The thermal effects of rock in long-term varying low-temperature environment are mainly expressed by the mechanical parameters, thermal coefficients of rock and the pore ice expansion coefficient in the saturation state changing with the decreasing temperature. These changes have some significant influences on the deformation and strength characteristics of rock. The constitutive equation considering the thermal effects and the ice expansion coefficient is established according to the nonlinear thermo-elastic theory of varying properties, and the changing relationships of the thermal coefficients with temperature and their determining method are given under the uniaxial compressive condition. Then, the relationships of the thermal effects with low temperature for granite are obtained by means of the uniaxial compression test results of granite under the different dry low temperatures and the saturated frozen, and the influence of the different conditions on the compressive strength characteristics of granite is discussed. The analysis results show that the thermal coefficient and the ice expansion coefficient of granite decrease gradually with the increasing of the relative temperature difference under the varying low-temperature environment, and the reducing rate of thermal coefficient is lower than that of the ice expansion coefficient. The coefficient of the thermal expansion is greater than that of the ice expansion under the same temperature difference. The thermal stress and the ice expansion stress increase with the low temperature nonlinearly. The compressive strength values of granite in the two states are both increasing; but the thermal stress is the dominating, and the axial stress increment caused by the thermal coefficient is always larger than that caused by the ice expansion force. The proposed method and the obtained results can be supplied for the research on material deformation properties and engineering application under long-term varying low temperatures.

The vibrations of vehicle-track-saturated ground coupling system subjected to moving train loads are investigated by a semi-analytical approach. The theoretical model is divided into three components: the vehicle is described as a multi-rigid-body system, and a linear Hertizian contact spring between each wheel and the rail is used to simulate the dynamic wheel-rail interaction forces; a periodically supported Euler beam is introduced to simulate the track system; a fully saturated poroelastic half-space is used to simulate the ground and governed by Biot’s theory. Train loads include two parts: the axle loads and the dynamic wheel-rail loads assumed to be generated from the track irregularity. The governing equations of each component are solved by using Fourier transform, and these components of the whole system are integrated to meet the displacement compatibility and force equilibrium by the substructure method. The time domain responses of the ground are obtained through the fast Fourier transform. On the basis of the analysis of the dynamic wheel-rail loads, the dynamic responses of the ground subjected to the axle loads and the dynamic wheel-rail loads are investigated. Influences of the sleeper span and the soil intrinsic permeability on the soil dynamic responses are also analyzed. It is concluded that the dynamic wheel-rail load has important contribution to the far-field ground vibrations, and also the sleeper span has obvious influence on the track and ground vibrations.

Due to new tectonics movements and drastic climate change, there are different types, and thicknesses of sediment on Quaternary soft clay in Hangzhou region, which have some characteristics of structural properties in particular. In order to investigate the dynamic characteristics of Quaternary soft clay in Hangzhou region, a series of dynamic triaxial tests are conducted. The stress-strain backbone curves and some kinds of dynamic property parameters of structured soft clay in Hangzhou are obtained. It is discovered that the change of the sediment environment is a cause to structural properties of soft clay in Hangzhou region and affects initial dynamic elastic modulus Ed0 obviously. On the side of the maximum amplitude on dynamic strain, the control of structural properties of soft clay is random and unobvious. Generally, there is a good power function relationship between the shear wave velocity and buried depth of structural soft clay, but the different kinds of structural soft clays may have different relationships. In addition, it is shown that structural properties of soft clay could have some influences on the relationship between damping ratio and shear modulus.

In order to study the behaviors of uplift pile subject to cyclic load, cyclic loading tests are carried out on two uplift piles at Xiaoshan, Hangzhou. Stress gauges and steel pipes are pre-buried in the test pile to measure the changes of pile shaft stress and the pull-out amount of both pile tip and pile head. Through the analysis of the pile shaft stress and the pull-out amount, the influence of cyclic load on bearing capacity and pull-out amount are studied. Comprehensive analysis of the pull-out amount, pile shaft force and pile side friction, it is drawn a conclusion that the uplift pile damaged after two or three cycles when uplift pile subjects to cyclic load, and the critical cyclic load level is close to 1.

In order to study the three-dimensional (3D) isolation vibration effectiveness of wave impeding block (WIB) in layered and vertical heterogeneous foundation under horizontal-rocking coupled excitation, a 3D semi-analytical boundary element method (BEM) model based on thin-layered method (TLM) efficiently to study the wave propagation in layered ground and BEM precisely to solve infinite domain problems is presented. The analysis is accomplished with this model, on which the Green’s function is regarded as fundamental solution of a stratified half-space. Then the active isolation effectiveness of WIB is studied in layered and vertical heterogeneous foundation. The results show that the stratification parameter and the heterogeneity have significant influence on the vibration isolation effect of WIB, and the isolation vibration effectiveness of the upper stiff-layer and lower soft-layer ground is better than it of the upper soft-layer and lower stiff-layer ground.

