During the process of earthquake and rock fracturing, the fracture mechanisms, source parameters and rupture energy can be obtained by moment tensor inversion. In this paper, the moment tensor theory and its inversion method are introduced in detail; and then a comparison of merits and demerits about three major inversion methods, namely the absolute moment tensor, the relative moment tensor and the hybrid moment tensor is conducted. On the basis of detailed classification and summary of the domestic and foreign references, the application status of moment tensor is reviewed in the fields of hydraulic fracturing, mining and deep tunnel, etc., and combining with its application example in analysis of the focal mechanisms of Hamm Heringen region microseismic events. The results show that the focal mechanisms solution and seismic parameters can be achieved by moment tensor inversion, which played a vital role in the fields of disaster warning and prevention of rock engineering, monitoring and control of hydraulic fracturing, etc. Finally, the factors which influence the accuracy of moment tensor inversion and the insufficient factors including the low precision of microseismic events location and difficult of waveform identification and processing when it is applied to rock engineering fields are analyzed. Meanwhile, the application prospect in the rock engineering field about mining, petroleum engineering, etc., the improvement, as well as the problems need further study are discussed, so as to provide an important reference for applications of moment tensor inversion method.

To extend the application of consolid system in loess soil improvement in China, this paper intend to verify that consolid system helps maintain a dry interior condition of loess soil. consolid system was mixed into remolded Q3 loess soil for laboratory tests including water drop penetration time test, flexible-wall permeability test, drying shrinkage test and soil-water characteristic curves(SWCCs) test, to investigate the water entrance ability, water permeability, and the dewatering ability of loess soil to different consolid system content. Test results show that, with the increasing proportion of consolid system in the modified soils, water repellency ability of the soils is sharply increased, much better than the soils modified with flyash, cement or lime. Permeability of modified loess soil is almost the same as the un-solidified loess soil, indicating that water flow capacity remains unchanged. Both of the moisture content in drying process and the soil-water characteristic curves(SWCCs) on the capillary action area of modified soils have little changed, indicating that dewatering ability of modified loess soil remains almost the same. These observations are consistent with scanning electron microscope(SEM) test and mercury intrusion porosimetry (MIP) test results, that consolid system has little influence on volume content of big and middle pores. It is concluded that consolid system is benefit to maintain a dry interior condition in loess soil because it sharply increases the soil water repellency ability but has little variation on the original permeability and dewatering ability of the loess soil.

The mining-induced damage of vertical shaft wall under complicated stress conditions is a great threatening to safe production. Thus, accurate and fast evaluation of its security has been the focus of relevant researchers. In this paper, calculation model of vertical shaft wall with three-field coupling of stress-seepage-temperature has been established; the main damage modes and influence factors of vertical shaft wall have been studied combined with orthogonal design principle and multivariate statistical method. A rapid and accurate safety evaluation model has been given for the assessment of project and reference of the vertical shaft wall monitoring. Finally, the proposed method has been used for analyzing the vertical shaft of Wen Jiazhuang project, so as to verify the validity of this method.

Unified viscoplastic model hypothesizes material strain is divided into elastic part and viscoplastic part. Including stress part in its strain rate expression，that reflects the rock material characteristic of dependency of strength to loading rate, the characteristic of strain creep under continuous load and the characteristic of stress relaxation when with constant displacement. But showed the constitutive model of differential equations also result in difficulties in computation. Transformed the differential equations of constitutive model into integrated form, approximated the integrated form expressions by uniformly valid asymptotic expressions, and then the Newton-Raphson iteration pattern is established based on the approximate solution. A series of triaxial relaxation experiments is carrie out under different confining pressures, then based on the experiment data, a back analysis is made to get the parameters of the module. The results indicate that this model is able to describe the mechanical behavior characteristics of argillaceous siltstone under long-term loading.

Land subsidence caused by decompression of confined water is comprised of deformations of aquifer, aquitard and phreatic stratum. When the decompression features short duration so that consolidation deformation of aquitard is little, the aquitard is supposed to be watertight. Theory for elastic layered system is adopted to calculate layered soil deformation caused by dewatering of single well and the third type of foundation pit dewatering that the waterproof curtain inserts into the confined aquifer. The calculated results are compared with numerical simulation and in-suit tests results. The analytical results show that elastic modulus of the overlying soil has little influence on ground surface displacement; yet thickness of overlaying soil layer shall be taken into consideration. The settlement of soils overlying confined aquifer increases up to down nearby the pumping well. Over a certain distance, the settlement does not change with depth. The drawdown outside the foundation pit can be estimated according to the demand for drawdown inside the foundation pit.

It has significant theoretical and practical meaning to propose a method of unsaturated soil slope stability analysis accounting for seepage, deformation and stability simultaneously. Firstly, coupled analysis of transient unsaturated seepage-stress is achieved using the double-stress variables theory of Fredlund. Comparative analysis with pore pressure field is done by the traditional uncoupled method. Variation process of phreatic lines are close to each other, and the maximum relative error of pore pressure is 8.8% at the bottom of embankment; thus the reliability of coupled analysis results are verified. Secondly, it is possible to consider the matric suction term as a part of the cohesion of the soil, and the spatial distribution law of strength parameters of the slope is obtained. Analyzing program of vector sum method of unsaturated soil slope stability analysis subjected to transient seepage based on Matlab has been developed. Finally, taking the influence of drawdown of reservoir water level on slopes stability of embankment for example, comparative analysis between traditional method and proposed method indicates that potential slip surfaces are similar and the difference of safety factors are less than 0.096; thus the rationality of the method proposed in this paper is verified.

Natural rock contained a large number of microcracks generated and accumulated in the long-term geological activity. In early loading stages or under a low stress level, rock would experience a fracture compression phase, in which rock showed out nonlinear instantaneous plastic deformation. Without considering rock instantaneous plastic deformation by fracture compression, the normal rock creep model reflected lower instantaneous deformation value than the real. Therefore, it is necessary to consider effect of initial damage on rock creep in process of constructing rock creep constitutive model. Considering different degrees of initial damage existing in the natural rock and new damage caused by crack extension under loading in the process of rock creep, the creep properties of rock with initial damage in different stress levels is overall described. With the increase of stress, rock creep would experience steady creep with instantaneous elastic deformation, steady creep with instantaneous elastoplastic deformation and accelerated creep. Based on the relationship between stress and normal deformation of the unclosed structural plane, concluded by BANDIS S C and BARTON N R through many tests, a mechanical component of fracture rock plastic deformation body is put forward to describe instantaneous plastic deformation in rock creep process. Considering the initial damage having effect on accelerated creep, an initial damage factor is introduced to Kachanov creep damage variable evolution equation, a damage variable evolution equation of the rock with initial damage is built. Furthermore, a creep damage body component is put forward to simulate accelerated creep of rock. The fracture rock plastic deformation body component and the creep damage body component are series connected to the generalized Kelvin model which can describe instantaneous elastic deformation and viscoelastic deformation of rock, to form a whole creep process constitutive model which could reflect instantaneous elastoplastic deformation, steady creep and accelerated creep of the rock with initial damage. The method of model parameters determination through a small amount of tests is put forward. At different stress levels, the theoretical curves can coincide with the creep test curves. The new rock creep model can simulate nonlinear increase of instantaneous deformation by stress level. Compared to accuracy of the accelerated creep simulation only by traditional Kachanov creep damage variable evolution equation, the accuracy of the new model has been improved after introducing the initial damage factor.

A new bounding surface plasticity model considering the effect of anisotropy on the behavior of saturated soft clay under cyclic loading is proposed within the framework of critical state elastoplasticity. A non-associative flow rule and an internal variable reflecting the anisotropy of soil are introduced in the model. The initial anisotropy is depicted by the initial value of the internal variable and the evolution of anisotropy produced by cyclic loading is described by a rotational hardening rule with robust rationale and availability of model parameters. A radial mapping rule with the updated projection center and an interpolation function of plastic modulus associated with the length of the deviatoric plastic shear strain trajectory are adopted in the model to describe the fundamental behaviors including nonlinearity, hysteresis and strain accumulation of stress-strain responses of soft clays subjected to cyclic loads. The roles played by model parameters and their determinations are also explained. In particular, a rational method to calibrate the initial internal variable for describing anisotropy of specimens is developed. The validity of the new model is verified by comparing the predicted results with the cyclic triaxial test results under isotropically consolidated and anisotropically consolidated conditions for saturated soft clay.

As a kind of special soil, loess is widely distributed in seasonally frozen regions. The test samples are the undisturbed Q3 loess with obvious anisotropy from a building site in Xi’an city. The saturated hydraulic conductivity of undisturbed loess considering the influence of density is measured by triaxial permeability apparatus GDS. It can be obtained that the hydraulic conductivity in horizontal is higher than that in vertical. The saturated hydraulic conductivity decreases with the increase of density. However, the anisotropic permeability of undisturbed loess increases with the increase of density .The loess, which has the same density but a different initial moisture content, experiences freezing-thawing cycles in an closed system. The results show that the saturated hydraulic conductivity of the samples, which has experienced freezing-thawing cycles, increases with the initial moisture content increasing. However, the anisotropic permeability of loess experiencing freezing and thawing reduces with the initial moisture content increasing. The saturated hydraulic conductivity increases first, then reaches a steady state with increasing freezing-thawing cycles. However, the anisotropic permeability of undisturbed loess changes significantly with increasing freezing-thawing cycles. The ratio of loess permeability decreases significantly with the increase of freezing-thawing cycles. The test results indicate that the anisotropy of loess structure has a significant effect on the anisotropic permeability. Meanwhile, Freezing-thawing changes the permeability of loess by changing its microstructure.

Hydraulic fracturing is an important technique for unconventional oil and gas reservoir. The far field measurement technology has represented by down-hole gauge, the split extending shape has been applied to the effect evaluation of hydraulic-fracture. The major factors on surface and subsurface inclined fields are studied upon hydraulic fracturing; and then the model is verified to be correct. Using rectangle crack model, a quantitative analysis of the formation and fracture parameters are carried out. Research results show: (1) The ground tilt field is sensitive to the change of azimuth and dip angle of the crack, the crack size and depth of the crack centre is not sensitive. (2) The inclination of the field is sensitive to the crack size and depth of the crack; but to the azimuth and dip angle of the crack is not sensitive. The results can be applied to optimization design of hydraulic fracturing in reservoir.

