The thermo-visco-elasto-plastic constitutive model describe the stress-strain relationship of soil under the combined effect of temperature and time. In the construction of some new-type geotechnical engineering, such as nuclear waste disposal as well as geothermal extraction and storage, it is necessary to consider the influences of both temperature and time. Therefore, it is theoretically and practically meaningful to establish a thermo-visco-elastoplastic constitutive model. Firstly, an isotropic stress-strain-time- temperature relation is established by considering the temperature effect on clay volume and strength parameter into the isotropic stress-strain-time relation. Afterwards, hardening rules are deduced from the isotropic stress-strain-time-temperature relation. Through combining the hardening rules with the yield functions of the unified hardening constitutive model, a thermo-visco- elastoplastic constitutive model for overconsolidated clay is proposed. Finally, the proposed model is used to predict laboratory tests. The predicted results show that the proposed model can describe the combined effect of temperature and time on the clay volume, the isotropic compression curve and the preconsolidation pressure.

In order to verify contact model and parameter rationality for structured sand in discrete element simulation, a set of apparatus for specimen preparation and tests on contact mechanical behaviors of idealized hemispherical bonded granules are designed. Throughout the specimen preparation devices, two aluminum hemispheres with the same size were cemented together by adhesive in a size-controlled mode. Then, a series of tests were conducted, including tension test, compression test, shear test, bending test and torsion test, using secondary loading devices. The results show that the apparatus are able to investigate the contact mechanical behaviors of two bonded hemispheres. The consequences are in good agreement with those extracted from the achievements of 2D tests in references. The peak shear force, bending moment, torque of two bonded hemispheres increase to a peak value with the normal force firstly, and then decrease with the normal force. In addition, the critical normal forces in different loading conditions are almost the same.

In order to explore the effect of suction between soil and water on the mechanical response of unsaturated soil, the water in soil is divided from its existing environment into the free water which is store in capillary tubes of soil predominantly by the sucking action of liquid surface tension and the adsorbed water which is bound surrounding soil particles predominantly by the absorptive action of matrix electrostatic charge. After the soil particle matrix together with the absorbed water is thought of as soil skeleton phase, the free water is thought of as fluid phase and the gas in soil is thought of as gas phase, respectively, the work expression is obtained for unsaturated soil considering absorbed water. Based on the thermodynamical dissipative theory，entropic flow and entropic product expressions for unsaturated soil in the process of adiabatic deformation are derived from the work expression and local thermodynamic equilibrium assumption. The adsorption equation of adsorbed water in soil is achieved by the thermodynamical adsorption equilibrium theory; and a practical soil-water characteristic curve for adsorbed water is further proposed. Employing the thermodynamical conjugates of entropic product expression together with Drucker’s plastic postulate in dissipative space, the soil-water fully coupling elastoplastic theoretical framework of unsaturated soil in consideration of absorbed water is established by virtue of a couple of stress variables named as pure simplified effective stress and effective suction. The flexibility matrix with respect to net stress and suction is obtained from this theoretical framework, which can be used to compare directly theoretical model with experimental results in the application of the above theoretical framework on establishing the practical model.

To explore the strength properties of undisturbed sample and remolded sample of Zhanjiang strong structured clay under different stress paths and its relevance to the soil structure, the stress path tests of such as conventional triaxial compression(CTC), reduced triaxial compression(RTC) and conventional triaxial extension(CTE) under different consolidation conditions are carried out, the mechanical behaviors as well as the strength properties of strong structured clay are analyzed. The results show that the shear failure modes of Zhanjiang clay mainly include unitary type, double crossover shear zone and waist drum type; and the stress-strain properties mainly include mild strain softening, intense strain softening, mild strain hardening and intense strain hardening. The failure strain of all the samples under anisotropic consolidation is less than that of isotropic consolidation while the breaking strength and initial elastic modulus are larger. The strength properties of clay under different stress paths are mainly reflected in the change of effective cohesion before the structure yielded; undisturbed sample has a higher cohesion and lower frictional angle compared with the remolded sample; but after structure yielded, the cohesion decreases and the frictional angle increases gradually. The transition from undisturbed sample to remolded sample is a growth and decline process of cohesion and friction inside the microstructure of clay. Based on the results, it is pointed out that the strength indexes of strong structured clay before the structure yielding has a quite strong dependence to the stress paths.

The shallow granite residual soil from a constructional engineering in the coast of Southeast China is selected as the test samples, and then the ultrasonic technology of rock-soil damage detection is used to test and calculate longitudinal ultrasonic wave velocity of the samples under the different impact loads. The longitudinal wave velocity is selected as damage variable to calculate the damage degree, and the influence relationship of the impact frequency, as well as impulse on damage degree is analyzed. Based on the actual situation of sample damage, the characteristics of sample damage evolution under impact load have been analyzed at the same time. The results show that the damage degree of residual soil has a tendency to increase with the increase of impact frequency of impulse; and the impact damage evolution process of residual soil can be divided into several different stages, including small deformation, crack in the telos, bulging or crack in front of 1/3, crack propagation and surface spall in the telos with the increase of damage degree. The research results will provide the scientific basis and quantitative parameters for us to disclose the rule of damage evolution of the residual soil under dynamic loading.

Hardening-soil model, which was based on shear and volumetric yielding mechanism, has been widely applied to geotechnical engineering due to its relative accuracy in the reflection of complex stress path of the soil. However, misunderstanding of its volumetric mechanism widely existed in related domestic research. And the description of its inner parameter solution algorithm is not correct, thus its advantage in simulating the uniaxial compression and K0 consolidation process cannot be reflected. Based on the discussion of the meaning of its inner parameters which controlled its volumetric yielding and hardening, its volumetric yield mechanism is explained in detail; and the explicit analytical solution of these two parameters is also given. Furthermore, a modified Euler mid-point integration method is employed for the constitutive integration procedure since there exists numerical implementation difficulty caused by both of nonlinear elasticity and multi-yield surface plasticity of HS model, and the above work has also been testified by the experimental and numerical results of relevant reference.

The dragload of tapered pile can be reduced by inverted tapered angle. However, the researches focused on the relationship between tapered angle and neutral point position are relatively little. In order to analyze the pile-soil interaction mechanism of tapered pile and equal section pile under surcharge load, based on transparent soil material and particle image velocimetry(PIV) technology, model test on neutral point position of tapered pile and equal section pile are comparatively carried out. The pile and layered soil settlement under different surcharge loads are non-intrusively measured. The pile-soil relative displacement and neutral point position versus surcharge loads are analyzed and discussed. The results show that transparent soil material is technically feasible for studying the neutral point position of piles problems. The results also show that the neutral point position of tapered pile and equal section pile decrease with surcharge loads increasing in this model test condition.

The squeezing soft clay (with stone) method is widely used in soft soil treatment for structures or dike foundations, in which the water content is high and shear strength is low. The construction technology of the squeezing soft clay (with stone) method is easy to carry out and the economic benefit is obvious. The stones penetrate into the soil foundation by squeezing out soft soil until the weight can balance the bearing capacity of foundation soil. The study of section morphology and depth of the dike by the squeezing soft clay (with stone) method is very important in design stage. In this paper both the inverse trapezoid section and rectangle section morphologies are assumed and the effect of the soil upheavals is considered. Then the calculation formulas of penetration depths of the bulk consisting of crushed stones are deduced by the limit equilibrium concept, in which the weight of crushed stone bulk and the bearing capacity of the soil foundation are balanced. The accuracy and applicability of the formulas are verified by model test results and the observed data from practical construction projects. It turns out that the model test and observed data are consistent with the calculation results of formulas very well. The study results can provide reference for designing the squeezing silt.

The traditional rainfall infiltration boundary, decomposing the rainfall intensity according to the slope direction, does not conform to the actual non-orthogonal rainfall infiltration. Firstly, for the purpose of studying the rules of non-orthogonal rainfall infiltration on the unsaturated silty clay slopes, the defects of the slope infiltration models and boundary conditions now available were revealed and analyzed by the review of infiltration theories. Secondly, the infiltration tests of unsaturated silt clay slopes under different rainfall intensities, slope angles, and void ratios were carried out by designing an artificial rainfall device. The test results indicate that the rainfall infiltration on surfaces of unsaturated silt clay slopes is non-orthogonal infiltration rather than simply decomposed orthogonal infiltration; for a given soil slope with a definite angle of and a void ratio, there exists an optimum rainfall intensity at which the maximum infiltration can be achieved; the smaller the void ratio is, the faster the infiltration rate changes at the beginning stage of a rainfall and quicker to come to its stable state. There is an optimum slope angle at wich the amount of infiltration is the smallest, which indicate that the rate and total amount of infiltration are not vary with the slope angle monotonically.

The formation of soil arching effect and load transfer mechanism are the key technological problems for analyzing pile-soil interaction in piled embankment. In order to research the evolution process of macroscopic soil arching effect morphology, the photoelastic experiment technology is applied and realizing stress visualization in piled embankment model by using a locally developed loading device and optical measurement mechanics image processing system. The rules of generation, distribution and changes of the force network can be directly observed. Then based on comparatively analyzing the pile-soil stress ratio obtained from experiment and finite element numerical simulation, it is shown that the soil arching shape transforms from triangle to semicircle; and pile-soil stress ratio decreases gradually when reducing the height-span ratio. When the ratio of filling height to pile spacing, , is greater than 1, full soil arching is observed; when , the effect of soil arching begins to disappear.

The effect of three influential factors including the pause period, the loading rate and the undrained shear strength of soft clay on the axial friction property is investigated using the laboratory model test, when the relative axial displacement of the full-scaled PE-coated pipe and the soft clay take place. The research revealed that there are two forms of force-displacement curves of pipe-clay axial interaction: hardening type and softening type. The peak resistance mobilization distance ranges of 0.005D to 0.02D (D: the diameter of the pipe) for softening type while appears in the last stage of the loading process for hardening type. The peak measured friction coefficients ranged from 0.12 to 0.23 are less than the API recommended values. The peak fiction coefficients are positively related to the loading rates; but the loading rates have no significant effect on the forms of force-displacement curves. The fiction coefficients of clay with high shear strength are lower than the fiction coefficients of clay with low shear strength within the scope of common undrained shear strengths. The conclusion provides references for determining the friction coefficient of axial interaction between buried marine pipeline and clay.

Presented herein is an experimental analysis result of Xi’an Bailu Tableland loess tested by true triaxial apparatus, developed by Xi’an University of Technology, with the different consolidation pressures and intermediate principal stress parameters. The occurrence of loess shear band in cubical specimen may be related to its peak strength or the process of hardening regime. Some characteristic changes of the intermediate principal strain and volume change, and strength law on the meridian plane and octahedral plane have also been explored by the measured results of true triaxial tests. Strength, failure strains and the shear failure model of loess specimens have been analyzed to investigate the judgment basis of shear band occurrence under the condition of complex stresses. The results show that the obvious shear band appear in the loess specimens under true triaxial principal stresses, the softening behavior of intact loess occurs under the smaller confining pressure and intermediate principal stress parameters; and the hardening behavior occurs under the larger confining pressure and intermediate principal stress parameters. Consistent turning points on the curve of the intermediate principal strain and volume change with large principal strain indicate the behavior of deformation changing. Structural soil mass in the side of shear band, which is responding to the intermediate principal strain turning point, has a relative sliding and development of shear band. The strength line on meridian plane is linear; and the strength curve on the octahedral plane is a curved-edge-triangle shape that approaches to -SMP strength criterion. The complex changing of shear band of failure pattern is relating to the structural characteristic of natural loess and loading condition of different stresses.

In the engineering of soils stability, evaluation of earth pressure, foundation bearing capacity and slope stability are all related to limit equilibrium conditions. Limit equilibrium conditions of a soil element are extended to limit equilibrium conditions of a slip surface. Necessary and sufficient conditions required for determining the limit equilibrium state is proven. Based on the extension, a stability method combining limit equilibrium analysis with finite element stress analysis to provide a factor of safety is proposed. And the physical interpretation of the definition of the factor of safety is offered. Then several representative two-dimensional examples about soils stability are analyzed. The results show that the method could be used to analyze the stability of geotechnical structures.

To find a simple and precise method for rigid pile composite foundation is still an urgent problem which is not resolved as yet. A simplified method for calculating its settlement is proposed. The settlement of soil between piles was assumed linear due to the bearing capacity of soil between piles play a little in rigid-pile composite foundation. When the load level of pile is not high, the settlement of pile can be considered linear. If the pile may enter nonlinear even plastic, the load-settlement curve of pile is deemed to satisfy hyperbolic law; thus the nonlinear process of pile can be well considered. According to the mathematic property of hyperbolic equation, the nonlinear load-settlement equation can be deduced by the settlement under the characteristic values of bearing capacity of single pile. For the composite foundation with loading test, the hyperbolic equation of pile can be established by directly using the test curve. Based on the deformation coordination between soil and piles and the static equilibrium equation, the actual foundation settlement can be calculated. On the whole, it is a simplified method for calculating settlement of rigid piles composite foundation. By case studies this method is demonstrated to be not only simple but also be precise and can provide an effective and practical calculation method for engineering practice.

Comparing to the other critical state model, the thermodynamics-based critical state (TCS) model can meet principle of the thermodynamics without introduction of plastic potential function. This model can be used to model the influence of K0 consolidation by modification of it. The return-mapping algorithm is utilized to conduct the redevelopment of TCS model in ABAQUS. The certification of this model can be given by the comparison with modified Cam-Clay (MCC) model offered by ABAQUS. Otherwise, the variation of the yield surface shape controlled by two parameters is discussed. The influence of these two parameters on the stress-strain relationship and dilatancy is also analyzed. The modification of parameter in TCS model can be used to describe non-ellipse yield surface extending available range of TCS model. Different parameters have different influences on the shape and size of yield surface. Meanwhile, it is shown that the stress-strain relationship and dilatancy are different between described by TCS model where the K0 consolidation and stress rotational hardening are considered and described by MCC model without consideration of them are shown. For the real soils, K0 consolidation and rotational hardening are basic mechanical properties of soils. This paper demonstrates that TCS model can be used to describe these features of soils compared with MCC model where the rotational hardening and K0 consolidation are not considered. So, it is more available.