The monotonic shear tests are carried out to investigate the mechanical properties of rock mass joints with the second-order asperities, which simulated by small regular saw tooth; and gypsum material is used to simulating rock mass joint samples. Five artificial joint samples with different heights of second-order asperities are tested under low normal stress, which keep constant during the tests. Characteristics of shear strength and deformation are analyzed; an interpretation of the joints failure modes is given. Based on the experimental results, it can be found that the second-order asperities have important influence on the shear mechanical properties of joints, and the mechanical properties are different from the joints with first-order asperities only, for which shear stress vs. shear displacement curve just has one peak shear stress; by contrast, the joints with second-order asperities have multi-peak shear stress, which decreases gradually one after one with the increase of shear displacements. As well, the dilatancy curves of the joints with second-order asperities show wave shape. With the increase of second-order asperities height, peak shear strength increases; the failure modes appear wearing, many-times shearing of asperities, and one-time shearing failure of asperities.

The distribution and weathering characteristics of granite in the western coastal site of Guangdong province are described. A series of in-situ tests are conducted, including the velocity tests, load tests and in-situ shear tests, along with laboratory tests involving conventional compression test and consolidation test. Based on test results, the physico-mechanical properties of highly weathered granite are analyzed. It is indicated that: (1) Due to strong physicochemical weathering processes，the unstable elements in bedrock are leached which further result in formation of aluminum-rich-and iron-rich types of thick weathering crust. Heterogeneity of rock is obvious. (2) Natural moisture content and void ratio of highly weathered rockmass vary greatly, while natural density and modulus of compression change moderately. (3) Particle sizes have a great impact on the physical characteristics of weathering granite. The physical indexes are stronger as the decrease of particle sizes. (4) Wave velocity is closely related to the weathering degree and particle composition. (5) Water content has more apparent effect on cohesion than friction angle. The attenuated effect on cohesion of highly weathered granite is obvious in particular. The research results can provide basic data for construction of nuclear power station and optimal design.

On-site experiments are crucial to study rock mechanics due to the complexity and diversity of rock mass. In the past, test conditions restrain the test load setting of rock creep to transient creep, thus it cannot reflect steady-state creep and accelerated creep. The mechanical characteristics of weak rock mass are vital factors which affect the long-term stability of a dam and its underground structure. The creep model which is identified through the two stage characters of transient creep and steady-state creep is presented in the test curve of the bearing plate in dam foundation. Viscoelastic general solutions of deep rock rigid and flexible bearing plate are deduced by applying viscoelastic theory, and uniform expression of Maxwell modal , generalized Kelvin and Burgers model are also given. The rheological parameters obtained through the combination of theoretically analytic inversion and the experiment data form the basis for analyzing long-term stability of dam foundations.

Based on irreversible thermodynamics, the paper elaborates two fundamental constitutive issues: (1) existence or inexistence of the flow potential; (2) the flow potential can or cannot be decomposed into a damage potential and a plastic potential, namely, whether the two mechanisms can be decoupled. Within this framework, sufficient and necessary condition for the existence and the decoupling of the flow potential are given, and they are strictly proved in theory. According to the mechanical property of the geomaterial, the inexistence and the un-decoupling of the flow potential are also proved; meanwhile, it is shown that the existence and decoupling of other solid materials can theoretically be obtained from the two fundamental theories.

The pile head settlement of a single pile in homogeneous soil and multilayered soils can be subdivided into three aspects, including the pile tip settlement induced by mobilized load at the pile tip, the compression of pile shaft, and the settlement caused by the skin friction. Based on the settlement of a single pile and the equivalent pier method, a simplified calculation approach for average settlement of pile groups is obtained. The nonlinear relationship between the pile tip load and the settlement at the pile tip, and the nonlinear settlement induced by the skin friction can be taken into account, as well as the pile shaft compression. The settlements of a single pile and pile groups drawn from the present method are generally in good agreement with the measured values and the calculated values estimated from other methods.

To study the load settlement characteristics and load-transfer mechanism of cast-in-situ X-shaped concrete piles, full-scale model pile load test of X-shaped pile is carried out by using the large-scale test trench of Hohai University. The interaction behavior of the vertical loaded X-shaped piles is obtained by means of the reinforcement stress gauges set in the pile and earth-pressure boxes embedded in the pile bottom. The experiment results show that: X-shaped pile load settlement curve is an adjustment curve; pile side friction and tip resistance show incremental development with the increasing pile settlements; but with the increase of pile top load, the ratio of pile side resistance sharing pile head load is regressive, its sharing ratio decreases from the initial load of about 90% to 70% of the limit state, while the ratio of tip resistance sharing the load is incremental, the pile top load-sharing ratio of about 10% from the initial state up to 30% of the limit. The research results are useful for the design and analysis of X-shaped piles under vertical load.

Factors affected the rock mass shear strength parameters are complex with uncertainties. A comprehensive model with multiple index is established combined with quantitative and qualitative indicators. It can effectively determine the shear strength of rock. The multivariate nonlinear statistical method is introduced to study the rock mass shear strength parameters. Twelve qualitative and quantitative indicators are selected, based on the large number of projects through the collection of data, nonlinear explicit equations of cohesion, and friction angle for rock mass shear strength are established; their determining coefficients are 0.992 729, 0.999 998, respectively. This model not only considers quantitative factors, but also considers qualitative factors. It is verified by field data. Results show that the models have high accuracy. It is easy to solve the rock mass shear strength parameters with high practical value, and it has high practical value for projects.