Aiming at the problem of horizontal well hydraulic fracturing in formation with dip angle natural fractures, theoretical and experimental studies on the initiation and propagation of hydro-fracture from natural fracture are carried out. Simplifying the natural fracture as a transverse fracture perpendicular to the well axis, the method of calculating initiation pressure and stress intensity factor (SIF) are given, based on the theory of linear elastic fracture mechanics and the maximum stress criterion. Meanwhile, using a prefabricated transverse fracture to simulate natural fracture, laboratory hydraulic fracturing test is carried out to investigate the fracture geometry and initiation pressure. Theoretical calculation shows that: (1) after initiating from the prefabricated transverse fracture tip, the prefabricated transverse fracture and the fracture can be regarded as a whole and treated as a transverse fracture to calculate SIF when the fracture propagates longer than the radius of the notch tip. (2) when the distance between the fracture tip and the wellbore wall is longer than four times of the wellbore radius, the wellbore effect can be neglected and SIF equation for penny-shaped crack can approximately be used. Experimental studies show that (1) hydraulic fracture initiates at the tip of the prefabricated transverse fracture and propagates to form a transverse fracture orthogonal to the wellbore; fracture propagation shows the feature of model Ⅰ fracturing; the fracture geometry is near round; no longitudinal fracture is observed. (2) pumping rate has a significant effect on the net breakdown pressure and net initiation pressure with larger pumping rate leading to higher net pressures; the discreteness of net initiation pressure and calculated critical fracturing value KⅠ are small under both large and small pumping rate conditions. Research results can provide guidance for improving near wellbore fracture geometry of naturally fractured reservoir and reference for designing hydraulic fracturing with prefabricated transverse fracture in coal mining.

As part of the rock mass, the non-persistent joints inherently affect the rock mass mechanical behavior. Nearly most of the existing calculation methods of the rock mass damage variable can only consider the influence of the joint geometrical property on its mechanical behavior. Therefore, this study focuses on the mechanical behavior of the rock mass with a set of non-persistent joints in order to propose a new calculation method of the rock mass damage variable which can both consider the influence of the joint geometrical and mechanical properties on the rock mass mechanical behavior. First, the hypothesis of elastic complementary energy equivalence is adopted to replace the Lemaitre strain equivalence hypothesis in order to study the anisotropic damage of the rock mass induced by the joints. And based on the connection of the increment of additional strain energy caused by the existence of one joint in fracture mechanics and the emission of damaged strain energy in damage mechanics, the calculation formula of the rock mass damage variable caused by one joint is deduced. Second, the calculation formula of the stress intensity factor(SIF) KⅠ and KⅡ of a single joint tip under uniaxial compression is studied according to the fracture mechanics theory. Third, the calculation formula of SIF KⅠ and KⅡ of a set of one or more-rowed joint tips is given by considering the interaction among the joints. Finally, the calculation formula of the rock mass damage variable caused by a set of non-persistent joints is obtained; and then its validity is verified by the existing test results.

In order to illuminate the anisotropic rheological characteristics and the damage evolution of quartz-mica schist from Danba Hydropower Station, the stress relaxation tests are carried out for the mica-quartz schist samples, which were divided into the parallel group and the vertical group. Each of these samples sustained the different loads for almost 720 hours on the program-controlled creep test instruments. The test results show that the relaxed process contains three phases, i.e. rapid relaxation phase, slow relaxation phase and steady-state relaxation phase, and is non-fully damped relaxation. This conclusion is suitable for both parallel and vertical groups. And the difference exists in that the damped duration of the parallel group is longer than that of the vertical, because of the influence of schistosity direction. Furthermore, based on the relaxation characteristics of mica-quartz schist, the rheological constitutive equation of Bingham model are improved by introducing the damage factor of dissipated energy into the equation. And the stress relaxation equation are derived by the modified Euler method of finite difference, in order to identify the parameters of the improved model for the mica-quartz schist by the method of integrating artificial neural network. The results demonstrate that at the rapid relaxation phase, the damage evolution develops very fast and damage rate decreases with the relaxation processes, which is also fit for both parallel and vertical groups and is parallel to stress relaxation. In addition, it is obvious that the theoretical solution is highly consistent with the test data. So it means that the improved model can well describe the relaxation properties of mica-quartz schist, so as to provide significant guidance for the soft rock engineering.

With the aim of researching the law of dynamic surface subsidence, based on normal distribution time function, mathematical models utilized to predict progressive surface subsidence at any point and any moment are derived combining surface subsidence predictive formulas. The influence of curve pattern coefficient and calculation error of normal time function is analyzed. Besides, space-time completeness of normal distribution function is also discussed. Predictive formulae to predict surface dynamic subsidence are established based on normal time function. Furthermore, taking coal extraction of the fifth panel in Xinzhi coal mine, Shanxi province for example, predictive parameters of surface dynamic subsidence are deduced by means of dimensional curve surface fitting. According to those parameters the subsided tendency of surface key points is predicted. The results of this research indicate that the acceptable magnitude of curve pattern coefficient δ should be greater than 2 as predicting surface subsidence. In this way relative mean error of theoretical predictive magnitude will not exceed ±4.55%; and the error will decrease gradually as the increase of δ. Normal distribution function represents the completeness of space-time distribution in response to surface subsidence, subsided speed and accelerated velocity. The methodology of curve surface fitting based on superposition theory can automatically calculate predictive parameters of surface subsidence. And maximum mean error of subsided tendency prediction of key points is ±64 mm, relative one is ±5.7%, which is better fitted with what actual occurs. Subsidence predictive models of normal distribution time function can represent time-spatial distribution characteristics of progressive surface subsidence.

In order to study ground disturbance induced by tunnel construction and characteristics of lining structure under load in underlying horizontal thin coal mined-out area, numerical analysis software is used to simulate the vibration of ground stress from meso-level; meanwhile, indoor tests of similarity model is carried out to measure earth pressure acting on tunnel lining and structure internal force of secondary lining(axial force and bending moment) in the strata beneath thin seam mined-out area to analyze the influences of pitch on the earth pressure and internal forces of secondary lining under confining pressure. The test results demonstrate that the loosening zone of surrounding rock induced by tunnel excavation takes on O-shape in underlying horizontal thin coal mined-out area; and the particle contact force of the underlying wall rocks of the tunnel is less than that of the overlaying rock of the tunnel. The greater the convergence of tunnel inner perimeter, the greater the particle contact force of discontinuity region. The smaller the pitch, the larger the particle contact force discontinuity region, when the pitch is larger than 2.0D, the impact of underlying mined-out area to particle contact force fade away. The subgrade reaction is reduced by underlying mined-out area; the smaller the pitch, the higher the degree of reduction. Internal force of secondary lining is discrete distributed. As the weak part of main structure of tunnel, the first crack appeared in invert of secondary lining.

The principal stress rotation has a significantly influence on the dynamic characteristics of soil. According to the function that GDS dynamic hollow cylinder torsional apparatus(HCA) can apply four dynamic loads, namely inner pressure, outer pressure, axial load and torque, the loading mode is put forward for three possible stress paths which are applied in practical engineering with the principal stress rotating, and three kinds of tests are conducted to confirm that the stress paths can be realized in the HCA. When the four dynamic loads meet some corresponding requirements, the following stress paths can be realized: ① When the mean principal stress p, the intermediate stress ratio b and deviatoric stress q are kept constant. ② the cyclic deviatoric stress q is applied when the mutation of α, i.e. the rotation of major principal stress relative to the vertical direction, is 90°. ③ When the cyclic deviatoric stress q is applied with the principal stress continue rotating. In addition, the first path provided theoretical foundation for experiment of simulating the stress paths under wave loading; the second path can be applied to simulate the dynamic characteristics of soils subjected to earthquake load; and the third path can be used to simulate the stress paths of soil around the pile under wind and wave loads and the stress paths under traffic loads.

The achievements of rock and soil mechanics research have been obtained until now. A zipper type transducer is used to measure the radial deformation of a cylindrical sample of traditional triaxial test, in fact; it is assumed that the failure type of testing sample is symmetrical; it is reasonable for the failure to occur by “X” type or along the symmetrical axis of sample. The physical significance of the slope between the average stress (or deviatoric stress) and volume strain relationship doesn’t existed, but it is existed under the condition that an equivalent loading or unloading in the three directions is performed at the same time. Yield proportional limit stress and peak stress keep constant under elastic segment; when an applied stress is greater the yield proportional limited stress, the yield proportional limited stress and peak stress spaces are changed with the damage state; the load and displacement relationship is a comprehensive representation of mechanics and structure of material post-failure, the stress and strain must be changed to be defined as “quasi-stress and quasi-strain”. Traditionally, it isn’t reasonable for the areas of hysteresis to present the energy dissipation of rock and soil material under cyclic loading-unloading case; it is reasonable for the areas of hysteresis to behave the storage, conversion and dissipation of energy. Based on the mechanism analysis, a traction stress criterion must be suggested to describe the failure along the symmetrical axis of testing samples, that is rational to explain the fissure existence in the natural integrated rock mass. It is more reasonable for the material parameters to determine by the linear segment of unloading curve; a formula is suggested to classify the linear segment. When applied stress is greater than yield limit stress, a non-drainage test is performed for the porous interconnection material; the water pressure unloading is conducted to be near zero at a stress state; the material parameters can be obtained by means of linear segment of water pressure and strain curve. A hexahedron testing sample (50 mm×50 mm×100 mm) is suggested to take the place of cylinder. The damage variables keep constant within the yield proportional limited stress, when the applied stresses are greater the yield proportional limited stress, the damage evaluation is different in the different main stress directions, and is changed with stress paths.

Evaluation indexes of surrounding rock stability are usually in forms with normal distributions in finite intervals, and their classification boundaries are of fuzzy characteristics. So it is hard to interpret these characteristics using a normal cloud model. A novel cloud model coupled with connection number is described here to take into account of the fuzziness and conversion situation of classification boundary, and interval nature of evaluation indicators for surrounding rock. In the model, the connection cloud model in finite intervals is first discussed. Then combined with index weights, a concept of contact probability is introduced to specify the comprehensive certainty degrees of the measured evaluation indicator to various classification grades. The results from case study and comparison with other methods show that the model proposed is feasible and effective; and it can overcome the shortcomings of inability to simulate quantitatively certainty and uncertainty relationships among indicators of interval distribution form from a unit way, so as to extend serviceability for the cloud model.

Because the loose circle is an important basis and parameter for designing the tunnel support and estimating whole stability, how to determine its area accurately and fast has become all issues of concern. By taking the tunnels inner highway from Zhangjiakou to Shijiazhuang as study background, the loose circle of tunnels with different overburden depth and rock mass grade was studied by combination of ultrasonic detection and theory analysis. Based on the criterion of Drucker-Prager, the calculation method of theoretic analysis for the loose circle of surrounding rock mass is founded, whose calculated results is lower than those from ultrasonic detection of single hole but has similar variation rules each other. For considering the strain softening after peak strength, the analysis method based on damage theory more approach to results from the field test than the ones of elastoplasticity. The estimation of loose circle of surrounding rock mass with damage theory, especially for low graded rock mass, is feasible. Besides, the study results have some consult effects on the similar engineering.

The uniaxial compression experiments of rock-like specimens with multiple intermittent joints are conducted by 10MN microcomputer-controlled electro-hydraulic servo large multi-function action force triaxial apparatus to further research mechanical behaviors of multiple-jointed rock mass with different joint dip angles. Researches on the relationship of crack characteristics, coalescence patterns, failure modes, stress-strain characteristics of multiple-jointed rock mass with joint dip angle were performed. The results show that: (1) Crack types of multiple-jointed rock mass mainly include wing crack and second coplanar crack. The propagating path of wing crack is different than that in condition of single joint. Wing cracks propagated a longer distance in the initial direction and directly coalesce with neighbouring joint or wing crack. Four patterns of crack coalescence are found (2) Three failure modes are found on specimens containing multiple joints, i.e. failure through a plane, rotation of new blocks failure and stepped failure. (3) The stress-strain curves of multiple-jointed rock mass at the strain softening stage show different characteristics of nonlinear deformation behaviors and according to that the curves are divided into four types. (4) The anisotropy of strength and deformation of multiple-jointed rock mass is highly obvious. The values of both strength and elastic modulus are maximum at joint dip angle of 90° and minimum at joint dip angle of 30°.