Energy transmission is an essential feature of material. Uniaxial compression test is performed by particle flow code to study crack propagation, energy transmission and damage evolution. It’s revealed to be more reasonable to research the energy through PFC, which overcomes the defect of macro mechanical theory and makes it possible to achieve multiple cracks failure form of specimen. In the compression process there is a one to one correspondence between cracks, energy and damage evolution. The relationship between macro-and micromechanical parameters is analyzed under three working conditions. It is concluded by least square fitting that microcracks are in power function with axial strain. Damage variable is defined with secant modulus. The accelerated decline of elastic modulus is taken as damage threshold which equals to 0.158. It has been proved that there is a linear regression relationship between damage and microcracks, so as to provide reference for further research on damage evolution.

The comparative compression tests were performed on the natural sedimentary undisturbed clays and corresponding remolded samples. The test results indicate that the destructuration after gross yield is a progressive process; the post-yield compression curve displays a nonlinear behavior in the plot of ; and the compression index, Cc, designated by the slope of the curve, is not constant in the entire stress range, which cause trouble to settlement calculation. Therefore, the double logarithmic coordinates system is used to represent the compression curve. A good linear relationship between the logarithm of the specific volume and logarithm of consolidation stress is obtained for clays with different initial structures. The soil structural yield stress and compression indices in the pre-yield and post-yield phases are effectively and simultaneously determined. And then taking into account the sample disturbance, a method of modifying the compression parameters is presented to predict the virgin compression curve; and a bilinear compression model is developed for the structured clays. Based on the experimental data in this paper and other literatures, the empirical relationship between the yield stress and undrained strength, and relationship between compression index and stability index (SI) as well as liquid limit (wL) are established. This study results provides a reasonable basis for determining the consolidation and settlement calculation parameters.

The composite liners (a geomembrane in intimate contact with a mineral liner) have been widely used as the barrier system for landfills. Diffusion is the predominant mechanism controlling organic contaminant transport within the composite liner. Steady-state diffusion of the organic compounds through the geomembrane was assumed in the models. The diffusion coefficient of the organic compounds through the soil liner was assumed a linear function of distance; and the effect of contaminant degradation was considered. An analytical solution for zero concentration on the bottom boundary was presented. Based on the proposed model, the sensitivity of the relevant parameters was discussed and analyzed. The results show that the relevant parameters have a great impact on the calculation results; and the contaminant half-life also has a great influence on pollutant migration. The proposed analytical solutions can only be used to calculate the organic contaminant through two-layered composite liners, and can be used for preliminary design of landfill composite liners.

The specimens of Nanyang expansive soil compacted at the same initial condition, were subjected to one to six wetting-drying cycles; and then the specimens after one, three and six wetting-drying cycles were selected for measuring the relationship between suction, water content, void ratio and saturation degree by the vapor equilibrium method using saturated salt solutions; and thus the soil-water characteristics of compacted Nanyang expansive soil was analyzed. When every drying process finished; the picture of the specimen top surface was taken. The pictures were dealt by the digital image processing using cutting ring as a frame of reference, and then the shrinkage and crack areas were extracted. The shrinkage and crack areas developing with drying-wetting circles were analyzed by calculating the ratios of shrinkage and crack areas to cutting ring area. The test results show that with the increasing of wetting-drying cycle, water content decreases, void ratio increases and water retention capacity decreases, and the shrinkage and crack areas after oven dry increase. But the changes in the above behavior become less with increasing the cycle. The above test results are useful to study soil-water and shrinkage characteristics of expansive soils during drying-wetting circles.

A series of one-dimensional consolidation tests is conducted on soft clay from dredger fill site of central fishing port area in Tianjin. The relationship among stress, strain and time is obtained; the characteristics of the consolidation and secondary consolidation of dredger fill and natural sedimentary soil are compared, providing theory evidence for the deformation model of soft clay foundation of dredger fill site and the prediction of long-term settlement after construction. It is shown that strain rate has a good linear correlation with double logarithm curve of time for both dredger fill and natural sedimentary soil. After processing, the water content and compressibility of dredger fill is low, while that of natural sedimentary soil remains high. With the increase of consolidation pressure, the coefficient of secondary consolidation of dredger fills changes a little. For natural sedimentary soil, the coefficient of secondary consolidation increases first and then decreases, levels out eventually. The coefficient of secondary consolidation still has a good linear correlation with compression index. It keeps a logarithmic downtrend with the increasing of time.

Significant post-construction settlement will be induced under the action of cyclic traffic load in saturated soft soil subgrade and it is also responsible for most differential settlement. To predict the long-term settlement of subgrade, experiential explicit constitutive models based on cyclic triaxial test or hollow cylinder test is combined with equivalent finite element method and it has achieved good effect. The pore pressure model used above is accumulating instantly and dissipating gradually, but the true pore pressure model is accumulation and dissipation proceeding simultaneously. This difference between them will make the settlement calculated by older pore water pressure model be smaller than normal. This paper improves the pore pressure model used currently by applying an analytical expression which can reflect the rules of pore pressure accumulation and dissipation under condition of vibration and natural drainage; and the improved model is used to predict the long-term settlement of the first runway subgrade in Shanghai Pudong International Airport. Compared with the current model’s result, the result based on improved model is closer to the measured actual data.

Based on quantities of test data, a elliptic equation is set up for the elastoplastic stage of pressure meter test with the method of curve fitting; and then, the SMP yield criterion and ROWE flow rule are used to deduce the relationship matrix of the stress increment and strain increment in plastic stage. In the elastic stage, the stress and strain is supposed to obey the generalized Hooke’s law; so the elastoplastic constitutive model is set up, in which the stress-strain relationship is clear; and the parameters are easy to be obtained obtain from the pressure meter test. Accordingly, the calculating program is worked out to compare the model result and the actual test curve, which can validate the model primarily. Furthermore, the model is compiled as a UMAT subroutine, which can be used for finite element analysis in ABAQUS. The comparative analysis shows that, the deformation of this model is larger than that of elastic model and smaller than that of Mohr-Coulomb model, which is consistent with the model assumptions. The elastoplastic constitutive model of soil based on pressure meter test is easy to obtain the parameters and convenient to be used in engineering.

In view of the problem that the conventional elastic method tends to overestimate the pile-pile interaction, the finite element method is applied to establish the shear stress equation of pile shaft for pile groups in the semi-infinite soil mass. The equation is decoupled by considering the pile-pile interaction in a approximate way, a simplified analysis method is proposed for calculating the pile shaft shear stress and displacement to implement the high-efficient analysis of large-scale pile groups. The problem of interaction between two piles and differential settlement of pile groups with flexible cap are analyzed; and then comparisons with the existing results are presented. Parameters analysis show that the interaction factor calculated by the present method is more close to the result given by a rigorous integral equation method, while slightly smaller than Poulos’s results. The differential settlement ratio of pile group with flexible cap in three cases are relatively close to the existing conventional result when the pile spacing is small; while with the increase of pile spacing, a slight difference occurs between the methods. The results show that the present method can greatly reduce the amount of calculation and can be applied to the efficient analysis of large-scale pile groups.

Frozen soil exhibits accelerated creep behavior under high stress level. Nishihara model can describe both decay and stable creeps, however it is not suitable for accelerated creep. Non-Newtonian viscous element is used in the modified Nishihara model to describe the accelerated creep behavior. The coefficient of viscosity in viscoelastic part is modified to be a function of time; and the non-Newtonian viscous element is used in viscoplastic part. The creep compliance of the modified model is a function of stress level and time; therefore, the accelerated creep behavior of frozen soil under high stress level can be considered. One-dimensional and three-dimensional creep behaviors of frozen soil under different stress levels are fitted by using the modified model. The results show that the proposed model can describe the accelerated creep behavior under high stress level after decayed creep stage and stable creep state. The proposed model is suitable for describing different kinds of creep behaviors of frozen soil under different stress conditions.

The large quantity and high filled embankment makes the post-construction settlement very obvious, which influences the operation of the engineering. It is significant to study the method for calculating the post-construction settlement of high filled embankment in order to control the post-construction settlement. The creep deformation is an important component of the post-construction settlement of high filled embankment. Experimental results indicate that the creep deformation of high filled embankment is affected by both time and stress history. A method for calculating creep deformation that can consider stress history is proposed by combining the instantaneous elastic compression line and the framework of the time-dependent unified hardening model. Afterwards, the calculation results are the same as the results of the laboratory creep tests. Besides, the parameters used in the new calculation method are easily to be determined.

The progressive failure of expansive soil slope at shallow depth occurs frequently; but the traditional limit equilibrium theory can not reflect properly particularities of shallow instability of expansive soil slope. Based on a series of large static physical model tests of the compacted expansive soil slope, this paper firstly simulated the moisture field distribution by the unsaturated model of two-phase flow of FLAC; and then, by referencing the temperature expansion theory, a back analysis of the moisture swelling coefficient of expansive soil is conducted according to the indoor expansion tests with or without vertical loading. Finally, a multifield coupling numerical analysis method with moisture field, swelling deformation field and stress field is proposed. Combining the physical model tests with multifield coupling numerical analysis, the expansion failure mechanism for the shallow instability of expansive soil slope is expounded.

Based on the research of empirical rainfall threshold and numerical analysis, the landslide early warning rainfall threshold was calculated with advanced model of FEM code Plaxis, considering the rainfall infiltration and the characteristics of unsaturated soil. The influence of rainfall distribution mode was firstly studied. The results show that separating rainfall into two phases is better than one averaged phase in slope stability calculation. Then, the antecedent rainfall is redefined with explicit physical significance as the rainfall causes the change of matric suction of the unsaturated soil within the slope surface and the potential slip surface. And the antecedent rainfall duration is directly proportional to maximum depth of potential slip surface and inversely proportional to the saturated permeability coefficient of the soil. The two parameters in the expression of the duration are investigated and the suggested values are given. Lastly, the amount of antecedent rainfall is introduced to the I-D curve as the third coordinate axis to develop A-I-D rainfall threshold surface. A case study of slope on bed rock is carried out to demonstrate the process for establishing this space curve, which is compared with the test data. This verification proves the reliability of the method proposed.

The separate and combined calculation of water-soil pressures on underground structures affects not only the design of supporting structures of excavations, but also the setting of uplift piles. Based on the field data, it has been proved to be reasonable to calculate the water-soil pressures by the separate calculation method for sandy soil. However, whether the combined calculations of the water-soil pressures is scientific or not for clay has been the focus dispute between geotechnical engineering and academic circles. In order to resolve this dispute, the author has proposed a calculation method to unify the separate and combined calculations of water-soil pressures. As a logically self-consistent theory, it carries out the transition between the two conventional calculation methods and provides a theoretical basis for the combined calculation method of water-soil pressures. This paper reviews the process of this theory initiation and further illustrates its rationality. Finally, it analyzed the value and development prospects of this theory.

Loose sandy soil subject to undrained shearing manifests deviatoric softening, and such a behavior has been referred to collapse of static liquefaction. Feedback analysis of some slope failures reveals that the static liquefaction induced by underground water may be one of the implicit mechanisms of the slope failure. Densely packed assemblies exhibit similar phenomenon when sheared along certain proportional strain loading paths. For granular materials, such as soils, which are non-associated materials, diffusion failure can occur for stress states strictly included within the plastic limit condition. The expression “diffusion failure” is used in contrast to “localized failure”, to highlight the failure mode characterized by the lack of localization patterns. The mechanical response of dense assembly of irregular shaped particles subjected to proportional strain loading paths was studied using the combined finite-discrete element method(FDEM). According to Hill’s instability theory, a stress-strain state is stable if the stress and strain increments linked by the constitutive behavior of the material produce a strictly positive second-order work. The second-order work criterion is linked to the occurrence of a diffusing failure mode. In the meridian plane, the stress space is divided into dilation and compaction as distinguished by the controlling parameter of proportional strain loading path. The instability line is built by joining the points marking the onset of diffusion failure from each confining pressure.

In order to evaluate the feasibility of improved clay based on sewage sludge ash(SSA) used as landfill liner-soil materials, a series of the direct shear strength tests and low temperature nitrogen adsorption tests were carried out to analyze shear strength and pore structure of improved clay in laboratory. The improved clay was composed of 95%-99% of raw clay and 1%-5% of SSA. The results show that the isotherms of improved clay containing SSA is belong to type VI isotherms, and it had type H3 hysteresis loop; The pore of improved clay was mainly composed of mesopore of 2-6 nm. The shear strength of raw clay corroded by landfill leachate sharply decreased. The cohesive strength and internal friction angle of sample declined 60.12% and 19.17%, respectively. The maximum adsorption capacity of raw clay corroded by landfill leachate declined 16.19%. The shear strength and pore volume of improved clay increased with an increasing of SSA.

With the development of offshore engineering in recent years, foundation stability in ocean environment has become a hot topic for scholars and engineers. It is important to set up a simple saturated clay cyclic model for design of offshore structures under long-term cyclic loading. According to cyclic degradation behavior of saturated clay, a simple nonlinear model considering cyclic degradation of saturated clay is developed based on Hardin-Drnevich equivalent nonlinear model. This model can be adopted to describe the cyclic hysteretic characteristic of saturated clay, in which a degradation law for strength and stiffness with accumulated plastic strain as a variable is introduced. The physical interpretations of shape parameters and n, as well as residual ratio and damping factor are illustrated through parameter analysis. This model is proved to be able to describe the stress-strain hysteresis loops of different shapes and different degradation laws for strength and stiffness of saturated clay well by simulating the results of one-way cyclic triaxial tests and two-way cyclic triaxial tests in the literatures. With higher calculation efficiency, this simple model will be more suitable for engineering application comparing with the traditional elastoplastic models of soils.