Exploring saturated calcareous soil explosion compacting mechanism and effect through the experimental study have great theoretical and practical significance on engineering construction in calcareous soil area. First, longitudinal wave velocity and surface settlement are tested at different moments before and after explosion under different explosive parameters through indoor mini-explosive compacting experiment. And then, wave velocity characteristics and settlement rules are studied to reveal dynamic characteristics of saturated calcareous soil explosion compaction through analyzing and contrasting the test results. It is suggested that high void ratio and particle breakage characteristics of calcareous soil have great impact on compacting effect. After explosion, breakage and compression cavity are formed in the neighborhood of explosion because of calcareous soil particle breakage resulted from the heavy shock of explosion, compression cavity would relax along with time lapse, the explosion compaction process is completed within two hours.

Laboratory experiments on the cooling capability of crushed rock embankment samples with a perforated ventilation pipe and an air permeable top surface are performed. The impact of mechanism on the cooling capability of the open crushed rock embankment enhanced by a perforated ventilation pipe is analyzed. The analysis indicates that the heat transfer processes in the crushed rock embankment with a perforated ventilation pipe and an air permeable surface include pure heat conduction, forced convection due to the pore air motion in the crushed rock layer forming directly a complete circulation in conjunction with the ambient air by the small holes of the perforated ventilation pipe wall, convective heat transport between the ambient air and the surface of pipe wall, and forced convection that occurs in the crushed rock layer around the perforated pipe forming directly a pore air circulation in conjunction with the ambient air by the small holes of perforated pipe wall. Under the air permeable top surface and only ventilating during the negative temperature period, a crushed rock embankment embedded a perforated ventilation pipe may enhance the cooling capability of the embankment base due to winter-time air motions in the crushed rock layer forming a complete pore air circulation in conjunction with the ambient cold air via the small holes of perforated pipe wall and the air permeable top surface.

Flexible supporting system with prestressed anchors is a new technique developed from anchored retaining wall for retaining deep foundation pit or improving stability of existing slope. In order to further study the behaviors and working mechanism of the flexible supporting system with prestressed anchors, the anti-pulling force of anchor is analyzed and studied. The improved solution method of anti-pulling force of frictional grouting anchor is proposed. The study indicates that in the supporting system of flexible supporting structure with prestressed anchors, the anti-pulling force should be decomposed into two parts: the anchor-soil interaction and the soil self-supporting. In the supporting system, anchor, as a force transfer component, firstly transfers the anti-pulling force coming from the soil self-supporting; then provides other anti-pulling force by the anchor-soil interaction. The two anti-pulling forces are solved theoretically; and the theoretical calculation formulae are given respectively; then the total anti-pulling force of anchor is determined. Two case studies are introduced to prove the rationality of the solution of anti-pulling force of anchor. The values of limit anti-pulling force of anchor based on the improved solution method are larger than these of the traditional methods; and the concept of anti-pulling force solved according to the improved solution method is more clear, which further enriches the working mechanism of prestressed anchor supporting system from theoretical aspect and provides the scientific basis for engineering practices.

The failure damage of granite under cyclic load is caused by the propagation and coalescent of cracks at mesoscale, so it is helpful to understand the mechanical behaviours of rock by quantitatively investigating on meso-damage of granite. The uniaxial cyclic fatigue tests on granite coming from Changjiang of Hainan province are done on the RMT-150B multi-function automatic rigid rock servo material testing machine. Stress amplitude of 10 MPa and sine wave cyclic loads with five different frequencies of 0.01, 0.02, 0.05, 0.1, 0.2, 0.5, 1 Hz are adopted as dynamic disturbance. A great deal of mesostructural images of Changjiang granite in Hainan province have been obtained by means of scanning electron microscopy(SEM). The mesostructural images of marble are processed by regional growing theory based on image processing technique. The meso-damage information of granite microcracks is obtained from SEM images. Quantitative analysis of meso-damage characteristics under cyclic fatigue load is made from angle, length, width and area. It is shown that with the frequency of cyclic load increasing, the dispersion of microcrack growth azimuth value increases and the average of microcrack growth azimuth value fluctuates in the range. The development of microcrack length is fast; but only when the frequency is 1 Hz, the microcrack width begins to develop and the method of energy dissipation changes.

Pile groups are widely used in offshore wind power generation as its foundation. The bearing capacity and deformation of foundation, with strict requirements for the wind power generations, is of great significance to be investigated under horizontal loads that is the control factor of the fans tower. Centrifuge model tests for offshore pile foundation and typical clay ground are conducted to actively study the pile behavior and the deformation characteristics of the surrounding soil. The test results show that: under horizontal loads, the displacement of pile top increases with the increasing load, while the increasing rate speeds up after the critical horizontal load. The bending moment of pile has a maximum in the 1/5 of burying depth and a minimum in the 3/5 of it, while there is a certain value at the bottom of the pile. The deformation of the soil around the pile, which is divided into active region and passive region, decreases as the distance from the pile increases, while the influence area expands with the increasing horizontal load, and finally stabilizes at twice the pile diameter range.

Based on the self-made model experimental system of dynamic frozen soil-pile interaction, experiments about dynamic property of model pile foundation under lateral dynamic loads in -5℃, -3℃ and partially thawed permafrost were conducted. This paper mainly studies the displacement-force relationship of pile head, dynamic stiffness of pile foundation in horizontal direction and bending moment distribution of pile body in different permafrost mentioned above. The results show that the dynamic response character of pile foundation and frozen soil temperature is closely related. Pile foundation has a lager lateral stiffness in frozen soil, and the displacement-force curve of pile head presents a reverse S-shaped when the gap between soil and pile interface becomes larger. The dynamic property of pile will improve with the decrease of permafrost temperature; and it will decrease significantly when a thawed layer presences in the top of frozen soil; in this case, dynamic stiffness of pile head will reduced greatly; and the pile could generate a larger lateral displacement under relatively small dynamic load; at the same time, the greatest bending moment of pile is larger and the depth of this moment point is bigger than those of pile in completely frozen soil. Therefore, it should pay more attention to the seismic damages of pile engineering in permafrost zone when a thawed soil layer exists in summer.