In order to investigate the behavior of reinforcement-soil interface under dynamic load, a series of cyclic direct shear tests focused on geogrid，woven geotextile，non-woven geotextile with sand interface are performed through large-scale direct shear device. The shear stiffness and damping ratio of the interface in different conditions are gained; and then the relationship between cycle number and shear stiffness or damping ratio are analyzed. Results show that, in the same cycle number, the geogrid-sand interface has the largest value of shear stiffness; and the woven getextile-sand interface has the largest value of damping ratio. The interface exhibit cyclic shear hardening in the three values of normal stress with the cyclic shear amplitude of 3 mm. The damping ratio of the interface in different normal stresses tends to a same stable value with the increase of cycle number. The interface shear stiffness is increased and damping ratio is decreased with sand relative density, and with the increase of cycle number the damping ratio of the interface in different sand relative densities tends to a same stable value. Cyclic shear degradation is observed in the interface suffering cyclic direct shear with shear amplitude of 5 mm; the interface with a larger shear amplitude in cyclic direct shear has larger value of stiffness.

The cubic mudstone specimens are indented with constant cross-section(CCS) disc cutter to study the fragmentation characteristics of soft rock in indentation tests with or without lateral confinement. The acoustic emission technique and scanning electron microscope analysis are employed to analyze the failure information. The load-penetration curves and acoustic emission parameters are studied with the observation and detection of macrocrack formation processes and mesoscopic failure characteristics. The results show that: (1) The load-penetration curves appear distinct peak value in both cases, after that the unconfined specimen is completely broken down and the confined one still could bear load at a pretty high level. (2) The acoustic emission parameters reach the peak values when the main macroscopic crack forms and propagates in the unconfined test; the acoustic emission parameters arise for several times in accordance with the initiation and propagation of certain number of macrocrack in the confined test. (3) Micro-slips within mudstone specimens can act as evident shear cracks; and the mudstone fragmentation pattern in indentation test with CCS disc cutter is mainly controlled by shear failure.

To explore the deformation and gas seepage rules of coal and rock under variable axial compression loadings, with coal pulverized coal specimen pressed for the study, using triaxial stress thermal-hydro-mechanical coal containing gas permeability system, five kinds of coal in different axial compressive loading paths under three axial compressions and gas seepage test were carried out. The results show that: Deformation of coal body can be divided into four stages: compaction, stable development, non stable fracture development and fracture. Strain rate of change of the specimen compaction stage mainly related to open structure surface and the fracture and regardless of the axial compressive load range; the stable development stage, while the axial compression loading rate is different, but in the axial compression loading the same interval, variation of axial strain rate is basically the same. The coal permeability and axial compression loading rate is negatively correlated with changes during the variable axial compression loading early stage and the permeability variation rate and axial compressive loading rate and little correlation in the late period. The above conclusions have important significance to guide the monitoring and early warning of rockburst and coal and gas outburst.

Rheological property is one of the deformation characteristics of rock; and great importance shall be attached to the long?term strength of the rock mass among mechanical properties in most geotechnical engineering. According to the triaxial creep test of limestone after high temperature, a thermal damage factor based on longitudinal wave velocity is introduced to quantify the thermal effect on the rock mass, and a series of observations are used including isochronal curves of strain method, transient creep method and steady creep rate method to predict the long-term strength of limestone and put forward an improved method of steady–state creep rate curve-tangent method. The results show that the thermal damage factor which based on wave velocity can quantify the thermal effect accurately; and the thermal damage factor shows a close correlation with the long-term strength. The limestone threshold temperature is 380 ℃ determined in this tests; lower than which the property of limestone shows a reinforcement effect and beyond which shows a damage effect. The steady-state creep rate curve-tangent method predicting the long-term strength of limestone is much accurate and consistent with the actual situation. The failure modes of limestone at different temperatures are characterized by shear failure; and the sub-crack transforms gradually from the parallel to the main shear plane to the irregular extension.

Spiral CT（Computerized Tomography）and intelligent ultrasonic velocimeter were used in the non-destructive testing of five sandstone samples of different scales under the condition of drying and of different degrees of saturation. The test results show that water absorption of vacuum saturation method is a bit bigger than that of natural immersion method(D = 50 mm); saturated water absorption and the height of specimen are almost linearly related; the water absorbing ability of the specimen is weakest when the height to diameter ratio(h/D) is maximum and its value is 3.5, while it is relatively strong when the size ratio in the two directions is near two; duo to the anisotropy of rock caused by its natural defects, the smaller specimen size is, the higher anisotropy index will be, and the macro-uniformity of the specimen will be obvious when the size of it is large enough; both of the macro mechanical parameters and micro mechanical parameters of sandstone are of scale effect, The variation of the elastic modulus of the rock specimen is huge when its height to diameter ratio is less than two(h/D＜2.0) and the calculation elastic modulus of the rock specimen increases slowly with the increase of height when its height to diameter ratio is greater than or equal to two(h/D≥2.0). Nondestructive testing parameters’ scale effect equation of sandstone of different moisture contents is obtained in this article; the formula shows that squares of the test specimen’s longitudinal wave velocity and numbers have inverse correlation to the water absorption effect of sandstone; the result is of certain guiding significance for the research of water rock interaction when considering the scale effect of the specimens.

Different from the typical stress path often used in triaxial or plane strain test, a stress path with decreasing confining pressure was applied to plane strain compression test on Toyoura sand. Influence of initial consolidation pressure and initial relative density of sand specimen was investigated. By using the 2D digital image correlation(DIC) method, shear band formation process was analyzed. Shear band thickness and inclination angle, as well as their influencing factors were analyzed quantitatively. Study results show that shear band in the Toyoura sand appeared before the peak shear strength. For dense Toyoura sand, with increasing confining pressure, shear strength(principal stress ratio) decreases and its peak value appears later; shear band thickness is smaller but shear band inclination angle change is not obvious. With increasing relative density, peak shear strength increases and appears at an earlier strain; shear band thickness becomes smaller while shear band inclination angle becomes higher. Moreover, the Coulomb’s equation based on the peak internal friction angle can relatively accurately predict the maximum shear band inclination angle of Toyoura sand under plane strain compression.

The soil under foundation is assumed to be a rigid plastic medium and obey Mohr–Coulomb failure criterion; slip-line theory has been used to determine the bearing capacity of rough strip footings. The bearing capacity of footings is calculated with the finite difference method for given boundary conditions. The value of bearing capacity factor Nγ is consequently obtained without superposition approximation. The formula shows that Nγ is not only related to internal friction angle of soil φ but also to the dimensionless ratio F. The Nγ is a constant with the determined φ and F. The calculated Nγ is compared with other researchers’ results. It’s found that different assumptions made by other researchers are chief factors that lead to errors. The calculations of Nγ with different values of F and φ are presented and compared with results. Finally, two forms of suggested expressions to approximate Nγ are proposed according to numerical calculations. The errors between approximated values and numerical results are clarified. The approximated results are close to the numerical ones so as to prove to be practical to evaluate the ultimate bearing capacity.

Magnesium phosphate cement(MPC) is used to stabilize/solidify lead-contaminated soils. Unconfined compressive strength tests are conducted to investigate the variation of stress-strain properties of MPC treated lead-contaminated soils along with MPC dosage, curing time, water content and lead concentration. The results show that stress-strain curves of lead-contaminated soils can be divided into three stages: compaction stage, elastic stage and destruction stage. The qu, and E50 increase significantly with MPC dosage and curing time, while the εf change oppositely. There are threshold values for water content and lead concentration in terms of its influence on qu and E50, where qu is the threshold value of 0.45 and E50 is the threshold value of 500 mg/kg. The qu, and E50 increase with the lead concentration and water content before they reach the threshold value. The qu decreased as power function with the increase of εf. E50 increase linearly with qu while decrease monomially with εf, where below the critical value.

Self-balanced loading test (also called O-cell test) has been widely used in the testing of pile foundation with the benefits of solving many difficult problems not to be resolved by the static load test. Determining the value of conversion coefficient (the ratio of downward shaft resistance to the upward shaft resistance) is crucial issue to the calculation of bearing capacity. On the other hand, because the universal existence of clay soil in China, the study of conversion coefficient in clayed area is required. Thus, based on the project of Taizhou bay bridge, the value of conversion coefficient of self-balanced loading test is studied by field tests. Three cast-in-situ piles, 1.5 m in diameter and 83.5 m in length in clay soil are loaded by self-balanced loading method firstly, and then by kentledge loading method. In order to eliminate the effect between these tests, kentledge loading test was carried out 4 month after self-balanced loading test. At each soil layers, strain gauges are installed in each pile to obtain the value of shaft resistance. The value of shaft resistance of each layer from self-balanced loading test will be compared with one from kentledge loading test. The values of conversion coefficient are obtained. Also, the compared results from the other two similar projects are collected. From above researches, the ratio of downward shaft resistance and the upward one in Taizhou bay bridge is rational ranged from 0.7 to 0.8; and the ratio from other two different projects also proved this result.

The engineering problems of saline soil in inshore, including expansion, dissolution and water absorption, which result in the decrease of the compressive property are studied, Unconfined compressive test on fiber-saline soil is carried out in the conditions of three water contents (13%, 15% and 17%), three dry densities (1.77, 1.80 and 1.84 g/cm3), five fiber lengths (6, 12, 19, 25 and 31 mm) and five fiber contents (0.1%, 0.15%, 0.2%, 0.25% and 0.3%). The results show that the compressive strength fiber-saline soil decreases with increasing water content and increases with increasing dry density, but firstly it increases, and then decreases with increasing fiber length and fiber content at the limited point of fiber length 19 mm and fiber content 0.2%. All stress-strain curves are strain softening; the water content is a major influencing factor. By means of the nonlinear multivariate stepwise regression method, the sequence of adverse effect on the compressive property is water content, dry density, fiber content and fiber length respectively. It has been proved that reinforcing fiber can contribute to enhance the compressive property of saline soil significantly.

The group anchor，as one of popular foundations, is widely used. The soil deformation mechanism around group anchors when uplifting is sophisticated due to the interaction between anchors. The non-contact digital image correlation(DIC) method is used to perform model tests to study the behavior of group anchors when uplifting. The curve characteristics of uplift force-displacement relationships and soil deformation mechanism around anchors when uplifting are analyzed. The test results show that the relative density and embedment depth have significant influence on force-displacement relationships. Shallow and deep group anchors and single anchor have the similar curve characteristics of force-displacement relationship at the same relative density and embedment depth. Superposition effect is observed for group anchors. The factors such as relative density, embedment ratio and spacing between anchors have significant influence on group efficiency. The degree of influence of relative density, embedment ratio and spacing between anchors on group efficiency are obtained by deformation fields.

