Coral sand of land reclamation in island of South China Sea are biocemented by microbially induced carbonate precipitation(MICP) method; triaxial compression tests of biocemented coral sand columns are conducted; the test results are analyzed; and the damage constitutive model of biocemented coral sand columns is proposed based on the theory of rock damage mechanics. The test and analysis results show that, coral sand can be biocemented well by MICP method; and the stress-strain curves of biocemented columns can be divided into approximate linear stage, yield stage and ductile flow stage. Biocemented columns are divided into homogeneous unit cell, damage evolution analyses are conducted and damage variable is defined based on the theory of effective stress and hypothesis of strain equivalence; and damage constitutive model is proposed with the assumption that the strength of biocemented columns obey the Weibull distribution and Druker-Prager criterion. The model parameters including mechanical parameters and Weibull distribution parameters, which are defined based on tests data and calculated by linear regression method. The rationality of model is preliminarily verified by tests data.

The state of tensile-shear stress can easily lead to rock mass damage and even instability. To investigate the tensile-shear failure law of jointed rock mass, numerical simulation of rock mass containing coplanar intermittent cracks under tensile-shear test is carried out through FLAC3D simulation software. For getting high fidelity actual conditions, Mohr-Coulomb constitutive model and maximum tensile stress criterion are amended with rock statistical damage and a function is applied to make the initial mechanical parameters obey the Weibull distribution. Then, failure modes and laws of rock mass are studied under tensile-shear loading. And the influence of homogeneous degree, normal tensile stress and shear rate on rock mass failure modes and processes, as well as its mechanical properties were discussed. The main conclusions can be drawn as follows: (1) Due to the heterogeneous characteristics of natural rock mass, the failure mode is dominated by tensile failure, with little tensile-shear mixed failure. Meanwhile, the initial rupture zones are scattered and then form a strip-shaped fracture surface. The macroscopic mechanical properties of heterogeneous rock mass are obviously weakened than homogeneous rock mass without damage evolution. (2) Heterogeneity has a significant impact on the failure process and strength of jointed rock mass. That is, with the increase of homogeneous degree, the failure mode changes from diffuse type to the concentrated, and the rupture surface roughness increases. The macroscopic strength of jointed rock mass enhances, but there is a ceiling which represents strength of the homogeneous. (3) Under the low stress level, the increase of tensile stress does not change the main rupture mode of rock mass which is tensile failure. However, the proportion of shear and mixed failure are obviously less. Meanwhile, the shear strength of rock mass decreases and the roughness of fracture surface increases. (4) The shear rate has a significant effect on the mechanical properties of rock mass. In the static loading range, the shear strength of rock mass increases with the growth of shearing rate, and the magnitude of the increase is getting smaller.

Roughness is one of the important factors that affect the strength and deformation characteristics of jointed rock mass. In this paper, 3D printer has been employed to making molds firstly, and casting the different roughness joint rock specimens(joint roughness coefficient JRC = 2, 7, 12, 17 and 22). Triaxial compression tests are carried out on rock specimens with different roughness joints by using GCTS triaxial rock testing system of high temperature, high pressure and dynamic-static coupling loading to obtain the triaxial stress-strain curves. Then, based on the curves, we analyze the influence of JRC on the triaxial compressive strength and deformation characteristics of rock. At the same time, acoustic emission test system has been adopted to reveal the acoustic emission characteristic of the different roughness jointed rock specimens in the process of triaxial compression tests. Finally, the morphology of the joint surface is observed by digital three-dimensional video microscopy system, and the relationship between the peak strength of jointed rock specimens and JRC under different confining pressures has been discussed. The results show that the presence of joint results in a significant reduction in the strength of the joint rock specimen; JRC also has great influence on the morphology, quantity and spatial distribution characteristics of failure crack of rock. With the increase of the JRC value, the shear strength of rock joint increase, the triaxial compressive strength also increase, the rock specimen will changed from brittle failure to ductile failure.

