Borehole stability analysis is one of the key scientific issues in the deep drilling engineering. Adoption of a reasonable strength criterion facilitates the prediction accuracy of borehole stability and reduces the chance of borehole breakout. Since the widely-used Hoek-Brown strength criterion neglects the effect of intermediate principal stress, the potential of rock strength cannot be fully realized. To solve the above problems, a newly proposed modified Hoek-Brown strength criterion that overcomes the shortcomings of singularity and non-convexity that exist in most classic strength criteria, is used for the stability analysis of horizontal, vertical, and inclined borehole, respectively. By calculating the minimum mud pressure required for ensuring borehole stability, comparisons with several classic strength criteria such as Mohr-Coulomb, Drucker-Prager, Hoek-Brown, 3D Hoek-Brown, Mogi-Coulomb, and modified Lade strength criterion are conducted, coming to the following conclusions: the predicted results of the adopted modified Hoek-Brown strength criterion are close to those predicted by 3D Hoek-Brown, Mogi-Coulomb, and the modified Lade strength criterion; the relative error between the predicted value and the mud value used in two actual projects are 2.1% and 0.76%, respectively; those results prove the accuracy of the modified Hoek-Brown criterion for borehole stability analysis; the minimum mud pressure increase linearly with increasing borehole depth; meanwhile, it is affected by the inclination angle and the azimuth angle of the borehole; both Mohr-Coulomb and Hoek-Brown criteria are conservative in predicting the minimum mud pressure, increasing the amount of mud that actually used; and the Drucker-Prager criterion over-predicts the rock strength, bringing about an unsafe predictive value of minimum mud pressure; base on the modified Hoek-Brown criterion, the theoretically optimal drilling position can be obtained (i.e. the minimum required mud pressure value), which provides a useful reference for the drilling engineer to optimize the position of borehole.

Based on the statistical damage mechanics theory of Weibull distribution, the limitations of the traditional constitutive model for the initial state damage and the post-peak feature characterization are optimized; and the constitutive equation which can characterize the initial damage to the mechanical behavior is established. The constitutive equation determines the mechanical properties and damage state of key feature points in the whole stress-strain process of rock, and divides the damage process of rock damage into six damage stages, explaining the damage evolution in the whole stress-strain process of rock. Meanwhile, combining with RFPA-2D numerical simulation analysis, it is determined that the structural instability point of the rock mass on the post-peak curve is the peak strain (1.00-1.32) times; the damage threshold is about 0.4-0.6 and the damage initiation strength is about 15% of the peak intensity; and the structural surface penetration breaking strength is about 41% of the peak intensity. It is theoretically determined that the residual strength point strain is about 4 times the peak strain.

A corresponding analytical model is established to solve the construction problem of shallow circular tunnel with a cavern in a stratum. In this model, the tunnel conforms to the specified deformation boundary condition, and the cavern satisfies the zero surface force boundary condition. Schwarz alternating method and function of complex variable method are used to solve the problem; meanwhile the iterative computation is realized by a program. In addition, combining with the characteristics of numerical calculation, the calculation accuracy is discussed. The influences of tunnel boundary conditions, location and size of the cavern, and clear distance between the tunnel and the cavern on surface settlements are analyzed. The results show that, compared with no cavern conditions, the cavern has an obvious influence on surface settlements. The rule of surface settlements is different significantly, when the tunnel boundary condition and the cavern’s location are changed. When the cavern is located at the lateral sides of the tunnel, the differential settlements are distributed symmetrically about the cavern axis for uniform radial displacement and oval deformation boundary conditions, but the regulation is opposite for vertical subsidence boundary condition. When the cavern is located at the inclined top of the tunnel, the differential settlements are anti-symmetric for uniform radial displacement and oval deformation boundary conditions. All of the surface settlements above the tunnel are reduced for the three basic deformation boundary conditions when the cavern is located at the top of the tunnel.

The main sliding direction is directly related to the slope stability evaluation and the determination of residual thrust force. At present, the sliding direction of the slope is mainly determined with semiempirical or empirical approach, such as whole vector direction of the displacements monitored inside the slope, parallel to the bottom of potential slip surface or the hypothesis made based on the failure mechanism of the slope. According to the principle of minimum potential energy, 2-D and 3-D sliding direction are rigorously deduced on the basis of current stress state of the slope. Moreover, this theoretical solution is verified to be rational by simple sliding block placed on an inclined plane and 3D slope examples. Besides, the curve of the sliding direction angle along the slip surface is also determined, which accurately supplies theoretical foundation to slope stability problem and the determination of residual thrust force.

During the two-step mining process in the high stage, the cementation quality of one step was of great significance to the safe recovery of the two-step pillar. In the Lilou iron mine, the difference strength between the in situ samples and the surface test blocks is analyzed based on the strength detection and scanning election microscope(SEM) experiments. The in situ strength increment of high stage cemented backfill is "hump" morphological distribution. It is divided into the upper part (-330 - -310 m), the middle part (-360 - -330 m) and the lower segment (-390 - -360 m). The porosity of 3 peaks and 4 valley values of 1:4 filling stope is extracted by the SEM pore characterization technique; and the nonlinear negative correlation between the strength increment and the porosity is explained, in accordance with the exponent function of y = 29.281e–0.032x. Combining engineering arrangement, the mechanism of deadweight pressure and drainage arrangement on the curing strength of high stage cemented backfill is revealed from the coupling macroscopic(exposing and in situ coring) and micro-pore structure development characteristics. Then the ratio parameters of filling slurry in the high stage stope are adjusted, which in the middle part is reduced from 1:6 to 1:8 and the heights of -325, -350 m and -375 m are reduced from 1:4 to 1:6, to ensure the safe and efficient mining.

The mixture of fault gouge and rubble which taken out from fault zone is used to make the soil-rock mixture(SRM) sample with rock block proportions of 20%, 30%, 40%, 50%, 60% and 70% respectively, and using GDS triaxial test system to measure the seepage characteristics of SRM sample under the different loading and unloading confining pressures, to research the variation law of permeability coefficient of the SRM(soil-rock mixture) sample with different rock block proportions under different confining pressure levels. The test results show that: (1) The permeability coefficient of the SRM sample with different rock block proportions decreases as the pressure increases; and the decrease rate of permeability coefficient in the initial stage of confining pressure loading is obviously higher than in the semi-late period. (2) In the stage of confining pressure loading and unloading, the permeability coefficient of SRM sample at different confining pressure levels present a common trend that with the increase of rock block proportion; it decrease first then increase, the permeability coefficient of the sample with rock block proportion 40% is the smallest; 70% is the largest. (3) In the stage of confining pressure unloading; the recovery degree of permeability coefficient of SRM sample is ascend with the increase of rock block proportion, and the recovery rate of SRM sample with rock block proportion 70% reached 50.2%. (4) In the stage of confining pressure loading and unloading; the sensitivity of the permeability coefficient of SRM sample to the rock block proportion showed a rule of decrease first, then increase and then decrease; and when rock block proportion reached 60%, the sensitivity is highest. (5) In the stage of confining pressure loading and unloading, the relationship between permeability coefficient and confining pressure can described by exponential function.