High-calcium fly ash is an industrial by-product generated during the combustion of coal for energy production, which is characterized by higher concentrations of calcium, carbon and hydraulic minerals. Previous studies have proved that high-calcium fly ash can enhance the strength of heavy metal contaminated soils and lower the mobility of heavy metal ions. In this paper, laboratory experiments and theoretical analysis are used to investigate the properties of strength, leaching, drying and wetting cycle of Pb and Zn contaminated soils solidified/stabilized by high calcium fly ash. The results show that the unconfined compressive strength of soil decreases due to the presence of heavy metal ions. Adding high-calcium fly ash to the contaminated soils can significantly improve the strength and reduce the amount of heavy metal ions that filter out. The strength of Zn contaminated soils solidified with fly ash is superior to the Pb contaminated soils. Both Pb2+ and Zn2+ can be effectively immobilized at low concentration; while Zn2+ is more effectively immobilized at high concentration. With the times of wetting and drying cycle increases, the unconfined compressive strength increases first, and then decreases. The heavy metal concentration of leachate increases as the times of wetting and drying cycle increases when the content of heavy metal in the soil is low. Times of wetting and drying cycle have little effect on the leaching properties of heavy metal when it is at a high level in the soil.

Great amount of engineering practices indicate that the single index Dc, degree of compaction could not well control the quality of embankment filled with high liquid limit soil (including the improved high liquid limit soil), and may cause quality hidden dangers. Through experimental study, this paper proposes a quality control method using two indices to control the quality of embankment filled with high liquid limit soil; and the two indices are the volume ratio of air Va and the degree of compaction Dc. When Dc is more than 93%, the suggested value for high liquid limit soil (or silt) is 4%≤Va≤8%, and the suggested value for high liquid limit sand soil (or silt) is 6%≤Va≤13%. The feasibility and validity of this two indices quality control method was verified through tests in laboratory and test sections. The results show that adopting the two indices (Va and Dc ) could not only guarantee the intensity and stiffness, but also ensure better water stability, so as to provide technical supports for further full use the high liquid limit soil as embankment filler.

This study conduct a mode III fracture toughness measurement test on a sandstone specimen with an edge crack in an anti-plane, shear-loading situation and obtain the mode III fracture toughness by using derived theoretical formulas. The testing conditions do not include confining pressure, and the mode III fracture test is conducted under a uniaxial load application. In addition, the study used a change in specimen properties, caused by exposure to high temperature, as a variable condition for further discussion. The research results show that the proposed method of performing the mode III fracture toughness test is reliable and stable. Heating at temperatures up to 200 ℃ enhance the sandstone specimen’s mode III fracture toughness. The toughness decline after 200 ℃ and then leveled off after reaching 600 ℃. The uniaxial compressive strength, dynamic Young’s modulus, dynamic Poisson’s ratio, and mode III fracture toughness show a declining trend following an increase in sintering temperature. The specimen appeared to be molten, and evident micro cracks appear on the surface.

The shallow landslides are often triggered by heavy rainfall in weathered granite soil slopes. These slope failures usually occur in a strongly weathered granite layer which has a big pore size. These can cause great casualties and property losses. Through field investigation and laboratory experiments, the effect of saturation on the shear strength of highly weathered soils and completely weathered granite soils taking from the intersection of Yulin and Wuzhou are investigated. It is found that there exists an "optimal saturation" at which the shear strength of the soil reaches the maximum. The influence of saturation on both cohesion and internal friction angle does not show a unique trend. It is also shown that the cohesion is significantly effect by the saturation of the soils; but the friction angle is not. Completely weathered granite soils and the highly weathered granite soils are significantly different in their lithological, composition, construction and shear properties. The characters of the highly weathered soil and completely weathered granite soil are significantly different, especially in the relationship between saturation and shear strength .Based on the analysis of cementation effect and the principles of matric suction, a sound explanation for the mechanisms underlying the above-observed discrepancy is provided.

Filter paper method is an indirect method to measure unsaturated soil suction, and it is necessary to get the calibration curve which can express the relationship between soil suction and filter paper’s moisture content before the suction of the soil is determined by filter paper method. This paper introduces researchers related researches in the calibration curve of Whatman No.42, Schleicher & Schuell No.589 and domestic Shuang-quan quantitative filter paper; it is found that the researches considering the temperature effect of filter paper’s calibration curve is still rare. The domestic Shuangquan 203 filter paper’s wetting calibration curve respectively at 20 ℃, 25 ℃, 30 ℃ and 40 ℃ is obtained by utilizing NaCl solution at different molar concentrations. The experimental results show that the water retention capability of filter paper is decreased with the increasing of temperature; and temperature has a greater impact on the water retention capability of filter paper when filter paper is in the period of low suction. The filter rate equation considering the effect of temperature is established by multiple linear regression analysis. The microscopic structure of filter paper is observed; and by means of surface chemistry theory, the mechanism of temperature effect on the filter paper rate curve is analyzed.

In practical engineering, pile foundations are often subjected to dynamic loads. For example, piles under high-speed railway are subjected to cyclic loading induced by train movement. Studying on the dynamic bearing characteristics of pile foundations under cyclic loading is of great importance in engineering design. The X-section pile is a new type of technique improved based on the traditional circular section pile. Its load-bearing mechanism is different from traditional circular section piles. The objective of this paper is to make further study on the dynamic characteristics and load-settlement relation of the X-section pile under cyclic loading; and then large-scale model tests on the performance of the X-section pile subjected to axial cyclic loading in sand are conducted. The results show that cumulative settlement of X-section pile is induced by the cyclic loading; and the settlement increases with increasing amplitude and frequency of the cyclic loading. At the initial period, the dynamic stiffness of X-section pile decreases and the axial stress of the pile increases. Furthermore, the friction resistance at the pile side decreases. After the initial period, they tend to be stable. These indicate that the dynamic performance of the X-section pile is better than the circular section pile; moreover, the friction resistance of the X-section pile is larger, the cumulative settlement of the X-section pile under long-term cyclic loading is smaller. The study results may provide some guidelines for the engineering design of the X-section pile under dynamic loading.

On the basis of geological process analysis in the topple failure of rocky slope, provided that the equilibrium state and interlamination resistance which prevent shearing offset damage do always exist between upper and lower edges of stratum, the stress of some point on rock mass can be simplified to vertical self-weight and horizontal lateral stress. In this way, the formula of the critical depth for topple failure can be deduced by turning the geological and mechanical process into plane strain model and adopting maximum stress failure criterion. Living example and discussion show that the critical depth theory about toppling failure applied widely, conform to actual failure，and also take horizontal stress into account . Besides, the slope and stratum dip angle as well as the thickness have greater influence on rock toppling failure, especial the slope of stratum angle between 50° and 70° is the most likely to topple.

The interface between two soils is a weak place where the seepage failure occurs easily. In order to investigate the seepage and seepage resistance properties of the interface between sandy gravel and sand, based on the seepage failure tests for the sandy gravel, the impact factors of the seepages and seepage failure, the occurrence and evolution of contact scouring under the conditions of vertical and horizontal seepages are studied by using large-scale vertical permeameter and self-built annular radial horizontal permeameter. It is concluded from the test results that the typical contact scouring process can be divided into three stages, i.e., stable seepage, transitional and failure stages. The three stages can be divided by two characteristic hydraulic gradients. The hydraulic gradient corresponding to the limit of the stable seepage stage is called starting gradient and that of the transitional stage is called failure gradient. The permeability of the combined sample of sandy gravel and sand decreases with increasing of the dry density, or decreasing of the particle size of the sandy gravel. But the seepage resistance of contact scouring increases with increasing of the dry density, or decreasing of the particle size of the sandy gravel. On the condition of horizontal seepage, the permeability of the sample is larger but the seepage resistance of contact scouring is less than that of vertical seepage.

Gypsum minings use room and pillar method frequently; the creep characteristics of gypsum mine have an important impact on the stability of mined-out area. In this paper, Jinghua gypsum mine is taken as the background, using RC-2000 microcomputer to control triaxial creep test machine to carry out experiments with Jinghua gypsum mine rock under confining pressures of 0, 2.5, 5.0, 7.5 MPa respectively. Creep test data obtained are analyzed, selecting the appropriate model for the test curve, and utilize the stress-strain curves method to obtain long-term strength under different confining pressures. The analytical results elaborate that the gypsum mine rock creep contains attenuation creep and constant creep; attenuation creep appears when the axial stress is small; constant creep and attenuation creep appear when the axial stress is big enough; using Nishihara model to fit the test curve. Results show that Nishihara model can describe the creep mechanical properties of gypsum mine rock nicely; the correlation coefficient R is more than 0.9. The ratio of long-term strength to creep strength is within 0.89-0.95 under different confining pressures, which means that the confining pressure has little effect on the long-term strength. The results findings will provide a basis for studying stability of gypsum mine mined out areas.

Because of the angularity, crushability, and high void ratio, calcareous soil has peculiar mechanical properties. Large-scale direct shear laboratory tests are conducted on calcareous gravelly soil taken from coral reefs, South China Sea. This paper intends to study the shear characteristics of calcareous soil under the conditions of various gradations, water contents, densities and mineral compositions. The results show that the extremely different mechanical properties of calcareous gravelly soil compared to the common non-cohesive soil. (1) Calcareous gravelly soil has a greater cohesion, larger internal friction angle, and lower softening value than quartz sand. (2) The internal friction angle increases with increase of dry density, while its apparent cohesion increases with increase of the median particle size (D50). (3) After shear failure, the apparent cohesion decreases from the peak value significantly; while its internal friction angle decreases slightly. The experimental results can be provided for the engineering constructions on coral reefs.

The studies focused on the thermal-mechanical behavior under cycle thermal load with a working load are relative little. Based on the laboratory model test method, this study aims to study the heat transfer performance and bearing characteristics of the pile under working load when cycle thermal load is applied. The temperature of pile and surrounding soil, horizontal soil pressure, thermal strain and pile head settlement are measured. The results show that the temperature of pile and surrounding soil varies little; and horizontal soil pressure recovers nearly to initial value after cycling. Moreover, it is also shown that a little residual strain will be produced in the pile, and the settlement will accumulate as the cycle thermal load is applied, so as to influence the bearing characteristics of structure.

Drilling blasting is the main mining mode in open-pit mine. Impact effect induced by blasting will lead to damage and fracture of rock surrounding the blasting area; and then affect the stability of slope. An approach to evaluate equivalent damage field of rock induced by blasting is introduced; and it is named as borehole water seepage field test. Some steps should be taken in this method. Through water seeping in each testing borehole, recording water level and seepage time, drawing water level and seepage time curve, and at last, analyzing it, the damage degree and damage depth are obtained. A relative damage factor is used to represent the damage degree induced by blasting, and the intersection point between sharp decreased stage and gentle changing stage is used to denote damage depth and damage distance. According to field testing; the maximal damage distance of rock induced by blasting is 20 m approximately; and maximal damage depth is about 12 m. The blasting resistance of iron ore is stronger than limestone. At same position, the relative damage factor of iron ore is 7.5% smaller than limestone; the maximal damage depth and maximal damage distance of iron ore is 4-6 m smaller than limestone. Sometimes, water level will decrease to certain elevation rapidly, and then keeps constant. It means a penetrated fractured zone forms; and the electronic peering instrument would be used to observe and check this phenomenon.

