This paper reviews the characteristics of soil liquefaction-induced damage observed from the Northridge, USA earthquake, 1994, the Hanshin, Japan earthquake, 1995, the Kocaeli, Turkey earthquake, 1999, the Chi-Chi, Taiwan earthquake, 1999, in China, the Wenchuan, China earthquake, 2008, the Maule, Chile Earthquake, 2010, the Darfield and Christchurch, New Zealand earthquake, 2010 to 2011, and the great East Japan earthquake, 2011. There are several characteristics in the occurrence of liquefaction and consequence damage which are different from a number of cases experienced in these earthquakes. These are summed up as follows: (1) The unprecedented long duration of the shaking and extensive makes the occurrence of liquefaction in the newly reclaimed land, fill area is 300~400 km distant from the epicentral area attributed to the rarely encountered huge moment magnitude Mw9.0 earthquake. (2) A number of site liquefactions and lateral spreadings are observed in seismic intensity scales of Ⅴ and Ⅵ, an area of low intensity is attributed to the encountered magnitude scale Ms8.0 and Mw8.8 earthquakes. (3) Severe liquefactions in sites are observed having young alluvial, lacustrine deposits along rivers and sea bay areas, and in reclaimed land, fill area contains fine-grained soils, gravel sands in less than fifty years. (4) Severe liquefaction in natural gravel sand deposits occurs. (5) Soil liquefies in depth of 20 m. (6) Liquefaction and re-liquefaction of the sites over a large region do not result in densification of the loose deposit, future earthquakes of sufficient magnitude can again induce liquefaction. (7) Severe liquefaction occurs in low to moderate plasticity soils containing more than 50% fines content (grain size is, smaller than 0.075 mm) or more than 25% of clay content (grain size is, smaller than 0.005mm), however, field evidence of liquefaction may not be observed in transition behavior fine-grained soils between sand-like and clay-like behaviors. (8) Ground cracking without venting of sand boils is more likely as the depth and thickness of the liquefied layer increases and decreases, respectively; vented material, provided field evidence of liquefaction, may be absent due to the large depth to, and small thickness of, the liquefied layers. There are a number of spectacular case histories of liquefaction of sediments deposited in late Pleistocene time Q3. The clay content is not a reliable index for evaluating between clay-like and sand-like behaviors in a fine-grained soil. Fine-grained soils with the low plasticity index PI and high water content wc are susceptible to liquefaction; the use of the PI and water content to liquid limit ratio wc/LL is a good criterion of liquefaction possibility; for soils. Based on work in progress of the case histories of liquefaction and the results of laboratory tests for fine-grained soils from Boulanger, Idriss, Bray and Sancio, Seed and Cetin et al, a new liquefaction possibility criterion for soils is proposed as follows: soils with PI<12 and wc/LL>0.85 are susceptible to liquefaction; soils with 1220 or wc/LL<0.80 is not susceptible to liquefaction.

The buffer material as one of the most important components of engineered barrier system is the last defence between waste container and host rock. This barrier plays an important role in stabilizing the repository excavations under the coupled thermal-hydro-mechanico-chemical (THMC) conditions, and in providing low permeability and diffusivities, and long-term retardation. To guarantee the long-term safety of the engineered barrier, a large-scale mock-up facility, named China-Mock-up is constructed in the laboratory of BRIUG. This facility concentrates on the research on Gaomiaozi-Na-bentonite, which is currently considered as the candidate buffer and backfill material for China's high level waste (HLW) repository. Methods of construction and test for buffer material Mock-Up is established. The current experimental data of the facility are reported and analyzed in the paper. The saturation process of the compacted bentonite is influenced by the competing mechanisms of drying effect induced by the heater and the wetting effect by the water penetration. The stress evolution of the compacted bentonite may be influenced by the thermal expansion induced by high temperature and the swelling pressure generated by bentonite saturation. The evolution of displacement of the heater which is to simulate vertical placement of a container with radioactive waste is validated for the first time. The experiment is evaluated THMC processes taking place in the compacted bentonite-buffer during the early phase of HLW disposal and to provide a reliable database for numerical modeling and further investigations of EBS, and the design of HLW repository.

The properties of deformation, strength and structural evolution of cylindrical hole damaged expansive soil are investigated by eight CT-triaxial tests. The results show that the strength of the samples with the cylindrical holes is significantly weakened because of the hole damage. Howerver, the hole size has little influence on the strength of the sample. The hole section area decreases when net confining pressure increases under a certain suction. The reduction of the hole section area is more obvious when the suction is larger under the same net confining pressure. Moreover, the net confining pressure plays an important role on the structural evolution of the cylindrical holes in the remolded expansive soils. The increment of the mean value (ME value) is enhanced gradually when the net confining pressure is changed from 50 kPa to 200 kPa. It means the sample becomes denser when the confining pressure is larger. Accordingly, the decrement of the standard deviation (SD value) increases gradually. The structure of the sample becomes homogenized during the test.

Excess pore water pressure will be generated in the core during the construction of high rockfill dam, and it dissipates slowly. After water storage, the core will change the unsteady seepage state to the steady flow state; so the seepage characteristics are very complicated. The pore water pressure generated during construction can not be considered in the finite element method for seepage calculation; and the seepage characteristics of earth-rock dam can not be fully understood. Changhe Dam is a gravelly soil core rockfill dam, with maximum height of 240 m. Centrifuge modeling tests are carried out to study the seepage characteristics of Changhe Dam through analyzing the generation and dissipation of pore water pressure in construction and operation periods. Test results show that the pore water pressure would go through periods of generation in the construction, the dissipation after construction, the generation and dissipation in the unsteady seepage state, the stabilization in the steady seepage state. The pore water pressure and duration of each period are influenced by the position and filling water content of the core. The higher the position or filling water content of the core is, the larger the coefficient of pore water pressure during construction is, the shorter the duration of steady seepage is. The higher the position or smaller filling water content is, the larger the potential is. The potential in unsteady seepage state is larger than that in steady seepage state. It is instructive for design and construction of high core rockfill dam.