In order to analyze the influence of bedding and water on the creep characteristics of shale, five kinds of shale are prepared in the laboratory, including 0, 30, 60, 90 degrees and no bedding. Each kind of bedding shale is treated with 4 kinds of water bearing state, which is dry, natural, water unsaturated and water saturated. The results show that: (1) The bedding angle and water content have great influence on the creep characteristics of shale. At the same moisture content, with the increase of the angle of stratification, the initial instantaneous elasticity of shale decreases exponentially and the instantaneous elastic modulus increases exponentially. At the same layer angle, with the increase of moisture content, the initial instantaneous elastic strain linear growth of shale and linear decrease of instantaneous elastic modulus. (2) The creep of shale is described by Burgers creep model with elastic elements, viscous elements and Kelvin body, and the parameters of the model inversion and the verification. The results show that the model can better reflect the features of the shale creep. According to the law of the influence of the bedding and water on the creep deformation of shale and based on the fitting relationship between the instantaneous elastic modulus, the viscosity coefficient and the bedding angle, water content, the instantaneous elastic modulus and viscosity coefficient of the creep model are replaced by a function of the bedding angle and moisture content; thus a creep model which can reflect shale bedding and water content is constructed.

The object of this paper is to study the coupled impacts of medium deformation and slippage effect on variation of apparent permeability for micro fractures, and to investigate the mechanism of effective stress condition and pore structure parameters on gas flow in shale gas reservoirs. A dynamic apparent permeability model for micro fractures is presented, which accounts for the coupled effects of medium deformation and gas slippage simultaneously based on the smooth plate model and combined with the fractal theory, as well as microscopic gas flow mechanism. Then the reliability verification and sensitivity analysis of the established model are performed. The results show that: The apparent permeability decreases firstly and then increases slowly as pore pressure reduces, and the critical pressure is about 5 MPa. The huge difference between the two coupled mechanism (medium deformation and slippage effect), resulting in the variation of apparent permeability curve with different effective stress states, which also explained the variation of stress sensitivity for shale with different loading modes in testing from microscopic perspective. The deeper "groove" of the apparent permeability curve when the maximum aperture is smaller. In addition, the higher the porosity and fractal dimension of the aperture, and the lower the tortuosity fractal dimension, the greater the apparent permeability is.

Some tunnels are inevitably built to cross the landslide zone in actual engineering. Besides, under the action of late geological evolution and construction disturbance, the slope that has no obvious deformation or more stable slope will appear larger deformation and even develop into a landslide. Consequently, the landslide has negative effects on the tunnel structure. So tunnel structure will be affected and even be interrupted. At present, most scholars at home and abroad are focus on stress and deformation of landslide body caused by tunnel excavation. There are few studies on the force, deformation and reinforcement of existing tunnel structures under the action of landslide. In order to study the stress and deformation of the reinforcement measures of the existing tunnel cable in landslide mountain area, firstly we establish the geomechanical model test and study on the interaction between the landslide and the tunnel structure that with the reinforcement of the different number of anchors and compared with that without the reinforcement. Then, we use the numerical software to establish the model under the corresponding conditions, compared with the physical test results. It shows a good consistency. The results can provide a theoretical basis for the anchor cable reinforcements of the tunnel in the landslide mountain area.

Rock creep is the evolution result of the interaction of hardening effect and damage effect inside it. A series of uniaxial compression creep experiments of raw lean coals are conducted by stepwise loading in this work, and the increasing instantaneous elasticity modulus and decreasing viscosity coefficient are taken to analyze the hardening-damage mechanism of lean coal. The results show that at low stress load, coal strain is just instantaneous, and only hardening effect exists. When the stress reaches or exceeds the creep start stress threshold, damage effect emerges, and interacts with hardening effect, resulting in transient creep and steady creep. In long term creep, coals are first hardened and then weakened and finally fail due to large accumulative damage. On basis of the strain characteristics of lean colas at different stress loads, a combined viscous-elastic plastic model is established; and then the hardening function and damage function are both introduced into the model; thus the creep constitutive equation is obtained. This model is used to depict lean coal’s creep curves and the results show the model curves fit the experimental data very well. This model is simple with clear physical meaning, and it can reflect the hardening-damage creep characteristics of lean coal in uniaxial compression very well.