Taking Wuhan Yangtze River tunnel as the project background, the shear creep tests on dry and saturated sandstones are conducted. Based on the test results, the effect of water on shear creep characteristics of sandstone and its mechanism are elaborated from both shear creep strain and mechanical properties. The results show that water can promote the development of creep strain and accelerate creep strain rate of sandstone and also decrease its creep rupture strength. Therefore, the effect of water on the creep characteristics of sandstone can not be ignored in the engineering design and construction of important project.

Through analyzing mineral composition of the rock salt and rock gypsum-salt in Chuandong gas field, the creeping test study is carried out with the TAW-1000 deep pore pressure servo test system. The impacts of mineral compassion, deviator stress, temperature and confining pressure on creep have been analyzed. Based on the creep curve and rock parameters obtained by the experiment，steady-state creep rate constitutive equation is proposed. The results show that the main mineral compassion of rock salt and rock gypsum-salt in Chuandong gas filed are sodium chloride and calcium sulfate; the highest percentage of sodium chloride can be as much as 93%, inherent mineral composition is the internal factors of rock creep. The higher sodium chloride content is, the larger transient creep and steady-state creep rate become; the higher deviator stress and temperature are, the larger steady-state creep rate will be, on which the effect of confining pressure is very small. The parameters of Heard creep constitutive equation are obtained by fitting test data; and then the steady-state creep rates of rock salt and rock gypsum-salt under different deviator stresses and temperatures can be acquired. Eventually, it can provide theoretical basis for safe drilling of rock salt and rock gypsum-salt for Chuandong gas field, mud density calculation and abnormal casing deformation.

In order to study the relationship between safety factor of slope and its slip plane during the slope stability calculation by strength reduction method, the theoretical deduction and numerical calculation of strength reduction method by FLAC3D are done. The safety factor and location of slip plane for slope are analyzed for a homogeneous slope with the variation of cohesion and friction angle . The analysis results show that (1) the safety factor of slope is influenced by anyone of cohesion and friction angle, but the location of slip plane is instead influenced by the combination function of c and φ, which has the formula of , where is the height of slope; (2) when equals to a constant, the locations of slip plane will not change by the variation of shear parameters and ; with the increase of , the failure mode of slope changes from shallow slippage to deep slippage, the slip plane becomes more and more smooth while the top of it moves farther away from the vertex of slope, and slipping volume becomes greater.

A series of experimental researches of swelling pressure and swelling strain of bentonite-sand mixture are conducted by using self-developed swelling apparatus. Based on the experimental data obtained, the relationships between swelling pressure and time, vertical and horizontal swelling pressures, swelling strain and time, and swelling strain and water-absorbing volume are analyzed. The results show that the maximum swelling pressure and the maximum swelling strain of bentonite-sand mixture depend on the initial dry density and bentonite content of mixture, and increase with the increasing of these two factors. The increase of the dry density results in the decrease of the ratio of horizontal and vertical swelling pressures, and a linear relationship can be obtained between them. For bentonite-sand mixture with different bentonite contents, a hyperbolic relationship is obtained between swelling strain and time, and an approximate S-curve relationship is obtained between swelling strain and water-absorbing volume. Furthermore, the maximum swelling strain and bentonite content of bentonite-sand mixture demonstrate an exponential relationship. The experimental results are of reference value for design of buffer and back-filling materials in high-level radioactive repositories.

Degradation of saturated clay during cyclic loading can be assumed to be caused mainly by two mechanisms, pore water pressure build-up and the damage and remolding of soil fabric. Based on these mechanisms, a damage-dependent bounding surface model for cyclic degradation of saturated clay is proposed using the generalized isotropic hardening rule. In the model, the degree of damage and remolding of soil during cyclic loading is quantified by introducing a damage variable and the size of the bounding surface decreases with damage accumulation to characterize progressive degradation and nonlinear behavior of the saturated clay. By taking the stress reversal point as the generalized isotropic hardening center of the bounding surface as well as the mapping origin, the forms of hardening modulus can be adopted flexibly so as to predict the accumulation of plasticity deformation and pore pressure and the hysteresis property of clay. The cyclic behaviors for undrained one-way cyclic triaxial tests are predicted by the model. Moreover, the effects of the number of cycles, cyclic stress level and consolidation history on the cyclic degradation behaviors are analyzed. The agreement of predicted results with experimental data indicates that the model can realistically simulate the cyclic degradation behaviors of saturated clay.

Based on the understanding of geological conditions, tunnel excavation response and the physico-mechanical properties from laboratory tests of rock, deformation gradation and safety factor of the soft rock tunnel are proposed. Considering that the root cause of tunnel instability after excavation is the excessive energy of the tunnel native rock; the energy, which is combined with the ratio of the total deformation and elastic deformation, is used to analyze the stability of the tunnel; and on the basis, the safety factor is obtained by increasing-decreasing energy of the original rock. Through the practical application and compared with traditional evaluation methods, the method metioned above is proved to be reasonable and practical. The geological conditions of surrounding rock, the cross section shape, size, excavation and other factors, which are rarely considered by traditional evaluation methods are taken into account, so as to supply important references for the underground engineering.