Natural soil may be cracked due to wetting–drying cycles, shearing or other effects. Most cracks tend to be connected and form a network. A crack network on a natural soil surface is a random and disordered system. It is hard to describe the distribution characteristics of cracks by the traditional statistical method. Generally, the crack network has fractal dimension. The theory of fractal dimension can be used to describe the distribution characteristics of cracks. Crack images are taken by a digital camera on a soil surface and converted to gray images. A method for determining fractal dimension by photograph is established based on the fractal theory. Then, the fractal dimension of soil cracks can be obtained. According to the physical meaning of representative elementary volume (REV), a method for estimating the cracked soil’s REV based on the fractal dimension is presented; and some examples are analyzed. The results show that the fractal dimensions are increased with the increasing of crack density, crack aperture and the development of secondary crack. The REV is related to the homogeneity of crack density and crack aperture. It is easy and credible to estimate the cracked soil’s REV by the method mentioned above.

The theory of cylindrical cavity expansion has been widely used in many geotechnical engineering, such as analysis of pressure meter testing and effect of pile driving. Extended spatial mobilization plane (SMP) theory, which can display the effects of intermediate principal stress, in combination of finite strain theory, is used to analyze cylindrical cavity expansion problem in homogeneous soil. An analytical procedure to determine average volumetric strain of plastic zone is developed according to stress path hypothesis. Accordingly, “nondimensional” plastic zone radius and factors of cylindrical cavity expansion are estimated for varied rigidity index , Poisson ratio v and frictional angle . It is concluded that average volumetric strain decreases and “nondimensional” plastic zone radius and factors of cylindrical cavity expansion increase with the increase of 、 、 . Variation of has significant effects on factors of cylindrical cavity expansion in the case of greater . Furthermore, a comparative study of the solutions based on extended SMP and those based on Mohr-Coulomb is made to examine the effects of intermediate principal stress on cylindrical cavity expansion for various soils. The values of factors of cylindrical cavity expansion considering the effects of intermediate principal stress presented in this paper are of great significance for analyzing in-situ tests and estimating ultimate lateral friction of piles.

Beishan in Gansu province has been selected as the most potential area for the deep geological disposal of the high level radioactive waste. Considering the groundwater in the region containing the total dissolved solid (TDS), NaCl – Na2SO4 was chosen as a dissolved solid. In this paper, one-dimensional swelling deformation tests and swelling pressure tests were carried out on Gaomiaozi sodium bentonite saturated by the salt solution with different TDS concentrations and distilled water. Based on the concept of the montmorillonite void ratio, the deformation characteristics of Gaomiaozi Na-bentonite at saturation were consistently identified in the salt solution and distilled water circumstances, respectively. The results show that both the relationships of the montmorillonite void ratio versus the swelling pressure and the dry density versus the swelling pressure are the straight lines and parallel to the condition of distilled water circumstance in the double logarithmic coordinates when the concentration of TDS is 12.3 g/l, and the swelling pressure in the logarithm changes linearly with the concentration of TDS. As a result, a method to predict the swelling pressure and deformation is given from the dry density of the buffer materials and the ion concentration of salt solution.

Loess structure is more important mechanical properties of loess besides its particle size, density and humidity. Based on the theory of comprehensive structure potential, we made a synthesis of the existing structural parameters and their evolution, and structural parameter can be of two types: initial structural parameter and the process of structural parameter. Structural parameter tends to satisfy both the basic physical property of soil and its evolution under the condition of stress and moisture. Based on existing problem of structural parameters and their evolution, structure index is used to describe initial structure, and stress ratio structure parameter is used to describe the process of structure. The relationship between stress ratio structural parameter and comprehensive strain is studied. Finally, a mathematical model that can reflect the attenuation evolution of soil structure under the condition of initial stress and moisture is established. Theoretical analysis and triaxial test show that the model can avoid the influence of confining pressure under the condition of triaxial tests on initial structure, and it can consider the influence of body strain and shear strain under the process of stress and moisture. The model can more accurately reflect the damage evolution of loess.

By using equivalent rock mass (ERM) technique, the rock block and joint are represented by bonded particle model and smooth joint model, respectively. Then, the rock specimen containing two artificial intermittent joints is constructed, and its mechanical characteristics and fracture mechanism are investigated from mesoscopic viewpoint. Meanwhile, combining with lab test result, the suitability and reliability of ERM technique used in the mechanical characteristics research of jointed rock mass are validated by comparative analysis between calculative and experimental data. The main research results are as follows: (1) With the occurrence change of intermittent joint, the macro fractures of specimen can be divided into shear mode, wing tensile mode and mixed mode. However, the tensile micro crack between particles is the main inducement that causes various macro fracture mode. (2) Before the peak compressive strength of specimen, the acoustic emission (AE) events of fracture mainly generate near the tip of intermittent joint and accumulate along the link line between the tips of the two intermittent joints in rock bridge area. In this stage, the number of AE events is less and the fracture magnitude is lower. (3) After the peak compressive strength of specimen, the number of AE events increases rapidly and the fracture magnitude enhances. (4) In different specimens, all the relationships between cumulative number of AE events and fracture magnitude approximately meet Doseresp growth function.

A widely accepted two parameters theory of unsaturated soil mechanics by Fredlund, using net stress and suction as stress-state variables, cannot consider the effect of suction history and saturation on stress-strain behaviour and strength of unsaturated soils. In this paper，the triaxial compression test results show that even if the same path of net stress and suction, stress-strain behaviour and strength are not the same between the samples experienced different suction history. While other conditions are the same, the samples experienced drying-wetting cycle have higher relationship of stress ratio-strain, higher strength, smaller volumetric deformation than the sample not experienced drying-wetting cycle. The samples experienced drying-wetting cycle have low saturation but high relationship of stress ratio-strain and strength. It is because larger suction experienced previously is equivalent to larger effective pressure experienced, that makes the sample to become overconsolidated state. Study of effect of different suction histories on unsaturated soil behaviour is needed further for providing the basis of experimental data. With the data, the elastoplastic constitutive model coupling hydraulic and mechanical behaviour could express behaviour of unsaturated soils more accurately and quantitatively.