Surfactants can entry into soil and ground water environment through a number of ways, such as industrial, agricultural and daily activities, and thus lead to environment pollution and the change of soil behaviour. Silty soils are separately modified with anionic surfactant sodium dodecyl benzene sulfonate (SDBS) and cationic surfactant cetrimonium bromide(CTAB), then the strengths of modified silty soils are investigated. The internal friction angle become small when modify by surfactants, and the internal friction angle turn to be more and much smaller as increasing the concentration of surfactants. When the concentration of surfactants reached 2%, the internal friction angle of silty soil decreased approximately by 23.9%. The cohesion decreased by 91.8% when adding 2% SDBS to silty soil, namely, the cohesion of SDBS modified silty soil decrease quite a bit, while that of CTAB modified silty soil increase, and the maximum growth rate is 41.8%. The solution pH have a very slight effect on the internal friction of modified silty soil, while the cohesion of surfactants modified silty soil tend to decline as increasing pH. The change of pH can lead to the change of electric charge on soil surface, resulting in changes of electrostatic interaction between soil particles, and influencing the cohesion of silty soils.

The main purpose of this experiment is to do research on the synergism effect on leaching uranium ore and pyrite by Acidithiobacillus ferrooxidans(At.f) and Acidithiobacillus thiooxidans(At.t). The authors separate and purificate the thiobacillus of sandstone type uranium deposit by the method of enrichment culture, inorganic salt sodium silicate tablet. Through the analysis of the morphological characteristics, physiological and biochemical results of strain and 16s rDNA sequence, the strain status in system development are determined. And by using the method of shake flask culture design ore leaching test, added separated and purified At.f and At.t and mixed At.f and At.t to pyrite leaching system respectively. Measured the change of parameters such as pH, Eh. 40 d later, detected total concentration of iron and sulfate’s ion. meanwhile analyzed the composition and morphology of the surface of slag of pyrite. Designing the uranium leaching experiment based on the results of the leaching of pyrite, after 40 d, Measured the change of parameters such as pH, Eh, total concentration of iron and sulfate’s ion, calculated the leaching rate of tetravalent uranium. The results showed: SW-2 is identified as At.f, SW-3 was identified as At.t. At.f and At.t exisited synergy leaching pyrite and uranium ore, At.f was strong oxidant by oxidizing Fe2+ to Fe3+ before Fe3+ oxidizing UO2 to soluble UO22+ in leaching system. At.t could provide acidic environment for leaching system, the best amount combination of bacteria was 5:1(At.f:At.t), the leaching rate of UO2 was 55.60%, surface morphology of slag of pyrite showed that was a direct oxidation from the bacterial to pyrite. The condition of At.f and At.t that leaching pyrite also had the same significant role in promoting microbiological leaching uranium ore with pyrite as the associated minerals. The results of the study could provide certain support for industrial microbial leaching uranium and provide reference for microbiological leaching minerals with pyrite as the associated minerals.

Potential evaluation of rockburst is an important topic for risk estimation in construction, construction cost and planning project layout in the primary stage or feasibility study stage of the project. There still exist some disadvantages in application of the evaluation method of rockburst proneness or the stress-strength ratio. Therefore, an evaluation method was suggested on the potential rockburst problem, considering three aspects of both the interior and exterior of factors including rock mechanics properties, qualities of surrounding rockmass and in-situ stresses. The corresponding geological conditions of rockburst sections were summarized to conclude that rockburst occurs mainly in II or I grade of surrounding rock mass. The test method of rockburst proneness index was improved to inflection points of volume strain for unloading control points. A new index of potential index of rockburst was put forward by introducing three factors of elastic strain energy index, stress intensity ratio and principal stress ratio. Then, the corresponding threshold values of the new index were presented. The proposed evaluation method provides a simple and scientific way for estimation of rockburst risk in the feasibility study stage .

To make further research on the horizontal bearing capacity of caisson-pile composite foundation, the model tests on single pile and a series of caisson-pile composite foundations, under horizontal loads and the combination of vertical and horizontal loads in silty clay, are carried out. The relation between load and displacement, bending moments of pile shaft, lateral deflections of pile shaft and efficiency coefficients of group piles are investigated based on the model tests. With the constraint of caisson, the bending moments, displacements and soil resistance of pile shaft under the horizontal loads, can be reduced than the single pile without constraint; the horizontal bearing capacity of composite foundation can be improved. Under the vertical and horizontal combination loads, friction under the caisson bottom and vertical force on the pile top is also conducive to further improve the composite foundation bearing capacity. The efficiency coefficients of caisson-pile composite foundations with different pile numbers, constraint conditions on the pile top and loads on caisson are also obtained. For the case of pile distance is 6 times of the diameter, the mutual influence between each other pile is very small.

Based on the microseismic monitoring data at the left bank abutment slope of Jinping first stage hydropower station, the microseismic activity characteristic is analyzed. The S transform(ST) is used to decompose waveform, and this method is also applied to process the waveforms in the impoundment and construction periods of the left bank abutment slope to investigate the time-frequency characteristics of microfractures. The results show that: (1) Compared to the construction period, the rock mass of the abutment slope tends to be stable in the impoundment period, and the microseismicity is intimately related with the impoundment and geological structures. (2) The ST concentrate the advantages of short-time Fourier transform(STFT) and wavelet transform(WT), it has desirable characteristics in the time-frequency analysis of non-stationary signal. (3) The time-frequency characteristics are more stable than waveform characteristics; and the waveform decomposition based on ST can successfully reveal the damage information of seismic source location in the waveform. (4) Compared to the construction period, the frequency and mono-vibration proportion of microcracking signals of the left bank abutment slope in the impoundment period increases; and the duration decreases. These phenomena are due to the enhancement of rock mass integrity and strength at the left bank abutment slope during the impoundment period. Thus the microseismic signal shows different time-frequency characteristics. The time-frequency parameters of microseismic event can reflect the microfracturing information of rock mass and provide references for the stability evaluation.

A complete 3D numerical simulation by using FLAC3D is developed to investigate the features of surrounding rock deformation and stress field in squeezing ground excavation by double shield tunnel boring machine(TBM). The TBM model was based on the real geometry and the nonuniform gap between the shield and the ground. A great emphasis is placed on the key steps to simulate TBM tunneling in accordance with the practical construction. In this paper, we mainly studied the characteristics of displacement field, stress field and the plastic zone on the cross section and the longitudinal section profile of the tunnel. The results obtained in numerical modeling indicate that the surrounding rock which located in the lower part of the wall is contact to the shield of TBM, whereas the crown is not. Three loading and unloading phenomena are observed in the surrounding rock of floor, which can be attributed to the impact of the geometry of size difference on the cutter head and shield and the conicity of the front shield and the rear shield. Moreover, the circumferential stress and the radial stress in floor is greater than the crown; and the wall and the orientation of major principal stress is severely perturbed and obliquely crossing the radial of the tunnel. But the ground on the lower part of 70° is in elasticity. The plastic zone outside the front shield gradually decreases from top to bottom on transverse section and increases with the greater distance away from the excavation face. But, it has no obvious change in ground outside the rear shield.

In order to study the effect of landfill gas on pore pressure below the leachate level in wet municipal solid waste landfill, a new model for predicting the time and depth dependent development pore pressures due to the formation of landfill gas is derived. Considering the specific flow conditions of pore gas below the leachate level, the model combines the Darcy law, the ideal gas law and the theory of dynamics of fluids in porous media. A finite difference solution is obtained for the liquid-gas migration problem, which is caused by the continuous formation of landfill gas within the wet waste. The calculation results show that the pore pressure below leachate level is mainly influenced by the additional pore pressure caused by the increasing of phreatic surface and the excess pore pressure due to the continuous formation of gas. The pore pressure varied over time during the gas generating period. At the beginning, a maximum gas pressure is identified because of gas eruption, and then, gas escaped from the surface leading to an immediate pressure reduction along with a significantly increased gas permeability; finally, the pore pressure is depended by gas-liquid convection. In the landfill, high gas yield rate, high leachate level and low permeability make waste to form high pore pressure. Drawdown of leachate level is found to be the most effective and workable emergency measure to reduce the pore pressure in wet landfill, which is caused by the continuous formation of landfill gas.

New tunnel crossing over existing tunnel will inevitably change the already balanced ground stress field and cause ground stress relief, which will result in longitudinal heave of existing underlying tunnel. An analytical method is proposed to assess the longitudinal displacement of the existing tunnel subjected to above-crossing tunneling. The existing tunnel is simplified to be Euler-Bernoulli beam resting on the Pasternak foundation model. Two-stage analysis method is adopted to analyze this problem. First, the vertical distributed unloading load induced by the construction of above-crossing tunnel is computed by Mindlin′s solution. Second, equilibrium differential equation is established under the corresponding vertical distributed load due to unloading and it is solved numerically based on the finite difference method. The applicability of the presented method is validated against two well-documented case histories. A consistent trend between the measurements and predictions is observed. It means the proposed method can be reasonably reflect the law of the longitudinal displacement of existing tunnel subjected to above-crossing new tunnelling in close distance.

The determination of the weights of the influencing factors in evaluating the suitability of engineering sites varies greatly among the conventional methods which are generally found unreliable when applied to some engineering sites with complex geology for their failure to reveal the complex relationships between the geological factors. To satisfy the need of selecting proper sites for large-scale key projects, we improve the constant weight to variety weight and introduce the matrix of multifactor interactions into the suitability evaluation of engineering sites, and propose the concept of engineering site suitability index (ESSI), a comprehensive index which is capable of considering the correlations between the influencing factors and the variation of their impact under various tamporospatial dimensions; and therefore put forward a multi-discipline system for evaluating the suitability of engineering sites. The system is used in the site selection for China Spallation Neutron Source(CSNC) Project, and found applicable and reliable by the follow-up engineering investigation. The ESSI system which is based on the matrix of multi-factor interactions is proved scientific, reasonable, and applicable by case studies; and it is expected to provide a reference for similar large-scale engineering

Layered rock mass is a kind of common rock mass in underground engineering, and its mechanical properties often take on distinct anisotropy. Selecting appropriate yield function and suitable strength parameters variable law, combining elastic constitutive function of anisotropy, then elastoplastic constitutive function of anisotropy is obtained. Gonghe tunnel is numerically modeled by utilizing this constitutive function. Firstly considered the influence of crustal stress and rock property, support design scheme is modified and optimized from these aspects such as deformation of surrounding rock mass, style of failure, magnitude of yield field and bolts tension; secondly considered the influence of construction difficulty and engineering cost from the actual project, it is concluded that the modified design I is better. Modified scheme I is even adopted in the process of tunnel construction. So constitutive model has great effect on the result of calculation, calculation result of appropriate model can provide scientific proof for the actual project.

