Crack initiation stress is an important stress threshold in rock failure process. A better understanding of the rock failure mechanism can be obtained by studying its initiation criterion and a more reliable prediction of the rock properties can be acquired. The crack initiation tests on green sandstone from Chongqing under uniaxial and triaxial compression were conducted. The crack initiation mechanism and micromechanical feature were analyzed based on the multiple strain response，and it was found out that the induced tensile stress concentration caused by rock defects was the main reason for crack initiation. The initiation model of opening crack under the low pressure of confinements and the initiation model of sliding crack under the high pressure of confinements were obtained based on the above analysis. The maximum tensile stress around the rock defects was studied by employing the Griffith theory. The tensile stress increases as the deviatoric stress   rises，which is strongly influenced by the friction effects under the high confining pressure. An empirical criterion of crack initiation prediction based on the different crack initiation patterns was proposed by introducing the parameter   as the influence coefficient of the confining pressure. The parameter  ，closely related to the internal frictional angle of rock，characterizes the friction effects in crack initiation，so the proposed empirical criterion can be applied to conditions of different confining pressures. The revised empirical criterion of crack initiation was verified with three sets of triaxial test on sandstone，granodiorite and granite，and its validity and applicability are much better than the conventional linear crack initiation criterion. It was also found that the crack initiation mechanism based on the analysis of   is mainly tensile under the confining pressure of 60 MPa.

The loading-unloading tests to gas-bearing shale under the true triaxial stress conditions with different intermediate principal stresses were carried out with the multifunctional true triaxial test system developed in house for fluid-solid coupling to explore the influence of intermediate principal stress and bedding direction on mechanical properties and permeability characteristics of shale. The results indicate that the effect of intermediate principal stress on the permeability of shale is greatest when the intermediate principal stress is perpendicular to the bedding plane，is lower when the minor principal stress is perpendicular to the bedding plane，and is lowest when the maximum principal stress is perpendicular to the bedding plane. When the intermediate principal stress is perpendicular to the bedding plane or parallel to the bedding plane，the intermediate principal stress is negatively correlated with the permeability. The permeability is more sensitive to the intermediate principal stress when the intermediate principal stress is perpendicular to the bedding plane than parallel to the bedding plane (the difference is 1 or 2 orders of magnitude). In addition，the expression of the damage variable D was defined. The slope of the damage variable-intermediate principal stress curve changes little during the loading process and changes obviously during the unloading process. The damage variable is bigger when the intermediate principal stress is perpendicular to the bedding plane than parallel to the bedding plane during the whole process.

In order to study the corrosion damage of anchorage structure，the indoor accelerated corrosion tests and the mechanical tests of corroded specimens were carried out considering the effects of oxygen concentration and local corrosion. The electrochemical measurement and the local strain monitoring of reinforced material were conducted during the corrosion tests. The relationships between the pre-stresses，the environment pH values，the oxygen concentrations，the corrosion current density，the appearance damage characteristic，the corroded weight per unit length and the mechanical properties of anchor bars were analyzed based on the test results. The local strain development of the pre-stressed anchor under the different oxygen environment was also studied. The results show that the stronger the acidity is，the higher the corrosion rate in the weak acid environment. The oxygen has significant effect on the corrosion of the pre-stressed anchor and the corrosion rate increases whit the oxygen concentration increasing. However，the effects are insignificant when the concentration of oxygen exceeds a certain value. The corrosion weight per unit length increases as the oxygen supplying rate rises under the experimental conditions. The ultimate elongation，ultimate tensile load and elastic modulus decrease significantly with rising of oxygen concentration. At the same oxygen-supplying rate，the reduction rates of the ultimate elongation，the elastic modulus and the ultimate tensile load are highest，lower and lowest. The local corrosion leads the deviation of the force acting on the corroded section. The tensile strain shows an increasing trend at the oxygen-rich side and is changed to the compressive strain at the anoxic side.