Water-ice phase transition often produces frost heaving pressure in fractured rock mass in cold regions. The repeated action of frost heaving pressure will drive crack propagation, coalescence and even fracture failure of rock mass. Through prefabrication of single open crack with different inclination angles in quasi-sandstone specimens, freeze-thaw and uniaxial compression experiments are conducted on those crack-containing specimens under precooling and non-precooling conditions, to investigate the influence of freezing mode and crack inclination angle on the process of frost propagation, rupture characteristics and uniaxial compressive strength. The experimental results show that: the frost heaving pressure is the main driving force of frost propagation, which is closely related to the freezing mode of crack water. It is hard to produce frost-heaving cracks under precooling conditions, because most of the crack water is squeezed out. Generally, the frost-heaving cracks propagate along the coplanar direction of the prefabricated cracks; and then they gradually turn to the short sides due to the boundary effect. There is a positive correlation between the length of coplanar propagation and the inclination angle of crack. When the prefabricated crack inclination angle is 60°-90°, the rock mass can easily be compressed and destroyed along the direction of frost-heaving crack, resulting in the reduction of uniaxial compressive strength of rock mass. The research results can provide reference for revealing the freeze-thaw damage mechanism of fractured rock mass and developing rock engineering in cold regions.

The loading rate effect in post-failure region of three kinds of water-saturated rocks is investigate by triaxial compression alternating loading rate test. The influence of confining pressure on the loading rate effect in post-failure region is discussed with alternating loading rate method under triaxial compression. The results show that: (1) The loading rate effect coefficient n at peaks of rocks is increased with the growth of the confining pressure. It is indicated that the loading rate effect at peak of rocks weakens with the growth of the confining pressure. (2) Rocks show obvious loading rate effect in the post-failure region. Then the loading rate effect of tage tuff and region tuff become more obvious and the loading rate effect of sandstone is weakened with growth of the confining pressure. (3) Using four kinds of loading rate effect coefficients in the post-failure region to correct the stress-strain curves in the post-failure region, the results show that the good coincidence of the stress-strain curves at a high load rate and the stress-strain curves at a low load rate in the post-failure region. It is indicated that four kinds of loading rate effect coefficients can use quantifying the loading rate effect in the post-/failure region of rocks. The nd of loading rate effect coefficients in the post-failure region is the most applicable to quantifying the loading rate effect in the post-failure region of rocks.

The stiffness of segment joint is an important parameter for the design of shield tunnel linings. While, in stuctural calculation, estimation the bending stiffness of segment joint usually rely on empirical formula or full-scale tests. In order to evaluate bending stiffness of segment joint more conveniently and accurately, the authors try to establish an analytical model of segment joint, which providing theoretial foundation for determining the bending stiffness in structural calculation. In this paper, according to the structural features of segment joints, the authors mainly discuss the mechanical behavior of bolted segment joints considering them as semi-rigid, and then the moment-rotation behavior of the joint is studied. A physically based mathematical model using the joint dimensions and material properties is proposed. Considering joints connected by two long curved bolts as examples, parameters in the model are evaluated, and moment-rotation curves for the joint are presented. The model distinguishes joint’s mechanical behavior before and after joint opening, and agrees well with real mechanical behavior of the joints. Comparison with previous tests of segment joint and other models (such as Janssen model and Gladwell model) is conducted. The model proposed is more accurate and universal. Joint opening angles, decay of bending stiffness and tolerance bending moment are playing dominent roles in the exponential-like model. The model can provide a theoretical method to determine key parameter, bending stiffness, of structural calculation in segment lining design.

In the layered soil foundation mainly composed of silty clay and silty clay, test piles with full cross-section pressure sensors installed at the end of piles are used to continuously and intensively collect pile tip resistances in the whole penetrating process with high density. throughout the entire process. According to the pile tip resistance curves of multiple penetration strokes, the change stage of the initial penetration of the pile tip resistance into the soil layer and the change stage of continuous penetration into the same soil layer are defined, which are divided into linear steep increase segments, nonlinear ramp segments, and platform segments, nonlinear slow-down section, linear steep drop section. When the pile end continuously penetrates through the interface of multiple soil layers, the change stage of the pile end resistance lacks a linear steep increase section compared with the initial penetration soil layer. The initial value of the steep drop of the previous stroke is close to the final value of the steep rise of the latter stroke, which can reflect the limit of the elastic compression of the soil, and is calculated by the average value of Qc, and is used as the pile foundation design. The pile tip resistance curve during the pile sinking process is similar to the static penetrating Qc curve. The maximum tip resistance of every layer in the layered soil is linear with the Qc value of the static penetrating probe and the average number of standard penetrations. Analysis of this situation found that the residual end-resistance after restoration was linearly related to the Qc value of cone penetration test(CPT) and the N value of standard penetration test(SPT). The fitting formula of elastic limit pile end resistance and ultimate pile tip resistance and residual tip resistance are put forward; and the fitting formula of ultimate pile tip resistance is more accurate than that of empirical parameter method, static cone penetration method and limit equilibrium theory.

The behavior of clay liner at the bottom of landfill site plays an important role in the effective performance of its long-term seepage and pollution control. In view of the high saturation state of soil barrier in the actual yard, the liquid phase (pore water) and gas phase (block bubble) are considered as mixed fluid in this study. By establishing soil stress equilibrium equations, mixed fluid mass conservation equations, and solute mass conservation equations, the interaction mechanism of soil particle, pore fluid, solute is considered comprehensively; and a hydraulic- mechanical-chemical fully coupled model for solute transport in high saturated clay liner is presented. The model can directly and accurately solve the deformation of soil layer, mixed fluid pressure and solute distribution with time and space. The multi-field coupled finite element analysis software COMSOL is used to carry out numerical simulation on the model; the results show that the model results are in good agreement with the results obtained by Peters. Meanwhile, the existence of compressible gas in the clay liner delayed the dissipation of the excess pore fluid pressure, increased the settlement of the soil layer, and had a delayed effect on solute transport in the clay liner.

The surrounding rock of underground gas storage is always under the action of cyclic loading. Constructing a suitable rheological model is the key to analyzing its long-term stability. Based on the principle of stress dissipation, a nonlinear dashpot element(DS-dashpot) and the differential constitutive equation of the DS-dashpot are established. A nonlinear rheological model(PT-DS) is constructed with the connection of Poyhting-Thomson model and the DS-dashpot in series. Meanwhile, a differential constitutive equation of PT-DS model is derived; According to the cyclic loading test process of rock salt specimen, the dynamic stress equation is established, which is divided into the initial uniform loading section and the cyclic load section. According to the analysis of PT-DS model, the constitutive equations of the time-dependent strain at the initial uniform loading and cyclic loading are obtained. The constitutive equation of cyclic loading section is simplified and analyzed and the equations of upper limit line, middle line and lower limit line are obtained. The cyclic loading test process of rock salt specimen are carried out; the test result is fitted using the constitutive equations of the upper limit line, the middle line, and the lower limit line of the PT-DS model; and the corresponding fitting parameters are obtained. The results show that the fitted curve and the simulated curve are very close to the test curve; so the PT-DS model can be used to describe the strain development process under the cyclic loading perfectly.

In order to study the effect of the ratio of geogrid aperture size to the average sand particle size on direct shear characteristics of geogrid-coarse soil interface, a series of direct shear tests are performed using a large-scale direct shear device. Four kinds of sand with different particle diameters, and a type of geogrids with square aperture, are tested under the condition of different vertical loads and different shear rates and different soil densities. The vertical loads are 30, 60, 90 kPa, respectively; the shear rates are 0.25, 1, 2, 5 mm/min, respectively; and the soil densities are 22%, 55%, 75%, respectively. The test results show that the peak shear stress and residual shear stress of geogrid-coarse soil interface both increase with the ratio of geogrid aperture size to the average sand particle size increases. When the ratio of geogrid aperture size to the average sand particle size increases from 0.04 to 0.20, the adhesion from peak stress of geogrid-coarse soil interface increases from 13.79 kPa to 64.23 kPa; and the adhesion from residual stress of geogrid-coarse soil interface increases from 16.11 kPa to 51.56 kPa. When soil density is 22%, the soil exhibits contraction throughout the tests. When soil density is 55% and 75%, respectively, the soil tends to be dilatant. Shear rate has little effect on shear behavior of geogrid-coarse soil interface in direct shear tests.