Through the sludge solidification technology, the municipal sludge is transformed into a new type of municipal sludge solidified soil. In order to study the engineering properties of the sludge solidified soil, the unconfined strength test, shrinkage test, leaching toxicity test and microstructure test are carried out on the new type of municipal sewage sludge solidified soil. The test results show that the unconfined compressive strength of urban sludge solidified soil increases with the aging period, and basically stable after 28 days. The linear shrinkage of new city sludge solidified soil increases with age, and 28 days later tend to a stable value; compared with city sludge solidified soil after digestion, the leaching toxicity of city sludge solidification in soil decreased, the leaching amount of heavy metals are in line with the requirements of national standard. The peak of calcium hydroxide in the urban sludge after lime digestion diffraction peak is very high; but with the increase of curing age, the diffraction peak of calcium hydroxide in the city sludge solidified soil decreased; the diffraction peak of calcium carbonate increased. Microstructure studies show that there is a large number of fibrous material associated with soil particles and agglomerates of particles of city sludge solidified soil in SEM images, interactive spatial structure of soil skeleton fiber, which improves the strength of the soil.

In order to study how the tensile strength of sandstone influenced by loading rate, a series of splitting tests are carried out with five loading rates. Based on the comprehensive analysis of the splitting tensile strength, destructive features, the change rule and correlation between microstructure of the splitting surface and energy parameters, the results show that: (1) The split tensile strength of sandstone gradually decrease as loading rate increase, and generally go slow after the first steep upward trend. When loading rate is between 0.01 kN/s to 0.10 kN/s, the tensile strength grew significantly and then tended to slow down at 0.1 kN/s to 1.00 kN/s. (2) Total energy the sample absorbed increase as loading rate increase, and the ratio of elastic strain energy to total energy increases while dissipated energy go down, the time when the crack propagation formed into splitting surface is an order of magnitude less, which indicates the sudden destruction of rock sample enhanced resulted by release of elastic strain energy when peak stress reached, which result in tensile strength enhanced and increasingly complicated micro morphology characteristics. (3) During the rock splitting test, loading rate, energy parameter, features of splitting surface and tensile strength are closely related; first of all, the loading rate affects the total amount and distribution of energy ,and the changes in energy parameters affects its destruction process and features of splitting surface; finally, the difference in tensile strength shows. The related analysis methods and ideas references can provide a better reference for similar tests.

In order to explore the basic engineering characteristics of loess modified by red mud, of which the optimum ratio is obtained based on unconfined compression test, direct shear test and seepage test; and then an empirical formula for shear strength, unconfined compression strength and resistivity is established. The cumulative plastic deformation, dynamic elasticity modulus and leaching toxicity of the modified loess under cyclic dynamic loading are analyzed by dynamic triaxial test. The results show that with the increase of red mud content, the unconfined compressive strength and cohesion of the modified loess first increased and then decreased; and when the amount of red mud is near 15%, the unconfined compression strength of 28 d reached 3.5 MPa, which is improved by about 34.7% than no red mud. The permeability coefficient decreased rapidly with the increase of red mud content, and reached the stability when the amount of red mud is 5%. There is a good linear relationship between the shear strength, unconfined compressive strength and resistivity. The critical dynamic stress of the modified loess reaches 600 kPa under cyclic dynamic loading, of which the maximum dynamic electricity modulus is 6 times ones of loess. The leaching solution of the modified soil does not have the toxicity of leaching.

Analysis method of slope stability can be classified into local and global kinds. These different points have their historical rationality and limit. Taking limit equilibrium method and strength reduction method for examples, the difference of typical local and global one such as slip surface, equilibrium condition, definition of safety factor, material parameters and un-stability is studied and summarized. Using a PFC slope fail case presents that real slope un-stability has observably spatiotamporal series and progressive features. Practical slope failure is a process of terrain reconstruction and stabilization and a process of potential and kinetic energy transition and dissipation. Aiming at these, the theoretical framework and technical route of slope stability vector sum method considering generalized softening are established. The relative program is implemented too. Whose reduction has material degradation back-ground. Its safety factor only relates to stress state of the slope. There are few assumed conditions in the method, which can realize dialectical unity of local and global stability and reflects progressive characteristics and spatiotamporal effect of slope un-stability. The safety factor and slip surface obtained by the method proposed compared with results of LEM and SRM, show that slip surface of local one is more stable, safety factor is whole life cycle and is larger than that of global one by 5%. The difference between local and global slope stability analysis method is caused by their assumed conditions.