In order to study the mechanical characteristics and progressive failure mechanism of the roof-coal pillar structure，uniaxial compression tests were carried out to five groups of sandstone roof-coal pillar structure bodies with different height ratios. The acoustic emission(AE) monitoring technique and the digital video camera system were used to investigate the failure process of the structure. The structural strength of the structure is the combined strength of sandstone，coal and interface. The contact frictional effects enhance the strength of coal in the interface，but weaken the strength of sandstone in the interface. With the decrease of the height ratio of sandstone to coal，the macroscopic failure initiation strength，the uniaxial compressive strength and the elastic modulus of the structure body reduce gradually. Under the same conditions，the more developed the primary cracks in the coal is，the lower the macroscopic failure initiation strength，the uniaxial compressive strength and the elastic modulus of the structure body are. The macroscopic failure initiation of the structure body causes the occurrence of the turning points on the stress-strain curves while the AE energy index reaches a peak value. After the macroscopic failure initiation，the AE energy index drops to the original level. Generally，the macroscopic failure initiations are located in the coal. When the height ratio of sandstone to coal is 9∶1，however，the macroscopic failure initiation occurs firstly at the interface. The propagation and coalescence of cracks in coal make the coal more broken and the local damage occurs in the coal. The coalescence of the local damages leads to the coal failure finally. The sandstone failure is caused by the crack propagation in coal cross to the sandstone interior. Due to the difference of the propagation ability，velocity and angle of cracks in the coal，the sandstones display the split failure，shear failure or no damage. With the increase of the height ratio of sandstone to coal，the degree of damage of the coal body and sandstone increases，and the coal body is broken more.

Triaxial cyclic loading-unloading tests on Beishan granite from deep underground were conducted using the rock mechanical test system MTS815 to investigate the variation of strength parameters of the rock. The variation characteristics of rock strength parameters were discussed in detail according to the Mohr-Coulomb theory. The measured complete stress-strain curves under the different confining stresses were analyzed. The plastic shear strain was regarded as the plastic parameter to describe the strength and dilation behaviors of rock. The results indicate that the damage stress can be regarded as the zero point of plastic parameter and as the start point of the strength parameter variation. When applied stress is larger than the damage stress，the cohesion of the rock decreases exponentially with increasing the plastic parameter and finally approaches zero. Meanwhile，the frictional angle increases to the peak value and then decreases gradually to a constant value as the plastic parameter increases. The logarithmic normal distribution can be used to fit the data. The dilation behavior of the rock after the damage stress is similar to that of the post-peak stage. The dilation angle decreases with increasing plastic deformation and confining stresses，and is sensitive under the low confining pressures. The established models were implemented in the numerical software(FLAC) to simulate the triaxial compression tests. The predictions reproduced the main features of actual mechanical and dilation behaviors of Beishan granite.

The large deformation of surrounding rocks is easily induced in the tunnel excavation in steep dip and soft rock strata under high geostress conditions. Yangjiaping Tunnel was investigated to identify the factors causing the large deformation，to analyze the failure mechanism and deformation characteristics of surrounding rocks and the internal forces in the supporting structure and to propose a rational method of control. The in-situ sampling was carried out to analyze the significant anisotropic characteristics of chlorite phyllite and to determine the relationships between the load direction and failure mode of rock. The in-situ observations and numerical simulation results showed that the deformation of surrounding rock converged as a whole and the horizontal displacement of convergence was larger than the vault settlement. The bending damage in horizontal direction and the separation of bedding planes were found mainly in the side walls of tunnel. The maximum principal stress in the side walls is distributed like“＜”and“＞”. The main failure mode of tunnel vault and invert is shear slip      failure and the maximum principal stress is along the tangential direction of the tunnel. The factors inducing the large deformation are high tectonic stress，adverse stratigraphic occurrence and low rock strength. The results of in-situ experiments show that combinations of long and short bolts intersected with rock strata with large angles together with grouting can strengthen the surrounding rock effectively and adjust the surrounding rock pressure. Reducing the excavation steps led to the initial support be closed sooner and the bearing capacity of primary lining was thus fully utilized. Optimizing the cross section profiles can improve the loading on the support structures.

