined loading. Under non-coplanar combined loading, the shape of failure envelope does not depend on the aspect ratio of bucket foundations, which may be approximated as a circle or ellipse in normalized load space. Based on finite element analysis, the existing equation of failure envelope in three-degree-of-freedom loading condition is extended to the six-degree-of-freedom case, then an equation of failure envelope involving all six-degrees-of-freedom is suggested, which can be used to evaluate the bearing capacity of bucket foundations in soft soil under combined loading condition. Values of the eccentricity parameter in the proposed equation are also presented for a range of practical embedment ratios.