The natural sedimentary soft clay behaves the structural characteristic, the influence of which can not be reflected in the process of computing secondary consolidation of soft clay by conventional method. Secondary consolidation test on undisturbed and remolded soil samples from Zhangzhou and Qingdao are performed for researching the influence of soft soil structural characteristic on the secondary consolidation coefficient . It is shown that soft soils' increases with the increasing pressure P, and it gets to maximum while P gets close to yield pressure , and then it decreases and influenced little by P. Finally, it tends to be consistent with remolded soil clays' . The remoulded soft clays' which is influenced little by P is regarded as a constant. Determing according to may have some error. The normally consolidated soft clay may show false over-consolidation because of soil's structural characteristic, therefore, it is improper to illustrate structural soft clays' by using normally consolidated soft clay; it can be well illustrated according to the damage of soft clay structure under different pressures.

After Three Gorges Project completion, the reservoir water level will be raised to 175 m and lowered to 145 m every year. During the fluctuation of the reservoir water level, the quality of rock mass of the bank slopes will be deteriorated gradually in water-rock interaction of saturation-air dry cycles. Thereafter, taking sand rock at the fluctuation of reservoir water level as a representative, an experiment model the process of saturation-air dry cycles is designed. Test results show that comparing with the conventional immersion experiment, the rise or decline of water pressure and the cycle of saturation-air dry have cumulative and magnified effect on the damage of rock mass. Tests also show that the greater change of water pressure in immersion, the greater impact on the ion concentration and secondary porosity; at the same time, the more cycles of saturation-air dry, the more serious damage to the rock mass. Based on the change of ion concentration, the computational method of secondary porosity change law in the rock which is consistent with measured changes of secondary porosity is proposed. It can be applied to on-site monitoring, which can speculate the water chemical reaction in rock, and how the secondary porosity rate has developed through long-term monitoring of ion concentration. Research results lay the foundation for the study of rock mass quality of the bank slopes deteriorating in the saturation-air dry cycles.

A new pile type, X-shaped cast-in-place concrete pile (XCC pile) was developed for coast or river soft soils treatment. XCC piles have many technical and economic advantages, such as large surface area, high shaft friction, conveniently construction, and high economic effects. But there were relative little studies focused on the pile-soil load transfer characteristics of XCC pile composite foundation. Based on a sewage treatment plant soft ground improvement engineering, field tests for the pile-soil load transfer of XCC pile composite foundation were carried out. The load-settlement, pile-soil load sharing, pile-soil stress ratio, and the distributions of axial force of pile shaft were measured. Then the pile-soil interaction and neutral plane of XCC pile under different conditions were analyzed. In order to do comparative analysis, the static load tests for circular pile which has the same concrete amount with that of XCC pile were carried out. The results show that, the neutral plane of XCC pile in composite foundation is mainly occurred in 0.2 times of pile depth. The maximum value of positive skin friction is about 140 % of those of negative skin friction. The pile-soil stress ratio of XCC pile in composite foundation is increased with the decreasing of pile spacing under the same pile length.

Research on the whole process and nonlinear law for coupling evolution of new and old overlapped tunnel systems is still in exploring stage. Based on the coupling mechanism analysis of the overlapped tunnel systems in undercrossing and after construction, the whole change processes of stress state and displacement state are quantitatively analyzed in its coupling. According to the nonlinear analysis of tunnel stability, the nonlinear law for coupling evolution is studied from viscoelasto-plasticity, dynamics and energy dissipation. The coupling standard and evolution function are established. On this basis, the general characteristics of coupling evolution are systematically summarized. The expansibility in space and furtherance in time of the coupling mechanism are also pointed out. Such kind of study is able to provide valuable theoretical guidance for stability quantitative analysis and control of overlapped tunnels.

The value of joint stiffness based on in-situ deformation experimental results of columnar jointed rock mass in Baihetan dam region was discussed. The value of columnar joint stiffness is obtained by using experimental data of flexible central hole deformation test. The regulation and deformation properties of rock single concept model are analyzed. Rock deformation is made up of two parts, one of rock and one of rock joint, and its hysteretic properties are determined by joints’ mechanical behavior. Moreover, the formula of deformation deduced can calculate the equivalent elastic modulus of multi-set intersection joint rock and describe the anisotropic characteristics of jointed rock. A random model of columnar jointed rock mass is established. The rock mass is stimulated by using discrete element method and the stiffness of reverse calculation; and equivalent deformation parameters obtained are in the range of test results.

The filter paper method and the pressure plate method are used for measuring the suction of Gaomiaozi bentonite-sand mixtures. The soil-water characteristic curves (SWCC) obtained during drying from the tests at different void ratios and different mixing ratios of Gaomiaozi bentonite to Fujian sand are compared. The effects of void ratio and the mixing ratio on SWCC are analyzed according to the test results. The results show that when the SWCC is expressed by the relation between suction and saturation degree, the SWCC moves up and right with the decreasing void ratio for a mixture with the same mixing ratio. That’s to say, the saturation degree increases with the decreasing void ratio at a constant suction. Especially when the suction is less than 10 MPa, this phenomenon is evident; at constant void ratios, the SWCC moves up and right while increasing the mixing ratio. In other words, the value of air-entry suction increases with the increasing mixing ratio. In addition, when the mixing ratio and void ratio are the same, the SWCCs of Gaomiaozi bentonite-sand mixture and Kunigel bentonite-sand mixture are quite similar.