There are many micro-flaws in rock. In this paper，it is proposed that every cell in the numerical model includes a virtual micro-fissure without the thickness and with the normal distribution in dip angles and length. The growth rate and the mode of the micro-fissure are determined based on the fracture mechanics and growth mode of cracks. When the micro-fissures grow to the boundary of the cell，the cell fails. The failure cells coalesce together and form the failure surface in rock. Taking the Burgers model as an example，the numerical modelling method is incorporated into the software FLAC. It is applied to the intact rock and to the cracked rock with single or two pre-existing flaws under uniaxial and biaxial compression loads respectively. The simulated results agree well with that from laboratory tests，which validates the proposed method.

In order to understand the mechanism of slab buckling rockburst in deep tunnels in hard-rock，a large scale true-triaxial rock test system was used in the modelling experiments on the red sandstone samples(100 mm× 100 mm×100 mm) with a prefabricated hole. The minimum principal stress was set in the horizontal direction perpendicular to the axial direction of the tunnel，the maximum principal stress was set in the vertical direction perpendicular to the axial direction of the tunnel and the initial stress state was achieved in three directions. The loading in the vertical direction perpendicular to the axial direction of the tunnel was increased until the tunnel wall began to damage, while the initial stresses in the other two directions were maintained the same. The stepwise loading was executed until the rockburst occurred while the specimen as a whole was not completely damaged. The whole process of rockburst occurred in tunnel wall during the test was monitored and recorded in real time with a miniature camera installed. The entire process of slab buckling rockburst of the deep hard rock tunnel is thus reproduced. The results show that the slab buckling rockburst can be divided into four periods，i.e.，the quiet period，the fine particle ejection and peeling period，the slab buckling damage and the strong damage. The slab buckling rockburst may occur lagging behind the stress，has a time effect，and is obviously affected by the loading rate. The failure depth of slab buckling rockburst reaches the stable state of higher static stress level. The formation of the V-shaped notch has a stress insensitive period. The optimization of geometric parameters of the tunnel cross-section plays a role in the size effect of the structural strength，which has a certain inhibitory effect on the slab buckling rockburst.

A larger number of systems for geological hazard monitoring have been developed with the rapid development of computer network technology. In the meantime，these systems exhibited a number of bottlenecks. For instance，the early warning threshold is difficult to be determined and the traditional server is limited by the hardware reliability. It is proposed to embed the cloud server(ECS)，cloud database(RDS)，cloud sites and other data security storage system in the“Newton force change monitoring and early warning system” based on the multi-source data fusion technology. The long-term，short-term，imminent sliding mode and warning threshold were established statistically according to the needs of disaster monitoring and warning. An APP terminal for disaster information release，a WeChat public platform and an automatic search system of GIS monitoring were developed to integrate the multi-source information publishing and searching technology. The developed system issued a long-term forecast 45 days in advance of the“2016–1101 landslide”of the open pit iron mine in Nanfen，issued a medium-term forecast 30 days in advance and issued a sliding disaster warning 4 hours ahead to the whole mine，which avoided possibly a large number of casualties and property losses.

To overcome the numerical singularity of the yield surface based on the Hoek-Brown strength criterion， a new approach was presented to smooth the edges of the yield surface. The ideal elasto-plastic constitutive model was implemented in ABAQUS software with the fully implicit backward Euler integral algorithm employed in the stress updating. The strength reduction method in finite element method based on the Hoek-Brown criterion was implemented with the smoothed yield function. The similarities and differences of the strength reduction techniques applied with the Mohr-Coulomb strength criterion and the Hoek-Brown nonlinear strength criterion were discussed. The modeling on a circular tunnel shows that the numerical results of stresses and plastic zones in the surrounding rock agree well with the analytical results. The modeling on a rock slope shows that in comparison with the linear strength reduction technique of the equivalent Mohr-Coulomb model，the nonlinear strength reduction technique based on the Hoek-Brown model produced the slip surface which agree better with the characteristics of the slip surface of a rock slope，which are shallower in location and steeper in shape.