Mudstone is widely used as the host rock medium in oil and gas reservoir. The creep behavior is extremely complex and directly influences the failure of casing under high temperature and high confining pressure. This study focuses on the gypsum mudstone in deep oil and gas reservoir engineering. Firstly, under 130 ℃ temperature and 30 MPa confining pressure, triaxial creep tests are performed under different deviatoric stress on multiple samples with a single-stage loading method. The mechanical behaviors of mudstone exhibit significant time-dependent and the creep stress threshold is small. The stress and duration has significant effects on creep behavior of mudstone. The steady creep and accelerated creep failure can be obtained under a long duration even in a small deviatoric stress. The start time of accelerated creep can be described as an exponential function of deviatoric stress; and the start time decreases with an increase in deviatoric stress. Secondly, the accelerated creep and strength damage characteristics of mudstone are discussed in detailed. The threshold of start time of creep damage is proposed. It is considered that the internal creep damage variable of mudstone can be described as an exponential function. Finally, based on the creep damage variable and the start time, the improved Burgers creep model is established. The model is nonlinear and can describe the accelerated creep stage. Then the creep parameters are identified and analyzed. The model can accurately describe the creep characteristics of the deep gypsum mudstone. The research results provide dependable reference for the safety evaluation and long term stability analysis of deep oil and gas reservoir engineering.

The application of bearing test achievement is determining deformation properties of foundation soil or to calculate modulus of deformation and ultimate load etc. The phase of unloading and reloading of bearing test is researched through unloading ratio, rebound proportion, reloading ratio, recompression ratio etc. to get the regularity of rebound deformation and recompression deformation; and it is consistent with the law from consolidation test. The characteristics of bearing test can remedy some shortcomings of consolidation test; the exploratory research on applying the bearing test achievement to calculate the rebound deformation and recompression deformation is beneficial. Combined with engineering project, based on the analysis method of consolidation test achievement, some improvement is adopted; and then the new method is applied to calculate the rebound deformation and recompression deformation based on bearing test achievement. Compared the calculating result, the result from original method and the result from engineering measurement, the new calculating method is efficacious. But the shortcoming of the bearing test achievement is obvious; according to the need of new calculating method, some improving suggestions are proposed, so as to point out the direction of the next research step.

To avoid insufficient bolting or excess bolting and to quickly and accurately evaluate the stability of the surrounding rock stability of anchored tunnel, firstly, considering the complex of rock and bolt into the reinforcement body with homogeneous material, the physical and mechanical parameter expression of the reinforcement body is derived based on the elastic theory. Then, the coordinated deformation mechanical model of surrounding rock and the reinforcement body is established, the model is analyzed by mechanics, and the evaluation method of surrounding rock stability is put forward. Finally, this theory is compared with existing theories and numerical simulation; and the influence of different bolting strengths on the stability coefficient of surrounding rock is studied. The results indicate that the radius of plastic circle of tunnel surrounding rock and the radial displacement of tunnel wall obtained by this theory are different from the calculated results of the existing theory by 0.8% and 2.1% respectively; and the theoretical calculations are in good agreement with the results of numerical simulations, which verifies the rationality of the theory of this article. The length of the bolt and the spacing between the bolts have a great influence on the stability of the surrounding rock; and the bolt support design follow the principle of long and sparse, short and dense. The optimum bolt length is reduced when the distance between the bolts is reduced or the pretension is increased. This theory can provide a relatively simple and fast quantitative calculation method for the stability study of tunnel surrounding rock under bolt support.