Cement mixing gravity retaining wall is widely used as a supporting method in soft soil area. It is not clear enough about the reliability analysis of gravity retaining structures in Shanghai region, and doubts about the mechanism of various factors still exist. By analyzing some practical projects collected in Shanghai, this paper discusses some problems on both the reliability levels and stability of gravity retaining wall. The influences of some factors such as the insertion ratio, the excavation depth and the width of wall on its stability are also evaluated. The results show that the safety level of practical projects is usually higher than requirements in the design code. In these typical stabilities, the sliding stability is usually judged as the controlling mode of stability checking. The security status of sliding stability and overturning stability can be improved obviously when the width and insertion ratio of the gravity retaining wall. In addition, the increase of insertion ratio contributes much more than the increase of the wall width in improving the security status of overall stability.

Reinforcement technology by geogrids has special effect for controlling geo-hazards occurred in expansive soils. But at present the research on the characteristics of interface between geogrids and expansive soils is insufficient; with laminated shear test apparatus, a series of pull-out tests is carried out to study the interaction between plastic uniaxial geogrid and expansive soils under different vertical loads. The soils are taken from the weathered expansive marlite in Xinxiang, the middle route of the South-to-North Water Transfer Project. The research results show that: the pull-out process of geogrid from expansive soils falls into three main stages, i.e. the interfacial static friction stage, progressive shear stage and the overall motion stage. There is obvious difference on the stress characteristics in each stage. As the normal stress increases, the ratio of the static friction to the interfacial shear strength shows a logarithmic increase, is from 0.20 at 50 kPa to 0.57 at 400 kPa; and its extreme value can reach 0.75. When adopting geogrid to reinforce retaining wall and high slope, the maximum static friction proportion should be considered; there is different vertical stress at vertical height of geogrid; sectional design is more reasonable.

Soil is a complex granular medium and its strength and deformation characteristics behave strong particle size effect. On the basis of the physical effects of cohesion and friction generated by the interactions between soil particles at different scales but not just the geometric dimensioning, a soil cell element that can describe the internal material information and particle characteristics of soil is constructed by dividing particle size into different scales to investigate the influence of soil particles at different scales on the macro-scale mechanical properties of soil. According to the mechanical responses of soil at various scales, the notion of ratio between micro-forces and gravity is introduced; and a multiscale and hierarchical soil cell element model is proposed to interpret the mechanism of the particle size effect of mechanical properties of soil. Therefore, the microscopic soil mechanics is promoted from qualitative analysis to quantitative calculation. A series of unconsolidated and undrained triaxial compression tests on saturated, remoulded soil are designed to study the particle size effect of soil and to quantitatively determine the strain gradient and intrinsic length scale of soil. The experimental results and theoretical analysis show that the particle size effect of the strength and deformation of soil is increased with raising volume fraction and decreasing size of the reinforcement particles, which suggests strong particle size effect. The theoretical prediction of size effect is in good agreement with that of the test result.

A novel phosphate-based binder(KMP) and Portland cement(PC) are used to stabilize the contaminated soils spiked with Zn and Pb. The strength and durable characteristics are evaluated by toxic characteristics leaching procedure(TCLP) tests, unconfined compressive strength(UCT) and sequential extraction procedures(BCR) after freeze-thaw cycle. The TCLP result shows that the leaching Zn and Pb value exceed the limit of china MEP regulatory but up to the stander after solidified by KMP and PC binder in the untreated soil. The UCT result shows that solidified soil is lower than the stander curing soil treated by freeze-thaw cycle. After 12 freeze-thaw cycles the qu of heavy metal contaminate soil solidified by KMP is higher than the PC. The MIP result shows that the pore size increases with the increase of freeze-thaw cycles. The BCR result shows that the exchangeable fraction Zn and Pb reduce with the increase of curing time but the residual fraction increases which soil solidified by KMP and PC.

The compression wave (P-wave) and shear wave (S-wave) in dry sand are measured simultaneously by a bender-extender element incorporated in a resonant column apparatus. The characteristics of the output P-wave and S-wave signals are analyzed; and the effects of the input signal frequency, soil density and effective confining pressure on the signal characteristics are investigated. According to the wave propagation theory and measured S-wave and P-wave velocity, the elastic properties of the dry sand are calculated, including shear modulus, constrained modulus and Poisson’s ratio. The results indicate that to some extend the frequency of the output signal increases with increasing input frequency, soil density and effective confining pressure. Compared with S-wave, it is easier to determine the P-wave travel time and thus the wave velocity. The elastic modulus of the soil increases with increasing density and effective confining pressure, especially the shear modulus. The Poisson’s ratio decreases with increasing density and confining pressure, instead of a constant. Attempt is also made to estimate the Poisson’s ratio based on shear modulus considering the convenience of application in the practical engineering.

When the earth pressure balanced shield is tunneling in the stratum with a high water table (for example, a tunnel constructed below the river by the shield), the hydraulic head difference between the ground and the shield’s chamber can produce seepage force acting on the tunnel face. The seepage force can lead to the failure of the tunneling face, in order to investigate the failure of the tunneling face considering the seepage flow. A device for the centrifugal model tests is developed, including: rigid model container, tunnel model, loading system, water table control system and water storage tank. The size of the rigid model container is 1 000 mm in length, 450 mm in width and 1 000 mm in height. Due to the symmetry, the tunnel model is made from a D-shape steel tube. The diameter of the tunnel model D is 100 mm the tunnel face is a D-shape aluminium plate with the drainage holes. The drainage holes allow the seepage water to flow into the tunnel. Loading system consists of a hydraulic actuator, a cylindrical loading rod, a linear variable differential transformer (LVDT) and control software. The loading system is used to fulfill the tunnel face retreating. The water table control system consist a flow pump, some hoses, a metal pipe with some holes and a solenoid valve. The water table control system allows keeping an invariant water table and steady seepage during the tests. Water storage tank is used to store seepage water. A series of the model tests with different water tables are conducted. The depth between the crown of the tunnel model and the water table are 1D, 2D and 3D. The depth of the overburden is 1D. The silty sands are used in the tests. The sands are collected from the beach on Qiantang River. A pressure cell is placed between the tunnel face and the loading rod. It is used to measure the support pressure. The armature of LVDT is connected to the loading rod. The LVDT is used to measure the horizontal displacement of the tunnel face. The results show that the effective support pressure decreased when the face plate is retreating. The effective support pressure increased slowly after reaching the minimal value. In the limit state, effective support pressure increased linearly with the hydraulic head .

The urban track traffic develops rapidly with the economic growth in China. Among the common diseases of shield tunnel, longitudinal settlement will put adverse influence on the longitudinal performance of shield tunnel. The structural stiffness of shield tunnel structure is one of the most important mechanical performance index. The longitudinal equivalent continuous model is adopted; and the longitudinal effective rigidity ratio is assumed to be constant and variable longitudinally. The longitudinal equivalent rigidity is back calculated based on settlement curve to analyze the influence of longitudinal settlement on the longitudinal equivalent rigidity of shield tunnel. The results indicate: (1) When the longitudinal equivalent rigidity is constant, the longitudinal effective rigidity ratio reduces and change to be steady as the ratio of actual settlement and theoretic settlement increases. (2) When the longitudinal effective rigidity ratio is variable longitudinally, the back-calculated at the middle part is larger than that at both ends less than 1; and the back-calculated at the middle part is smaller than that at both ends for are greater than1. (3) The settlement curve which is calculated based on back-calculated has some differences with the actual settlement curve.

In light of the adjacent high-speed railway pile foundation problem induced by the process of shield tunnelling in the saturated sandy stratum, the isolation piles, including bored pile and jet grouting pile, were applied to resist the displacement of the pile foundation. An experiment was investigated in order to determine the effect on high-speed railway piles by the adjacent construction of bored pile, jet grouting pile and shield tunnel. The monitoring in-situ was carried out. The results shows that the settlement of high-speed railway piles is induced by the performance of bored pile, the settlement value may account for almost 75%-125% of maximum ones. The heave of the high-speed railway is induced by the performance of jet grouting piles; the heave value may account for the -50% of the maximum settlement. Meanwhile, the process of the heave can last for a long time. The specific operation of shield tunnel machine affects the magnitude of the adjective high-speed railway piles subsidence; the closer the distance between the shield tunnel and the piles, the larger the influence; the cumulative settlement is associated with operation of the shield tunnelling.

Based on traditional empirical equations for calculating vertical displacements of sands during tunneling in sands, effect of tunneling on nearby pile foundation in respect of axial force in sands is investigated. According to ground and subsurface settlement troughs induced by tunneling in sand, a simplified calculating method for evaluating effect of tunneling in sands on axial force of nearby piles is firstly proposed by considering nonlinear pile-soil interaction. Meanwhile, the two-step method was adopted and the nearby piles were taken as vertical passive piles. The results calculated using the simplified method is then compared with experimental results obtained from geotechnical centrifuge tests, which validate the rationality of the proposed method. In addition, many influence factors, including tunnel cover, tunnel diameter, distance between tunnel and pile, tunnel volume loss, pile length and pile diameter are also investigated during the study. It has been found that the axial force of pile decreases with the increase of tunnel cover thickness, while increasing with the increase of tunnel diameter and soil volume loss ratio. The axial force reaches to the maximum value when the distance between tunnel and pile is approximately 2.5 times of the tunnel diameter. The axial force of pile increases with the increase of pile length and pile diameter.

The foundations of power transmission towers and offshore wind turbines are prone to huge overturning moment loading from the super structure; therefore the overturning bearing capacity is crucial for the design of such foundations. To investigate the overturning bearing capacity of suction caisson foundation, four centrifuge model tests including a displacement controlled cyclic loading test, a displacement maintained loading test, a load controlled cyclic loading test and a monotonic loading test were carried out in saturated soft clay. The test results show that the instantaneous rotation center of model caisson can be simplified to be at the depth of about four fifths of the skirt length right below the lid center, when the ultimate capacity was reached. When the amplitude of the cyclic moment is smaller than three-fifths of the bearing capacity moment, the rotation of the caisson cease to accumulate, and gradually become stable. The stiffness of the soil-structure interaction significantly softened under cyclic loading, and a threshold of cyclic degradation factor t = 0.15 can be obtained from the peak stiffness curves of the caisson. The moment-rotation curve of peak value of maintaining tests is universally quite in accordance with that of monotonic loading test. The capacity of the model caisson corresponding to the moment-rotation curve of the valley values is much lower than that corresponding to the moment-rotation curve of the peak values in maintaining tests, and a 30%-40% reduction is needed when considering the maintaining overturning capacity of the caisson foundation in design.

According to the time-settlement data of an expressway in Taihu Lake region and the laboratory test results, the compression characteristic of alluvial lacustrine soft soil and the variation of settlement for subgrade are analyzed. The effect of engineering geological conditions and depth of fill on settlement of subgrade are investigated. The normalized index is used to estimate the settlement of subgrade. Meanwhile, two kinds of commonly used whole process subgrade settlement prediction methods are compared. The results show that the alluvial lacustrine soft soil in Taihu Lake region is a strong structured soil. The settlement of subgrade at similar geological conditions is quite different and soil structure is one of the important factors affecting the settlement of subgrade. A simple formula for estimating settlement is obtained with the analysis of normalized index. The whole process settlement prediction methods commonly used for the final settlement prediction have certain deviation; a more accurate estimated value of settlement can be got by comprehensive analysis.

Evolution of breakage for geomaterials is critical step for understanding the complex process of the particle breakage. Research on the breakage of uniformly graded granular materials is the basis of nonuniformly graded samples. This paper starts from the perspective of probability statistics and focuses on the evolution of the three parameters-breakage probability p and crushing state parameter a and b proposing by the authors’ previous works, which are aimed to describe the breakage evolution of uniformly graded granular materials. Through the three selected experimental data with different experimental materials and experimental types, it is suggested that the values of three parameters tend to be a constant value during the development of breakage. This also reflects the existence of ultimate of breakage from the viewpoint of numerical method. Based on these, a method for calculating the ultimate particle size distribution of uniformly graded samples is proposed finally. Then it is easy to obtain the ultimate fractal dimension of the three samples, which is about 2.3, 2.34 and 2.28 respectively.

The improvement of the train operation speed will increase roadbed vibration, and undermine its dynamic stability, and may cause great subsequent settlement; when it reaches the limit value, the roadbed structure will get a bulking failure. Therefore, the dynamic response and disastrous mechanism of subgrade structure under high-speed train load has become an international and urgent research subject in the process of high-speed railway construction and operation. Relying on Wuhan inter-city typical engineering, a large-scale model test of vibration due to train load is carried out by using a self-developed excitation system. By simulating the process of loading with vibration exciter, the time history curve of velocity and the space distribution features of different subgrade layers under the action of different frequencies of vibration force is obtained; and then the velocity transfer and attenuation law of subgrade under the train load is revealed. The experiment results show that. The curve of velocity on subgrade structure has a obvious cyclical peak under different frequencies of vibration force; the speed amplitude on subgrade structure will ever-reduce along the depth direction and show a trend of exponential decay under frequencies of vibration force. The research results will provide a certain reference for designing, construction and operation of practical engineering.