The morphology parameters proposed by Grasselli fully described the three-dimensional roughness of rock joints. Based on Grasselli’s three-dimensional parameters, Xia et al, Yang et al, and Tang et al developed new peak shear strength models. It is revealed that Xia’s model didn’t agree well with the boundary conditions. Yang’s model can not explain the mechanism of tensile failure during the shearing of rock joints. Tang’s model showed a low accuracy in predicting the peak shear strength of a rock joint. In light of these problems, a new peak shear strength model is established. The new model is verified based on the 63 groups of rock joints published by Grasselli, Tang and Yang, the results show that the new model has the same accuracy with the published model, and the new model is simple in terms of form so it can provide a reference for rock engineering. Besides, it will improve the accuracy in predicting the peak shear strength between the calculated results and the test results when the relationship function f(?n) takes the morphological parameter into consideration.

In order to evaluate the risk of highway slope more comprehensively, the set pair analysis theory and the ICP(iterative corresponding point) algorithm are optimized and improved; and then on this basis, based on improved entropy weight set pair analysis and vehicle borne laser scanning technology, a risk assessment model of highway slope combining the overall evaluation with the local evaluation is proposed. During the specific implementation, firstly according to the geological conditions, the highway slope is divided into several sections; and the overall evaluation is conducted by the improved entropy weight set pair analysis model; and the dangerous slope is found out. Secondly the vehicle laser scanning technology is used to obtain the point cloud data of two stages for every dangerous slope; and the improved ICP algorithm is applied to unmatched control of point cloud data of two periods for the dangerous slope; then, the slope surface models of two periods are built by non-Uniform rational b-spline(NURBS) technology and the local evaluation is carried out; and the specific danger point in the dangerous slope is found. Finally the evaluation results, expert opinions and field visits are summarized and analyzed; and the reasonable suggestions for disaster prevention and control are proposed. Taking a road in Xiuwu County for example, the experimental research is carried out by using this model. The results show that this model has exerted a good evaluation effect, not only the dangerous slope is determined, but also the specific risk points are found, so as to provide a new idea for the disaster prevention and mitigation of the highway slope.

Electrical conductivity is a direct measurable parameter reflecting the soil and water coupling properties of the island, and permeability coefficient play an inportant role on formation of underground freshwater; so it is of great significance to study the variation law of electrical conductivity under different geological conditions and to characterize the permeability of soil. Firstly, the conductivity of single size calcareous sand is measured in different dry densities, water contents and solution concentrations. Because calcareous silt contains clay, its surface electric double layer has influence on conductivity. Therefore, the conductivity of calcareous silt under the condition of orthogonal dry density and moisture content is measured separately, and the variable head permeability test is carried out. Secondly, graded soils with increasing content of calcareous silt are prepared, their conductivities are measured companied by constant head permeability test. The results show that there exist relationships between the conductivity and the dry density, water content and solution concentration. Conductivity of calcareous soil increases slowly first, then quickly, and finally trends to steady with the increasing of silt content. Permeability of mixed soil decreases slowly first, then rapidly with the increase of conductivity. The permeability coefficient of silt increases with the increase of electrical conductivity, showing a law of large in medium stage and small in initial and final stages. Finally, empirical formulas of conductivity and permeability coefficient of calcareous soil are deduced preliminarily.

The combination of weathered sand and expansive soil as a subgrade has the advantages of simple operation process, environmental friendliness and low cost. The law of influence of confining pressure and vibration frequency on dynamic characteristics such as dynamic strength, dynamic elastic modulus and equivalent damping ratio of weathered sand improved expansive soil is studied by GDS dynamic triaxial test. The results show that: The stress-strain backbone curve and the damping ratio and strain relationship of the modified expansive soil improved by weathered sand can be described by hyperbolic function; with the increase of dynamic strain, the dynamic elastic modulus of the modified expansive soil decreases, the damping ratio increases; Under the recycle action, the stress-strain relationship curve of the modified expansive soil in weathered sand is closed hysteresis loop. The axis of the hysteresis curve increases with the increase of the dynamic stress and the slope decreases. The soil sample exhibits typical strain softening characteristics. With the confining pressure and the loading frequency increases, the dynamic elastic modulus of the expansive soil is increased, and the damping ratio is decreased. The effect of the frequency on the dynamic elastic mode is concentrated in the range of strain εd less than 0.2%, and the influence on the damping ratio is concentrated in the range of εd less than 0.1%.

As for the accumulation landslides with steep-sliding planes, the calculation of the anchorage depth of anti-sliding piles is one of the key technique problems of support structure design. Taking the K285 landslide along Neijiang-Liupanshui railway as instance, based on the similarity principle, the physical modelling tests of the interaction between anti-piles and sling mass is adopted to study the stress state and failure characteristics of sliding bed in front of the piles. The results show that: (1) The resistance force of sliding masses in front of piles is triangular distribution; and the resistance force at the sliding belt is the largest. (2) The maximum bending moment point of the piles decrease gradually along the piles with the loading increasing, and the bedding rock in front of the piles occurred wedge fracture, of which the depth corresponded to the maximum bending moment position. (3) As the length of the anchorage section increase, the position of wedge fractures of the bedding rock in front of the piles gradually move closer to the sliding surface; and its fracture angle decreased gradually. Based on the above analysis, the anchorage depth can be divided into non-resistance anchorage section, invalid anchorage section and effective anchorage section. Furthermore, the length formula of such three sections and the total anchorage depth of the anti-pile are deduced respectively. When the research results are applied to optimize the anchorage depth of the anti-slide piles of K285 landslide, the total length of the piles is reduced by 6 meters on the basis of ensuring the effectiveness of the treatment. The research has important engineering practical value.

Laboratory tests are conducted to study the physico-mechanical properties of water cooling treated granite under room temperature to 500 ℃. Variations of physico-mechanical properties are analyzed in detail. Meanwhile, the physico-mechanical changing mechanisms of water cooling treated granite are revealed by the pictures of scanning electron microscope (SEM). The results show that: (1) The volume of the water cooling treated granite specimens under high temperature increases, while the mass and density decrease; for specimens treated at 500 ℃, the volume increases by 1.32%; the mass decreases by 0.21%; and the density decreases by 1.51%. (2) Longitudinal and transverse wave velocities of the water cooling treated granite both decrease; when temperature rises, and the decrease of longitudinal wave velocity is greater in rate than that of transverse wave velocity, when a granite specimen is heated to 500 ℃, longitudinal and transverse wave velocities decrease by 64.9% and 46.8%, respectively. (3) Uniaxial compressive strength and elastic modulus of water cooling treated granite decrease with temperature; and they decrease by 51.9% and 48.6% respectively at 500 ℃; the specimens show an obvious ductility characteristic when they are heated to 300 ℃. (4) The pictures of SEM show that many microcracks inside granite specimens are generated and extended after high-temperature treatment. With further increase of the temperature to 300 ℃, the quantity of microcracks rose gradually and the sizes of microcracks also increased gradually; and there will be a microcrack network appearing inside the granite specimen, causing deteriorations of physico-mechanical characteristics of water cooling treated granite.