The reinforced gabion wall on the west line of Xiangtan to Hengyang highway in Hunan province was studied with the large scale pullout model tests and numerical simulations to obtain the interface friction characteristics between the double twisted hexagonal gabion mesh(2.2 mm and 2.7 mm respectively) and red sandstone. The experimental results showed that the pullout displacement-shear stress curve could be roughly divided into 3 sections：the rapid growth，the steady progression and the yielding sections. The thinner gabion mesh led to the higher peak shear stress，larger cohesion and friction angle under the same normal stress. The pullout displacement-shear stress curve from the numerical simulation had two sections，namely，the rapid growth of shear stress and the yielding of gabion mesh. Under the same conditions，the 2.2 mm meshes resulted in the larger drawing coefficient and pseudo-friction coefficient and thus presented the better interface friction properties. The conceptual model suggested that the proportion of pullout force shared by the horizontal bars and longitudinal bars relied on the magnitude，the length，the coefficient of earth pressure and the friction factor，etc. The pullout bearing resistance on the transversal bars(T1) comprises the largest proportion of the total resistance (about 62%–72%)，on the other hand，the proportions of the annular pullout friction on the longitudinal bars(T2) and the interface friction acting on the surfaces of all nodes(T3) both grow against T1 when the normal stress increases.

A new mechanism of two-dimensional failure was proposed for the upper bound analysis of nonhomogeneous slopes with the friction angle varying spatially. This failure mechanism obeys the associated flow rule and geometry uniform condition and was established based on the idea of discretized slip surface. The velocity discontinuity surface was generated point by point. The rate of external work and the internal energy dissipation were derived. The critical height of the slope was derived through the methods of sequential quadratic programming(SQP) and bisection searching. The effectiveness of the presented method was verified in homogeneous，anisotropic and nonhomogeneous conditions respectively. Finally，the critical height of the nonhomogeneous slope was analyzed using the failure mechanism with the friction angle increases linearly with the depth. The results show that the nonhomogeneous coefficient of friction angle has the significant effect on the critical height.

A direct approach for calculating the support pressure of a tunnel at the given reliability level is proposed in terms of quantified safe margins from the view of acceptable risks. The statistical characteristics of the parameters based on the data from laboratory and field experiments are derived using the generalized three-sigma rule. The tunnel design is based the values of strain and the performance function is established by utilizing the limit state function from the deterministic method. A detailed procedure of calculation is set up by combining Nataf transformation with Cholesky decomposition. The local safety coefficients are determined. The proposed method is verified with the first-order second-moment method(FORM) using the typical parameters of weak rock. The impact of correlation and initial in situ stress on the calculation result are analyzed. The tunnel support pressure and corresponding local safety coefficients are derived under the condition of different acceptable risks.

In the high speed railway tunnel，the mechanical behavior of surrounding rock is greatly affected by the spatial variation of rock parameters. A non-intrusive stochastic finite difference model was thus proposed to explore the influence of spatial variation of parameters of surrounding rock. The stratigraphic structure of the tunnel was simulated with Monte-Carlo methods. The proposed model was applied to analyze the mechanical behavior of the tunnel after excavation，with emphasis on the impact of parameter variation and spatial correlation. The mechanical behaviors influenced are the deformation characteristics of the surrounding rock，the mode of the plastic zone development，and the morphology of the ground surface settlement. The proposed model was compared with the deterministic model. The low-intensity structural load was found to dominate the mechanical behaviors. The anisotropic behavior is significant in the tunnel structure after excavation. The sensitivity and nonlinearity of the performance function were analyzed. The distributional and transitional effect of performance function was provided.