The model test study is one of the important means to explore the mechanical response mechanism of soil and structure system. Aimed at model simulation of Xi'an Metro Line 2 tunnel, this paper firstly discusses the similar scale relation of tunnel structure model test, analyzes the selected principles and the key problems of similarity material in model test. Then based on two different geometry similarity levels, the effects of geometric similarity levels on the results of stress and bending moment between the model and prototype tunnel structure are compared and discussed, and the stress error of tunnel prototype structure is more than 12%; while the error of bending moment is more than 140%. The study results show that the geometric similarity level determines the rationality design of model similarity scale, thus it becomes one of the key restriction factors whether the model test can reasonably and accurately simulate the mechanical response of prototype structure.

In order to study the failure displacement criterion of shallow-buried vertically loaded anchors(VLA) in soft clay, displacement-controlled and load-controlled static loading model tests are conducted by using an electric servo loading apparatus developed by the authors. The embedment depth of vertically loaded anchors is 3 times of the plate width and the acute angle between the plate and horizontal line is 30°. The normalized curve is obtained by normalizing the normal load and displacement based on the ultimate bearing capacity and width of the anchor plate; then, the failure displacement criterion of the vertically loaded anchor can be determined according to that. The model test results show that the failure displacement is about 0.38 times the width of anchor plate when the anchor failure occurs. Besides, on the basis of the size of anchor plate, the burial depth and the strength of soil for tests, the ultimate bearing capacity of anchor is calculated by using the empirical formula. It turned out that the ultimate bearing capacity of vertically loaded anchors determined according to the failure displacement criterion is nearly identical to the value determined based on the empirical formula. The difference between them is less than 10%. The rationality of the failure displacement criterion is verified by the comparison.

High water content silt in urban dredging and construction process has high liquidity typical characteristics which may lead to extremely inconvenient in transport and turnover. Carrying out the experimental study of decreased flow ability of silt by using high water absorbent material. The results show that flow ability of silt increased with moisture content rise, the mathematics model of flow ability and moisture content is got from the curve fitting of the test results which is quadratic function. A little cost of high water absorbent material can obtain the good effects on decreasing silt flow ability to an appropriate level that is very conducive to transport and turnover. The net flow value is introduced to quantitatively describe improvements of silt’s flow ability caused by high water absorbent materials. The net flow value of silts with different initial water contents would reduce at an identical ratio level when added high water absorbent material. The result for decreasing flow ability by adding high water absorbent material is immediately obvious. In the case of low mixing uniformity with high water absorbent material and silt, the decreased flow value of silt is close to optimum. Mixing duration and intensity have little Impacts on the flow ability of the silt. Time consuming and work intensity would reduce obviously when it’s taken to engineering application.

During the construction process of subway tunnel, maximum inclination rate of surface longitudinal settlement and release rate of surface settlement on the excavated face are significant for safety assessment of surface and underground building. Cumulative probability curves can not completely describe the characteristics of longitudinal settlement. Firstly, the characteristics of the surface longitudinal settlement caused by covered digging of subway tunnel in loess are researched. Secondly, a new function is sought to reflect the characteristics of surface longitudinal settlement. Thirdly, the maximum inclination rate of surface longitudinal settlement and the release rate of surface settlement on the excavated face are analyzed in the different regions of loess. Finally, Predicting method of surface longitudinal settlement is put forward based on the two characteristic values. The results indicate that during the construction process of subway tunnel by covered digging in the region of loess, the two characteristic values in the paleosol strata are both maximum, but on the contrary in the saturated soft loess strata. Through the rigorous mathematical derivations, a predicting analysis method is proposed considering maximum inclination rate of surface longitudinal settlement and release rate of surface settlement on the excavated face. Its sensitivity with characteristic values is analysed; and rationality of these methods is verified based on the monitoring data. It has a significant meaning to analyze and predict the influences that differential settlements on the surface have an effect on the ground and undergroud building.

The prestressed concrete cylinder pipe(PCCP) has been widely used in underground water conveyance projects, especially in the south-to-north water diversion project. Pipeline interface belongs to the semi-rigid structure; while the relative angle of adjacent PCCP is larger than the allowable angle, PCCP will produces internal force in bell and spigot. However, if it is located in the serious uneven soft soil foundation, it may produce excessive angle and even destroyed. Therefore, how to control the PCCP produce excessive angle in soft soil foundation becomes one of the key issues in researching pipeline safety. Firstly, what factors lead to relative angle is analyzed. Then combined with field test and numerical analysis, the key factors for control PCCP angle is determined. Research results show that the thickness of the gravel cushion, the thickness and compactness of the sand cushion are the most important factors to control excessive angle. As the thickness of the gravel cushion, the thickness and compactness of the sand cushion increase, the relative angles decrease. The research results can provide basis and guidance for PCCP pipeline engineering design in soft soil foundations.

The dynamic properties of frozen clay are studied by hysteresis curves. The test results show that when the temperature of frozen clay is -0.5 ℃- -4 ℃ and the vibration frequency is 1-10 Hz, the stiffness increases, but the viscosity, degree of microscopic damage, residual strain and energy dissipation decreases with the decreasing temperature and increasing vibration frequency. There is no apparent change in the dynamic properties due to the stability of the mechanical properties of frozen clay while the soil temperatures are less than -4 ℃ and the vibration frequencies are greater than 10 Hz. With the increasing dynamic stress amplitude, the stiffness decreases; but the viscosity, degree of microscopic damage, residual strain and energy dissipation increases gradually. With the same dynamic stress amplitude, the influence degree of temperature, vibration frequency and confining pressure on the dynamic properties of frozen clay is maximum, middle and minimum. The degree of microscopic damage and residual strain are affected by temperature, vibration frequency and confining pressure apparently. The viscosity and energy dissipation are affected secondly, and the stiffness is impacted minimally.

Particle crushing after impacted by loading or other mechanical factors is the intrinsic property of geotechnical material, so proposing the reasonable parameters to describe the crushing state is the primary step to study particle crushing. Considering the fact that the proportion of smaller diameter particles increases with the particle crushing and there is a tendency for the grading to become increasingly “self-similar” or “fractal”. This paper proposes a concise method to describe the particle crushing state based on the slope and correlation coefficient of fitting line. On this foundation, the concepts of crushing fractal index(CFI) and crushing fractal correlation index(CFCI) are defined and their development law are both elaborated. Compared with the experimental data, the indexes proposed in this paper are consistent with the data; and an obvious relationship between particle crushing state and the two indexes is existed. Therefore, the CFI and the CFCI can be used to reveal both the degree of particle crushing and the trend of particle crushing development, so as to provide a new approach to study grain breakage problems.

Based on the field test of vacuum combined with surcharge preloading reinforced soft ground in highway test section, the centrifugal model is built to perform the centrifugal test on vacuum combined with surcharge preloading reinforced lacustrine soft soil. The settlement law of soft ground under the effect of vacuum combined with surcharge preloading is analyzed. The test settlement is compared with the measured settlement in order to study the settlement relationship between them. By the above analysis and comparison, the results show that the settlement of soft ground during construction is more than 87% of total settlement under the effect of vacuum combined with surcharge preloading, which is effective to reinforce lacustrine soft soil. Using the vacuum combined with surcharge preloading to reinforce soft ground, the settlement development of soft ground after construction is slow; the settlement value of soft ground after construction is no more than 2.5 cm in two years; and the settlement difference of embankment section is less than 5 mm. It is clear that the settlement of soft ground after construction will not affect the normal operation of highway. The settlement trends of centrifugal test and field test are basically similar; but the settlement values of them have differences due to the impacts of the condition of field test and the errors of centrifugal test.

In order to acquire the characteristics of ground settlement under the high energy dynamic compaction, the geometric nonlinear finite element method and the cap model in LS-DYNA finite element program are used to analyze the deformation mechanism of dynamic compaction. Firstly, according to the actual situation of site construction to establish the finite element model as basic computing model to model the process of dynamic compaction, and comparing with the actual monitoring data, the results indicate that the calculated results acquired in the analysis are close to the actual data measured in dynamic compaction; and the basic model used to calculate the settlement of surface ground is appropriate. Furthermore, the different energy level, different momentum, and some friction parameters effect on the settlement of surface ground are analyzed based on the basic model. Lastly, some useful conclusions are drawn. The results show that the horizontal force between hammer and the foundation soil is not to be ignored under the high energy dynamic compaction.

The thick soft marine clay of Hong Kong-Zhuhai-Macau Bridge(HZMB) ground was reinforced by sand compaction pile (SCP) method. A large scale plate load test was designed for evaluate the bearing capacity and deformability of the SCP composite ground. Better settlement result was obtained by utilizing the high sensitivity liquid level sensor system underwater. The research results show that the pile-soil stress ratio of SCP composite ground is closely related to load level that decreased with the load level increasing. On the same level, the ratio gradually reduced to a certain value finally. Four computing theory including Brauns’ method, Wong formula, Hughes & Withers formula and passive earth pressure method were discussed in bearing capacity calculation of SCP composite ground. The results by passive earth pressure method agreed best with the field experimental data. For this high-replacement ratio SCP composite ground, it is demonstrated that the settlement calculated with a reduction factor which was derived from Technical code for ground treatment of building is most close to the measured result; while there is significant difference when the overseas Coastal Area Development Institute of Japan(OCDI)’s experiential formula is employed. This research results provide useful data for the marine SCP composite ground design and deep sea in-situ test.

Foundation treatment of large-scale refinery is very complex. In view of this condition, in-situ test of vibro-replacement stone pile was carried out. With static cone penetration test dynamic penetration, pile density was detected and saturated sand liquefaction was judged. Based on results of pressuremeter test, standard penetration test and heavy dynamic penetration test, foundation bearing capacity change and soil engineering characteristics change during construction process of vibro-replacement stone piles were analyzed. The bearing capacity of composite foundation was evaluated by static load test of single pile and composition foundation. The results show as follows. Firstly, vibro-replacement stone pile has a compaction effect on the sand soil of pile length range. Engineering characteristics and field uniformity has been improved apparently. Sand liquefaction possibility for pile length range can be eliminated. Secondly, static load test results show that the bearing capacity of composite foundation has reached the design requirement. Thirdly, the compaction effect on clay soil, which is under sand soil layer, is not apparent. And soil strength in some depth range even reduces. Finally, the bearing characteristics will not significantly be affected when no more than 5 m thickness of soft soil interlayer exists 10 m depth below the ground surface.

The post grouting technology is used to format the screws of a grouting screw pile, which can be constructed easily in soft clay area and has been applied to engineering project currently. According to the stress change of soils around the screws in the uplift process of the grouting screw pile, the Mohr circle stress analysis is conducted to analyze the development of slip line along the screw; and it can also give the relationship between the angle of slip line and the ratio of screw pitch to screw dimensions，which is expressed in the mathematical equation of incremental normal stress and shear stress of soil around the screws. The condition to judge the shape change of slip line between the screws from cylinder to truncated cone is obtained. Based on the shape of slip line, the calculation of uplift capacity of screw pile can be divided into three cases, the formula of which is obtained through limit equilibrium method. The application and rationality of the presented method is proved by comparison with finite element analysis and a field test.

The Green-Ampt model is a simple method for infiltration analysis. Due to its ease to use, the Green-Ampt model is potentially very useful for the prediction of slope failure under rainfall infiltration. A key parameter in this model is the permeability coefficient, which is different from the saturated permeability of the soil. This study investigates the relationship between the permeability coefficient in the Green-Ampt model (kg) and the saturated permeability coefficient of the soil (ks) through comparison with results from the more accurate Richards’ equation. The ratio of kg to ks is called the permeability coefficient adjusting factor. It is found that the adjusting factor depends on the factor of the duration of the rainfall as well as the soil type. For the soil studied in this paper, an adjusting factor of 0.7 seems to be optimal in reproducing the pore pressure distribution calculated based on Richards’ equation.

In order to investigate the mechanical property of municipal solid waste(MSW) at medium and high ages, the artificial model MSW was made up by adding appropriate mass ratio of turf into the mixture of Quartz sand and kaolin clay, and then a series of consolidated drained and undrained triaxial tests were conducted. The tests results showed that the stress-strain of MSW at both high and medium age demonstrate continuous hardening characteristics during shear. The volumetric strain of medium age MSW in drained tests is little bigger than that of high age, the pore water pressure of high age MSW in undrained test is bigger than that of medium age. When the shear stress at 15% axial strain is adopted as the shear strength, the reduction coefficient of the pore water pressure and shear strength parameter were obtained by according to the Skempton's principle of effective stress. The reduction coefficient of the artificial model MSW is shown to increases with the age, the cohesion of the artificial model MSW decreases with the age, while the friction angle increse with the age.

The meso-morphology of granite from Shandong Linyi has been observed under the real-time temperature using polarizing microscope LEICA DM4500P. The relations of microstructure morphology with intensity and acoustic emission of granite have been carried on the preliminary discussion by combined with results of axial compression and acoustic emission detection test at different high temperatures. Research results show that the changes of mesostructure and morphology of granite under high temperature are mainly embodied in crack initiation and different propagation speeds at different temperatures. With the increase of temperature, the more internal crack formation and internal damage for granite, and the more frequent acoustic emission activity of granite under uniaxial compression. The mechanical properties and acoustic emission characteristics of granite with the formation of internal crack network of granite has a corresponding relationship. The peak stress curve and ringing cumulative number curve of granite have stable trend when crack expansion is slow. While crack network expansion is rapid, the peak stress curve and ringing the cumulative number curve of granite will appear inflection point and cause mutation. It is expected to infer the change reason of physical and mechanical characteristic parameters for rock in the thermal cracking procedure through observation changes of rock internal structure under heating states.