The deformation and failure process of natural soil under loading can be obtained by research on structured clay ,on which the design of construction and soil improvement can be based when the structural influence is considered. With the construction of high, deep and great buildings, the research on the structured soil has recently become more and more important. Natural soils are structured and anisotropic. A new method is developed here to prepare artificially structured soils with initial stress-induced anisotropy. Silty clays are mixed with cements, salt grains and kaolin soils to form structured soil samples with initial stress-induced anisotropy. The bonding between soil particles can be formed by the hydration of cement, the big pore distribution can be produced by the dissolution of salt grains, and the initial stress-induced anisotropy can be developed by applying external forces on the ends of the samples with confining pressure states during the process of hydration. Triaxial shear tests under drained conditions are performed on initial uniform structured soil samples, initial stress-induced anisotropic structured soil samples and reconstituted soil samples. The influence of initial stress on the stress-strain properties of structured soils are analyzed and the breakage mechanism of structured soils with initial stress-induced anisotropy is also investigated.

Xenon long-arc lamp is used to simulate solar radiation. Deferent radiation intensities are acquired by adjusting lampshade height. Sunshine state is acquired by controlling the illumination time. Single factor controlling condition is achieved by constant temperature and humidity environment. Then, moisture-heat coupling behavior and rainfall-evaporation effect of undisturbed expansive soil sample in solar radiation are studied. When solar radiation and rainfall occur, the moisture migration and temperature variation present different states. With the to-and-fro moisture migration, the shallow soil tends to the fractured and loosened. In the solar radiation, the amplitude of moisture content variation increases, which aggravates the fissure development. To expansive soil, the characteristics of swelling and fissure are inner being, and atmospheric action is incentive. The behavior of expansive soil is changed gradually in the exchange progress of moisture and energy between atmospheric and soil. The simulating device on solar radiation is used to study the moisture-heat coupling behavior and rainfall-evaporation effect of undisturbed expansive soil. And the experience in research could be applied to the study of other soil types. In view of the engineering properties of expansive soil, the quantitative analysis of moisture migration mechanism of expansive soil could be further developed in the influence of solar radiation.

The freeze-thaw cycle tests are carried out under different compacted degrees and initial moisture contents to explore the mechanism and the influence of the long-term strength of improved silt under freeze-thaw cycle effect. And then, unconfined compressive strength tests after different freeze-thaw cycles are conducted. The influence law of the long-term strength of improved silt subjected to freeze-thaw cycle effect is discussed. It is found that the unconfined compressive strength decreases with the number of freeze-thaw cycles increasing. Finally, it reaches a stable stage after 6 freeze-thaw cycles. The higher initial moisture is, the more attenuation amplitude of the compressive strength is after the same number of the freeze-thaw cycles. In order to find out the influence law of the microscopic structure under the effect of freeze-thaw cycles, the microscopic tests of improved silt are carried out. And then the damage mechanism of the microscopic structure under the effect of freeze-thaw cycles is found out. It shows that different numbers of freeze-thaw cycles and initial moisture contents have less effect on the small pores ( 10 nm). Freeze-thaw cycles have main influence on the large pores (0.01～100 μm) between the soil aggregates, so it makes the strength of improved silt decreased.

Considering the annular drainage section of concrete-cored sand-gravel pile composite foundation, both radial and vertical flows within the sand-gravel pile and soil construction disturbance, using the initial condition of load beared by soil and pile, the governing equations of consolidation problem of composite foundation with concrete-cored sand-gravel piles are derived; the analytical solution to the governing equations is obtained; the overall average degree of consolidation defined in terms of stress and deformation is given; and the influences of several factors, such as the permeability coefficient of sand-gravel piles, diameter ratio of concrete-cored pile and sand-gravel pile on the consolidation of composite foundation are analyzed. The results show that the solution of overall average degree of consolidation in terms of stress is not equal to that in terms of deformation; the greater the permeability coefficient of sand-gravel piles is, the faster the consolidation rate is; under the condition of a certain diameter size of sand-gravel piles, with diameter of concrete-cored pile increasing, the consolidation rate is increased at first and then decreased. Finally, a comparison between the present solution and two previous solutions is made. Compared with two previous solutions，the present solution considers the influences of annular drainage section and load beared by soil and pile together, the overall average degree of consolidation calculated by the present solution is between two previous solutions.

Due to the low rate of consolidation of clay, the time effect of negative skin friction on pile is obvious. However, the correlative research work is not deep enough and needs to be continued. The model tests of negative skin friction on pile and double pile are designed and conducted, which can apply pile load and large surcharge load on soil surface. And the soil in the test adoptes sand and clay interlayer. During the consolidation of clay, pile stress, pile settlement and settlement at each soil layer are measured. The results indicate that settlement and negative skin friction have significant time effect. The pile settlement increases with soil settlement under the surcharge load, which increases rapidly in early stage and slowly in later stage. The negative skin friction in clay is smaller than that in sand on the initial stage of loading, and the change rule is similar to the settlement. Since the settlement stability time of sand layer surrounding pile base is short, the neutral point rises slightly with the increase of pile settlement. Furthermore, the settlement of the double pile with small pile spacing is small under the action of the same load because the dragload is relatively small. The group effect coefficient of the double pile under negative skin friction is from 0.71 to 0.77 at 3D pile spacing and there is no group pile effect when the pile spacing reaches 6D under the present model test conditions.