Micro-seismic source location is crucial for the micro-seismic monitoring technology. The existing algorithms usually minimize the function of time arrival values(time difference) from all detectors to obtain the location of micro-seismic source. The positioning results deviate usually from the actual locations of the sources because all the known micro-seismic parameters have errors. To overcome the shortcomings of the present algorithm，a two-step inversion method for the micro-seismic source location is thus proposed. The first inversion is to identify the abnormal detector，and the second inversion is to search the exact location from the space coordinates of sources. The 3–parameter，4–parameter and 5–parameter inversion models on the assumption of uniform velocity are established and compared. A multi-objective genetic algorithm(Non-dominated Sorting Genetic Algorithm–II，NSGA–II) is used for the first inversion. A single objective optimization algorithm is suggested in the second inversion in order to achieve the accurate source searching and to reduce the computing time. The results from a case study indicate that the proposed method can effectively identify the abnormal detectors and the positioning is greatly improved compared with the results with the abnormal geophone. The 4-parameter inversion model is better than the 5-parameter inversion model.

To investigate the deformation and structure variation of lignite under the thermal-mechanical action，experiments were performed to the lignite samples of 50 mm in diameter and 100 mm in length with the high temperature and trixial stress testing platform. The structure variation was studied with Micro-CT，mercury intrusion and liquid nitrogen adsorption methods. Several fundamental characteristics of lignite deformation were obtained when the temperature rose from 23 ℃ to 400 ℃ at a rate of 3 ℃/min under the triaxial constant stress of 7 MPa. The deformation process of lignite can be divided into three stages：a slowly swelling stage with the temperature rising from 23 ℃ to 170 ℃，a rapidly compressing stage with the temperature rising from 170 ℃ to 289 ℃ and a relatively slowly compressing stage with the temperature rising from 289 ℃ to 400 ℃.  The critical temperature of the brittle-ductile transition for lignite is about 180 ℃. During the constant load and temperature process，the final value of the axial strain increased firstly then decreased with the largest value of 2.5% at 200 ℃ and the smallest value of about 1.3% at 100 ℃. The largest total radial strain is about 19% and the largest total volume strain is about 41% at 400 ℃. The lignite deformation has great effect on its structure evolution. The total porosity of lignite increased firstly then decreased with the temperature rising. The largest total porosity is 21.46% at 200 ℃ while the smallest total porosity is only 7.61% at 23 ℃. The diameter of the main fissures increased with the temperature rising. The lignite porosity in the heating process has good fractal characteristics. The fractal dimension value decreased firstly then increased while the value of lnA0 increased firstly then decreased with the temperature rising.

The resonant phenomena occurring in the small reservoir due to the earthquake are always neglected. The burst of a small moraine-dammed lake may trigger the catastrophe because of the chain effect in Parlung Zangbo river basin. Little attention has been paid to the research of moraine dam failure under the interaction of seismic forces and resonant hydrodynamic pressures. The characteristics of hydrodynamic pressures are studied with the large-scale shaking table. An empirical equation using the mass-spring model is proposed to predict the maximum resonant hydrodynamic pressure. The pseudo-dynamic approach is implemented for the seismic force and a new mode for the global stability analysis based on the limit equilibrium theory is established to take into account the seismic force and resonant hydrodynamic pressures. The differences of global stability with and without water resonance are analyzed. The burst risk assessment of 35 small moraine-dammed lakes are completed for Parlung Zangbo river basin.

The wetting-loading，loading-wetting and loading-wetting-loading tests using the triaxial equipment for shearing and permeability measurement of unsaturated soil were performed to the intact loess under isotropic stresses. The influence of suction on the behaviors of deformation and yielding induced from loading and the influence of stress on deformation and yielding upon wetting were analyzed. The comparisons between the results of single and double triaxial equipment tests confirmed that the wetting induced volumetric deformation was dependent on the loading and wetting paths，and there was no unique yield curve identified from the loading and wetting paths. The elastoplastic volumetric model for the intact loess under isotropic stress was proposed. The results showed that the suction and stress had little effect on the compressibility and collapsibility parameters before yielding，but had remarkable impact after the yielding. The wetting induced volumetric deformations determined from the single and double triaxial equipment tests both increased first and then decreased with the increase in stress. The stresses at the peak points were independent of the suction loss，loading and wetting paths and were close to the initial yield stress of soil at the natural state. The wetting induced deformation was dependent on the loading and wetting paths. The wetting induced deformations from the single-triaxial equipment tests were smaller than the ones from the double-triaxial equipment tests. The difference decreased with the increasing of suction loss and approached to nearly zero until the saturation state was reached. The suction decrease(SD) induced yielding curve lay under the loading-collapse(LC) induced yielding curve for the same plastic volumetric strain. The LC yielding curve expanded with the increase in the loading-induced plastic volumetric strain，which produces the coupled outward movement of the SD curve，and vice versa. The proposed elastoplastic volumetric model predicted well the compression deformation at a given suction. The wetting-induced volumetric deformations before saturation at different stresses were better predicted with the model than with the unique loading-collapse yield curve.