During the four piles static load field test, soil pressure boxes are arranged. With the testing of stress on the top of C-piles namely the rigid piles, the top of M-piles namely the semirigid piles, and soil between piles, the piles-soil stress ratio and load sharing ratio are calculated. Then, the stress state of piles and soil during the CM-piles composite foundation static load test is analyzed. Besides, combining the large plate test P-S curve after setting different thicknesses of cushion layer with the single C-pile static load test, the failure mode and cushion effect are analyzed. The test results are as follows. First, when the CM-piles composite foundation is working, C-pile top stress concentration phenomenon is obvious as the pile-soil stress ratio of C-pile are more than 10, while that of M-pile are less than 10. As the test loading, piles-soil stress ratio increasing gradually, increasing rate of pile-soil stress ratio of C-pile is larger than that of M-pile. Second, under the conditions of design load of CM-piles composite foundation, load sharing ratio among C-piles, M-piles and soil is around 6:3:1. Considering M-piles and soil between piles as a whole, namely, after the foundation treatment, it is more reasonable for the soil between piles compared to C-piles to have a pile-soil load sharing ratio of 6:4. Third, as the thickness of cushion layer increases, the CM-piles composite foundation settlement values increase. While the quality of C-pile is better and cushion failure mode is pierced by C-pile, the material and thickness of cushion layer should be properly selected.

In this study, cement and geopolymer are added to lightweight soil as binders. For the purpose of comparison, unconfined compressive strength test is conducted to evaluate the effects of wetting-drying cycles and sodium sulfate soaking on the strength properties of lightweight cement stabilized clay(LCSC) and lightweight geopolymer stabilized clays(LGSC). The change of unconfined compressive strength and mass loss with wetting-drying cycles and sodium sulfate soaking are discussed. The results show that the values of unconfined compressive strength of LGSC are 2 times that of LCSC under the standard curing condition. Upon wetting-drying cycles, the unconfined compressive strength of LGSC decreases more rapidly than that of LCSC. Compared with LCSC, the wetting-drying durability of LGSC is weaker. After sulfate solution soaking for 120 days, unconfined compressive strength of LGSC declines slightly. However the surface of LCSC cracks. Compared with LCSC, the wetting-drying durability of LGSC is stronger.

According to the geological conditions of intermediate weathered sandstone ground, static load test of single anchor foundations and group anchor foundations were carried out. Based on the test results, the typical failure modes and the ultimate uplift bearing capacity of foundations are analyzed. Internal force distribution and effective anchorage depth are investigated through strain measurements. The results show that the rock anchor foundation can meet the bearing requirements of the upper structure for transmission line engineering. Rock anchor foundation benefits economically and socially when applied to intermediate weathered sandstone ground. When the anchorage depth of anchor is less than effective anchorage depth, the uplift bearing capacity of foundations can be improved by increasing anchorage depth and rock-socket depth. Horizontal load can affect the uplift stability of group anchors foundation adversely although it is not a control factor of foundation failure.

To improve the strength and resistance to desiccation cracking of clayey soils in engineering practice, fiber-reinforced soils are made by mixing polypropylene fibers together with soils. The polypropylene fibers and kaolin are mixed together and statically compacted into fiber-reinforced kaolin in the laboratory. Then the influences of fiber incorporation on the consolidation and compression characteristics of the fiber-reinforced soil are studied by one-dimensional compression experiments. Test results indicate that both the coefficient of consolidation and compression modulus first increases and then decreases with the increase of the fiber content, under constant dry density and fiber length. When the fiber content is 0.2%, the coefficient of consolidation will reach a peak value. When the fiber content is 0.1%-0.15%, the compression modulus will arrive at a peak value. The coefficient of consolidation first decreases and then increases with the increase of the fiber length under constant dry density and fiber content. When the fiber length is 10 mm, a minimum value of coefficient of consolidation will be achieved. When the vertical pressure is relatively high (≥400 kPa), the compression modulus of the fiber-reinforced kaolin will decrease with the increase of the fiber length. Furthermore, generally the compression index of the fiber-reinforced kaolin increases with the increase of the fiber content. However, a minimum value of the compression index is found when the fiber content is 0.15%-0.2%, or the fiber length is 10 mm.

Natural soils are usually under unsaturated state, especially soils at shallow depths below ground. The small-strain shear modulus of unsaturated soil is an important parameter for predicting ground deformation and dynamic responses of earth structures. Bender element tests were carried out on unsaturated compacted silt triaxial specimens to investigate the effects of suction and wetting-drying on small-strain shear modulus. Test results show that the small-strain shear modulus anisotropy of unsaturated compacted silt is negligible. The small-strain shear moduli G0(vh), G0(hh) and G0(hv) all increase with suction nonlinearly. For specimens under same suction but along different wetting-drying paths, their saturation degrees are different. Small-strain shear moduli decrease with increase of saturation degree. These observations are mainly due to the changes of average skeleton stress and meniscus water effect. Semi-empirical equation for describing small-strain shear modulus of unsaturated soil is modified based on test results; the effects of suction and saturation degree are both considered.

Tip post grouted super-long bored piles are generally used in large-scale bridge and super high-rise building projects. However, the reasonable method for calculating the pile shaft ultimate friction is still limited. According to back analysis of some measured data, the lateral soil pressures of the pile shaft are larger than the earth pressures at rest when the method is adopted. The influence factors of the lateral soil pressures of pile shaft are discussed. Then, the traditional method is improved. A method for determining the lateral soil pressures of pile shaft is established. Moreover, a formula for calculating the lateral earth pressure coefficients of the pile shaft is also given. At last, field test piles of two project cases, Shanghai World Expo Underground Substation project and Shanghai Center Tower project, are calculated by the improved method. Through comparing with the measured results, the recommended values of the site investigation and the specification values, the calculation results are more consistent with the measured results. This shows that the calculation method of pile shaft ultimate friction of the tip post grouted super-long bored pile is feasible and rational.

In order to study the cyclic strength of natural Shanghai clay under cyclic loading, especially the degradation behavior of dynamic shear modulus, after sample’s isotropic consolidation, a series of undrained stress-controlled cyclic triaxial tests are conducted on natural Shanghai clay with different cyclic stress ratios (defined as , in which is the cyclic deviator stress and is the cell pressure) and different loading frequencies. The effect of dynamic stress ratio and loading frequency are investigated. According to the test results, for layer No.4 of Shanghai clays, the soil sample damage occurred until the dynamic stress ratio is 0.2. The relationship between shear modulus and strain is not affected by dynamic stress ratio and loading frequency; and shear modulus decay falling mainly in axial strain 0?1% range. For the dynamic shear modulus degradation index , it is smaller with the smaller frequency and with the larger dynamic stress ratio under the same number of cycles. Through the analysis of the effect of dynamic stress ratio and frequency on dynamic shear modulus, a mathematical model for shear modulus degradation is presented. The tests data and the model calculation are good agreement.

A novel ground treatment technique, microbial-induced calcite precipitation(MICP), has recently emerged in geotechnical engineering, which utilizes the calcite precipitation to bind loose particles together; and therefore, the mechanical properties of sand can be enhanced. The objective of this study is to investigate the effect of chemical treatment on the strength of bio-cemented sand. Sporosarcina pasteurii is used to induce calcite precipitation, and all the specimens are prepared by injecting a single concentration or multiple different concentrations of chemical solutions. In this study, 0.5 and 1.0 mol urea-calcium chloride solutions are used for the former chemical treatment, while for the latter one, 0.5 mol urea-calcium chloride solution is firstly injected; and subsequently, 1.0 mol urea-calcium chloride solution is utilized. Based on the experiment, the strength, failure modes and calcite content are analyzed. From the experimental results, it can be found that chemical treatment has significant influence on the unconfined compressive strength of bio-cemented sand soil, but no pronounced effect can be seen in the failure modes and calcite content. Injecting multiple different concentrations of chemical solutions can be beneficial to obtain relative high compressive strength by using less treatment times. Finally, the mechanism analysis corresponding to the effect of chemical treatment on the strength of bio-cemented soil is further conducted.

Based on grouting simulation experiments and numerical analyses, the formulations are established for predicting grouting amount, grout diffusion radius and compressive strength of stone body in the gravel soil; the proposed formulations are validated by indoor grouting experiments. Experimental results show that there are about 10%, 5% and 10% differences respectively between the theoretical values of grouting amount, grout diffusion radius and compressive strength of stone body and their actual measurement values; but these differences valuse are admitted. So, the formulation can be used to predict grouting amount, grout diffusion radius and compressive strength of stone body in actual grouting engineering of gravel soil. Therefore, the research results may not only provide theoretical supports for actual grouting engineering of gravel soil, but also provide technical references for disaster prevention and mitigation of landslide and debris flow induced in the gravel soil.

Geostatistics is one of the most powerful techniques for modeling the inherent spatial variability of soil properties. In geostatistics, the semivariogram is utilized to describe the continuous variation characteristics and then the Kriging interpolation is applied to provide the best linear unbiased estimates of soil properties. Geostatistics is used to model the inherent spatial variability of piezocone penetration test(CPTU) cone tip resistance qt in a testing section of Suqian-Xinyi Expressway for site characterization. First of all, theoretical background of the geostatistics involving constructing experimental semivariogram, theoretical semivariogram fit and Kriging prediction is reviewed briefly. Least square regression analysis is performed to remove the linear trend function within the qt data to generate the weak stationary residuals. It is found that exponential theoretical semivariogram can accurately describe the correlation structure and variability of the residuals at this site. Significant anisotropy is observed in the correlation structure of qt residuals. Results show that the vertical range is about 1.2 m while the horizontal range is 4.05 m for qt at this site. The distribution map of qt data at the target site is obtained using ordinary Kriging interpolation and compared with in-situ measurement data. It is concluded that the Kriging estimates are comparable to the measurements at this site. However, the reliability of estimates may decrease at the locations corresponding to peak values and those far away from observations. This research can improve the reliability of geotechnical design in practice since the inherent spatial variability of qt data is accurately evaluated.

The improved slope mass rating method(SMR) is proposed, through integrating the gray system theory with traditional SMR method. The quantitative indexes value of traditional rock mass classification methods was very discrete, resulting in the step change in classification. The problems of small samples and discrete issues are solved by using features of gray system theory. Firstly, the evaluation indexes of traditional rock mass quality classification are classified. Also, the weights of indexes are determined; and the triangle whiten function for evaluation indexes is built. Furthermore, the rock mass quality classification of slopes is valued based on the maximum degree. Finally, combining with a slope case study and comparing general engineering rock mass classification methods(RMR and SMR), the result judged by improved SMR method can agree well with engineering facts; and it expresses a high and strong quality grade stability. For rock mass quality classification in slope engineering, this study shows that this method is scientific and accurate.

In a bender element test, the most key problem is associated with the determination of travel time of shear waves. The objective and accurate measurement of shear wave velocities remains a challenge. A new side-mounted bender element testing system in which each set of bender elements consists of one transmitter and two receivers has been developed. Bender element tests are carried out on Shanghai soft clay by using the newly-developed system. Three different methods, i.e., first arrive time method, peak-peak method and cross-correlation method are used to calculate the shear wave velocities. The test results show that the first arrive time method is the most subjective method and the shear wave velocities are highly dependent on input frequency. Picking the second peaks of received signals gives rise to consistent shear wave velocities. Cross-correlating two received signals generates most objective and consistent shear wave velocities in the frequency range of 20-30 kHz provided the similarity requirement is fulfilled.

There are about 4 methods, i.e. scalping method, equivalent substitution method, similar gradation method and hybrid method, to model the site gradation of soil materials according to the code. And 15 modeling gradations of coarse-grained materials from an engineering site have been modeled by using these gradation scale methods; by the same token, their equivalent particle diameters are 60, 40, 20 mm. The maximum dry density tests also have been conducted to these modeling gradations in the same vibration energy; and the distributing law of maximum dry density value can be concluded. In conclusion, the maximum dry density value goes together with the nonuniform coefficient, curvature coefficient, maximum particle diameter and lower groups (≤5 mm), etc. And a corrected gradation parameter has been put forward to normalize the relationship between maximum dry density and relative parameters of gradation. To justify the rationality of normalized formula, the site coarse-grained materials compaction tests have been conducted with the sample diameter of 1 m.

The large-scale triaxial apparatus is indispensable in the experimental application of soil materials with gravel for which have much larger grains in high core rockfill dams. Also the great percentage of clay has increased the level of challenge in the experimental work because of low permeability coefficient, difficulties of saturated and consolidation, long test period and so on for large scale specimens. To solve these practical problems effectively, sand cores has been reserved to accelerate saturation and consolidation in this paper’s tests. Analyses have been conducted on the creep strain and the creep model parameters of clay material with gravel tested by large-scale rheological triaxial apparatus. The results indicate that the rational power function relationship between creep strain and load time could exactly be described by the creep model of Yangtze River Scientific Research Institute. It is also revealed that the clay materials with gravel have smaller creep strain and lower model parameter indexes than the same materials without gravel. Consequently, mixing appropriate amount of gravel into clay soil could improve the engineering characteristics. The creep indexes of unsaturated materials are obviously lower than them of saturated materials in conditions of clay or clay with gravels. This fully shows that the sand cores reserved to accelerate draining play an very apparent role in the test process.

Foundation design of high-rise buildings in karst region is always the difficult point of ground treatment in a construction project. The karst foundation has the properties that many soil caves and caverns are found; rock surface is greatly undulating; ground water there is unpredictable and so on. These complex conditions in karst area to some extent make the foundation design of high-rise buildings extremely challenged. In this paper, a foundation design of high-rise buildings on cobbly soil karst ground is introduced in which the abundant and reliable data were obtained through the loading test of undisturbed soil, ramming-reamed pile composite foundation, punching pile composite foundation and other in-situ tests. According to the scientific analysis of test results, thickness of covering layer and development of karst, the scheme of ground treatment with multiple types of pile below raft foundation is adopted at last. This scheme can not only satisfy the requests of the load and the settlement, but also consider the risks of the cave collapse and the differential settlement, which is even more economical. And the calculated settlement was made to be compared with actual observations to illustrate the rationality of the chosen scheme. It will be a good reference for handling ground treatment of high-rise buildings in complex karst region.