According to the site investigation of Wenchuan disaster area’s statistics data as the background, the experiment model is made selecting Yugongmiao slope as the reference. The similarities of main parameters are analyzed based on dimensional analysis. The underwater blasting is used to simulate seismic wave (near-field), and a large number of model tests are conducted. The results show that the failure model of bedrock and overburden layer slope under seismic loading is surface loose media flowing caused by the tension of superficial layer, and with the increase of explosives (seismic intensity), seismic accelerations increase. It is very useful to design of gravity retaining wall and pile-wall structures. These conclusions can provide some bases for analysis and research of high-steep slopes along railways and highways.

Contraposing the deficiencies in studying the punching failure mode for pile foundation in karst region, combining the load-carrying capability characteristics of the concrete slab, the punching failure mechanism of cave roof at pile tip is established by using limit analysis principle which accords with practical engineering in karst area. Introducing Griffith nonlinear rock strength criterion, based on work-energy principle, the ultimate load of rock strata at pile tip anti-punching failure is derived. Then, the generatrix equation of the punching failure body is obtained by the variational principle. Furthermore, the calculation formula of safe thickness for the rock strata anti-punching failure is obtained by differential equation. Parameter analysis shows that the punching failure mode mainly depends on the ratio n of compressive and tensile strength, the smaller the value of n is, the smaller the bottom diameter of the punching failure body, and on the contrary, the bigger it would be. Under normal circumstances, the value of d1 /d is in 2.0 to 4.0. The ratio n is also a main influencing factor determining the safe thickness of anti-punching failure. As increasing of the value of n, the safe thickness of security can be increased appropriately. For limestone region, the safe thickness generally taking 2 to 3 times the diameter is reasonable. Comparative analysis result of an engineering example shows that the calculated values by the presented method agree well with the measured data.

The geological conditions of the high and steep abutment slope at left bank of Jinping-I Hydropower Project are very complicated, mainly developed with the faults of f5, f8, f42-9, the lamprophyre veins of X, the release fractures oriented parallel to slope surface and deep fractures. The combination of the fault of f42-9, the lamprophyre veins of X and the deep fracture of SL44-1 form a tensile dehiscent deformable body at the abutment slope of the left bank; the stability of the abutment slope is very bad during construction, especially when the slope is excavated to the elevation of 1 780 m, all rock masses that prevent the tensile dehiscent deformable body from sliding are excavated; the outcrop of the fault of f42-9 at the surface of the excavated slope makes the stability of the tensile dehiscent deformable body abruptly become worse. The strength reduction FEM considering excavation process is applied to calculate the stability safety factor of the abutment slope; and a new slope instability criterion is proposed as follows: in finding the mutant site on the relationship curves between of key points and the strength reduction factors, the critical state of instability of the slope could be determined; in this criteria, , which stands the change rate of horizontal displacement with the strength reduction factors, is the ratio of the horizontal displacement’s increment and the strength reduction factor’s increment. Comparing with other slope instability criteria, a new criterion is proved to be a reasonable and practical slope instability criterion; based on this criterion, the stability safety factors are calculated when the slope is excavated and reinforced to different elevations; the overall stability and security of the abutment slope at the left bank are reasonably evaluated during its construction.

The nature of composite foundation is the load from the overlying shared by the reinforcement and ground soil via the deformation compatibility. Cushion plays a coordinating role of pile-soil deformation; however, its characteristics of the work and deformation characteristics are not yet clear. Designing cushion thickness still depends on experience or reference standard. It can not fully play the bearing capacity of foundation soil. The pile-soil deformation is usually adjusted by cushion in current composite foundation design. The pile-end piercing settlement coordinates pile-soil deformation and plays the role of foundation soil bearing capacity is ignored. Using pile-end piercing settlement to adjusted pile-soil deformation and bring foundation soil bearing capacity into full play, the cushion thickness is reduced or not to set cushion, and the designed pile length is shortened in order to reduce the cost of ground handling and achieve the purpose of load shared by pile and soil finally. A design method for pile-soil self-balanced composite foundation is established through controlling pile-soil deformations adjusted by pile piercing settlement. Through contrasting with the cushion method and project examples, it is proved that the method can show the foundation soil bearing capacity better, and provide references for the optimal design of composite foundation.

Brittle rock mass generally reserves high strain energy under high ground stress condition. As it is excavated, rock burst will take place as a rapid release of the reserved strain energy. The rock burst is a hackneyed type of power unstable geologic hazard, which immensely threatens the builder and equipment safety. As a major construction of the Jinping II hydropower station on the Yalong River, deep water transfer tunnels face the problems of rock burst in hard rock under high geostress. According to the characteristic of the rock burst in Jinping II hydropower station, the method of preventing the rock burst by rapid releasing stress is put forward; and the scheme of inclined radiation blasting hole is selected through numerical simulation. The numerical simulation results show that the method can make the initial stress of rock mass rapid unloaded and the stress concentration area transferred to the deep place of rock mass. Through the testing and application in water transfer tunnels of Jinping II hydropower station, sonic wave testing has been applied to verify the effect of rapid stress releasing scheme; it turns out that the method of preventing the rock burst by rapid stress releasing is validated. The research results provide theoretical foundation and ways for preventing the rock burst in similar projects.