In order to study energy release and ejection velocities of rock fragments induced by pillar rockburst in rock mass engineering, pillar model specimens are designed and prepared with three different types of rock materials. The ejection processes of rock fragments in failure are recorded by the high-speed camera in uniaxial compression tests; and the ejection velocities of rock fragments are calculated with experimental data. Based on Griffith' energy release theory, the released energy in failure of test models are calculated by ANSYS finite element software under both plane stress and plane strain; and the theoretical ejection velocities of fragments are calculated by the principle of conservation of energy after removing a certain percentage of energy dissipation. The results show that the compressive strength, elastic modulus, and rockburst proneness, as well as the released energy and ejection velocity of fragments increase sequentially (following the sequence of red sandstone, shidao red granite and camellia white granite). The failure degree is severer for the pillars with the larger width. The energy release under the plane strain condition (which is closer to the pillars in the field engineering) is greater than that under the plane stress condition(which is closer to the tests in this study). Therefore, the compressive strength, elastic modulus of rock materials and the shape and size of rock structure determine the disaster degree of pillar rockburst. The theoretical ejection velocities of fragments are basically close to the measured velocities in model tests on pillar rockburst. Without considering the size effect, it is proved that the ejection velocity occurred in the large-scale model (engineering scale) is basically equal to that in the small-scale model(test scale) under the same stress condition.

Strain localization is the warning sign of rock damage. In order to reveal the key mechanical factors that control its occurrence time, position and growth direction, digital image correlation method is used to obtain the whole deformation process of specimens under uniaxial compression tests. The maximum and minimum principal strain field, displacement field are then calculated. Combining with the axial load-displacement curve, the strain localization evolution characteristics of different specimens are compared and analyzed comprehensively. It is found that for brittle rock-like material under uniaxial compression the strain localization belt grows at the direction of maximum principal strain (maximum compressive strain) and deflects with the direction change of maximum principal strain; the position of the strain localization belt is controlled by minimum principal strain; the transient displacement field indicates that damage of brittle rock-like material in the strain localization belt is mainly caused by tensile deformation not shear deformation; strain localization not only occurs at the point close to peak load, but also at the inflection point where deformation accelerates but the load is low; the appearance of localization belt and opposite horizontal displacement vector along the belt are two proper failure prediction indices.

The salt layer in the deep stratum is usually used to form cavern for natural gas storage. The behavior of dilation of salt rock is the important criterion for the safety of storage. In this paper, the volumetric dilation behavior and the dilation angle model of salt rock with mudstone is analyzed from the compressed test under different confining pressures. Experimental results show that strain-hardening law and obvious volumetric dilation during the test. From Mohr-Coulomb plastic potential function, the dilation angle of samples increases with the increase of plastic shear strain. And the dilation angle can approach 7o-10oat last. Finally, the dilation angle model with plastic shear strain and confining pressure is constructed. The dilation angle model that simulates perfectly the volumetric strain of salt rock with mudstone is verified by the numerical simulation.

Based on the limit equilibrium theory, a new formula is proposed to calculate the ultimate pullout force of anchor cable. The influence of soil pressure on distal of the bonding segment is considered in the formula. Prestressed anchor cables in three practical engineering cases are investigated. The values of ultimate pullout force calculated by the formula proposed are compared with those by the existing formula and measured values, respectively. The results show that distal soil pressure of the bonding segment in cohesive soil has evident influences on ultimate pullout force of anchor cable. Also it is shown that the ultimate pullout force can be calculated by both the formula of this paper and the existing formula when anchor cable used in sandy soil; but it should use the formula of this paper when anchor used in cohesive soil.

In order to study the rheological characteristics, based on indoor triaxial compression test, the stress relaxation characteristics of saturated sliding zone soil from Huangtupo landslide in the Three Gorges Reservoir are analyzed. The XRD and XRF tests are carried out to investigate the mineral composition and chemical composition. The GDS triaxial test equipment is used to carry out the stress relaxation test of saturated sliding zone soil so as to describe the stress relaxation characteristic under different confining pressures and different strain increments. The test results show that the stress relaxation of saturated sliding zone soil has a relationship with confining pressure, axial strain rate, axial strain increment and relaxation time. The peak strength parameters and residual strength parameters can be obtained by the stress relaxation curves. The amount of stress relaxation and residual stress ratio of sliding zone soil increase with increasing confining pressure when the axial strain is close to the failure strain(15%); but the ratio of stress relaxation decreases. The volumetric strain in constant axial strain phase of sliding zone soil is much larger than that in increasing axial strain phase. When the strain rate is very small (0.02mm/min), the stress relaxation occurs during loading.

Hydraulic filled calcareous sand is usually used as foundation soil in island projects; and the marine environment surrounding has certain requirements for its permeability properties and seepage failure resistance. By mixing up microbial treatment solution and calcareous sand, microbially induced carbonate precipitation(MICP) technology might be applied to ground improvement through hydraulic progress. Permeability experiments of MICP treated and non-MICP treated calcareous sand with different relative densities are conducted and their permeability properties are evaluated. The results show that the mixing method could reduce the permeability of loose sand to the same level of dense sand; the critical hydraulic gradient increased substantially as well; and the mode of seepage failure changed from piping to flowing soil.

At low temperature, deposition rate induced by bacteria is often low, which restricts the practical engineering application of microbial solidification technology. The growth and reproduction characteristics and urease activity of Sporosarcina pasteurii and Bacillus megaterium are analyzed by controlling different temperature and pH value. By adding nutrients to the gelling solution and controlling urea concentration and calcium ion concentration the precipitation yields of different strains is studied, and XRD test is conducted to analyze precipitation crystal type. The solidification effect of different strains is studied by the comparison of permeability and unconfined compressive strength tests. The results show that at low temperature, the growth and reproduction of Bacillus megaterium are faster, and urease activity is higher, and the optimum pH value of Bacillus megaterium is 8, meaning that it is more suitable for alkaline environment. The precipitation yields can be increased by adding nutrients to the gelling solution, increasing concentration of urea to 1.5 M and controlling calcium acetate concentration at 0.5 M. The deposition rate of Bacillus megaterium is always higher than Sporosarcina pasteurii at low temperature, and the precipitated crystal is more stable calcite. The permeability of samples solidified by Bacillus megaterium is reduced by 3 to 4 orders of magnitude, while that with Sporosarcina pasteurii is only 2 to 3 orders of magnitude. The smaller the particle size, lower the permeability. Under the same conditions, the strength of samples solidified with Bacillus megaterium is stronger than ones solidified with Sporosarcina pasteurii. Therefore, Bacillus megaterium is more suitable for practical engineering applications at low temperature.

The geological structure of cleaved basalt section of Zhongyi tunnel of Lixiang Railway is complex; the surrounding rock is weak and broken; the groundwater is well developed; the ground stress is extremely high; and the side wall deformation disaster is prominent; therefor three field test researches on construction control measures for large deformation of surrounding rock have been carried out. The field test results show that: From the perspective of support reinforcement, working condition 1 and working condition 2, the deformation of the side wall of the test section has been well controlled; and the arch changing rate decreased from 100% to 38.50% and 22.22% respectively; the ringing time of the excavation section has a great influence on the control of side wall convergence and deformation; the section support after excavation of the tunnel face should be closed as soon as possible; the perspective of support and surrounding rock two-way reinforcement of the working condition 3 of “large deformation type II support + side wall with 6.5 m long anchor rod” is adopted to successfully control the large deformation disaster of the test section side wall and the arch changing rate drops to 0%. The research results can provide reference for similar projects.

When interacting with structures in different engineering applications, the degree of consolidation of loess under normal stress is different. By changing the initial moisture content of loess and the drainage condition, shear tests on the loess-concrete interface are performed using a large direct shear apparatus. Test results show that the shear stress under consolidation condition is bigger than that under unconsolidation condition; and the difference between them increases with the increase of initial moisture content of loess. The relationship between shear stress and shear displacement has three types: weak softening form, weak hardening form and strong hardening form. When normal stress is relatively small, the shear strength of interface under consolidation condition firstly increases and then decreases with the increase of initial moisture content of loess, and finally approaches a constant. When normal stress is relatively big, the shear strength of interface under consolidation condition decreases with the increase of initial moisture content, and finally approaches a constant, and so does the shear strength of interface under unconsolidation condition regardless of the value of the normal stress. With the increase of initial moisture content, the cohensive force of interface firstly increases and then decreases under both consolidation and unconsolidation conditions; while the internal friction angle decreases and finally approaches a constant. Therefore, the shear characteristics of loess-concrete interface under consolidation and unconsolidation conditions are remarkably different; and when analyzing problems of loess-structure interaction, the adopted parameters should be obtained according to the actual consolidation condition.