The calculation method of total earth pressure behind row piles from clayey backfill considering soil arching effect is researched. Against on the single-row retaining piles, the total earth pressure behind row piles which considering the soil arching effect is divided into direct earth pressure and indirect earth pressure. Firstly, in light of the previous researches' weakness, the principal stress rotation theory of retaining wall is used and improved by considering that the value of principal stress is changed after rotating. On this basis, by means of a stress analysis of soil arch element and solving the equilibrium differential equation, an analytical expression for the direct earth pressure is derived. Compared with the analytical solution of predecessors and the measured data, the computed result of the improved method is more consistent with the measured data. Then, the improved method is applied to the indirect earth pressure of the clayey soil, and the analytical expressions for indirect earth pressure and total earth pressure are derived by regarding indirect earth pressure as the integral of the shear stress along the slip surface of the soil between piles. Finally, the change rule of total earth pressure with cohesion and soil-pile friction angle suggested that the soil arching effect mainly affect the lower part of H/3-depth pile body, causing the total earth pressure of this part decrease; and the closer it get to the bottom of the pile, the larger the decrease is. The study can provide a basis for the rational design of row piles.

Sandy pebble soil has the characteristics of large internal friction angle, poor mobility and high permeability coefficient. It will be excavation difficulties, cutter head wear, groundwater spewing and other problems in the construction of shield in sandy cobble stratum. Through foam optimization test, the foam liquid concentration is 2%-3% when the foam half-life and foam expansion ratio are optimum. Based on the sand-pebble stratum of Chengdu metro line 7 in Sichuan Province, the soil with 20%, 40%, 60% and 80% of the gravel content is prepared. Large-scale indoor shearing test, slump test and permeability test are carrie out, it is shown that with the increase of foam injection ratio, the content of foam soil wrapped around sand and pebble soil increased, the phenomenon of sand and stone separation gradually disappeared; the shear strength and internal friction angle decreased nonlinearly; and the slump gradually increased. The impermeability can be obviously improved; and the foam injection ratio of different stone contents gravel soil satisfying the requirements of “ideal state soil” in shield construction is obtained. The result can be of great importance in solving the problems encountered in the construction of shield in sand pebble stratum.

The active earth pressure acting on the flexible retaining wall during excavation of foundation pit is analyzed. The retaining wall is assumed to deflect as bulge shape that the maximum displacement is located at the excavation surface. The slip surface is assumed as a plane through the wall toe. A general slip surface angle is deduced by considering excavation depth and support of foundation pit. The active earth pressure distribution, lateral soil force and its application are obtained based on the horizontal thin layer analysis method. The results show that the theoretical results are consistent with the measured results. As the excavation depth increased, the angle of the slip surface decreased; the influence scope and the active earth pressure are enlarged; the influence on the position of resultant force is small. When the excavation depth decreases, the soil friction angle and soil wall friction angle increase, the nonlinear distribution of active earth pressure becomes more obvious; the resultant force decreases; and the distance between the application point of resultant force and the wall toe increases.

One of the effective ways to study the excavation and unloading effect of roadway (tunnel) is to carry out excavation and unloading test of small-scale rock specimen. In order to make it easier to prepare and control the strength of the small surrounding rock speimens, firstly the high-strength gypsum-based materials are selected to carry out the ratio test. The proportion of the corresponding materials with the strength range of 5-20 MPa and the influence of the similar materials composition on the strength of the specimen is obtained. Secondly, a small wall rock specimen (thick wall cylinder type: 290 mm high, 100 mm with diameter, 200 mm outer diameter) is processed. The tunnel excavation unloading model test system with independent intellectual property rights has been used to simulate the unloading and failure of the surrounding rock specimens. The excavation unloading process can simulate the excavation conditions of the actual engineering on the principle of mechanics; that is, the axial compression, external pressure and internal pressure are applied to the surrounding rock specimen to simulate the original rock stress. Excavation (that is, when unloading), unloading the internal pressure and keep the other two pressure constant. During the test, the relationship between the strain in two directions along the axial direction and the tangential direction of the surrounding rock specimen is collected. The strain-time curve and the relationship between the strain and the pressure drop are obtained. And present: the inner strain is larger than the outer one and the specimen expands inward during unloading; at the same measuring point the tangential strain is larger than the axial strain playing a leading role. When the unloading damage occurs, the failure direction of the surrounding rock specimen destroys toward the inside of the cave, that is, along the radial direction. Failure pattern presents stratified rupture.