In order to research the surrounding rock deformation and failure mechanism of deep thick top coal roadway, taking Zhaolou coal mine in Juye mining area as engineering background, a large scale model test is carried out, the stress and displacement evolution laws of surrounding rock supported by pressure relief anchor cable box beam supporting programs are researched. And the results show: the vertical stress release is more intense in roof and floor of the roadway than that in the side wall, while the horizontal stress is the opposite; central of roadway roof is the main position of vertical stress release. By being compared with field test results, three main deformation and failure characters of the surrounding rock of deep thick top coal roadway are summarized: the deformation and failure of roof is more serious than that of side wall and floor; deformation and failure of roadway roof occurrs mainly in the coal below coal-rock interface; central of roadway roof is the key position of the deformation and failure. The corresponding mechanism is analyzed: the factors such as soft and broken features of roof coal, its poor self-supporting ability, vertical stress releasing more severe in roof and its central, poor force state of rectangle roadway, cause low radial stress of surrounding rock in roof, serve bulking deformation, bending deformation and roof separation, and worsen the roof force structure, finally, they lead to controlling trouble of roadway roof.

Connecting the plastic component and the viscous component in parallel, then connecting these two components and the elastic component in series, yields the three component model, where each component has a unique nonlinear constitutive relation. Based on the three-component model, a elasto-plasto-viscosity model is proposed by considering the effects of wetting on the viscous component and the plastic component. The effects of wetting on the plastic component are described by a decrease in the inviscid yield stress at a fixed irreversible strain, while the effects on the viscous component are described by the increase of the rate-sensitivity coefficient. Both the effects on the two components can be fully determined based on test results. Subsequently, based on this collapse-rheology model, a numerical analysis is performed on the collapse-rheology behavior of Kaolin clay in a 1D consolidation test. In the test, the creep is observed in a dried condition, while the collapse is observed during the stepwise wetting. The water content and strain in the test are precisely measured. The validity of the analysis method is shown by the well simulated water content-strain-time relation and the definite difference between the collapse during wetting and the creep under dried condition.

Sandy soil reinforced with denti-inclusions is a new concept of reinforced soil. In the grid with denti-inclusions, besides the conventional latticed inclusions, vertical reinforced elements are also placed in the soil. The behavior of interface between soil and geosynthetics is a significant factor for analysis and design of reinforced earth structures which is simplified as pullout performance. This paper presents the results of pullout tests and numerical simulation aimed at studying the interaction mechanism of reinforced sand. The pullout test is carried out to study the macroscopic mechanism. PFC is adopted to simulate pullout tests and the interface between geosynthetics and sand with emphasis on the meso-analysis. On such a basis, the model of PFC is established by using parallel-bond model to simulate the reinforcement. The sand particle movement trajectory and the particle contact orientations are studied. The results show that the shear bond is influenced by the denti-inclusions and the stress concentration occurs nearby the denti-inclusions. The intrinsic factors which form and change the mechanism of the interface properties are the “cohesion” provided by friction, occlusive force and passive resistances. The study results can provide a new understanding for future studies on the mechanism of the reinforced interface.

To study absolute rock stress measurement under different fracture media, by using large chamber true triaxial hydraulic-pressure fracture simulating system, a hydraulic fracturing experiment in lab is carried out with 400 mm×400 mm× 400 mm granite specimen on effect of the water and the relative densities of 1.1 g/cm3, 1.2 g/cm3, 1.3 g/cm3, 1.4 g/cm3 respectively, the continuous pressure-time curves are obtained. By using 6 kinds of methods, closure pressure points on pressure-time curve are distinguished; 4 kinds of methods, for example single tangent, are consistent with actual situation through contrasting the actual minimum horizontal principal stress ( 5 MPa). Considering the effect of experimental flexibility, the measured reopening pressure and theoretical reopening pressure are contrasted. Finally, the pressure of extended rock fissures in continuous pumping pressure is analyzed. The experimental results show that the slurry relative densities of 1.1 g/cm3, 1.2 g/cm3 have little effect on pressure characteristic parameters; and its error is no more than 1 MPa; the slurries with relative densities of of 1.3 g/cm3, 1.4 g/cm3 have great effect on values of pressure characteristic parameters. The experimental results have an important guiding meaning for application of hydraulic fracturing technology to measurement of absolute stress under different fracture media.

Unsaturated granite residual soil is mainly ferruginous cement, its strength decreases sharply in water, structural significant, showing brittle-elastoplastic damage characteristics, whose soil particle joint function is the core problem of structure and brittle- elastoplastic damage. The unsaturated soil particle joint function is discussed; it is divided into contact and non-contact joints, and these two kinds of joints are expressed as suction effects in soil particle intergranular interactions, that is the suction between grains composed of variable structure suction and wet suction. For unsaturated granite residual soil, particle joint function should be paid more attention. Unsaturated granite residual soil’s contact joint is dominated by ferruginous cementation and all levels of granularity composition mixtures as sand, clay and so on; they cause the suction between grains changing greatly in water or disturbance, resulting in the properties of the brittleness in the mechanics of unsaturated granite residual soil. Then through theoretical derivation, by referencing coordination number, the Smith formula, and the Fisher formula in mineralogy, crystal powder mechanics and engineering, quantitative calculation formula of variable structure suction and the soil accumulation mode, dry density, void ratio, water / saturation are given; and the rationality of the calculation formula is verified by tests. Then we research and realize that free iron oxide cement is the fundamental point of granite residual soil’s property of brittle-elastoplasticity, so a masonry model is used; and then void ratio and structure parameter are applied to construct the brittle damage process function; a theory model which can reflect the damage of unsaturated granite residual soil elastoplasticity is established. Through the comparison of calculation and experiment results. The results show that the model established above can well reflect the unique stress-strain relationship of unsaturated granite residual soil. It can explain well the mechanism of unsaturated granite residual soil which is easily destroyed in water or disturbance according to theory.