The layered salt rock formation in China has the characteristics such as thin in depth, too many interlayers, and high impurity contents. The vertical gas storages sometimes couldn’t get enough volume to meet the demands of economy when the thickness of the salt layer is thin. By improving the horizontal dimension, the horizontal gas storages were built in the salt formation which didn’t have interlayers could satisfy the demands of economic volume. To discuss the mechanical feasibility of horizontal gas storage, we propose the simplified mechanical model of horizontal ellipsoidal gas storage. Using the elastic theory method, we acquire the computational formulas of stress distribution of the key points with the help of other researchers’ results, which are the function of ellipsoid shape ratio, the material Poisson’s ratio, the operating internal pressure and the far field stress. The theoretical solution and numerical solution are compared; and the average error is about 3%. Taking Druker-Prager yield criterion into account and by applying the theoretical formula, we calculate the minimum operating internal pressure when the horizontal ellipsoid shape ratio kept constant, acquire the relationship between ellipsoid shape and the minimum internal operating pressure and discuss the range of operating internal pressure of the horizontal ellipsoid gas storage.

CFG pile(cement-fly ash-gravel pile) is an important type of ground improvement, and its role is becoming even more prominent as more accessible soft foundations become increasingly exploited by the surging urban industrial development in China. Yet despite its significance, the load-settlement behaviour is poorly understood on this pile type; particularly in the context of probabilistic assessments. Based on a series of repeating full-scale field load tests for CFG piles (21 samples) and the pile-soil intermediates(PSI) or composite foundation systems (32 samples) under static axial compression loading, the data of the loading-displacement curves were gathered from a field site in Beijing city. A regression curve is facilitated by approximating the load-settlement curve for each load test using a two-parameter, hyperbolic or power law curve-fitting equation. Moreover, when assessing the regression parameter values from entire pile load measurements across the test site, the scatter in load-displacement curves attributed to inherent soil variability can be found. Thus, the uncertainties of the load-displacement curves at the site are represented by a relatively simple bivariate random vector containing the regression parameters as its components. A bivariate Copula-based mixed distribution is further applied to capture the dependence characteristics between these regression parameters. For the CFG pile, the Pearson correlation coefficient between the power-law regression parameters is calculated to be -0.621; and the best-fitting Copula is identified as normal through the Akaike information criterion(AIC). In the case of PSI, the correlation coefficient of the regression parameters is -0.645 and their dependence structures are best described by the normal Copula. Finally, a simple Copula-based simulation model(CBSM) is used to estimate the reliability index at any specific allowable settlement for the serviceability limit state(SLS) design. The effect of the various Copulas on the reliability indexes is clarified. These analyses of the load-displacement behaviour give an insight into the probabilistic design and safety assessment of the CFG pile foundation.

The accumulated plastic strain and the pore water pressure of the soft clay under traffic loading condition were given by empirical models. Based on the layer wise summation method, a pseudo-static method is proposed to calculate the long-term settlement of the soft subgrade. The settlement is obtained by the superposition of two deformations, the one is the deformation caused by the accumulative plastic strain of the soft soil induced by undrained cyclic loading; the other one is the deformation caused by the dissipation of the accumulative pore water pressure. According to the experimental data of the dynamic hollow cylinder tests, the parameters for the empirical model of the accumulative plastic strain and pore pressure are established. The stress distribution induced by the traffic loading in soft subgrade is obtained by the integration of the elastic analytical solution; and the calculation method of the total deformation is proposed by the layer-wise summation method. The proposed method has been used in real engineering projects; its rationality is verified by comparing the calculated settlement with the field measured result and the existing solution.

Energy pile is a new technique which can save underground space and construction cost. However, the research focused on regarding the thermomechanical behavior between the pile and soil during heating and cooling are relative little. Based on the model test method, the experiment aims at systematically studying the thermomechanical behavior, heat transfer performance and bearing characteristics of four heat exchangers type piles including U-shaped (lashed and embedded types), W-shaped and Spiral-shape on saturated sand. The temperature of the pile and surrounding soil, the variation of tip resistance and horizontal soil pressure, and the pile head settlement are monitored. Meanwhile, the thermal strain of piles over time is also extrapolated. The results show that the pile temperature, thermal strain, pile head settlement and surrounding soil pressure related to W-shaped pile varies more obvious than Spiral-shape pile and single U-shaped pile.

There are a lot of factors that affect sand liquefaction, and then it is necessary to establish a multi-index liquefaction prediction model. At present, all of the multi-index sand liquefaction prediction models based on a hypothesis—the selected discriminant factors are independent and there is no correlation between each other, which may lead to information superimpose between the different factors and mis-discrimination. In this paper, based on 25 cases of sand liquefaction in Tangshan earthquake, eight factors influencing sand liquefaction are selected as the initial discriminant indexes. The principal component analysis(PCA) is introduced in the correlation analysis of initial discriminant indexes and dimension-reduction processing is conducted to some indexes with high correlation. The new sample data are obtained based on the 4 principal component conversions. A predictive model for predicting sand liquefaction is established under the combination of PCA and distance dscriminant analysis(DDA). The forecasting results of 18 training samples are all correct by using the established model. The liquefaction of the other 7 cases is also predicted; and the results are compared with those of the standard, Seed method, BP method and DDA method. The results show that the prediction accuracy of the forecasting model is 100%. The model is applied to a practical engineering example, and the results are consistent with the actual situation, so as to show that the model has good prediction function and can be used in practical engineering.

Based on results of ground deformation monitored and the numerical simulation, the process of ground deformation is investigated in East Main Shaft of Chengchao Iron Mine; and then the characteristics and mechanism of ground deformation are given. Research results show that: When the underground mined-out area and the collapse pit form a certain scale, under the release and squeezing of horizontal tectonic stress in different directions, the surrounding rock cut columnar structure cut by geological in structures the surrounding rock toppled to collapse pit, then caused the ground deformation in the surface. Ground deformation is mainly dominated by horizontal displacement, and the vertical displacement is very little. With the constantly tilt of columnar structure, the ratio of vertical displacement to horizontal displacement is constantly increasing, and the funnel-shaped deformation curve forms in the surface.

Through the indoor model test, using the visual tracking technology, through observing the soil displacement field of anchor in the drawing process, and the soil particle porosity and particle trajectory tracking, and then the mechanism of anchor and soil nail is studied. The study found that the particles in the process of pulling anchor for the shear effect of the soil particles move to the soil nailing mobile, but because the boundary constraint of soil nail, the particles reverse, the final compaction zone is formed between the anchor and the soil nailing; the formation of compaction zone not only decreases the soil displacement, but also make the limit of soil nailing, and anchor pullout capacity is improved, which explains why the anchor composite soil nailing can decrease the soil displacement. The study results can provide a theoretical basis for the design of and construction of the anchor composite soil nailing.

Deformation of subgrade and pit observed during construction of foundation pit engineering near a railway are presented. The deformation and control measures are analyzed. The settlement of surface ground and subgrade increase linearly over time during slope excavation, which is up to 12 mm after the slope excavation is completed. Affected by the train load and water leakage, the subgrade settlements increase rapidly during the construction of jet-grouting reinforcement of foundation pit bottom, top beam and concrete strut; and a nearly 50 meters long settlement tank with maximum settlement 95 mm is observed. It is also found that over 60% of subgrade subsidence increment during the construction of aforementioned stages accounts for more than 70% of cumulative settlement. Most of the surface settlement is less than 20 mm, 2.4‰ of excavation depth. The shape of the ground surface settlement profile within the region of subgrade settlement tank is concave type and the maximum settlement occurs at the subgrade. Two fluid grouting at slope top can effectively control the surface and subgrade settlement and reduce the impacts of subsequent excavation on subgrade. But the grouting construction may cause displacement mutation of slope, especially the lateral displacement towards to the pit, which is harmful to slope stability and railway safety.

The assembled foundation for transmission line, which is composed of concrete laths and angle steel scaffolds, has been applied to practice. Due to the gap of laths, the bottom area of the foundation is not clearly defined when calculating the compressive load. Theoretical research on the ultimate bearing capacity of foundation indicates that soil arching effect exists between the adjacent slabs. The shallow soil under the slab of assembled foundation can be approximately equivalent to a rigid body, which resists the compressive load together with the slabs as a whole. The in-site experiments at different lath intervals testify that the difference of soil pressures under the laths and at the gap of laths is relatively large in the shallow soil. But the soil pressures are basically the same in the deep layer where the change of the lath interval has no significant impact on soil pressure. The difference value between soil pressure under the laths and that at the gap of laths is small in the position of 3times laths width. And the difference value can be neglected in the position 5 times laths width. The research result suggests that the whole area surrounded by the laths is preferable in the calculation of compressive load on the assembled foundation composed of concrete laths.

This paper discusses the geostress distribution of slope in deep-cutting gorge in Southwest China. Based on 95 test data of spatial stress and 50 test data measured using the method by adit-wall stress restoration from 10 large-scale hydropower projects in Southwest China. The change discipline of geostress field along with vertical depth and horizontal depth can be counted and analysed. Furthermore, the characteristic of geostress field in superficial zone of slope can be discussed according to the magnitude of principal stress and the change rule of dip angle. The results show that: (1) The stress field can be divided into two parts: superficial zone(0-300 m) and deep zone(>300 m) from macroscopic perspective. (2) The magnitude of principal stress and the dip angle is extremely volatile in superficial zone; the magnitude of principal stress and the dip angle in deep zone is stable. The magnitude of maximum principal stress is between 15 and 30 MPa; the magnitude of minor principal stresses is between 5 and 12 MPa; the dip angle is ranged from 0 to 30°, It is apparent that the magnitude of maximum principal stress is 1.5-3.5 times than minor principal stresses. (3) The change characteristics are that the principal stress magnitude in superficial zone changes from low to high and fluctuates violently before to stability while the dip angle of maximum principal stress is transferred from the nearly parallel with slope to high-variability, and then the two gradually shift to a consistent state with deep zone.

Aiming at the dynamic stress changes of roadway driving along goaf in mine, we use the method of drill cutting to get the dynamic change characters of seam stress along the strike direction of roadway and analyzed the variation characteristics of roadway driving along next goaf in Zhangshuanglou Coal Mine. According to the observation and analysis, it is shown that the peak of coal stress affected by lithology, geological structure and the "O-X" broken feature of roof, appears periodically; and the cycle length is equal to the periodic weighting step distance. Effected by the stress state of surrounding rock, the new stress distribution induced by the roadway excavation and the overlying strata movement, the solid stress of coal in roadway driving along goaf varied with reduction, increase or transfer. The stress variation characteristics can be used to guide pressure relief plan of rockburst and rockburst prevention and control work significantly.

The collapse of unstable rock is actually the problem of fracture and extension in dominant fissure of unstable rocks. Based on fracture mechanics model of dominant fissure, this paper puts forward a fracture stability determination method for unstable rocks, and establishing stability coefficient by the index of union stress intensity factor. By this method tip stress distribution forms of dominant fissure and its calculation expression are deduced. Fracture mechanism model of tip in dominant fissure for unstable rocks is proposed; and then for this calculation method union stress intensity factor in tips of dominant fissure is deduced. Fracture stability calculation results of unstable rocks in Shouli Mountain, Wanzhou Area, Chongqing show that the calculation results fit well with the field situation, so as to show that the fracture stability calculation method proposed is more security, objective and practical than the existing “specification method”.