Cement connection of loess is an important intrinsic factor of loess collapse，which has the direct impact on the sensitivity of the collapse. In order to have a clearer understanding and to determine the sensitivity of loess collapse，the collapsible tests of loess in acid conditions were carried out to investigate the collapsible coefficient of loess，the stability time，the collapsible deformation rate and other sensitivity indexes of collapse under different pressures. The different concentrations of nitric acid were added to the immersion solution of distilled water. In addition，a scanning electron microscope(SEM) was used to detect the differences of the void space and structure of soil samples before and after the tests. The results show that the collapsible coefficient of the collapsible loess in the acid solution increases greatly under the low pressure，and that the stable time of the collapse is longer under all pressures. Loess collapsing has different ranges of pressure sensitivity in the distilled water and in the acid solution. The structural strength of the collapsible loess has the important influence on its embedded depth，etc. Two indexes that pertain to 90% of the finished time of collapse and the collapsible coefficient are utilized to evaluate the collapsible sensitivity of the loess and loess site. Chou Huang Canal，which collapsed before，is presented as a case study to demonstrate the application of this method. The results indicate that the collapsible sensitivity of the collapsible site is evaluated accurately with the proposed method.

In order to study the influence of cooling temperature on the properties of soil subjected to the cyclic freezing-thawing，a set of freezing-thawing tests under the different cooling temperatures and numbers of freezing-thawing cycles were carried out on samples of silty clay from Qinghai—Tibet Plateau. The triaxial shear tests were subsequently conducted on the samples after freezing-thawing under the different confining pressures. The volume increment and the moisture migration inside the samples were measured after one freezing-thawing cycle. Results show that the expansion and contraction exist simultaneously in the freezing process and both increase with the decrease of cooling temperature. The different ratios between the freezing expansion and the freezing contraction are one of the main reasons for different effects of cyclic freezing-thawing. The freezing expansion reach the maximum state earlier than the freezing contraction，so the volume increment increases initially and then decreases as the decrease of cooling temperature. The failure strengths of samples after freezing-thawing are reduced on the whole and vary the same as the dry density does，i.e.，they decrease initially and then increase with the decrease of cooling temperature. The unfrozen moisture content and the amount of moisture migrated both decrease with the decrease of cooling temperature. Hence the range of failure strength changing due to cyclic freezing-thawing becomes smaller when the cooling temperature is lower. The variation of cohesion and internal friction angle versus the cooling temperatures and the numbers of freezing-thawing cycles were fitted with the Logistic model.

The strain behaviors of the stripe reinforced soil with the rigid retaining wall are studied with the large-scale shaking table model test in this paper. The damage of the rigid retaining wall is investigated considering the relative density of the soil，displacement on the wall and characteristics of Fourier spectrum. The test results show that the main region of stress in the strips moves from the potential damage zone to the stable reinforcement zone with the increase of amplitude of seismic wave. The analysis of the strain of the strips show that the damage of the retaining wall begins in the middle of the reinforced area and develops downward gradually. The study of potential fracture plane shows that the form is similar to 0.3 H(H is wall height) which is adopted in the standard，but the area is larger. The relative density of the soil increases with the increasing input PGA(0.1 g–0.3 g) and decreases when the PGA is greater than 0.4 g. The Fourier spectrum of white noise after different seismic waves develops from a single peak to double peak when the seismic wave propagates up. The frequency of the second peak trends to increase when the PGA of wave is not less than 0.4 g.