According to the fundamental theory of upper bound theorem of plastic limit analysis and strength reduction technique based on pseudo-static method, the upper bound solution of the horizontal yield acceleration coefficient of slope stabilized by sheet-pile retaining wall, and two-step anchored bolt retaining wall is deduced rigorously. The critical values of the horizontal yield acceleration of multistage retaining high slopes with different heights of multistage retaining structures, the width of slope plain stages, soil shear strength reduction coefficient, the empirical coefficient of earth pressure along pile, the angle of anchored bolt retaining wall, the pretension force and angle of anchor rod are calculated. The influence factors sensibility sequences of the horizontal yield acceleration coefficient of the bedrock and overburden layer slope under earthquake loading are listed using the orthogonal experiment method. The study indicates that two factors such as the height of multistage retaining structure, and the pretension force of anchor rod are the key factors that influencing the sensitivity of the horizontal yield acceleration coefficient of the multistage retaining slope; but the sensitivities of three factors including the angle of anchor rod, the empirical coefficient of earth pressure along pile, and the width of slope plain stage are relatively small. Moreover, the parameters such as the angle of anchor rod, the angle of anchored bolt retaining wall, the width of slope plain stage, the resistance of sheet-pile retaining wall, the selection of earth pressure distribution type along pile, and cohesion among the shear strength parameters have little effect on the horizontal yield acceleration coefficient; but the internal friction angle has a great influence on it.

Taking a certain thick accumulation landslide for example, and based on the theory of unsaturated soil mechanics, this paper uses the finite-element method to calculate and analyze the slope seepage and dynamic stability under the condition of rainfall infiltration and studies the time effect of water movement in the slope mass on the slope stability. The results show that the loose structure of the slope accumulation body, the poor soil strength, the large gradient at the slope front edge and excavation at the slope toe have provided a convenient condition for landslide formation. Under heavy rainfall, the deformation instability firstly occurred near the slope toe, and then pulled the slope rear edge and caused the tensile fissures. The rainwater infiltrated along the slope surface, formed the seepage field in the slope body and weakened the rock-soil mass parameters. Meanwhile, the saturated runoffs formed on the slope surface generated the downward seepage force on the slope front edge, and promoted the slope front edge to slide and triggered the slippage of the hierarchical slopes. In the initial stage of the heavy rainfall, the safety factor of the landslide mass reduced rapidly, which easily caused the landslide. This study reveals that the rainfall infiltration induced the sliding mechanism of the slope with thick accumulation horizon, based on which, the paper recommends to take the measures of water cut-off, drainage and water plugging to drain off the water, and to set the rock-socketed anchor cable anti-slide pile and taking the measures of slope cutting and cleanup earthwork to control the slope. Good effect results have been obtained through the stability calculation.

When dewatering in deep foundation pit, the uncertainty of the leakage point location, size, and so on in the rock-socketed underground diaphragm in deep foundation pit cause the numerical simulation and prediction of the groundwater flow field very difficult to handle. Based on the analysis of the sealing effect of the rock-socketed underground diaphragm in Xunlimen station of Wuhan subway line No. 2, a method of longitudinal translation and put together is used to deal with the leak point in diaphragm while numerical simulation calculating. The results through 3D numerical simulation by this method are very close to the results obtained from actual measurement, it shows the possibility of using the method to deal with the problems of simulation and prediction of change process of the groundwater flow field in the case of dewatering in the rock-socketed underground diaphragm while it exists leakage point; it provides an approach to solve the problem. In the meantime, the actual sealing effect of the rock-socketed underground diaphragm is analyzed and discussed. The analytical procedure discussed for the project instance can be used for reference to the similar engineerings.

Trapezoidal trench installing (TTI) culverts are widely used in highway and railway in mountainous area. However, there are currently no published standards for the design of the TTI culvert. The performances of embankment installation (EI) and trench installation (TI) culverts have been investigated by a number of researchers; but the study of performance of TTI culverts is less common. To understand the complex soil-structure interaction issues related to the design of TTI culverts, a numerical simulation is conducted to investigate the stress states and the soil arches in the backfill over the reinforced concrete box culvert installed in trapezoidal trenches. A theoretical model is established based on the numerical results; and the formula for calculating the vertical earth pressure acting on the culvert is deduced. The theoretical results are in reasonable agreement with the field test data and numerical results. Moreover, a parametric study is carried out to investigate the important influencing factors on the vertical earth pressure acting on the culvert. Research results show that the stress states on the TTI culvert is different from those of EI and TI culverts. Two layers of soil arches at different levels form in the backfill over the TTI culvert when the fill on the culvert reaches a certain height. The lower soil arches incur the vertical earth pressure concentrating on the top of the culvert. However, the upper soil arches covering the lower ones alleviate the concentration effect. The vertical earth pressure on the culvert is determined by the soil arching effect, which is affected by the height of backfill over the culvert, the slope angle and bottom width of the trench, the dimensions of the culvert and the properties of backfill.

This paper studies the anisotropic mechanical characteristics of the layered rock mass and the analysis method of macro mechanical parameters. It proposes an anisotropic material modules on the basis of ADINA, uses the partition grading macro mechanical parameters simulation method, combining with the theoretical idea of representative unit to make an analysis of anisotropic mechanical simulation and macro mechanical parameters of the two-mica-quartz schist in Danba hydropower station. From the results, the different schistose angle parameters and variation rules of the anisotropic mechanical characteristics of Danba schist are obtained. The results show that with the increasing of two-mica-quartz schist in Danba, the convergence rates of parallel and vertical schistosity deformation modulus and are not synchronized, amplitude increases with the increase of angle, it has a higher convergence rate. The trend of horizontal deformation modulus is more gentle, the variation of Poisson's ratio is just the opposite; with the schistose angle increasing, the mechanical parameters of the two-mica-quartz schist in Danba tend to the limit value obviously.