A coupled nonlinearly three-dimensional track-embankment-foundation numerical model for double line high-speed railway with a design speed of 350 km/h was established based on precisely modeling and multi-scale method. The material nonlinearities of foundation soil and embankment backfill were incorporated in the model. The infinite foundation was simulated using three-dimensional viscoelastic static-dynamic unified artificial boundaries. The dynamic reinforced concrete base-upper layer of formation interaction was modeled using dynamic algorithm. Considering the influence of static stress state prior to activation of moving loads on subsequent dynamic analysis, the generation of initial stress state of foundation and construction of embankment and track system were modeled based on multi-scale computation and element birth and death method; and then the movement of loads was simulated. The loads corresponding to the wheel set locations of CRH EMU train with 8 carriages were applied to the surface of the top layer element of rail. The attenuations of vibration acceleration spectra due to moving loads in track-embankment- foundation were summarized based on the calculated results.

The complexity of slope engineering is not only reflected in the variability of geotechnical parameters, but also in the implicit and nonanalytic properties of the performance function. Therefore, the direct calculation of slope stability reliability under implicit performance function that based on Janbu method is researched. First, the slope limit equilibrium model is called to obtain basic geotechnical parameters, and then the initial samples that affect slope stability is acquired through the Latin hypercube sampling. Secondly, using the Kriging anisotropic association mapping method dependence mapping method, the slope function value is expressed as a function of the random process. Then combined with the active learning method, and based on the searching rules to adjust the training samples, the slope performance functions denoted by the random process that meet the accuracy of the actual project is determined through iterative cycle. Finally, the random process function is called to work out the failure probability of slopes through the checking point method (JC method). The case study shows that the accuracy of the proposed method is equivalent to that of the Monte Carlo simulation; but the calculation process is simple, highly efficient, and more practicable.

In order to define the status of calibration tank model test in the field of laboratory tests simulating in-situ technology research, the paper summarizes the world's existing large calibration tank according to extensive literatures at home and abroad that related to calibration tank model test report. Besides, the relevant research content of two most widely used calibration tanks at home and abroad are summarized after analyzing the advantages and shortcomings as well as the improvement process of each calibration tank. Meanwhile, the effect of related parameters and influencing factors is discussed; and the application results of calibration tank test are summarized. The analytical results show that the calibration tank model test research has a good application prospect on the applied research of in situ testing technology; and it combines the merits of boundary conditions control, the stress state control and soil sample control in one. Based on calibration tank test data, soil parameters calculation and checking are performed; and the empirical formula of different soil layers is analyzed compared with in-situ test. It provides the basis for evaluation and analysis of the in-situ test. However, the related research of calibration tank test still need to further strengthen and expand, i.e. the present main research is about sandy soil, less on the study on the cohesive soil and special soil. While in-situ test may strengthen the study on the parameters such as friction and pore water pressure.

Dynamic shear modulus and damping ratio are two important parameters for seismic safety assessment of engineering site and earthquake response analysis of foundation. In order to evaluate the dynamics of seabed sediment of the selected area, the 10.3-84.2 m depth range of mucky silty clay, silt and fine sand are analyzed by using resonant column tests. The double logarithmic model has been built for the increasing trend of maximum shear modulus with overburden pressure. The research suggests that the existing standard values of shear modulus ratio and damping ratio are not suitable for seabed sediment, even the previous research results are just applied to a certain degree of strain range and natural stress state. Martin-Davidenkov model and the empirical relationship between damping ratio and shear strain has been used to build the variation law of shear modulus ratio and damping ratio with shear strain; and the dynamic shear modulus ratio and damping ratio of 5×10-6-10-3 strain range are used as recommended values. The study results may provide technical reference for marine engineering design, construction and seismic analysis.

This paper divides the wall deformation into two parts, the parabolic flexible part and the trapezoidal rigid part. By solving the two-dimensional partial differential equations of plane strain, the basic solution of parabolic boundary problem is obtained. The settlement curves are given to show the characteristic of ground settlement. The theoretical solution is used to analyze the problem in practical engineering. The applicability of this theoretical solution is analyzed by qualitative comparing with the normalized settlement curves of four foundation pit excavation cases. The parabolic deformation of wall will cause concave-type settlement profile, in which maximum surface settlement occurs at a distance away from the wall back. The theoretical prediction indicates that the ground settlement is independent of the soil elastic properties; and the location of largest surface settlement is close to the measured data, as well as the pattern of soil settlement, which indicates that the theoretical solution is reasonable.

The shape changes of the minerals on the surface reflect the deformation/failure process of the rock material. In the current study, after analyzing the textual features of various mineral regions on a granite specimen surface, the video images photographed during the laboratory uniaxial compression test and the grayscale threshold segmentation were used to investigate the distributions of the minerals in each frame. The shape parameters were extracted from the frame to depict the configuration features of various compositions at any time during the deformations of the rock. The relations between the changes in shape parameters of various compositions and the propagation process of cracks were further explored. It is shown that during the deformation of the granite under the external load, the magnitude sequence of the circularity is feldspar, biotite, and quartz; that of the inscribed circle radius is biotite, feldspar, and quartz; and that of the variance index is feldspar, biotite, and quartz; the feldspar region beard the most part of the axial load; and the shape changes of the feldspar regions are much depended on the actual locations; during the failure of the specimen; the magnitude sequences of the areas are feldspar, quartz, and biotite where new cracks generated; and the most of the cracks propagated on the feldspar and quartz regions if the cracks developed quickly.

The Dagangshan hydropower station’s right bank slope is located on the fault block cut by Dadu River and Moxi fractures; over there, the high intensity earthquake happened frequently; the rock mass is strongly unloaded, with poor stability structure and intensively cracks. The importance of cable support in slope excavation process has been shown in existing researches; while the design of shear hole support has been studied comprehensively by a number of scholars. Based on the existing cable supporting and unloading theory, this paper evaluates, the effect of secondary support of designing shear hole and its seismic performance simulated by pseudo-static method. And through the displacement response of key points in different elevations, the necessity of the shear hole has been demonstrated systematically. An evident cracking area has been found between cable support segment and shear hole support segment by studying the change of stress. Finally, some advises for later project monitoring are put forward.

In the trailing suction hopper dredging, mechanical cutting methods are widely used to loosen the hard sedimented soil on the seabed. It is of great importance to find some effective techniques for higher soil loosening efficiency, so it is a key issue to study the mechanism of soil cutting resistance. A new experimental setup with monitoring system was developed in the tests to represent whole cutting process of the bed soil by a prototype draghead tooth. The experiments were conducted to investigate the large deformation / failure process and the pore water pressure response at the tooth-soil interface during the draghead tooth cutting of the fine sandy soil from Huanghua port, close to coast of the Bohai Sea in North China. The experimental results show that the intact soil ahead of the rake teeth was squeezed, cut and subjected to shear deformation. In the much short time of soil cutting process, the effective stress and deformation of the soil should be considered under undrained condition; and the pore water pressure decreased significantly due to the effect of soil shear dilation. The soil cutting resistance of the draghead tooth came from the increased effective soil stress which resulted from the significant decrease of the pore water pressure in the soil.

Three-dimensional finite difference model of cross tunnels is established by FLAC3D to compute deformation and stress of soft soil under metro train cyclic loading which is modeled by artificial numerical exciting force. Modified dynamic deviatoric stress model for long-term settlement of soft soil combined with layer-wise summation method are adopted to calculate tunnel settlement and predict long-term settlement of cross tunnels. Long term settlement in three train-running cases is studied. Case 1, one train traveled through tunnel #1, case 2, one train traveled through tunnel #2, case 3, two trains traveled through tunnel #1 and tunnel #2 separately at the same time. Influences of train speed, stiffness and thickness of tunnel lining on long-term settlement of cross tunnels are studied. The results show that the settlement induced by train loading mainly distributes within 20 m from the central axis of tunnels. Sum of settlement in case 1 and case 2 is less than settlement in case 3; and tunnel settlement decreases with the increasing of train speed, stiffness and thickness of tunnel lining; while the influence of thickness of tunnel lining is more than stiffness of the lining.

In order to figure out the difference of reinforcement effect between high-density polyethylene(HDPE) geogrids and polyethylene terephthalate(PET) geogrids in fill embankment with wrapped face, based on tensile tests of two geogrids, this paper analyzes the force-deflection characteristics of two different geogrids-reinforced embankment by means of FLAC3D and some in-situ tested data. The results show that the mechanical properties of geogrids have an obvious influence on the displacement of reinforced embankment; and the influence is related to its overlying earth pressure. In the middle and lower part of the embankment, because of the higher earth pressure value, there exists a relatively huge variance in strain value of HDPE geogrids along its length, and the variance of strain value of PET geogrids is within a narrow range; in the upper part of the embankment, the less earth pressure value leads to the lower strain value of geogrids and there is no various strain difference between the two types of geogrids. PET geogrids are better than HDPE geogrids in the effect of controlling displacement of the reinforced embankment. The distribution of vertical and horizontal earth pressures has less difference between PET and HDPE reinforced embankment.

The excess pore water pressure, which imposes a negative role on the stability of excavation face, generated in sand due to the train vibration load of a running metro when a slurry shield cross under the metro. This paper presents an investigation on the effect of the train vibration load on the generation of excess pore water pressure in three categories of sand specimens through dynamic triaxial tests. It is concluded that the excess pore water pressure increases with the rise of amplitude of train vibration load; but the increase of excess pore water pressure is not significant when the amplitude of train vibration load is less than 10 kPa; and the influence of train vibration load on the excess pore water pressure is more significant when the excavation face pressure declined; moreover, the decrease of vertical pressure plays a bigger role in the growth of excess pore water pressure than that of horizontal pressure. The vibration load has the most significant influence on the excess pore water pressure in saturated loose fine sand. The excess pore water pressure could reduce the resultant pressure on filter cake at least 33%.

Composite soil nailing wall composed by micro-pile and waterproof curtain is a frequently used type of supporting structure in foundation pit engineering. But the collocation of micro-pile and waterproof curtain in the design and construction of supporting structure is random. And the influence of different locations of micro-pile, like in front of or behind curtain, on mechanical behaviors of supporting structure is generally neglected. This article obtains deformation and mechanical characteristics, such as the displacement of supporting structure, axial force of soil nailing, in those two collocations through the contrastive analysis of the field test and numerical simulation based on a certain foundation pit project in Jinan. The analysis results show that the overall trend of deformation and internal force of supporting structure isn’t affected by different location of micro pile. And the difference caused by the location of micro-pile without top load is small; but the deformation of supporting structure is smaller and the stress of soil nail is more reasonable when micro pile is behind curtain under top load. And it can be suggested to preferentially adopt in practical engineering.

Due to many influential factors of the deformation of deep foundation pit, a unified summary research of 37 deep foundation pits in Zhejiang province(Hangzhou mostly) is proposed according to the different conditions of excavation depth. This paper analyzes the characteristics of inclinometer curve of deep foundation pits and the surrounding settlement curve under the background of Zhejiang soft soil; the relationship between maximum lateral displacement and excavation depth of foundation pits is obtained. Experimental results show that: maximum lateral displacement points of Zhejiang soft soil deep foundation pits are between 4m above the excavation surface and 7 m below the excavation surface; maximum settlement in parabolic settlement curves generally occurs at a distance of 0.5 times the excavation depth; maximum settlement and maximum lateral displacement increases linearly with the depth of excavation; the relationship between the maximum lateral displacement and maximum subsidence is mainly influenced by the soil quality. Based on the further statistics and the characteristics of lateral displacement curve, this paper proposes a method for forecasting lateral displacement curve of foundation pit which is in well agreement with the measured value.

Based on the engineering background of a tall building at the center of Xi’an, the project uses the technology of post grouting bored pile foundation treatment. In construction, the vertical compressive static load with and without bored grouting pile; and pile body internal force are tested. This paper calculated the post-grouting pile's ultimate bearing capacity of pile foundation based on five methods, including the building pile foundation technical specification, lateral resistance and end resistance coefficient method, the ultimate bearing capacity enhancement coefficient method and improvement of the bearing capacity of pile. The results show that the ultimate bearing capacity of pile foundation increased by 24% with the methods of post-grouting pile; lateral resistance and end resistance coefficient method, and the ultimate bearing capacity enhancement coefficient method is closed to field measurement. Building pile foundation technical specification and the method of only considering the improvement of pile’s bearing capacity are largely different from the measured results, and the calculated value is conservative.

The redundancy theory is introduced into the double-row steel sheet piles cofferdam design. The preliminary framework of the definition and design of double-row steel sheet piles cofferdam supporting system redundancy are proposed. Taking the rod system redundancy analysis for example, alternate path method is adopted to quantitatively analyze for redundancy of the rod system. The results show that the redundancy parameters of lower rods are significantly lower than the upper rods; their failure can significantly reduce the stiffness, strength and stability of cofferdam supporting system; their failure even leads to the destruction of the whole cofferdam to collapse; it is consistent with the engineering practice. The above analysis verified the applicability and feasibility of the redundancy theory for double-row steel sheet piles cofferdam engineering.