Based on previous statistics analysis on deep excavations with diaphragm wall as retaining structure in Shanghai, the deformation characteristics of dual-purpose diaphragm wall and impact on adjacent architecture outside are comprehensively studied through the analysis of field monitoring data of two typical and similar deep large excavations in soft soil region, as well as the effects of soft soil layer thickness in superficial stratum and excavation area. The research results show that: (1) The lateral displacement of retaining wall behaves as a parabolic curve during the construction. The deformation is almost generated in the excavation stage while the sequential deformation caused by the removal of struts is only about 10% of the amount of excavation stage. The thickness of soft soil layer in the depth of excavation has a great influence on the lateral displacement of diaphragm wall. (2) It is revealed that the thickness of soft soil layer can affect significantly not only on the maximum ground surface settlement and its location; but also on the acceleration of settlement and its stabilization. However, it will not change the groove shape distribution of ground settlement. (3) The upper of diaphragm wall and pillars are in uplift state; and the upheaval increases from the edge of the excavation to the middle during the construction. There is not a large difference for the upheaval between adjacent pillars in the middle of excavation; but it is relatively larger for the adjacent pillars at the edge of excavation. That difference boundary is about (1.0-1.5)He (He is the excavation depth) away from the edge of excavation. The thickness of soft soil layer and excavation area obviously influence great much on the upheaval value of pillars. (4) Especially, the type and depth of foundation and the distance away from the excavation contribute considerably to settlement of adjacent building outside.

The shale of Longmaxi formation in Sichuan Basin contains a large amount of shale gas for development. In order to study the mechanical properties of the shale, a uniaxial compression test is first performed on a shale sample; and then the test is simulated based on the particle flow code(PFC) numerical simulations (discrete element method). Finally, the numerical simulations of triaxial compression are performed to study the brittle failure characteristics of rock under different stress conditions. The research results show that the rock of the area is a typical brittle rock with high strength. It is found that the Longmaxi shale has a high content of brittle minerals; and it is the high compression strengths and high brittleness rock. The Longmaxi formation shale has similar failure characteristics under different stress conditions，and the peak strength of shale is linear with the confining pressure, which is consistent with the linear law of Mohr Coulomb. The distribution of microcracks does not have obvious directionality and regionality before the damage stress is reached; the microcrack distribution may be related to the heterogeneity of the rock at this stage; but the expansion of the microcrack will be affected by the stress after the damage stress is reached. The cracking stress, damage stress and peak stress of the shale are linearly related to the confining pressure; but the peak stress is more affected by the confining pressure. The reason is that the microcracks are independent at the crack stable growth stage; but it is necessary to consider the influence between microcracks, and the macroscopic crack surface are not smooth at the crack unsteady growth stages.

Taking a close range excavation to a metro line in southern area of Jiangsu province as the research object, a set of HS-Small constitutive model parameters are proposed preliminarily by empirical methods and soil tests. And then, based on the measured data of horizontal deformation of retaining structures and ground surface settlement in the field, inversion analysis is carried out to replay the excavation process by finite element method in order to further optimize and calibrate HS-Small model parameters. On this basis, the finite element model of the adjacent excavation of subway bridge pile foundation is built; and the influenced area of the existing pile deformation is established. The results show that: (1) When the spacing between pile and pit is less than 0.6 times of the depth of foundation pit, pile foundation settlement doesn’t perform an obvious trend to decrease; but when the spacing between pile and pit is more than 0.6 times of the depth of foundation pit, the settlement of pile foundation quickly decreases; pile horizontal displacement also shows similar pattern, but the critical point is located on the 1 times of the depth of foundation pit. (2) The close range excavation has a more obvious effect on pile horizontal displacement than vertical settlement; but when the pile-pit spacing is greater than 1.37 times of the depth of excavation, the deformation of pile foundation will not exceed the limit value; when the pile-pit spacing is greater than 1.90 times of the depth of excavation, the deformation of pile foundation will be less than the warning value (60% of the limit value). (3) The influenced zone of pile foundation deformation is divided into three grades as A, B and C, and the protection measures are put forward accordingly.

This paper takes the L-shaped grouting borehole reinforced surrounding rocks of the large section chamber in a 1 000 m deep coal mine of Huaibei Mining Group as the engineering background. The porous media seepage theory is used to establish a fluid solid coupling model of continuous medium grouting with considerations of characteristics of high pressure and near horizontal penetration of rock strata. By using numerical simulation, the relationship between grouting pressure, slurry diffusion radius and rock permeability coefficient under the condition of isolated hole and three-hole grouting are obtained. Moreover, the diffusion law of pre grouting slurry in deep rock strata under high ground stresses is also revealed. The numerical simulation results show the linear relationship between the grouting volume and the grouting pressure, the permeability coefficient and grouting time, and square root relationship between the spread radius of the slurry and the grouting pressure, the permeability coefficient and the grouting time of isolated hole. The simulation results also demonstrate that under the same grouting parameters, the grouting volume of single hole of three-hole grouting is lower than that of the isolated hole grouting; and the slurry diffusion radius is greater than that of the isolated hole grouting. Based on above mentioned results, the grouting reinforcement scheme and reasonable selection of grouting parameters are decided; and the expected results are achieved. The in-situ applications can be a reference for the design and construction of similar projects in the future.

In the excavation engineering, the soil settlement outside the excavation caused by pressure reduction in the excavation is closely related to the soil properties and stress state of the aquifer. However, the soil state and the settlement regularity of confined aquifers in Tianjin still lack of systematic research. Firstly, the stress states of the soils in the first and second aquifer groups of Tianjin are analyzed through the historical groundwater level changes. On this basis, combined with two groups of field pumping tests, the settlement and deformation laws of confined aquifers in the process of dewatering and recovery are analyzed. According to the analysis of historical data, the upper part of the first aquifer group in Tianjin is in the normal consolidation and light over-consolidated state affected by recharge and natural conditions. However due to the over-exploitation from 1960s to 1980s, the drawdown cone centered on the urban area was formed in deep aquifers of Tianjin, which caused serious surface subsidence. Now the groundwater level has been partially recovered due to the limitation of exploitation from 1980s. Therefore, the bottom of the first aquifer group and the second aquifer group are seriously over-consolidated. Based on the analysis of the pumping test results, the results show that the deformation of the first confined aquifer in the normal consolidation state is mainly plastic deformation during the pumping-recovery process, while the second confined aquifer in the over-consolidated state is mainly elastic deformation; and the plastic deformation will still occur in the cycle pumping-recovery process. When the groundwater level was recovered, the settlement of the soil cannot be fully recovered. Meanwhile, affected by “soil arching”, the location of the maximum settlement caused by the aquifer pumping was not on the ground surface, but near the aquitard over the pumping aquifer.

The geometrical shape effects on the anchorage systems and their mechanical characteristics in weak soils are the controversial issues to be resolved in the anchored structure field. In the full scale field experiments, the 30 m deep under-reamed anchorages with 4.44 diameter ratio of large fixed section to borehole section are investigated; the loading–displacement curves of under-reamed anchorages demonstrated the monotonic rising in common along with increasing displacement. The anchorage test results in weak soil layers show that their excellent mechanical properties and the good ductility as well, namely, the under-reamed ground anchorage can keep higher bearing capacity when it has a larger displacement. Based on the analysis of loading–displacement curves including elastic and plastic deformation, and bearing capacity comparison of measured data and calculated value, it is found that the strain–hardening characteristics peculiar to the bearing and deformation behavior of the deep under-reamed anchorage with capsule, and also the control value of anchorage displacement. Experimental research results can provide the significant instruction for the application of new anchorage system with capsule in Ningbo area.