Delineation of structural homogeneity of rock masses is the basis of statistics and modeling of discontinuities. In practice, an objective partition result is easier to obtain with key factors as indicators and optimal delineation as the final judgment criterion. In order to better characterize the discontinuities in Chinese high-level nuclear waste disposal preselected region in Gansu Beishan, the measure window truncation, sampling bias and grid variability correction are carried out to deal with the discontinuities of rock masses. Such programming realizes structural homogeneity delineation by using a variety of methods and has a preliminary probe into the distinguish capability, applicability and limitation in Beishan. The results show that, as far as the Beishan preselected area be concerned, different delineation schemes are obtained in which the applicability of the correlation coefficient method and the Mahtab’s method are weak in applicability while the Miller’s method is the best and the Miller’s method is increasing sequentially. It is worth mentioning specially that in the Miller’s methods, the 34-block scheme receives the most satisfactory result. At last, the optimal method is applied to Jijicao area; and the delineation result provides a useful direction for the structural network modeling and the following seepage flow path calculations.

In order to investigate the influences of continuous rotation of principal stress axis on the accumulative deformation of soft clay lying below subway tunnel under subway dynamic loading, the finite element method (FEM) combined with field measurement data is used to analyze the complex stress path in subsoil induced by subway loading, and then the hollow cylinder apparatus (HCA) is used to simulate the stress path in laboratory and to carry out comparison tests. Experimental results show that: the continuous rotation of principal stress axis increases the accumulative deformation of soft clay; and the effect is more significant at higher effective principal stress ratio (i.e. the ratio of the effective maximum principal stress to the effective minimum principal stress) or loading frequency. Under the realistic subway loading and the usual tunnel depth, the continuous rotation of principal stress axis magnifies the accumulative deformation of soft clay between 1.09 and 1.23 times (the higher the loading frequency is, the greater the magnification is). The actual accumulative deformation of soft clay under the realistic subway loading (i.e. with continuous rotation of principal stress axis) can be estimated by multiplying the accumulative deformation obtained from traditional cyclic triaxial tests (i.e. without principal stress axis rotation) by the ratio of axial strains between tests with and without principal stress axis rotation. The preliminary study shows there exists power function between the ratio and the maximum effective principal stress ratio of soil.

Crushed rock embankments embedded a perforated ventilation pipe are employed in the expressway construction of the Qinghai-Tibet Plateau. Laboratory experiments for the cooling effect in crushed rock embankment samples with air-open/air-tight surfaces embedded a perforated ventilation pipe are performed. Impacts of air-open/air-tight top boundaries on the cooling effect in crushed rock embankment embedded a perforated ventilation pipe are analyzed. The analysis shows that the air-open/air-tight crushed rock embankments embedded a perforated ventilation pipe can enhance the cooling capability of the embankment base due to forced convective heat transfer of the pore air motion in the crushed rock region near the ventilation pipe forming a pore air circulation in conjunction with the ambient air by the small holes of ventilation pipe wall, and the natural convective cooling effect due to pore air circulation may occur in the upper region of the crushed rock embankment during the negative air temperature ventilating period. Hence, the cooling effect in the air-tight crushed rock embankment embedded a perforated ventilation pipe is significant due to ventilating during the negative air temperature fluctuation period.

Based on the Hoek-Brown strength criterion and geological strength index (GSI) surrounding rock rating system, rock strength weakening behavior is analyzed, a method to determine the rock peak and the peak strength parameters is summarized, a simplified calculation method for the strain-softening model is proposed. By using FLAC3D numerical simulation software, and based on convergence constraint method, the stability of surrounding rock and the support in buried large section tunnel are analyzed, and the safety factor for supporting structure is calculated. The results show that: with the release of the rock stress, rock softening parameter decreases and strength weakening behavior becomes severe. Although the high GSI (GSI = 75) for rock, strength weakening is serious, the deformation is still small. For low GSI (GSI = 25) of the rock showing the perfect elastoplastic behavior. The proposed simplified Hoek-Brown strain-softening model is suitable for the tunnel close to the rock section of the surrounding rock. The convergence constraint method is applied to analyzing the stability of surrounding rock and support, which could provide a reference for initial support to optimize the design and safety evaluation in tunnels.

In order to accurately grasp the deformation and stability evolution law of Huangtupo riverside slump-mass No.I during the reservoir operation, exploration tunnel group was firstly used to expose the geological structure and spatial form of the slump-mass, a geological model of double sliding zone was established based on the exposed information. Then the dynamic groundwater seepage field could be obtained by saturated-unsaturated seepage finite element method, based on which the deformation and stability evolution process was studied. The research showed that the deformation of slump-mass mainly occurred in front of shallow landslide during the drop of the water level, and has significant traction movement characteristics. The deformation evolution law was verified by measured data of global positioning system (GPS) monitoring point. Stability of the shallow landslide was fluctuated obviously during the evolution process because of the dynamic fluctuation of groundwater seepage field’s, and its critical instability velocity of drawdown of water level is 2.0 m/d. Consequently, the overall stability of Huangtupo riverside slump-mass No.I is fine; but there still exists a possible that the front of shallow landslide may be instable locally under rainfall and reservoir water level drawdown.

Sand, as a kind of typical natural granular material, its special mechanical behaviors, such as compressive hardening, dilatancy, anisotropy, etc., are controlled by the internal meso-fabric and its evolution. How to quantify the meso-fabric by experiment and numerical simulation is essential to further study the deformation mechanism of sand. The optical measurement technique based on relevant digital image methods is combined with soil test; and then a measuring system named “meso instantaneous optical system for sands deformation”, which can preliminarily achieve the macro-and meso-mechanical behaviors of soil, is developed by visually upgrading the shear box. The laboratory meso-diret-shear tests for Fujian standard sand are carried out by using this system. And then, numerical direct shear tests based on the software of particle flow code in two dimensions (PFC2D)are performed; and some meso-information which are difficultly obtained from laboratory test are extracted as its supplement. The test results of macro-and meso-mechanical behaviors including displacement field, strain field, particle orientation, velocity field, coordination number and force chain are compared and analyzed; and then the meso-mechanism of sand mechanical behavior is further studied.