Based on the permeability and strength theory of unsaturated soil, this study used two expressway embankments consisting of soil with significantly different permeabilities as examples to investigate the variations in pore water pressure and stability coefficient of the embankments during different rainfalls. The results show: (1) The rainfall infiltrates better in lower parts than upper parts of the embankment formed with high permeability soils; however, it infiltrates almost equably in the surface of embankment formed with less permeability soils. (2) The minimum stability coefficient of the embankment slope with high permeability occurred normally after rainfall about 0.5-3 days during the short and high intense rainfall process, or less intense and longtime rainfall process. And the minimum stability coefficient of embankment with less permeability lag behind rainfall more obvious, normally lagging 7-15 days behind rainfall. (3) When the total rainfall is constant, the minimum stability coefficient of the embankment slope with high permeability decrease as rainfall intensity increase. The embankments with low permeability are influenced by both rainfall intensity and duration.

The connection effectiveness between cutoff wall and composite geomembrane of cofferdam, both of which are usually applied to the cofferdam, plays an important role in seepage control. Based on the site investigation of stage II cofferdam of Three Gorges Project, through the stress analysis of geomembrane in seepage control and direct shear tests on interface characteristics between composite geomembrane and gravel, the interaction between geomembrane and gravel is studied. The condition to prevent the geomembrane from being broken is proposed. Three centrifuge tests are performed to reveal the mechanism of the connecting form of cutoff wall and composite geomembrane by measuring the displacements of the cofferdam fillings and cutoff wall and the strain of the composite membrane. The results show that the friction between the composite geomembrane and the cofferdam fillings is so large that the expansion joint reservation cannot work under certain overlying load. Two main influencing factors include the settlement of the weathered sand foundation and the lateral displacement of cutoff wall, both of which play a decisive function in the fracture of the composite geomembrane. Furthermore, an improved method of the connecting form, which made the composite geomembrane not be tensioned, is proposed and validated by centrifuge tests. The improved method provides a reliable evidence for the design and construction of cofferdams.

The river-crossing project at Shanghai West Yangtze River Road is dual six-lane scale adopting large slurry shield of which the outer diameter is 15.43 m for the tunneling construction. Because the distance between the large diameter tunnel structures and pile-foundation is about 1 m, it is not in accordance with the relevant regulations related to the protection of engineering. So, it is necessary to study the influence of construction of side-crossing shield tunnel on adjacent pile foundation and the reinforcement effect of protection measures. In this paper, numerical simulation and field monitoring are employed to study the construction effect based on the ground loss, metro jet system(MJS) reinforcement of piles and different scopes of consolidation are taken into account. A safe and economical protect measure is presented by analyzing the deformation and bearing capacity of pile foundation. Finally, it is showt that the field monitoring data agree well with the numerical results. Therefore, the accuracy and rationality of the numerical simulation method is validated.

As one of the main types of subgrade, the slope instability of high-fill compacted loess embankment occurs frequently due to the increase of water content caused by rainfall. The effect of water content on density, dry density and shear strength of loess sampling from the embankment-fill of Shanyin-Pinglu expressway, is investigated by a series of laboratory soil tests mainly including compaction test and triaxial compression test. The results show that the water content has great influence on the density and dry density of loess fill. In addition, with the variation of water content, the cohesion increases while the internal friction angle decreases. According to the tests results, the numerical model is established using FLAC3D and the stability of reinforced and unreinforced embankment with different water contents based on strength reduction method is studied. The results show that the safety factor of embankment decreases with the increase of water content of compacted loess which can lead to the stability of embankment decreases. Moreover, the safety factor of embankment increases as the geogrid layers increase. The integrity of embankment is well enhanced with the inclusion of geogrid, thus the possibility of slope instability is reduced.

This paper presents the estimation and measured data analysis of the jacking force of a 3D curved pipe with 3.8 meter external diameter and 413 meter long distance. The jacking force consists of the face load and friction resistance; and it is influenced by many factors. The most widely used estimation methods of the jacking force include Chinese cord method; Japanese method and German method; but they all have specific application conditions, which make them have limitations for engineering application; especially when the friction resistance factors are offered by a wide interval. The jacking force are calculated by the above estimation methods in a 3D curved, 413 meter long distance and 3.8 meter external diameter jacking project, 3 intermediate jacking stations are set according to the calculation results. According to the site measuring data during the construction procedure, the composition of the jacking load and its relationship with the jacking distances and the curve radius are analyzed; and the site measured values of frictional coefficient are offer in table. Base on the analysis results, additional frictional coefficient of axis curve pipe jacking is truly exist, and there are deviations between the cord recommended values and the site measured values. but according to this project, the cord recommended values could meet the demands of scheme design in clay or in silt clay. At the end of this paper, suggestions of the jacking force estimation and intermediate jacking station arrangement are proposed, which provide references for similar construction.

This paper presents a case history of an investigation into the responses of the surrounding ground to the deep excavation of a metro station of Metro line 9 in the karst strata of Guangzhou, China. The metro station is 259.7 m long by 18.7 m wide by 15.81 m deep. The construction site mainly consists of two typical strata of the karst strata and sand layer. The karst strata, with poor mechanical properties and low self-stability, is a geological formation shaped by the dissolution of the carbon limestone. The thickness of sand layer is 0 15 m, which is of high hydraulic conductivity. During the field test, lateral deflections of the diaphragm wall and ground surface settlements were monitored. The test results show that the maximum lateral displacement of diaphragm wall is 12 mm and the maximum ground surface settlement is 10.1 mm. The monitoring results indicate that during construction there is minimal impact on the surroundings. Such field monitoring may allow for the formation of a database to guide the future engineering practices.

The fall cone tests are performed to determine the consistency limits of Guilin silty clay under different pore fluids; and scanning electron microscope(SEM) analytic technique is used to revel the influence of the chemo-mechanical coupling interaction between water and soil under variable water-chemistry conditions on structure properties of silty clay at a micro scale. The results show that the consistency limits of silty clay would be decreased with the increase of concentration of pore fluids. Besides, it has been found that the atterberg limit decrease as the radius of cation decrease and cation valence increase, especially it’s dominated by cation valence at the same concentration. These features of the sility clay behavior can be attributed to the mechanisms of the electric diffuse double layers which would be decreased after the ion concentration and ion valence increased. What’s more, it can be seen that the flocculation among silty clay particles has been facilitated by the chemo-mechanical coupling interaction between water and soil, and it leads to the formation of granulosity and the pores between particles have been extended at a micro-level.

Environmental vibration induced by underground moving metro trains has aroused much attention of the society as more and more subway tunnels are constructed in saturated soft soils in the coastal area of China. Taking the Shanghai metro line 2 for example, response of saturated soft soil layers induced by subway train in the shield tunnel is analyzed by using cyclic mobility constitutive model and water-soil coupled method, including ground surface vibration acceleration and dynamic displacement, as well as the dynamic response of excess pore water pressure(EPWP). The acceleration level of ground surface is adopted to evaluate the intensity of ground surface vibration. Numerical results show that dynamic response of saturated soil is much smaller than that of dry soil, vibration on the ground surface also presents distinct differences in the horizontal direction and vertical direction. As for excess pore water pressure, it diminishes along vertical tunnel axial direction, whereas it increases first and then decreases in the vertical profile several meters away from tunnel center. The results can provide guidance for vibration mitigation design and settlement control measures for nearby structures.

The process of shielding changes the additional stress of the above existing tunnel which causes the deformation of the tunnel and has certain influence on the structural safety of the existing tunnel. The Mindlin solution can be used to calculate the additional stress along the central axis of the existing tunnel caused by the shield driving parameters such as the compressing pressure of the cutter-head q, friction of the shield skin f, synchronous grouting pressure p. The additional stress caused by soil loss can be calculated by the image method theory. Winkler foundation model can be used to calculate the deformation of the existing tunnel. According to the different crossing processes, the total deformation of existing tunnel can be calculated by combining the above four parts of deformation. Finally, comparing the theoretical results with the measured data of metro construction project in Hangzhou, the valid of the method is confirmed.

Hole check-up is conducted on the construction of drilling cast-in-place piles in a practical engineering of Shanghai. Firstly, the changing law of hole diameter over time and space is summarized by analyzing the data of hole diameter considering unloading effect. The diameter reduction and time have positive correlation, and the reduction range is decreased gradually over time, until the hole diameter is stable. Variable quantity of hole diameter is disparate in different soil layers. The smaller the cohesion c is and the bigger the internal friction angle φ is, the poorer the stability of hole wall will be and the larger the variable quantity of hole diameter is. Secondly, a scientific and reasonable fitting formula is applied to fit the change of hole diameter over time in different soil layers; it is shown that the formula is of high degree of fitting and can truthfully reflect the changing law of hole diameter. At last, based on the Kelvin model, a changing formula of hole diameter is deduced by utilizing elastic theories and combining the fitting formula to explain the case more exactly. And another formula which is concerned with the stability of hole wall is also deduced to explain the different stabilities of different soil layers more reasonably. Some conclusions from this paper are of great reference value in the construction of hole-forming in drilling cast-in-place piles in Shanghai area.

Anisotropy and inter-particle bonding have large effects on the mechanical response of natural sand, which should be considered in engineering practice. In order to study the combined effects of these two factors, an anisotropic pure sand sample with elliptical particles and with a horizontal principal orientation is prepared in a discrete element method (DEM) code NS2D to simulate natural gravitational deposited sand. After the sample being deposited in a gravity field, a new bond contact model calibrated from statics of bond thickness in experiments is installed at the contacts. Finally, biaxial tests are conducted on the anisotropic structured sand sample. The simulation results are compared with laboratory test results to validate the DEM modeling. Besides, the micro-mechanical responses are also studied. Test results show that strain softening and dilation occurred with shearing. The number of bond contacts decreases and the principal direction of bond contacts are vertical during the tests. The variations of bond breakage percent and bond breakage ratio are consistent with the macro stress-strain and volumetric responses. The bonds are primarily damaged in tensile-shear failure mode rather than compression-shear; the principal orientation of particle arrangement is horizontal and the particle percent in horizontal direction increases slightly throughout the tests.

The bearing capacity of rock-socketed pile is usually large, and it is difficult and expensive to obtained to the ultimate state on the field tests. The data obtained from the field tests are hard to reflect the bearing capacity and deformation of the rock-socketed pile. Based on the data of field tests at Wuhan Lvdi Center, ABAQUS finite element method is used to analyze the bearing capacity and deformation of the rock-socketed pile, which including the property of rock, depth-diameter ratio of the rock-socketed pile, and the upper soil covering. The numerical analysis shows that based on the reasonable constitute model, and the reasonable parameter value, the calculation results of FEM is consistent to the field measurements. The numerical analysis shows that, the above mentioned influencing factors are all important to the rock-socketed piles. The rock property and the depth-diameter ratio of socketed pile has little influence on the side friction of the upper soil covering. Bearing capacity of rock-socketed part is the main components of the bearing capacity of the whole pile; while to the pile with deep upper soil, the side friction of upper soil covering is a very important part of the bearing capacity of rock-socketed pile.

The drainage controlling ground treatment method(DCM) is a new ground treatment method which accelerates the pore pressure dissipation to accelerate settlement as fast as possible during construction period and decelerates ground post-construction settlement to control the post-construction settlement furthest by confining the excess pore pressure dissipation of the ground during the operation period. Finite element method technique like hexahedron pore fluid element and linear prefabricated vertical drainage element is adopted. The relationship between ground post-construction settlement and the depth of anti-seepage curtain and prefabricated vertical drainage is revealed. The regularities of the distribution of the ground post-construction settlement and the excess pore pressure with time and space are also revealed. Conclusion is drawn as follows: The DCM has the special effect of achieving 0 post-construction settlement with relative low engineering costs and relative short duration; high performance price ratio can be pursued by setting relative shallow anti-seepage curtain and relative deep prefabricated vertical drainage; decrease of the effective stress during operation caused by increase of the excess pore pressure in the sealed scope is the main reason of DCM decreasing the post-construction settlement.

Constant thickness cement-soil wall technique, namely trench crtting and re-mixing deep wall method(TRD) construction method, has been widely used in deep excavations in recent years. This paper presents a numerical analysis of a 0.7 m thick, 8 m wide, and 56.7 m deep trial wall panel constructed by the TRD method. The trail wall was constructed at the site of Shanghai International Financial Center Project. Based on the small strain constitutive model of soils, the computed results of lateral soil displacements and ground settlements are compared with monitoring results. It is observed that computed lateral soil displacements of 5 meters away from the wall agree fairly with monitoring data; while the one which is 1.4 meters away from the wall is a little smaller than the field data when the wall depth exceed 20 m. It can also found that the maximum ground settlements are near the wall and it decrease with the increase distance to the wall. Parametric analysis has been carried out to investigate the influence of wall depth on the lateral soil displacement and ground settlement. The results show that both of them are increased with wall depth.It can also be seen from the normalized curve of ground settlement that ,the maximum ground surface settlement induced by TRD method is approximately 0.05%H(H is the depth of wall panel)and the settlement influence distance is about 1.8H.

Particle shape has a significant effect on the microscopic and macroscopic mechanical behavior of granular assemblies. This paper focuses on effects of particle angularity on the mechanical behavior of granular materials and evolution of the contact force anisotropy during direct shear tests. To this end, a discrete polyhedral element model with a general contact force law for arbitrarily shaped bodies is carried out. Particle angularity is defined in terms of the sphericity and the number of vertexes of a polyhedron. Four groups of assemblies with different particle angularities consist of non-cohesive mono-sized reasonably symmetric polyhedral particles. Direct shear tests are simulated using a modified version of the open source DEM code YADE. The results show that: the granular assembly has increasing shear strength and dilatation as particle angularity increases; the effect of angularity on the shear strength and dilative behavior of assemblies is more significant as the vertical loading is larger; the anisotropy of normal contact force increases at the start, then decreasing to remain a relatively stable value during shearing; and a larger change of the anisotropy of normal contact force after shearing is corresponding to a larger angularity.