In order to consider the damage effect of aging deterioration and water content weakened on the creep parameters of rock, a creep damage model is proposed, that is, the parameter correction and improvement of Nishihara model and the triaxial creep tests of basalt with different water contents are carried out. First of all, the creep regularities of rocks with different water contents are comparatively analyzed; and the mechanism of the influence of water content on the rock creep process is revealed. Secondly, in order to describe the rock creep process better, the aging deterioration effect and water content weakened effect are introduced. The damage variables and creep parameters are fitted by the experimental data. Finally, the calculated values of the model are compared with the experimental data. The results show that the initial creep value and steady creep value increase with the increase of water content. Furthermore, it is verified that the numerical calculation of the model agreed well with the experimental data by FLAC3D. The rock aging creep damage model proposed in this paper will provide a theoretical basis for the study of rock rheological properties.

The particle size distribution curves show that, there are few fine sands and silts in the investigated granite residual soils. And the unique grain size gradation of the granite residual soil results in large discreteness of the parameters commonly used in design with physical parameters. Based on engineering geology investigation reports of metro engineering in Xiamen, correlation analysis are carried out between physical state parameters such as the interfine void ratio, the granular composition and the strength parameters. Results show that, correlative equations, of residual gravel cohesive soil and residual sandy cohesive soil, can be established between intergranular state parameters, proposed by Thevanayagam, and modulus of compressibility, in which, the modulus of compressibility decreases with increasing of the interfine void ratio. And, as for estimating shear strength indices, the characteristic diameter ratio can be taken as a parametric variable. With increasing of the characteristic diameter ratio, the cohesive force increases, and the internal friction is just the opposite. The established empirical formulas of modulus of compressibility, and shear strength indices for granite residual soil in this paper, can be provided as a reference for engineering design in Xiamen.

The tunnel-type anchorage is the key force component to bear the main cable load of suspension bridge, and the mechanism of tunnel anchorage and surrounding rock joint bearing is very complicated. The simplified calculation model of tunnel anchor is established; and a formula for calculating the pullout capacity of tunnel anchor is deduced by using the wedge effect method. Furthermore, in order to verify the rationality and correctness of the "wedge effect" calculation method, the 14 groups corresponding indoor model tests are designed and carried out. Through the model tests, the uplift bearing capacity is obtained; and the relationship between the influence factors and the uplift capacity is studied. With the accurate related parameters of indoor model, using the calculation method of bearing capacity of indoor tunnel anchor model, and contrasted it with the results of model test, the results show that the theoretical calculation results are consistent with the law of influence factor and destruction characteristic. Research results show that it is scientific and reasonable to calculate the bearing capacity of tunnel anchorage by the simplified formula considering the “wedge effect”. This calculation method has the characteristics of clear mechanical meaning and concise formula form, so as to provide reference for engineering practice.

Theoretically, direct tensile test is the most simple and effective method for determining the tensile strength of rocks, which is both theoretically and practically meaningful. However, clamping the specimens is a major difficult problem, which leads to the difficulties in preparing the specimens and the complicated test equipment. Double concentric annular core tension test is an innovative approach to laboratory determination of tensile strength of rocks, which could overcome the above-mentioned loading disadvantages of the conventional direct tension tests. Firstly, the mechanics of the double concentric annular core tension test is discussed; and then the specimen size effect and optimal size range are investigated experimentally and numerically to obtain more reliable tensile strengths. The results show that the maximum stress near the inner and outer bottom are close to each other and reliable tensile strength could be obtained when the ratio of outer ring diameter to specimen diameter r1/R is 0.62±0.08; the ratio of inner ring diameter to specimen diameter r2/R is 0.45±0.12; and the ratio of inner ring diameter to outer ring diameter r2/r1 is 0.64±0.06. Tensile strength results obtained from these tests could achieve the optimum least standard error and coefficient of variation compared with Brazilian test and hollow cylinder test.