Shear tests and compression tests were carried out for soil samples of different initial water contents and initial dry densities in order to investigate the strength and deformation of soil-rock mixture in high filled projects. The shear strength and deformation of different soil-rock ratios varying with initial parameters were analyzed in detail. The smaller the initial degree of compaction is，the larger the confined compression strain of the specimen is. The larger the initial water content is，the larger the confined compression strain of the specimen is. The compression coefficient increases firstly and then decreases with increasing the vertical pressure. The compression modulus increases with rising the vertical pressure. The initial degree of compaction in the similar hill filled projects should be controlled to be more than 0.93，the initial water content should be controlled around the optimum water content within 2% to 3% of error，and the soil-rock ratio should be controlled between 2∶8 and 4∶6. The relationship between the dry density of the compacted mixture of silty clay and sandy mudstone and the vertical pressure is a power function. An algorithm was established to predict the strength and settlement according to the initial state and the loads of filled soil layer. The difference of settlement caused by the different compaction coefficient in the range of optimum water content is small. The settlement and deformation of foundation decrease obviously with the increase of compaction coefficient. The influence of compactness on the settlement of foundation when the ratio of soil to rock is 2∶8 is greater than when the ratio of soil to rock is 4∶6.

The longitudinal dynamic impedance at the head of the static drill rooted nodular pile is investigated based on the three-dimensional axisymmetric model in which only the vertical displacement of the surrounding soil is considered regarding the complexity of the pile body structure and the pile-soil contact conditions. Firstly，the soil reaction acting on the pile tip is simulated with the fictitious soil pile model，and the pile-soil system is divided into a number of segments according to the stratification of the surrounding soil and the distribution of the nodes of the pile. Meanwhile，the surrounding soil is discretized into several annular vertical zones to consider its radial inhomogeneity. Then，the analytical solution for the dynamic response at the pile head in the frequency domain is derived by means of Laplace transform and the impedance function transfer method. The degenerated solution is compared with other solution to verify its reliability. Finally，the influence of pile-soil parameters of the nodes of pile，the surrounding cement-treated soil and the pile tip soil on the dynamic impedance at pile head is investigated within the low frequency domain concerned in the design of dynamic foundation.

The unfrozen water content is a key factor controlling the moisture migration and causing the frost heave or thaw settlement during freezing and thawing processes. The freezing temperature is an important index to judge whether the soils are in a frozen state or not. The characteristics of the unfrozen water content and the freezing temperature and their relationships with initial water content during the freezing and thawing processes of the silty clay from Qinghai—Tibet Plateau were analyzed based on the frequency domain reflectometry(FDR) technique. The results show that for the soil with the higher initial water content，there are distinct super-cooling phenomenon and abrupt change of temperature and unfrozen water content in the freezing process. But for the soil with the lower initial water content，the phenomenon is not obvious. The soil with the larger initial water content is frozen earlier than the soil with the smaller initial water content and is more sensitive to the temperature jump. The lag effect of the unfrozen water content between the freezing and thawing processes is affected by the initial water content. The lag degree of unfrozen water content is mainly in the phase change zone. The peak value of the lag unfrozen water content decreases with the reduction of the initial water content. The initial water content has little influence on the freezing temperature of soil when the water content is equal or greater than the liquid limit. The freezing temperature of soil decreases with the reduction of the water content if the initial water content is less than the liquid limit.

The tunneling in Ningbo，China, used the newly-developed quasi rectangle EPB shield and the superimposed stress was analyzed based on the Mindlin?s solution with the consideration of the excess pressure in front of the excavation face and the unevenly-distributed friction across the shield surface. Results show that the superimposed stresses are different from place to place in the soil layer. The soil in front of the cutter face is compressed，while the soil behind is under tension. The superimposed stresses in quasi rectangle shield tunneling are close to the ones in tunneling with the large diameter circular shield machines and are much smaller than the ones in DOT shield tunneling. The soil disturbance caused is thus easier to control.