Due to the shortage of non-expansive soil resources in the Jiang-Huai section of the project of Yangtze River to Huaihe River water diversion, the study on the reclamation of weak expansive soil and slaking sandstone from the excavated and abandoned slag in the river course is carried out based on the experimental project, and the production technology of non-expansive soil is developed. According to the experiment of reducing water content of weak expansive soil, the optimal method of reducing water content of weak expansive soils is determined. Based on the properties of natural low moisture content, weak expansion and easy powder formation of slaking sandstone, a composite modified soil comprising "primarily of weak expansive soil, slaking rock powder and modifier (cement)" is developed. The study shows that compared with road mixer and plough, rotary tiller have a higher efficiency in reducing soil moisture content. The desired effect is not achieved by using cement and industrial salt as admixture to accelerate the reduction of water content. Slaking rock powder with less than 30% of the incorporation amount of weak expansive soil as the raw material of modified soil can meet the permeability and compaction requirements of non-expansive soil finished products and can improve relevant technical indexes. The moisture content of the expansive soil is negatively correlated with the degree of compaction of modified soil. The degree of compaction can however be increased by additional compaction of soil. The test results of cement distribution uniformity of the modified soil are related to the sampling interval. The sampling interval should not exceed 40m, and the corresponding uniformity index should be 0.7-0.8.

At present, the tunnel geological prediction(TGP) is one of the most commonly used method in advanced geological prediction of the tunnel; and filtering process of TSP data is a key link to decide reliability and stability of forecast results. To obtain the accurate results of TGP, 681cases of TGP data from highway and railway tunnels are counted and analyzed for the influence of filter frequency band range on prediction results, and soft interlayer, water inrush, broken zone and karst cave etc.5 typical geological conditions as examples are analyzed. The results show that: (1) Signal-to-noise ratio of data is high that should select wide-band filtering(appropriately increasing the difference between low pass and high pass or high cut and low cut) to ensure accurate positioning and effective recognition for abnormal body; generally, the main frequency width of 1.5-2.5 times can be used as low pass or high cut value of filter; however, the size of abnormal body is big and the grade of abnormal body is strong that should appropriately compress the filer range(reduce the difference between low pass and high pass) to highlight abnormal body, if wide-band filtering is selected in this case, it is easy to underestimate the geological condition and surrounding rock grade of surrounding rock; thus causing construction risk, and the filtering range should be determined according to the effective width of main frequency. (2) Signal-to-noise ratio of data is low: the dominant frequency is not obvious and no domain frequency, one should select narrow-band filtering so as to eliminate fake abnormality and save real geological conditions, the abnormal bodies still after filtering should be further judged by combined with other advanced prediction methods; the dominant frequency is apparent, one should choose wide-band filtering to avoid shifting of abnormal position and cause error judgement. The above-mentioned filtering method of TGP data has important practical significance for improving the accuracy and stability of TGP results and guiding the safe construction of tunnel.

The deformation characteristics of surrounding rock and the stress of supporting system during the construction of underground powerhouse group on the left bank of Wudongde Hydropower Station in steep stratified strata are analyzed. The deformation and relaxation of surrounding rock caused by rock mass structure and lithological difference are studied by means of in-situ monitoring, geological survey and numerical simulation feedback, with the main powerhouse as the focus, of which analysis of deformation with excavation time and space change law, shallow anchor and deep anchor cable on rock mass structure control effect. The study results show that the displacement of the surrounding rock of the underground powerhouse is 0-40 mm; the larger part of the displacement appears in the middle of the upper wall of the main powerhouse; the B breccia and the small intersection angle position. The larger parts of the excavation are mainly controlled by the rock mass structure and the rock property of B breccia, and the structure is sensitive to the blasting excavation; and the largest displacement of the caverns during the construction period is 65 mm; the displacement of the deep structural plane is the main displacement in this area; and the bolt and anchor cable support has played a good control role. The displacement is mainly in the period of excavation, and is step-growth type in the process of excavation. And the aging characteristics are not obvious; the overall stability of underground powerhouse is better; and the supporting system is in the normal working state.

Taking the serious rock burst accident in the heading face of three levels, 21 layers and three or four sections of a mine in Northeast China as the background, the mechanism of rockburst in the heading face of high stress area is studied by using microseismic and stress monitoring, field investigation and theoretical analysis. The results show that: (1) The high static stress formed by the 17 layers coal pillar concentrated stress and the lateral abutment pressure of the 21 layers coal gob are the main impact force sources; the disturbance stress formed by the heading face and the adjacent 17 layers coal mining face is the main inducing force source; and the superposition of the two influences induce the rockburst. (2) The estimation model of the stress distribution beneath the coal pillar and lateral abutment pressure in the goaf are established respectively, the influence of two kinds of stress superposition on the 21 layers coal is 132 m; and the impact risk range is 70 m. (3) According to the mechanism of rockburst accident, the production scheme of heading face is established; the safe transfixion of open-off cut is realized. The research results have certain reference significance for the safe production and mining design of heading face under similar conditions.

Based on the model of interaction of frozen soil wall and surrounding earth mass in unloading state, the stress and displacement analysis of frozen soil wall of vertical mine is carried out. Then the analytical solutions for stress field and displacement field are derived; and the relationship between the state and the design thickness of frozen wall is acquired as well. According to the solution, the outer surface load and inner surface displacement of frozen wall in different states are derived. Finally, the application of analytical formula is analyzed with an engineering example; and the calculated results from the solution are in good consistency with the monitoring results.

It is widely concerned about the issue of intolerant settlement and stability of high embankments constructed in mountain areas with soft clay. At present, there are very limited reports on the field measurements of high fill embankment supported by the prestressed high-strength concrete(PHC) pile. A series of field observation based on a project case has been carried out to examine the performance of a highway embankment (30 m high) supported by PHC pile over soft foundation. Measured data includes load acting on the head of the pile, settlement, excess pore water pressure and horizontal displacement. The results show that the effect of the soil lagging the adjacent pile in the development of vertical displacement is observed, and post-construction settlement of the soil during the period of half a year increased approximately at a settlement rate of 1/4 during the filling period. It is also found that the maximum horizontal displacement related to the width of front slope path does not always occurred near the foot of the embankment, where soil may flow around the piles, and even the bending or deflection failure of the piles. The research work is expected to provide the valuable reference for the further case studies on high embankment construction.

Auto-compensating steel struts can supply the part of prestress loss of steel struts caused by wall deformations to unexcavated side and limit deformations of retaining walls effectively. Based on working mechanism of auto-compensating struts and spring-beam model, the mixed boundary condition of single force and springs is used to build the equilibrium of retaining walls supported by auto-compensating struts. Then the process of excavation in a tunnel project using auto-compensating struts and prestressed struts is simulated. The controlling target of auto-compensating steel struts is axial force. The comparison of development of the bending moments and deformation behaviors of retaining walls during excavation is carried out. The results show that the auto-compensating struts can supply prestress loss and limit wall deformations better than prestressed struts. However, bending moments on unexcavated side increases significantly supported by auto-compensating struts. Finally, rationality of the method is proved by comparing with field data.