The combined foundation of pile-underground diaphragm wall is a new type of foundation, which has the advantages of high horizontal bearing capacity and low cost. The internal force distribution and deformation regularity of the new combined foundation under surcharge are studied by conducting a new type of combinatorial indoor model test. At the same time, a comparison test of the conventional model of the pile-concrete foundation is conducted to obtain the deformation control mechanism of the new combined foundation, for which in order to provide further theoretical and practical basis for the further promotion of this technology. The experimental results show that: (1) The combined foundation has a high bearing capacity relative to the foundation of the pile bearing platform. (2) The combined foundation is mainly driven by the front wall and the lower part of the combined foundation pile is small. (3) The combined foundation and the foundation of the pile are different in the shape of the deformation. The combined foundation is inclined to the stacking side and is in the direction of the whole subsidence due to the larger negative friction resistance. The pile foundation is shifted away from the stacking side. (4) The upper load has less influence on the horizontal bearing capacity of the combined foundation but increases the inclination of the foundation.

Epoxy resin and cement paste are chosen as grouting materials, uniaxial compressive tests are conducted on the specimens containing single grout-infilled flaw having different inclination angles. Experimental results show that grouting materials and flaw inclination angle have a significant influence on the uniaxial compressive strength and failure mode of rock-like specimens. The reinforcement effect of epoxy resin is better than that of cement paste, epoxy resin can effectively eliminate the stress concentration of the tips of the grout-infilled flaw. Whether the flaw is grouted with epoxy resin or cement paste, grouting has little improvement in uniaxial compressive strength(UCS) when the flaw inclination angle is very small ( <30°) or very large ( =90°), however, reinforcement effect is significant when the flaw inclination angle is 60°. For the specimens containing single flaw grouted with epoxy resin and cement paste, the failure path dose not cut through the grouting materials but cut through the interface between grouting material and model material. Sliding crack model is proposed. This model indicates that the UCS of specimens increases with increasing cohesion and friction angle of the interface between grouting material and model material. Different grouting materials have different improvement on the cohesion and friction angle of the interface, which is the reason why different grouting materials have different improvement on the UCS of specimens. This study will provide a theoretical frame for analyzing the influence of grouting materials and the inclination angle of flaw on the strength of rock mass in engineering projects.

The propagation and coalescence of microcracks of a fine-grained marble after treatment under different high temperature cycles is observed and analyzed using a polarizing microscopy in this study. The thermal cracking behavior in the tested rock specimen is investigated by statistically analyzing the length, width, and quantity of the generated microcracks. The main results obtained from this study are as follows: (1) The number and the total length of thermally-induced microcracks inside the rock specimens after different numbers of thermal cycles are disparate. For specimens without thermal treatment, the grains are compacted and cemented well with each other, and no obvious microcracks are observed. With four thermal cycles’ treatment, the microcracks are generally observed in grain boundaries. The width and length are significantly increased as compared with those of specimens without thermal treatment. The width of micro-cracks in rock specimen with sixteen thermal cycles’ treatment reaches 55 μm, which is about four times as compared with that in rock specimen with four thermal cycles’ treatment. (2) The anisotropy of thermally-induced microcracks inside the rock specimens after different thermal cycles is also analyzed. The results show that there is no obvious preferred direction in the thermally-induced microcracks. It also shows that the sampling position of thin sections has negligible effect on the number of the thermally-induced microcracks. (3) The linear crack density is also found to increase as the number of thermal cycle increases. The linear crack density in rock specimen with sixteen thermal cycles’ treatment is about 21 times when compared with that of rock specimens without thermal treatment.

The traditional rigid bearing plate load test (PLT) mainly determines the bearing capacity of foundation, and can not be used to invert the shear strength parameters , . In this study a flexible bearing plate has been invented through the installation of an air bag under the rigid bearing plate. Two self-made inductance displacement sensor are respectively set at the edge of two inner sides of the plate, in order to measure the variation of the thickness of the air bag at this area. When the flexible bearing plate is used to carried out the loading test, the compressive stress p under the plate is in uniform distribution. During the test, a constant uniform surface load q is applied on one side of the bearing plate by a flexible water pressure plate. So that two curves can be got, and two critical edge load values can be judged from the curves’ changing feature corresponding to zero surface load and q respectively. Then the c and can be inversed if we put the critical edge load values and q into the theoretical formula. The cohesive soil and dry sand have been tested respectively during the laboratory experiments; and the feasibility of the inversion method is proved. The applicability and the progressiveness of the inversion method are also approved through analysis.