Assuming the internal friction angles of backfills and their displacements are in nonlinear, to adopt the calculation model that was put forward by the author, combined with the indoor mode experiment, the authors calculate and analyze the passive earth pressure acted on the retaining wall in different movement modes: translation (i.e. Mode T), rotation around a certain point under the wall-bottom (i.e. Mode RBT) and rotation around some point above the wall top (i.e. Mode RTT). The analysis results show that the calculated values and the test values can agree with each other very well in the three ways of the distribution of soil pressure strength along the wall height, the values of the total earth pressure and the location of the action point of the total earth pressure. It is shown that: (1) It is feasible to use the calculation model to calculate the passive earth pressure in different movement modes. (2) For the agreement degree between the calculated values and the test values of the soil pressure strength distribution, it is the best in Mode RBT; next is Mode T; it is relatively the worst in Mode RTT. (3) For the required displacement to reach the Rankine's passive earth pressure force, it is the minimum in Mode T; next is in Mode RTT; it is relatively the maximum in Mode RBT. (4) For the location of the action point of the total earth pressure, in Mode T, those are all at the 1/3 wall’s height from the wall bottom; in Mode RBT, those are all over the 1/3 wall’s height; in Mode RTT, those are all below the 1/3 wall’s height; and in RBT and RTT mode locations of the action point all gradually trend to the 1/3 height place from the wall bottom with the value of n (the ratio of the distance from rotation point to retaining wall proximal endpoint to wall's height) increasing gradually. These views are completely consistent with the fact.

Oil viscosity affecting the mechanical characteristics of sandstone around the oil wellbore plays a significant role on oil extraction with the more viscous oil reservoir development. Based on cylindrical coordinate system, a numerical model using 3-dimensional particle flow code (PFC3D) of the perforation test is forward to simulate the oil extraction. For the numerical model, different viscous fluids are considered to simulate the mechanical response to practically reflect the process of the sand production. The macro stress curves indicate that under the same fluid flowing, the increasing fluid viscosity increases the tangential stress and deviatoric stress of the sand, and it also increases the shear failure probability so as to make the sand yielded more easily and have more sand production. And also, bond stress indicates that the largest stress is close to the inner oil, and the increasing fluid viscosity increases the tensile stress as localization and also increases the shear stress as globalization with obvious variation trend; the particle rotation also indicates that the increasing viscosity makes the particle rotated more strongly, and increases the probability of the dislodged particles from the sand to become the sand production. The above results agree with the practical response of the sand during oil extracting, and indicate that under the same conditions, more viscous fluid has greater influence on the mechanical response of the sand and has more obvious sand production. Therefore, the achievement will provide an important base for using effective sand control methods for different viscous oils.

Considering the exponential seepage flow law in soil and the nonlinear consolidation behavior of soil, the equations and solution conditions governing 1 D nonlinear large-strain consolidation, in which the excess pore water pressure served as variable, were founded in Lagrangian coordinates; and its numerical solutions were obtained by finite difference method. On condition that the exponential seepage flow law was degenerated into Darcy’s law; the reliability of numerical solutions was testified by comparing the finite difference solutions to semi-analytical solutions. Finally, the consolidation behavior of 1-D non-linear large strain consolidation with exponential flow law were analyzed; and the results show that the rate of nonlinear large strain consolidation of soft clay slows down with increasing the external load in case of 1, and accelerates with increasing the external load in case of 1. The rate of nonlinear large strain consolidation is faster than that of nonlinear small strain consolidation; and the difference between them may intensify with increasing the external load. Furthermore, the final settlement by the theory of large strain consolidation is smaller than that of small strain consolidation, and the difference between them also may intensify with increasing the external load.

Deformation behaviors of foundation pits adjacent to metro stations in different parameter groups (the distance, D, between the existing metro stations and foundation pits, the depth of the excavations, ) were examined via 36 comprehensive two-dimensional finite element parametric studies, which were compared with those without metro stations nearby. On the basis of the numerical analysis results, some major findings were obtained: (1) Maximum deflections of diaphragm walls closer to the metro stations became smaller and those of another side became greater; (2) The existing of metro stations had a remarkable influence on the ground settlements behind the walls far away from the metro stations when was closer to or greater than the depth of base slabs of metro stations. However, the settlement influence zone and the location of maximum ground settlement were not changed obviously; (3) As the increasing of , the shielding effect of metro stations became significant gradually when D was small. Nevertheless, the effect of on the shielding effect weakened by degrees as D became larger; (4) The ratios of maximum ground settlements behind the walls of excavations far away from the metro stations over the corresponding maximum diaphragm wall lateral deflections, δevm / δehm, were almost not effected by the existing metro stations. Moreover, δevm / δehm were effected by D and slightly.

Large strain consolidation theory is applied to calculate deposited cohesive sediment weight deposition and consolidation for the significant nonlinear large strain characteristics. Based on soft soil one-dimensional general large strain consolidation theory and the application of quasi-power functional consolidation constitutive relationships between effective stress, permeability and void ratio, nonlinear large strain consolidation governing equation can be built up according to Darcy law, effective stress principle as well as the soil continuous equation. By the coupling relationship of pore water seepage, element deformation and weight consolidation settlement, a full cohesive sediment weight consolidation numerical model is developed for the nonlinear large strain characteristics. With the fact that deposited sediment weight is as the consolidation loading, the new developed model assumes the deposited sediment layer is homogenous, and the consolidation settlement along with the pore water seepage only occurs in vertical direction, and then the sediment consolidation process can be seen as one dimensional weight consolidation. Moreover, nonlinear quasi-power consolidation constitutive relationship parameters are determined by the cohesive sediment settlement column experiment. Consolidation elements are applied to evaluate the effective stress, excessive pore pressure of different depths, and deposited sediment consolidation settlement is determined by the dissipation of excessive pore pressure in time scale. Numerical model performance shows that there is a clear adjustment process for the relationship of deposited layer effective stress and the void ratio according to the quasi-power functional constitutive relationship in the initial stage. An approximate 20% error between stress and strain consolidation degree means that deposited sediment consolidation settlement develops faster than excessive pore pressure dissipation, which also proves the asynchronous coupling relationship of consolidation deformation and excessive pore pressure dissipation in large strain consolidation. According to the numerical model performances in cohesive sediment consolidation with settlement column experiment, the new developed model outputs show a well agreement with the measured one.