The effect of pore water pressure plays an essential role in the analysis of stability and safety of geotechnical engineering. Formulation of a perfect elastoplastic model satisfying D-P criterion is presented based on Viesca’s poroelastoplastic model considering saturated pore pressure. Under the undrained condition, the equivalent strength parameters of geomaterial shall be used, which brings out the change of yield surface shape; and the expression of exact integration algorithms is modified based on the closest point projection method. The effect of undrained pore pressure is thus considered on the elastoplastic response of pore geomaterial; and the evaluation of geotechnical structure is implied by using the unbalanced force inheriting the concept of overstress. A heterogeneous slope suffering rainfall infiltration is simulated by using nonlinear finite element method code, which proved the practicability of the model. The nonequilibrium evaluation of slope stability can be quantified by combining our procedure with the unbalanced force. It is also found that the increment of Skempton’s coefficient weakens the layer of slope suffering sustained rainfall infiltration and threatens its safety.

A series of numerical simulation of constant b cubic tests are conducted using discrete element method to study the strength characteristics of granular materials under different stress paths. The influences of intermediate principal stress and stress path on the peak strength of granular materials are analyzed in 3-dimensional stress state based on the simulation numerical results. The variation of peak friction angle and peak stress ratio is also studied. Contributions to strength of granular materials are analyzed based on the true stress concept and the development of fabric tensor. Research results show that the variations of peak deviatoric stress with Bishop parameter are different in different type cubic tests; however, the stress-strain curves normalized by the initial confining stress are identical. The slope of peak strength line independent of stress path is only related to parameter b; and the peak stress ratio qf /pf decreases with an increase of b. Simulation results are in agreement with laboratory observations. Meanwhile, stress-induced fabric anisotropy is developed with the increasing strain. The strength of granular materials is the joint action of friction of particles and anisotropic fabric induced by the applied stress. Theoretically, the location of failure point in fabric ratio-stress ratio coordinate system is only decided by the particle apparent friction angle. The deviation between numerical simulation and theoretical analysis is origin from the effect of interlocking and rolling friction between particles and this influence is related to both particle friction coefficient and stress state.

Hard rock in cold region with surface cracks contact with atmosphere, therefore water in cracks would congeal caused by low temperature environment. The temperature would be mutation near the cracks, and the expansion caused by phase transition would produce frost heaving force. While the temperature field and frost heaving force are in the dynamic evolution on the freezing effects. Because the complex multi field problems include temperature field, seepage field and stress field. At present, a lot of related researches are based on the results of numerical simulation to summarize the distribution characteristics and rules of temperature field as well as stress field in fractured rock masses. While considering the perspective of analysis and calculation on basic theory, study on the evolution of temperature field and frost heaving force in fractured rock mass under low temperature environment is rarely reported. Depending on the freezing phenomenon of hard rock with surface cracks under low temperature environment, and according to the theory of heat transfer, phase transition, elastoplastic mechanics and fracture mechanics. This paper explores the evolution process of temperature field and rost heaving load in hard rock with surface cracks. Corresponding analytical expressions are put forward and introduce to the multi-physics coupling program Comsol-Multiphysics to analog computation. Comparison results show that the evolution analytical expressions of the temperature field and the frost heaving load are very close to the numerical simulation. The expressions can basically be suitable for the evolution analysis of temperature field and stress field on the semi-infinite plate model containing surface cracks. So the study provides a good reference value to the temperature field and stress field evolution analysis in fractured rock mass under low temperature.

Based on the meshless method, the self-developed program is proposed to analyze the rock mechanics. In the present program, the Mohr-Coulomb criterion is adopted and the softening of material after plastic yield can be considered. The deformation of defective rock under uniaxial compression can be analyzed; and the evolution of deformation localization in defective rock can also be clarified. The calculation results show that the process of destruction of rock specimen is evolutionary. The material destruction and acoustic emission occurs at the defective weak particle of rock specimen with the loading process. A localized deformation zone produced with the crack expanding. A distinct shear failure zone formed in the rock specimen with the expansion and development of localized deformation zone. Defective particles played a control role in the specimen damage process. Rock acoustic emission records the plastic failure process of rock materials. The development of shear failure zone and plastic zone of rock specimen has a very similar way. However, the plastic area is greater than the shear failure zone; and the shear failure zone is located in the plastic zone. It can be concluded that the localized deformation occurs before the stress-loading step (strain) reaches the point of peak strength.

In order to study the deformation and destruction law under hydro-mechanical coupling of coal, the relationship between macroscopic mechanical parameters and microscopic parameters of coal is discussed seriously by compression and tension test numerical simulation with PFC2D. Simulation of conventional triaxial test under different confining pressures and gas pressures are performed on coal with parallel bonded model and the inferred relationship. The comparative error is analyzed between test results and simulated results; and the changing law of coal macroscopic mechanical parameters is summarized. The results show that: The relationship inferred by numerical simulation can simulate the coal mechanical characteristics well and control the error less than 10%. With the improvement of confining pressure, the compressive strength, residual strength and elastic modulus show a trend of increase, and the Poisson’s ratio and the angle of coal fracture decrease, so as to prove that the confining pressure can strengthen the stiffness and strength of coal. That the compressive strength, residual strength and elastic modulus continuously decrease and the Poisson’s ratio and the angle of coal fracture increase with the gas pressure increasing shows the weaken effect on the stiffness and strength of coal.

Thermal cracking of rock is a critical subject in high radioactive waste disposal engineering. A laboratory simulation test was conducted to study the thermal cracking of Beishan granite. The temperature measuring device, acoustic emission (AE) system, ultrasonic computer tomography(CT) and microscope were applied to the test. The results show that the macrocracks originated at the outer edges of the specimen and then extended inward. The growth of cracks was mutational, and the latter cracks were suspected little impact of the former cracks. Four stages were observed during the test: stable thermal damage stage, macrocrack formation stage, macro-crack growth and the crack closure stage during cooling period. The evolution of AE locations reveals the growth of cracks’ propagation process. The ultrasonic imaging of the cooled sample was obtained by the elastic wave CT. The cracks’ positions and area suffered heat damage could be visualized in the CT imaging. The study shows that system combined AE and ultrasonic CT is effective to characterize the evolution of thermal-cracking process and quantify the damage. Temperature field obtained from a group of thermal couples can be used to verify the parameter for numerical simulation. The results of numerical simulation show that the high tensile stress at the time of macrocrack appearing is consistent with the tensile strength of Beishan granite. Thermal induced damage and thermal-mechanical induced crack are analyzed systematically, so as to provide reference for the future related tests conducted in underground laboratory.

According to the theory of fluid mechanics, considering liquefied soils as fluid, which analyzed the dynamic field by vector symbolic operation method and solved the analytical solution of dynamic field. It is used to analyze hydrodynamic characteristics of liquefied site by finite element method of ABAQUS/CFD; and the numerical solution of the dynamic field is calculated by the basic flow control equation. The results show that underground structure suffers pressure drag caused by surface pressure and frictional resistance caused by shear stress when liquefied soils flow in lateral. The flow velocity of liquefied soils around the tunnel is very small; but there is a velocity strengthening region below the tunnel structure. The analytical solution of the theoretical calculation is greater than the numerical solution of the finite element method; but the distribution of the overall trend is basically the same. The stress field near the tunnel structure is more intensive; and the stress distribution is mainly distributed in head position of liquefied soils.

Punch-through is one of the main threats to the safe operation of jack-up units. Perforation method has been successfully implemented in engineering practice to mitigate punch-through potentials. However its research and evaluation method are still limited. With the coupled Eulerian-Lagrangian method provided by ABAQUS, finite element analysis of punch-through mitigation with perforation is carried out. The spudcan is modeled as Lagrangian domain, while the soil is modeled as Eulerian domain, among which the holes created by perforation drilling is initially modeled as void. The mechanism by which perforation mitigates punch-through potential is analyzed, which shows that the perforation drilling turns general failure mechanism into local failure mechanism in stiff-over-soft clay layers. And the effects of hole number, hole depth, hole diameter and extent are studied. It is shown that the soil plug during penetration into stiff-over-soft clay decreases with hole number, hole depth and hole diameter. Correspondingly, the efficiency of punch-through mitigation with perforation is proportional to hole number, hole depth and hole diameter. However, the effect of hole diameter on the peak resistance is relatively very small. The extent of drilling holes outside the spudcan perimeter has little effect on the peak resistance, while it has a larger effect on the post-peak resistance. An evaluation method for the efficiency of peak resistance reduction with perforation method is proposed by fitting from 75 cases of numerical simulation. It takes into account the perforation drilling area both outside and inside the spudcan perimeter; hole diameter and hole depth, which is of great significance for engineering practice.

This paper predicts the lower-bound shakedown limit of an elastoplastic half-space under traffic loads based on the first dynamic shakedown theory. A three-dimensional finite element model with infinite element boundaries is built. And then the model is used to analyze the dynamic elastic stress under different speed moving loads, and a steady residual stress field is constructed through the dynamic elastic stress. A method to predict the dynamic shakedown limits through analyzing the residual stress is proposed as well. Then the lower-bound shakedown limits of half-space under dynamic traffic load and the influence of speed on shakedown limits are discussed. Meanwhile, the difference of shakedown limits between uniform load and Hertz load are studied. In addition, the shakedown limits will increase with the growth of moving speed when the load speed is lower than Rayleigh wave speed, otherwise the shakedown limits will decrease with the growth of moving speed when the load speed is faster than Rayleigh wave speed. It is also found that shakedown limits of uniform load and Hertz load are similar when the total weight load of this two load manners are the same.

In order to analyze the stability of slopes, by using coordinated particle swarm optimization(CPSO) and BP neural network, a CPSO-BP model is built to predict slope stability. BP neural network can describe the complex nonlinear relationship between the slope stability and its influential factors; six main influential factors, i.e. internal friction angle, slope angle, unit weight of rock, slope height, cohesion and pore pressure ratio, as a network input, the network output is the slope stability factor. BP neural network is so easy to fall into local optimum that take advantage of coordinated particle swarm optimization algorithm the ability of global to determine BP neural network connection weights and thresholds, let the advantages of BP neural network can fully play. Frinally we will approach to the aim that improving the accuracy of model predictions. Case study shows that the CPSO-BP model has better prediction accuracy and it is feasible to predict the slope stability.

Taking account of soil-structure interaction on seismic wave input, based on the theory of a two-step method, equivalent seismic wave input considering radiation damping effects is established. Firstly, the base response of single degree of freedom system is considered as the input of superstructure; and then damping ratio of the system is calculated by the state-space method considering soil-structure interaction, which is used to modify the damping coefficients of superstructure; thus the impact of soil-structure interaction is approximately calculated from the response of rigid foundation. Subsequently, a single degree of freedom system and a five-story frame structure are analyzed; numerical examples show that the calculation errors even exceed 100%; while directly taking seismic wave of free field and bedrock as the input of superstructure. However, the calculation errors of the two-step method are less than 10%; furthermore, the calculation errors will be less than 5% adopting the modified damping two-step method, which can satisfy the requirements of engineering.