The anisotropic characteristics of rock mass are related not only to the properties of the joints in the rock, but also closely related to the stress state of rock mass. According to the parametric statistics of rock mass, combined with strain energy, a series of constitutive equations of rock mass containing single structural planes is derived to determine the deformation parameters of rock mass, such as elastic modulus. The reliability of the theoretical formula of the deformation parameters is verified by comparison with engineering examples. On this basis, the concept of anisotropic index is developed to quantitatively describe the anisotropic characteristics of rock mass deformation with a single set of joint. An expressway example is introduced to discuss the influence of rock mass structural characteristics and stress state on the anisotropic deformation of rock mass. The research results show that the anisotropy index of deformation increases as well as a significant weakening of elastic modulus with the increase of normal density of the joints. As the change of joint inclinations, the elastic modulus of the rock mass varies with a V-shaped trend, while the anisotropy index of the rock mass deformation will not be affected. In addition, with the increase of confining pressure, the anisotropic feature will weaken until it completely disappears. In regard to the anisotropic deformation and failure phenomenon in carbonaceous slate tunnels of Lan-Yu Railway, the paper finally presents the interpretation in the light of the above conclusions. The intense anisotropic weakening of elastic modulus of rock mass in tunnels was triggered mainly on great discontinuity density and excavation caused unloading of confining pressure. The orientation of minimum modulus is controlled by the occurrence of structural plane, which also determines the position where the local excessive deformation arises in tunnel heading.

Large diameter soil-cement anchor cables are increasingly used in the excavations in recent years. However the anchor interval is still designed according to conventional small diameter ones which use cement mortar or cement slurry as anchorage body. Based on an excavation engineering case, the field single anchor and anchor group pulling tests are conducted. Meanwhile, 3D numerical models are developed to simulate field tests. In this paper, the effects of group large diameter soil-cement anchor cables are studied and the displacement coefficients of anchor group effects are presented. The displacement coefficient of allowable anchor group effect is also given according to the current technical code. Influence of the anchor diameter and the anchorage body material on anchor group effect is investigated. It is shown that when the other parameters keep the same, the greater the difference between the stiffness of the anchorage body and the soil, the more obviours anchor group effect, while the greater the minimum interval of anchors are required to reach the allowable displacement coefficient of anchor group effect. The interval of the conventional small diameter cement mortar anchors should not be less than 10D (D is the diameter of the anchor), and the large diameter cement soil anchors should be not less than 6D.

Prestressed pipe piles with ribs are new type of pile foundations; and they have better vertical bearing capacity than ordinary pipe pile. But there are few theoretical researches on their bearing characteristics. Based on field measurement comparative test analysis, the bearing characteristics of ribbed bamboo joint piles are studied by ABAQUS finite element method. The relationship between the vertical compressive bearing capacity of ribbed bamboo joint pile and the parameters such as modulus ratio of pile to soil, the ratio of rib to diameter and the friction coefficient are analyzed. The analysis results show that, the vertical compressive bearing capacity increase of ribbed bamboo joint pile is corresponding to the number of ribs. As the pile-soil modulus ratio increasing, the ultimate bearing capacity of composite pile with rib decreased. With the increase of rib diameter ratio, the ultimate bearing capacity firstly increases and then decreases. As the friction coefficient increasing, the ultimate bearing capacity and bearing capacity enhancement coefficient increase linearly. Based on the calculation and analysis, the effected factors are analyzed, so as to provide theoretical basis for the relevant engineering design.

The fissures have a significant effect on the mechanical properties of rock mass. Based on the experimental results of intact sandstone samples under uniaxial compression, the strength and deformation characteristics of sandstone samples containing z-type fissure are studied by the method of particle flow simulation. At the same time, the effects of inclination angle of ? (the angle of the upper and lower parallel fissure) and ? (the angle of the middle connecting fissure) on the strength, deformation and crack propagation mechanism of sandstone samples containing z-type fissure, and the fracture evolution mechanism of these samples are analyzed. The results show that the elastic phase is significantly shortened; and there are more stress-dropping of sandstone samples containing z-type fissure during the process of deformation. The peak strength and elastic modulus of the rock mass are obviously weaken by the z-type fissure; and the deterioration of the peak strength is greater than the elastic modulus. The peak strength and elastic modulus are increased with increasing of ? and ?, and the influence of ? on the deterioration of mechanical properties is greater than ?. The initial cracks mainly appeared at or near the crack tip; and the initial stress level is between 0.6 and 0.7. The failure modes of the sandstone samples containing z-type fissure can be divided into tensile failure, shear failure and tensile-shear mixed failure; and the main failure model is tensile-shear mixed failure. The stress mutation point on the stress-strain curve corresponds to the jump points of the accumulation curve of microcracks.

The element limit analysis method is used to study the influence of soil nail length on the overall stability of soil nailing in soft soil /hard clay foundation pit with vertical slope; and then the limit height is obtained.The influence of soil bearing capacity and slope angle on the overall stability of soil nailing in the soft soil is studied. The results show that the length of soil nails in the vertical foundation pit is 1.4 to 1.5 times the depth of the pit in the soft soil; and the depth of the pit is 0.8 to 1.0 times in the hard clay. When the bearing capacity of the bottom soil is increased, the failure mode changed from passing through the pit bottom soil to passing through the pit toe; and the safety factor is increased. Decreasing the slope angle has no much influence on the overall stability of the soil nailing in the soft soil.

Experimental studies indicate that the dynamic shear modulus of rockfill is related to confining pressure and stress ratio; therefore, it is necessary to include the influence of confining pressure and stress ratio in the dynamic constitutive model of rockfill materials. This paper briefly introduce the existing dynamic shear modulus calculation formula considering the confining pressure and stress ratio, and proposes an improved dynamic shear modulus calculation formula. Comparing with the experimental results of dynamic characteristics of Houziyan limestone rockfill, rhyolite rockfill, overburden gravel, transition material and cushion material, the model can better fit the combination of different confining pressure and stress ratios. The experimental data of dynamic shear modulus and dynamic shear strain show that the model has good applicability and prediction accuracy. The Hardin-Drnevich hyperbolic constitutive model is used to the finite element analysis of the dynamic response of Houziyan rockfill dams. The dynamic shear modulus is calculated using the conventional formula and the improved formula presented in this paper. The overall dynamic response of the dam is compared. Using the formula for calculating the modified dynamic shear modulus considering the confining pressure and stress ratio, the maximum acceleration response in all directions of the crest will increase; and the increase value will be about 20%-35%.The maximum dynamic displacement decreases by 14% in the river direction and increases by about 10% in both the vertical and horizontal rivers.

In general, the bank-tower-type water intake is built in the steep slope near the deep water zone, and the thickness of rock ridge used for the water retaining cofferdam is thin during excavation procedure of the foundation pit due to the construction. In addition, the upstream surface of the bank slope form a cavern subjected to water erosion, and the thin-walled rock ridge presents overhanging state; further the left bank slope is unstable induced by hydro-mechanical coupling and excavation action. Based on research about permeability theory and hydraulic aperture expanded model of fractured rock mass, the numerical method is adopted to simulate the excavation procedure of the foundation pit; further, compared the calculated deformation values with monitoring data. The results indicate that the permeability of thin-walled rock ridge become weakened after grouting, and the foundation pit excavation scheme that gradually install internal support is reasonable. The deformation of overhang rock ridge is in a reasonable range. Differently, the self-weight of rock ridge and water pressure of upstream face lead to inclined deformation of the thin-walled rock ridge towards river in initial excavation stage while towards the bank slope in later excavation stage. For the design and construction of foundation pit of water intake located on steep bank slope; the research results have important reference values and theoretical significance.