In this study, the Richards equation is employed for the simulation of saturated-unsaturated seepage field; and then the dam stability is analyzed and assessed based on the derived seepage field and the shear strength formulation of unsaturated soil. Numerical results show that the safety factor of dam appears to increase mildly followed by a rapid decrease during the rapid drawdown process of water level. According to the analysis and visualization of plastic zones and displacement fields, it is found that at the early stage of water level drawdown, the left dam slope shall be more dangerous and collapse firstly before the right dam slope; while the water level drawdown exceeds a certain level, the right dam slope shall be more dangerous due to its rapid decrease. One limitation is that only the lowest envelope of multiple safely factor curves can be achieved if of shear strength finite element method is employed for the stability analysis of slope with multiple slope faces. Core wall plays a water-blocking and seepage-proofing role; and it has a damping effect of water level drawdown.

Regarding the new technique of thermal drainage consolidation method, the finite element model of thermal drainage consolidation method for vertical drain foundation is developed through secondary development on the base of COMSOL. Multiphysics software in which the heat transfer process of U-shaped heat transfer tube in the vertical drains is simulated with the theory of non-isothermal conduit flow, and the effect of temperature on permeability of disturbed and undisturbed zone of the vertical drains is considered. Then, taking the prototype test of thermal drainage and consolidation of soft foundation treatment as an example, the consolidation degree of soft soil foundation is analyzed mainly on the condition of coupling, partial coupling and non-coupling model. It is shown that the rate of consolidation in the partial coupling model decreases in comparison with the non-coupling model used in the traditional drainage consolidation method, because the extra pore pressure induced by the temperature delays the development of consolidation of soil. In case of coupling model, the rate of consolidation is accelerated and consolidation period is shortened because the temperature effectively improves the permeability of soil in vertical drain smear zone, although the extra pore pressure can also be induced by the temperature. The result of computation is in agreement with the test results.

This paper describes an investigation of the reverse shear behavior of granular soil with fines by using the discrete element method(DEM) simulations of biaxial shear tests. The fundamental mechanisms underlying the so-called reverse behavior are scrutinized from both macroscopic and microscopic perspectives. The numerical simulation results show that the promotion of liquefaction resistance with increasing confining pressure tests mainly on the fact that as the confining pressure increases, both fine and coarse grains are to join the force chains more effectively, increasing the effective contacts between particles and thus enhancing the packing density of soil specimen as well as the stiffness of soil skeleton. The migration of fine particles in the soil skeleton plays a considerably important role in the liquefaction of granular soil with fines. It is found that during shear fine particles will be continuously dislodged into voids; and some coarse particles will also be removed from the soil skeleton due to the loss of the supporting effect from fine particles until the soil specimen is completely liquefied. In addition, fine particles are found to be mainly in weak force chains; while coarse particles are generally in strong force chains, and this has made fine particle more easily migrate in the soil skeleton as compared with coarse particles.

The coefficient of earth pressure at rest of granular soils is revisited by discrete element method (DEM) simulation. The effects of confining pressure, soil density and over-consolidation ratio(OCR) on the are systematically investigated. The coefficient of earth pressure at rest defined in the conventional form and in the incremental form are compared; and the effectiveness of Jaky’s equation and Mayne and Kulhawy’s equation in predicting is examined. The results show that the K0 and generally approach their “true” (or constant) values when the applied vertical stress is 6-10 times and 4 times of the initial isotropic stress. Meanwhile, the value remarkably decreases as void ratio decreases. The OCR has a significant effect on the K0 value and the K0 value is quite different in loading and unloading stages for the same OCR value. Better prediction is obtained by Jaky’s equation and Mayne and Kulhway’s equation if peak friction angle is used, although the prediction may be quite different from the measurement.

The multilayered soil slopes are very common in geotechnical practice. Not only there exists inherent spatial variation for soil properties, but also there shows obvious multilayered distribution characteristics within the natural soil profile. However, few attempts have been made to study the reliability of multilayered soil slope stability in spatially variable soils. This paper proposes a Monte-Carlo simulation (MCS) based slope system reliability analysis approach using multiple response surfaces. The flow chart for the proposed approach is presented. The reliability of a multilayered soil slope system considering spatial variability of soil properties is systematically investigated using the proposed approach. The results indicate that the proposed approach properly evaluates the slope system reliability at small probability levels (i.e., pf,s < 0.001) considering spatial variability of soil properties and achieves high computational efficiency in parametric sensitivity analysis.

Pile foundation driveability analysis is very important for pile design. In actual projects, precise pile driveability analyses would prevent the pile from being cut off or damaged when the pile couldn’t drive into the given depth, and could also keep pile bearing capacity not less than design capacity when penetration depth is deeper than the design depth. In order to analyze the pile foundation driveability accurately, this paper studies the sensitive factors which could affect pile foundation driveability analysis. 32 experiments are designed with orthogonal experiment and completed by GRLWEAP; the pile driving analysis results are obtained afterwards. Through the case study of Bohai sea oil field platform project, same conclusions can be drawn on the sensitivity regularity of pile foundation driveability influencing factors. The sensitivity of the factors that influencing pile foundation drivability from large to small is in this particular order: piling energy, geological conditions, pile diameter, pile length, cushion thickness, pile wall thickness, stop-driving time, stop-driving location and the pile section numbers.

Concrete-cored sand-gravel(CCSG) pile composite foundation is a new multi-type composite foundation. By incorporating the logarithm models of e-lgσ and e-lgk of soil, the characteristics of the nonlinear variation in the soil’s compressive modulus and the soil’s permeability during consolidation are considered. Based on equal strain assumption, the analytical solution is developed for CCSG pile composite foundation, which combined with itself characteristics and stress concentration effects. The existing consolidation solutions of sand drain foundation and gravel pile composite foundation under nonlinear characteristics of soil are special cases of this solution. Curves of the average consolidation degree of the composite foundation were observed based on the theoretical formula under the variation of various non-dimensional parameters such as the ratio of pile-soil modulus and soil compression index and penetration index, and load increment. The analytical results show that the average degree of consolidation in terms of stress is not equal to that in terms of deformation; in addition, the average degree of consolidation in terms of stress is greater than that in terms of deformation; the nonlinear characteristics of soil have a large affect on consolidation. The analytical solution is finally validated with the actual measurement data.

Soil arching effect is a key factor for the load transfer in a piled embankment. Based on the previous model test, a DEM model of a piled embankment is conducted by the PFC2D. The development of soil arching with the pile-subsoil relative displacement is analyzed based on the deflection of principal stress direction. Then, a soil arching model with a reasonable arch axis is proposed to depict the soil arching in a piled embankment. Meanwhile, a load-transfer coefficient α is introduced for the quantitative analysis of load transfer between the soil arching and the embankment fill below the arching. Numerical results indicate that the pile-subsoil relative displacement will induce the deflection of principal stress direction, which forms the soil arching in embankment. The features and heights of soil arching are related to the pile-subsoil relative displacement, and the maximum soil arching height is about 0.8 times of clear pile spacing. The decrease in α with the increase of soil arching height is found to follow a logarithmic relation.

The static drill rooted nodular pile is a new type of composite pile foundation; its tip bearing capacity is promoted as the existence of the enlarged cemented soil base. A group of model tests and ABAQUS simulation are used to investigate the tip bearing capacity of this pile foundation. The results of ABAQUS simulation show that the ultimate tip bearing capacity reaches the maximum value when the nodular pile tip is about at the middle of the enlarged cemented soil base in sandy or clayey soil; while the bearing capacity will be promoted with the thickness of the cemented soil between the nodular pile tip and base soil layer decreasing if the base layer is rock; as a result, the nodular pile tip should be at the middle of the enlarged cemented soil base as the static drill rooted nodular pile is mainly used as frictional pile foundation; the internal friction, cohesion and elastic modulus of the cemented soil have little influence on the tip bearing capacity of the static drill rooted nodular pile; the ultimate bearing capacity of the static drill rooted nodular pile will be promoted with the diameter of the enlarged cemented soil base increasing.

Based on the ultimate uplift bearing capacity tests of the enlarge base piles in Tianjin Yujiabao South Underground Garage Project, the uplift bearing behavior, the uplift failure mode and the bearing mechanism of the enlarged base piles is analyzed by numerical simulation. The results show that the ultimate uplift bearing capacity of the enlarge base pile with the increase of 8.5% of concrete material, increases about 50% more than the uniform section pile; the ultimate bearing capacity is significantly improved by the soil around the enlarged base. When the loading is small, the uplift resistance is mainly provided by the shaft fiction of the uniform section part of the enlarged base pile; the ratio of the uplift resistance of the enlarged base to the loading on the pile top increases approximately linearly with the loading increase. The shear failure firstly occurs in the pile-soil interface of the uniform section part with the loading increase; then the compression failure of the soil around the enlarged base occurs, and the uplift resistance reaches the ultimate bearing capacity. The ultimate uplift resistance of the enlarge base of the different length piles is almost the same when the enlarged bases are located in the same layer of soil; and the uplift bearing efficiency reduces as the pile length increases. The uplift resistance of the enlarge base is composed of the dead weight, the vertical component of the normal force and the shaft friction; the vertical component of the normal force provides the major uplift resistance of the enlarged base, the percentage of the total uplift resistance of the enlarged base is about 70%.

Gaomiaozi bentonite has been identified as the proper buffer/backfill materials of the high-level radioactive waste geological disposal in China. It’s significant to study its mechanical properties and applications to design the repository more reasonable. UH model for bentonite is proposed based on the UH model for unsaturated soils. By considering the expansion of the soil aggregate, the model is suitable for unsaturated bentonite. Based on the user subroutines, UH model considering the expansion of the bentonite has been developed in finite element software using the semi-implicit algorithm. 3D numerical simulations of the deep geological disposal are carried out with ABAQUS using the proposed model. The analysis of the seepage field and stress field are made preliminarily. The results show that the inner stress of the bentonite in the repository is increasing. Also, a good stability of the disposal repository can be noticed from the simulation results when using the Gaomiaozi bentonite as buffer/backfill material. Based on the above analysis. The Gaomiaozi bentonite is proved to be a reasonable buffer/backfill material; and the subroutine is proved to be valid by the numerical simulation.

Application of digital image processing technique to measuring specimen deformation in triaxial test can solve a series of problems about deformation measurement in traditional triaxial test. This paper introduces the development of triaxial image measuring system, which can be divided into three stages: (1) Digital image measurement system based on edge recognition, which determines the radial deformation of soil specimen by tracking the changes of the edge location and axial deformation of soil specimen by identifying the white mark line. (2) Digital image measurement system based on corner recognition, which measures and tracking each corner point (node) position, and obtains the displacement of soil surface node at any moment; we can obtain the displacement (deformation) field and strain field of the soil surface by using the finite element technique. (3) Whole surface digital image measurement system, based on the front surface corner recognition, together with two reflection mirrors situated inside the triaxial cell, a 360 degree coverage of specimen’s deformation could be achieved using only one video camera. Digital image measurement system for measuring specimen deformation in triaxial test has the unparalleled advantages comparing with traditional measurement methods, especially in the research of the constitutive model.

Nuclear density cone penetrometer(ND-CPT), incorporating the nuclear density probe into the probe of piezocone penetrometer, is a newly developed in-situ testing device that can simultaneously measure cone resistance, sleeve friction, pore water pressure and density. According to the principle that ND-CPT measures the average wet density of the soil within a spheroid volume around the central point of the source and the detector, the backscatter and average value models which can calculate the average density of soil within a spheroid volume are firstly proposed. Then, assuming ND-CPT is penetrated into various heterogeneous strata, the differences between the average density profiles and the actual density profiles are investigated; and the results show that the measured values are considerably different from the actual values near the boundaries of strata. Finally, the measured profiles of seabed sediments in Ariake Sea, Japan, are interpreted and the actual profiles are deduced. The research results can provide the basis for accurate soil classification using ND-CPT.

Triaxial test is an important mechanical test in geotechnical testing and also in study of strength and constitutive relation. Soil test procedures put triaxial tests as the major experimental projects at home and abroad. Triaxial research and development of triaxial tests are carried out simultaneously. In light of the deficiencies of the existing triaxial apparatus a new triaxial apparatus controlled by hydraulic servo is introduced. The apparatus has a double pressure chamber, surrounded pressures inside and outside the chamber and axial loads is imposed by the hydraulic controller using servo stepper motor drives ball screw pushes the piston to produce hydraulic pressure. Volume deformation measurement is using a stepper motor servo ball screw piston movement displacement to calculate. Data acquisition is controlled by computer. Experimental results show that the deformation of the instrument and volume deformation is measured accurately; instrument system performance is stable. The new triaxial apparatus has the characteristics of a simple structure, easy to operate, the true state of stress, high degree of automation, low production costs, etc. It played a relevant role in promoting the popularity and development of triaxial tests.

Under complex stress path including principal stress rotation, the research on remolded soft clay mechanical characteristics needs to improve its reliability, because the large volume’s method of specimen preparation reduces the physical balance and coring operation disturbances the sample. Based on vacuum preloading technology, a new kind of device and method is designed to prepare remolded specimen. The core component is the vertical drain body, which has a dual role of drainage and the inner wall molding. The important technology includes gradation loading of vacuum preloading and simultaneously preparing multiple samples. The method can prepare multiple hollow cylinder specimens quickly; the specimen’s moisture is better uniformity and consistency. This method can reduce the disturbance of the specimen of late coring operation. The verification tests is carried out under principal stress rotation path. The specimen’s reliability is proved, considering aspects of soil mechanical characteristics, when the specimen is applied to studying the of soil behavior evolution law under complex stress path. The specimen also provides the prerequisite for the static and dynamic mechanical characteristics systematic study and long-term stability of soft clay.