Based on Fisher discriminant theory, the Fisher discriminant analysis (FDA) model was established for forecasting the possibility of sand liquefaction. Eight factors were selected such as seismic intensity, epicenteral distance, groundwater level, sand depth, blow number of standard penetration test, mean granular diameter, coefficient of nonuniformity, ratio of shearing stress to effective overburden stress as the discriminant factors of the FDA model. A series of experimental data of sand liquefaction were taken as the training and testing samples, then some other practical data were used to verify this model. The results show that the FDA model is a simple, feasible and high accurate prediction method; and it is one of the efficient methods for solving prediction of sand liquefaction.

At present, there is no unified surface settlement rule and controlled criterion for the settlement induced by railway tunnel undercrossing highway, which is researched only based on an actual project. From the aspects of longitudinal-transverse slope, smoothness, and requirements for stability of highway, the requirements for smoothness are adopted to control road surface uneven settlement during construction. According to embankment height, tunnel size, depth, geology, construction method, construction process of single and dual-lane railway tunnels undercrossing highway is simulated by FLAC software. The rule of road surface settlement is studied. In addition, the width coefficient of settling tank and prediction model for the largest settlement are obtained. Based on them, pavement surface settlement controlled criterion is established for railway tunnel undercrossing highway. At the same time, the rationality of controlled criterion is verified through several case studies. The results can provide reference for establishment of pavement surface settlement controlled criterion for railway tunnel undercrossing surface buildings.

At the present, nobody proposes a comprehensive evaluation standard of applicabilities for gas storage in rock salt (ESAGSRS). ESAGSRS is came up based on studying a large number of underground gas storage accident cases. The standard is divided into two aspects, stability and sealability. Factors affecting the stability are natures of top and bottom, natures of salt beds and interlayers, natures of interface between salt beds and interlayers, the maximum and minimum pressures and gas recovery velocities, cavity shape and safe pillar width five aspects. Factors affecting the sealability including airtight cementing technology, natures of casing, natures of valve for casing, cavern pressure, natures of roof, natures of interlayer, penetration of rock salt conditions, stiffness ratio of salt rock and interlayer, geological conditions. Based on ESAGSRS, the total score of the applicability of gas storage can be gotten, and it can appraise the applicability of salt rock. The standard (ESAGSRS) considers miscellaneous factors, and it has a valuable reference and academic supports to practical projects.

The water level drawdown of reservoir or river often causes the decrease of stability of bank slopes. Establishing a rapid assessment approach for evaluating the stability of slope under the variation of water levels has an important practical significance. Based on the water level drawdown of reservoir or river, and the transient unsteady seepage in clay slope, the program based on shear strength reduction finite element method (SSR-FEM) is developed to compute the factor of safety (FOS) for the slopes under the action of surface water and ground water together. Considering the influences of soil properties, relative permeability ratio and boundary conditions on slopes stability, the relative stability graphic method is presented under the integration parameters of soil properties, relative permeability ratio, drawdown ratio, slope angle, etc. The suggested method can rapidly obtain the FOS of existing slope and the design inclination ratio of planning embankment, and it can also be a helpful supplement for the existing stability charts of simple slope.

The stability analysis of counter-tilt rock slopes is a difficulty in rock slope analysis, and there are many questions need to be solved. Limit equilibrium method is the most common and relatively effective method at present. Based on the cantilever beam limit equilibrium model by D. P. Adhikary and A. V. Dyshin, the form of fracture plane and the influences of cohesion and severe of different layers are mainly modified, and an improved cantilever beam limit equilibrium model is given. Based on the new model, a new method to analyze the stability of counter-tilt rock slopes is proposed by using residual unbalance force as standard, and a comprehensive research on the influences factors of counter-tilt rock slopes is made. By doing these work, some conclusions and laws which are useful for design and construction of these type of slopes are drawn.

Salt rock is good for reservoir forming as cap rock. Many reservoirs in Tarim basin are buried deeply underground in salt rock, drilling directional well to exploit reservoirs in salt rock will enhance recovery of single well. As the distance between salt layers and production layer is close, so the build-up process will be in salt layers; but the laws of wellbore shrinkage in build-up section in salt layers and effects on casing external load are little reported. So, a 3-D salt rock-cement mantle-casing coupling mechanical model is established. On the basis of rock mechanics test of Yangtake in Tarim, the effect laws of deviation angle and azimuth angle on wellbore shrinkage and casing external load are researched. Research results have been used to guide trajectory design, mud density design and casing program design for direction wells in Tarim, and lay a solid theoretical basis for well drilling and completion in salt rock in Tarim oil field.