Based on analyzing the mechanisms of the pavement diseases in the cut-and-fill embankment, the working mechanism of the geogrid reinforcement is analyzed. A series of field tests are carried out to investigate the vertical displacements of the pavement, the vertical earth pressures in the embankment fill and the tensile forces of the geogrid. In addition, a numerical model is established for simulations according to the dimensions of the embankment in situ. Through the numerical simulations, the tensile forces and the vertical displacements are observed after the period of construction of the embankment. The tensile forces and the displacements of the embankment are studied, in condition, different vertical loads act on the pavement, and the geogrid with different elongation stiffnesses is spread. The results show that, the geogrid used for cut-and-fill embankment treatment can alleviate the differential settlement of the cut-and-fill embankment. The vertical earth pressures are almost equal to the weight of the overlying embankment fill. The reinforcement of the geogrid has an effective length, the tensile forces and displacements of the geogrid layers are greater at the junction of the cutting and filling areas; the settlement of the upmost geogrid is the smoothest, while the tensile force of the geogrid at the bottom of the embankment increases sharply at the junction. Vertical loads have limited influences on the tensile forces and the displacments of the geogrid layers; and the influences are gradually reduced with the increase of buried depth of the geogrid. The settlements of the geogrid layers increase slowly with the increase of the vertical loads on the pavement; and the geogrid layers at the junction area have the greatest tensile forces. With the increase of elongation stiffness of the geogrid, the tensile forces of the geogrid increase obviously, while the displacement changes very negligible.

A physical model has been developed to study the whole evolutionary process of thrust load caused landslide under the multi-stage loading of MTS electro-hydraulic servo loading and analysis system. The displacement and deformation of the thrust load caused landslide model’s top surface are non-consecutively monitored with advanced 3D laser scanning technology. On the basis of multi-fractal theory, the variation of multi-fractal dimension of displacement in the evolutionary process of thrust load caused landslide is studied through the experiment. The experimental results show that the deformation and failure mode of thrust load caused landslide are dominated by general shear failure and it presents explicit developing phased characteristics. When the slope is in margin compressing stage, the deformation on the surface of the landslide is formed as some parts moving forward and uplift on the margin of the landslide, and the multi-fractal dimensions of displacement are decreasing orderly. When the slope is in uniform deformation stage, obvious displacement can be seen on the surface of the landslide model and the deformation keeps spreading to the front and sides of it. Uplift phenomenon can be seen in some parts in the front and center. During this stage, the multi-fractal dimensions of displacement decrease firstly, and then increase. When the slope is in accelerating deformation stage, landslide model surface presents sustained, rapid and obvious deformation associated with horizontal, vertical expansion cracks in the front and center part of it. During this stage, the multi-fractal dimensions of displacement are increasing gradually. Based on the landslide physical model test, FLAC3D numerical software is used to simulate the evolutionary process of thrust load caused landslide. It is verified that evolutionary process of landslide can be divided into the above three stages. Also the simulation discloses that the attenuation of the stability coefficient of landslide is nonlinear and the attenuation rate is decreasing.

Ever more attention has been paid to geotechnical problems induced by wetting and drying of soils recently. Suction up to 80 kPa, measured by tensometers, has been used for analyzing geotechnical problems such as slope instability during wetting and drying. However, existing tensometer generally has a long response time and is easy to cavitate since it has a large volume of water reservoir and complicated internal structure. These drawbacks affect the sensitivity and reliability of a conventional tensometer seriously. In order to overcome these shortcomings, a newly developed fabricated tensometer is introduced. This type of new tensometer with fabricated structure has a simple internal structure and a small volume of water reservoir. At the same time, a drainage hole is introduced to prevent large excess pore water pressure during the process of reassembling. More importantly, its saturation procedure is simple and efficient since the high air-entry ceramic disc and pore pressure transducer of this new tensometer can be disassembled for saturation separately and effectively. After the saturation of the high air-entry ceramic disc and pore pressure transducer, these key components are reassembled together as a tensometer ready for use. As compared with a conventional tensometer, the sensitivity and reliability of this new tensometer are justified. The results of calibration test show that the sensitivity of the new tensometer increases by 90% by comparing with the conventional tensometer. In the case of measuring the pore water pressure of -80 kPa, the equilibrium time required for this new tensometer is only 1.5 minite, about 10% of that for the conventional tensiometer. Moreover, the reliability of the new tensometer is better than that of the conventional tensometer. The measurement error of the conventional tensiometer is about 30%, when measuring the pore water pressure of -80 kPa. Subjected to the same conditions, the new tensometer shows a measurement error of only 0.7%.

The existing slope internal deformation sensors are easily influenced by rainwater, mud-rock flows, rolling stones and other environmental factors. The arrangement of equipments is not convenient for the internal deformation monitoring; and the internal deformation monitoring can not be realized by the present technology during middle and late periods of sliding. Based on the magnetic localization theory, the smart rock is fabricated with magnetic label; and smart rock is embedded in the deep part of slope. So the slope internal large deformation monitoring system is established with the combination of smart rock and full tensor magnetic gradiometer. The localization by magnetic gradient tensor contraction is used to track the three dimensional motion of smart rock in order to realize the slope internal large deformation monitoring. With regard to the precision of full tensor magnetic gradiometer and influence of earth magnetic gradient, the effective monitoring distance can reach 35 meters by the analysis of magnetic strength and magnetic gradient. In the experiment, the deformation monitoring accuracy is 0.06 meter, which can be used as reference in the further study and practical engineering monitoring.