In order to find out the bearing capacity and failure mechanism of interface between new grouting-screw pile and soil, the discrete element simulation(DEM) has been used. The DEM model has been built under existing experiment plan of pile-soil interface. According to servo mechanism, the normal pressure on the interface can be unchanged. Then the baseboard is moved at constant velocity, and the relation between shear stress and shear displacement, contact force transport mechanism and the porosity distribution could be obtained when screws of different numbers are adopted. The results show that there is an optimal flutes pitch which can make sure the ultimate shear stress reach to the maximum. And the vaulted failure surface will appear around the pile-soil interface. Moreover, the micro mechanism has a good agreement with indoor experiment.

Rockburst is one of the main engineering geological hazards occurring in the deep underground engineering construction. The classification of rockburst is an important issue which must be resolved in many underground engineering. Four quantitative indices including the ratio of rock′s compressive-tensile strength σc /σt，the stress coefficient of rock σθ /σc，the elastic energy index of rock Wet and integrality coefficient Kv are chosen as the predictor variables of rockburst，according to the unascertained factors of classification prediction of rockburst. The entropy method is adopted to determine the weighting coefficient for each evaluation index. Based on entropy method and the unascertained measurement theory，with 12 groups of typical engineering examples, rockbursts at home and abroad, an entropy and the normal cloud model to predict the possibility and classification of rockburst is established. Then the proposed model is validated with twelve typical rock projects and compared with the results of the technique for order preference by similarity to ideal solution method, the radial basis function-auto-regression method and the actual records. And then the model has applied to rockburst predicting calculation of Zhongnanshan tunnel ventilation shaft to study the effectiveness and feasibility of the model. The obtained results show a good agreement with practical rockburst classification. The results show the normal cloud model effective and available，and can be applied to the prediction for the possibility and classification of rockburst intensity in deep underground engineering.

Based on the principle of fluid-structure coupling numerical simulation program, PFC2D particles flow, which uses its built-in FISHTANK function library and FISH language, the flow equation and pressure equation of fluid domain have been defined. The process of grouting slurry diffusion in the formation and shape are simulated and calculated. By adjusting the parameter of step and perm in PFC’s command stream, grouting effects in different penetration gravels are obtained. Numerical simulation indicates that action modes between serous fluid and ground soil are mutually affected by the grouting pressure; foundation structure will be destroyed as the grouting pressure increases excessively. Stressed states around the drilling hole have been analyzed theoretically. The theoretical results are consistent with the simulation ones. When split grouting action occurs the porosity and strain increase.

There are large uncertainties in the overall stability of supporting structure of large-span double-row sheet-piled cofferdam. The projects with the same values of factor of safety may have different failure probabilities. It is found in practice that some projects with large factor of safety failed and vice versa. In order to improve the evaluation and reduce the uncertainties of stability analysis, Bayesian method is applied for reliability analysis. First, the prior probabilities of soil parameters are obtained based on statistic data. Then, the posterior probabilities are achieved by updating the prior with measured data based on Bayesian method. Finally, the method of “first order second moment” is applied to conduct reliability analysis of the supporting structure stability of deep excavation. Bayesian method theoretically solves the problem of integrating the information from both experience and measurements. The reliability analysis with Bayesian method may be closer to real cases.

Based on AutoCAD and OpenGL visual finite element modeling, a method is proposed for generating asphalt element in underground powerhouse finite element model through rewriting the model file with Fortran, which can significantly reduce the number of model elements and nodes and greatly boost the modeling and computational efficiency. Implicit lever element and column element are introduced to simulate asphalt-wrapped bolt and general bolt respectively and their stiffness matrixes and iterative calculation formulas are derived. This model is applied in the finite element analysis of asphalt-coating bolts for the rock-anchored beams of an underground powerhouse. The results show that adoption of this technology reduces the surrounding rock damage zone of rock wall, increases the stresses of deep bolts inside the surrounding rock and thus can improve the mechanical characteristics of rock mass in the vicinity of anchors and increase the overall safety of the surrounding rock and crane beam, which is also in line with the engineering practice. The calculation and mesh generation method in this paper are simple and easy to be implemented and it may be expected their application in the finite element analysis of similar projects.

Taking Lirang tunnel of Liang-Zhong Expressway in Chongqing city as an engineering background，based on the field joint investigation by scan line，the distribution density function of joint production is obtained; and the fractal distribution law of joint spacing and trace length is analyzed from the viewpoint of fractal geometry. In addition，the fractal dimension D from the distribution of joint spacing and trace length and fractal distribution probability density function can be derived. Based on these work，Monte Carlo stochastic simulation theory and Matlab software are adopted to obtain simulated joints data. Finally, a discrete fracture network(DFN) model which could reflect the distribution characteristics of the joints is established. The results of the study show that：the fractal distribution contain more information about the joint spacing and the trace length distribution than other distributions; and it is more close to the actual distribution. Fractal dimension D reflected the distribution of joint spacing and trace length in its variation range，and the fractal dimension D is determined depending on the ratio of the number of small spacing，the number of small trace length to the total number of joints. This study results provides a new method for the construction of the network model of jointed rock mass.

Due to the defects of traditional genetic algorithm(GA) such as premature and poor local search ability, a simulated annealing algorithm(SA) is introduced to modify GA for better optimizing result. Afterwards, the modified genetic simulated annealing algorithm(GSA) is implemented to search for the optimal weight and threshold of BP neural network, which improves the prediction accuracy of BP neural network by overcoming its drawbacks of local minimum and slow convergence. Thus, GSA-BP neural network model is established for the back analysis of surrounding rock mechanical parameters. Finally, the model is applied to an engineering case, Wudongde Power Station, to regress surrounding rock mechanical parameters of the underground powerhouse on the right side with in-situ measured displacement data. By applying the regressive mechanical parameters to numerical model, displacements of surrounding rock are computed; and the computed displacements agree well with the measured ones; which indicates the GSA-BP neural network model is feasible for back analysis of surrounding rock mechanical parameters in real-world engineering cases.

Reasonable selection of excavation footage is one of the tunnel key points ,which affects the safety and efficiency of tunnel construction. Compared with the tested data of Yangjiaping tunnel, the most realistic rock dilatancy angle is acquired by numerical simulation with a software ABAQUS. A tunnel excavation numerical model considering dilatancy angle based on Mohr-Coulomb model is built, then the deformation and stress distribution of tunnel are analyzed under different excavation footages, 1.5, 2.0, 2.5, 3.0 and 3.5 m. Simulation results show that the numerical modeling results considered dilatancy angle is in good agreement with tested results; when the wall rock is supported with bolt support system, and choosing the excavation footage of 3.0 m, better safety and efficiency can be reached; but the deformation of tunnel roof within the scope of 5.0 meters from the excavation working face shall be paid more attention to.

Cracked flattened Brazilian disk(CFBD) has the advantages to avoid the stress concentration of loading points, and to crack starting at the prefabricated crack tip, make it become one of the most commonly used specimens to study the fracture characteristic of brittle materials. A recent study found that T-stress can also affect the material fracture, but CFBD didn’t have an analytic formula of calculating T-stress. The finite element method combined with the analytical method is employed to systematically investigate the T-stress for the cracked flattened Brazilian disk under combined mode loading condition and systematically analyze the error and relative error．The calculation results show that within a certain range of load distribution angle, when the relative crack length is less than 0.65，the formula of the T-stress for the cracked Brazilian disk subjected to uniformly distributed pressure can be directly used to calculate the T-stress for the cracked flattened Brazilian disk under pure mode I, pure mode II and combined mode loading conditions．The relative error of T-stress increases with increasing of the relative crack length.

How to get the uniaxial compressive strength value of soft rocks is always a problem in engineering because of their low strength, loose structure and difficult processing. Needle penetrometer invented by Japanese, can be used to calculate compressive strength of soft rocks indirectly by testing its needle penetration index (NPI). The paper introduces experimental instrument, operating procedures, announcements and data processing methods of needle penetration test(NPT). Then the strengths of different soft rocks are tested by needle penetrometer in situ and laboratory. According to statistical analysis of test results, the discreteness of sampled value is closely related to rock uniformity and structural discontinuous surface. Finally, contrast methods of NPT and point load test on a set of soft rock samples. It turns out that the results based on these two methods are similar. Therefore, NPT is reasonable and feasible in soft rock strength test and it can be popularized and applied to the soft rock engineering in China.

In the self-balanced loading test, reasonable determination of conversion factor γ, ratio of downward shaft resistance to upward shaft resistance, is critically important for the accuracy of bearing capacity and final decision of pile loading test. To study the appropriate value of γ in sandy soil, 3 typical construction projects are chosen. All of their main soil layer are sandy soil; and the self-balanced loading test and head-down loading test are conducted at every site. And then a pile from self-balanced loading test and one from head-down loading test are picked as a group. In these groups, the geometrical sizes, geological condition and construction method of the two piles are same or similar. Because the results from traditional loading test are more convincing than ones from self-balanced loading test in general, the results from top-down loading test are taken as references; and then the Matlab is used to find the optimal fitting solution of γ, latterly, returning the value to the simplified capacity equation of the self-balanced loading test, and comparing the result of equivalent top-loaded settlement curve with ones from γ used in actual project and from head-down loading test, ? = 0.6 and 0.7. The results show that: (1) The fitted values of ? from 3 projects are ranged from 0.47 to 0.71, which are rather smaller than that used in actual projects. (2) The accuracy of ? has large effect on the values of Qs (skin friction) and sss (elastic compression from skin friction distribution) of upper piles of the equivalent pile. (3) Compared with the top-loaded settlement curve from traditional loading test, the results from the optimal fitting solution of ? fit much better than of which used in actual project ,which means that values of ? used in these projects are overly conservative, which cause overly conservative judgement of bearing capacity. (4) It is suggested that the value of conversion factor ? in sandy soil about 0.6 to 0.7.

Karst is one of the hidden dangers in the construction of bridge pile foundation. It is particularly important for the safety of the bridge to prove the spatial distribution characteristics of karst in the scope of the bridge. At present, the exploration of karst is mostly based on the combination of drilling and geophysical prospecting methods. But the specific karst exploration needs to choose the appropriate geophysical method according to the specific situation. Commonly used geological radar and other geophysical prospecting methods often can not accurately determine the boundary of the local area of the cave due to their limited scope of application. The cross hole electromagnetic wave CT technique reconstructed the distribution image of the medium absorption coefficient of the wells base on the difference of the absorption of electromagnetic wave in different media. The image visually shows the internal structure of geological bodies. It has the characteristics of high resolution and small exploration distance. It is especially suitable for detecting the distribution of karst cave in the local area such as bridge pier. This paper introduces the principle, working method and application effect of the electromagnetic wave method CT detection technology by an example of detecting the karst of Shuixi bridge pier of highway S119. The results show that cross hole CT technology has high precision and reliability. It can fully and clearly reveal the spatial distribution of the karst, so as to provide reliable geological data for engineering design.