In the presence of the strong material nonlinearity caused by post-peak strain softening of dense sandy soils, the solution of traditional finite element method (FEM) with implicit algorithm often becomes intractable. The dynamic relaxation (DR) method has a great reputation in solving highly nonlinear equations. A new dynamic relaxation-finite element method (DR-FEM) for strong nonlinearity caused by post-peak strain softening of sands is proposed, which takes into account the advantages of DR and FEM together. According to the explicit nature of DR and the central difference technique, the general governing equations of DR-FEM has been derived. The way of tracing the whole equilibrium curve in the stress-strain space has also been presented; and then the DR method is implemented into a general nonlinear finite element codes. The return mapping algorithm is used for stress updating, which is a first-order approximated Euler backward integration. Therefore, the strong material nonlinearity caused by post-peak strain softening of sandy soils can be simulated by the proposed DR-FEM combined with the corresponding material model. The DR-FEM is validated by simulating the result of physical plane strain compression test performed on sands. It is shown that the DR method has a superiority to solve the material nonlinearity.

Taking typical engineering problems of dam construction on dissolution foundation for example, the dissolution belt random field model is established based on researching characteristics of the spatial distribution of dissolution rocks. Then, the adaptability is evaluated to build dams on the foundation and the statistical properties of the dam are studied through stochastic finite element method (SFEM). The model simulates the disorderly distribution of rock dissolution, eliminates artificial assumption of the line corrosion rate, and avoids the shortage of rock dissolutions in the deterministic model. The method and conclusion also provide a useful reference to the numerical analysis under the complex geological conditions.

Adopting similar material simulation test and numerical simulation methods, the impact damage process of coal roadway under anchor bolt, U-steel and energy absorbing support are studied. The impact failure mechanism of roadway under interaction between coal and support is received. Similar material simulation and numerical results show that the impact damage laws under different support types are consistent with each other. Under impact loads, the roof sinks significant, the floor drum obvious, and the both sides have a large internal deformation; cracks expansion and through, even the coal thrown out. According to similar material simulation test and calculation results, it is shown that for different support types, different levels of impact damage, energy absorbing support has good cushioning and energy absorption characteristics, and advantages of small deformation and good stability. The test results also indicate that the energy absorbing support is better for rockburst roadway.

In order to study the damage distribution of tunnel’s surrounding rock, firstly, an elastoplastic damage constitutive model of Q2 loess is deduced based on triaxial shear tests and compiled as a user-defined damage model( UDM ) of FLAC3D. Then the conception of surrounding rock damage degree (SRDD) is put forward and compiled into a post-processing module. Based on the first loess multi-arch tunnel of road–Lishi tunnel, the damage position of tunnel’s surrounding rock of two construction schemes is numerically simulated. The research results show that the SRDD and damage localization rules can be simulated well at every excavation step; and it also provides reference for the optimization of tunnel construction scheme. The research results provide a new method for the optimization of tunnel construction scheme and choice of construction scheme.

When using FLAC3D which based on finite difference method (FDM) to calculate the seepage，the seepage surface is higher than the real situation’s and the permeability of unsaturated zone is a constant which is defined by mistakes. An adjusting element permeability method is used to develop the program secondly, and the modified adjusting element permeability method is proposed to correct the permeability of unsaturated zone strictly. After calculation, the exact continuous smooth seepage surface and saturated-unsaturated seepage are obtained. The FEM is used to analyze the seepage contrastively, and the feasibility and effectiveness of the method are validated. The method of attaching interface to downstream side is proposed to solve the problem in which the seepage points are hard to obtain on complicated three-dimensional boundary; then a three-dimensional complicated example is given to calculate the seepage field distribution of a slope; the result is accurate after verifications. The research results are helpful to guide the analysis of saturated-unsaturated seepage and the calculation related to seepage in the program.

Based on the previous work of eight large scale physical model experiments of landfill conducted on shaking table, nonlinear numerical simulation for the test is performed subsequently; and the experimental and numerical results are verified and supplemented one another in order to further examine the characteristics of the seismic response of landfill. The follow results can be got: (1) Due to the special sandwich constructions, landfill has two main response frequencies; the peak acceleration responses at top of landfill are obtained in the vicinity of the two main frequencies under horizontal earthquake. (2) When other parameters are fixed, seism-induced permanent displacement of landfill liner is shown to be approximately proportional to the amplitude of input motion. (3) The inclination angle of landfill cover and base slope have significant effect on the critical sliding acceleration of cover and base liner system respectively.

Through analyzing the measured values of in-situ stress field of Cangling tunnel area, reliable and representative of the actual measured points are selected as the object of the inversion regression. Using 3D numerical analysis combining with principle of regression analysis, the entire project area in-situ stress field distribution is obtained. Through comparative analysis between the regression and local measured values, it is found that apart from individual point appears difference, most of the measured points fit well and the distribution laws are roughly the same. The results indicate that stress-regression method is reasonable. On this basis, by using the stress-regression equation, the Cangling tunnel’s in-situ stress field distribution rule along the axial direction is obtained, and according to the angles of different sections of maximum principal stress and the tunnel axes directions, the tunnel stability is analyzed. Accordingly, further optimization of the route position of Cangling tunnel is proposed, so as to provide important basic data for tunnel design and construction.

By using the further developing platform UDM, a simplified bounding surface model based on modified Cam-clay model is developed in the FLAC3D program in the VC++ debug environment. The bounding surface model’s basic principles are introduced, and the key technologies and the concrete methods of implementation are explained. Numerical simulations of loading and unloading triaxial tests, undrained triaxial shear tests are performed to study the difference between bounding surface model and modified Cam-clay model. The computed results show that the newly developed bounding surface model is reasonable and reliable, and has great advantages compared with modified Cam-clay model.