In light of the deficiency of the mining-induced subsidence monitoring methods and prediction models at present in China, a method of exponent Knothe model parameters estimation combined leveling with InSAR(interferometric synthetic aperture radar) technique is proposed and the fitting and prediction accuracy of exponent Knothe model is analyzed. Firstly, one workface is selected as the study area, eight leveling measurements and five scenes of radar images are collected to achieve the time series subsidence information in the leveling points. Secondly, the results of rock strata movement deformation caused by mining activities are analyzed. Then, the unknown parameters of exponent Knothe model are estimated and two fitting subsidence curves are constructed by combining leveling with InSAR and only by leveling measurements, respectively. Finally, the two fitting curves are used to estimate the fitting values and prediction values; and the effect of InSAR observations on the fitting and prediction accuracy is analyzed by comparing the fitted and predicted data with the measured data in the leveling points. The results show that the measurement accuracy of InSAR technique meets the actual mining requirements and the ground deformation is consistent with the strata movements. In addition, the fitting subsidence curves can be optimized and the fitting and prediction accuracy of exponent Knothe model is obviously improved combined with InSAR technique in the leveling points.

Numerical simulations based on the PFC2D are conducted to investigate the vibration rolling compaction(VRC) of prototype rockfill. At first, an equivalent numerical model for vibrating roller is developed based on the analytical 2-degree-of freedom lumped mass model, in which interaction between drum and frame is considered carefully. Secondly, a practical modelling procedure for prototype rockfill is proposed; so that the segregation behavior of rockfill grains can be replicated truthfully. Thirdly, based on the prin-cipal of relative degree of density, settlement relationship between 2D and 3D sample is derived in an analytical way. Finally, a practical case in real project is replicated by the proposed discrete model; and simulation results are compared to the observed data in site, such as settlement, breakage ratio, grading curve and porosity. The research results show that the proposed numerical model can replicate the macro and meso-behavior of prototype rockfill during VRC progress in a reasonable way, proving the feasibility and correctness. Related researchments can help to understand the mesoscopic mechanism of dynamic response of prototype rockfill under VRC load, and lay the foundation of investigating the mechanical behavior of compacted prototype rockfill in future.

Earth and rockfill dams have always played an important role in all types of dams. In the construction of high earth and rock dams, combining with actual rolling compaction conditions filling process simulation have important guiding significance for the safety construction and long-term stability of earth and rock dams. In order to simulate the filling and impounding process of earth and rock dam more precisely, the mesh size of finite element calculation should be the size of meters equal to the thickness of filling. At present, the difficulties in large-scale calculation of earth and rockfill dams include mesh subdivision, storage and parallel calculation of total stiffness matrix, and equation solving. Under the C programming framework, this paper uses the mesh refinement method to complete the grid subdivision of larger scale calculation, and the programming language, total stiffness storage and calculation, finite element equation solution and other processes of the static calculation program have been improved to complete the larger scale finite element method simulation of earth and rockfill dams. The filling process of a typical core wall rockfill dam with a height of 200 m is simulated under the mesh size of 1 m. The simulation results conform to the general rules.

Based on the background of the increasingly serious composite disaster of coal and rock mass impact-outburst in the deep, and closely surrounding the key scientific problem of the evolution mechanism of coal-rock flow (gas) -solid coupling mechanical behavior under multi-field conditions, a true triaxial multi-parameter test system for coal and rock containing gas has been developed independently. The test system can fully simulate true three-dimensional stress environment and loading characteristics of coal and rock in the deep. It is hoped that the test system can clarify the mechanical behavior of coal and rock during loading and failure, the spatio-temporal evolution law of acoustic emission and charge induction signals, grasp the mechanism of impact-outburst compound disaster breeding, and establish scientific means of disaster prevention and control. The experiment system consists of 6 sub-systems, i.e. loading-unloading, load-displacement monitoring, methane environment application-monitoring, electric control, acoustic emission and charge induction. It has the characteristics of high-stress, true triaxial, multi dimension, high precision, good stability, multiparameter and multi loading-unloading path. Experiments of coal under different gas pressures, lateral pressure ratio and unloading path are carried out with the system, analysis of total stress-strain curve, acoustic emission and charge induction signal. The results show that the strength of peak and residual, ductility of coal are changed by methane; the anisotropy characteristics gradually weakened with the decrease of lateral pressure ratio; strain developed in the direction of low stress; the lateral pressure ratio and the loading/ unloading path are important stress environmental factors influencing mechanical behavior of coal rock. The system provides a reliable experimental basis for the follow-up study of fluid-solid coupling mechanical behavior of coal rock containing methane.

Circular hole and fissure are common flaws in rock mass; and their crack inoculation and evolution mechanisms have become one of the most important research subjects in the field of rock mechanics. Rock-like specimen containing circular hole and fissures are constructed and subjected to uniaxial compression based on digital image correlation(DIC) technology, computed tomography(CT) scanning technology, acoustic emission(AE) monitoring technology and particle flow code in PFC2D calculation data. Under the interaction between circular hole and fissures, the mechanical characteristics such as strength and deformation and fracture development are investigated in detail. Research results show that: (1) the number of acoustic emission events are relatively small and uniform in pre-peak; but the number of acoustic emission events are large in post-peak; and the greater the absolute value of the stiffness at the time of stress drop, the greater the frequency of acoustic emission events. (2) The macroscopic cracks generated by specimen failure can be classified into two modes, namely mode Ⅰ (tensile crack) and mode Ⅱ (shear crack). The mode Ⅰ crack first initiates from the ends of the fissures and the upper and lower of the circular hole, which is approximately parallel to the loading direction. The mode Ⅱ crack, extending at a certain angle with the loading direction, mainly occurs in the rock bridge area between the circular hole and the inner side of the fissures, and the area between the outer side of the fissures and the boundary of the specimen. (3) There are mainly two kinds of crack propagation paths, i.e. airfoil tensile crack propagation and secondary coplanar crack propagation. Among them, the main crack propagation is the airfoil tensile crack in the early loading stage, and the secondary coplanar crack growth is the main one in the late loading stage. (4) The DIC technology, CT scan technology, AE monitoring technology and PFC2D calculation method are adopted synthetically, which can establish the relationship between mesomechanical mechanisms and macromechanical response in the process of rock mass destruction and reveal the development and distribution characteristics of surface and internal fractures in rock masses intuitively and accurately.

The rheological properties of the weak and fractured rock masses surrounding the deep coal roadway can exert a significant influence on the mining activities. To study their rheological mechanisms and characteristics, a triaxial rheological testing equipment for in-situ rock mass is developed. This testing equipment mainly consists of three parts, including the loading system, displacement measurement device and the main frame. The loading, unloading, pressure-maintaining procedures on the rock mass sample are fulfilled using a mine-used explosion-proof electric hydraulic pump station, and the deformations of the rock mass sample in every direction are measured using a displacement measurement device. The connection of the equipments and the transfer of the system load are fulfilled using the main frame. By using this testing equipment, the rheological test in step-by-step loading mode is conducted on the in-situ rock mass sample in a deep coal roadway. The results show that this testing equipment can surely fulfill the rheological tests on the in-situ rock mass sample located at the roadway floor in deep coal mines. The rheological process of the in-situ rock mass sample can be divided into several stages with different rheological characteristics and the rheological characteristics under high or low stress are also different. When the exerted load increases to a failure stress value, the rock mass sample will enter the accelerated creep stage quickly and then fail rapidly.

The immersed tube tunnel of Hong Kong-Zhuhai- Macao Bridge is about 6.7 km long and 44 m deep under water. Because of the complexity of the geologic conditions, different ground treatment measures are used in this project, such as SCP and heavy-tamping broken stone piers. The deformation compatibility of ground treated by different methods should be verified before the immersed tube installation. In this paper, a loading test system designed for deep water is recommended. This system was used during the construction of Hong Kong-Macao-Zhuhai Bridge. The settlement of macadam bed in deep water is obtained and the deformation compatibility is verified by this system. Instant settlement is also obtained, which provides the basis for the elevation design of macadam bed. Settlement characters of the load test are the same as the settlement characters of immersed tube tunnel. So the reliability of the test system is verified.