With the increase of temperature, macroscopic mechanical parameters of granite often experience a slight increase, a slight decrease, a substantial reduction in several stages. The nanoindentation test is carried out on the main mineral components of the heat treated granite to reveal the microscopic mechanism of the evolution of the macroscopic mechanical parameters of the granite with temperature. (1) The microstructure does not change significantly under the temperature of 300 ℃; and no microcracks are found. At the temperature between 300 ℃ and 500 ℃, microcracks begin to occur in the interior of the rock mass; when the temperature exceed 500 ℃, a large number of microcracks are generated in the rock mass and gradually expand and increase. (2) The elastic modulus and hardness of quartz increased slightly at 300 ℃. When the temperature exceeds 300 ℃, the elastic modulus and hardness begin to decrease. When the temperature exceeds 500 ℃, the crystal structure changes from phase to phase; 400-500 ℃, the elastic modulus and hardness begin to decline. When the temperature exceeds 800 ℃, the elastic modulus and hardness drop sharply, for mica, the elastic modulus and hardness increase within 800 ℃, above 800 ℃, the modulus of elasticity and hardness decrease sharply. (3) The macroscopic mechanical properties of granite are related to the mechanical properties and microstructure of the main mineral components; it is mainly controlled by the former in the range of room temperature to 300 ℃ and controlled by the combination in the range of 300-500 ℃. When it exceeds 500 ℃, it is mainly controlled by the latter. The related research results can provide experimental data and theoretical support for studying the temperature effect of granite and other rocks.

Roof sand inrush is one of the safety threats faced by mining in shallow coal seam in Western China. By using the self-developed test system of fracture sand inrush, the simulation test of sand inrush process of aeolian sand under the condition of no water are carried out in this paper. The effect of sand layer thickness, fracture angle and crack opening on the rate of sand inrush is studied; and then the quantitative relation between different influence factors and the flow rate of aeolian sand in the fissure is obtained. The research results show that the change of sand layer thickness has little effect on the rate of sand inrush; and the change of the slit angle has an obvious influence on the rate of sand inrush. In the case of a certain crack opening, the rate of sand inrush increases with the increase of the slit inclination, and they are logarithmic relation. When the fracture angle is fixed, the rate of sand inrush increases rapidly with the increase of the crack opening, which is in accordance with the exponential relationship, the crack opening has the greatest influence on the sand inrush rate; and the weight of the sand layer thickness can be ignored. The research results can provide theoretical basis and scientific guidance for prevention and control of sand disasters in coal mines in Western China.

In order to study the permeability evolution of coal sample from Qinshui basin, an experimental device based on the transient pressure pulse-decay method for measuring the permeability of coal sample is developed. Permeability measurements using N2 and CO2 are conducted under common laboratory conditions which include constant pore pressure and variable confining pressures, constant effective stress and constant confining pressure and variable pore pressures. The Connell model is used to analyze the testing data. The reasons for the difference between the model prediction and the experimental value are discussed. The results show that: (1) The permeability of coal decreased with the increase of effective stress under constant confining pressure and variable pore pressures; the permeability of coal decreased with the increase of pore pressure under equivalent effective stress; as the pore pressure increased, the permeability of coal first decreased and then increased under the condition of constant confining pressure and variable pore pressures. (2) The permeability value predicted by the Connell model for constant confining pressure and variable pore pressures is greater than the experimental value. The difference between the permeability prediction and the experimental value may be due to the estimation error of the fracture compressibility and the adsorption strain coefficient. By carrying out permeability experiments and model studies in laboratory, it is of great significance to guide the experiment and simulation researches of CO2 sequestration and gas displacement in laboratory.

In order to accurately test the mode I fracture toughness(KIC) of shale, three point bending loading experiments are carried out using notched semi-circular bend(NSCB) and cracked chevron notched semi-circular bend(CCNSCB) samples under three types of prefabricated notches (splitter, arrester and divider), respectively. According to statistical results of standard deviation and coefficient of variation, discreteness of each group of KIC values is analyzed; and applicability of the two methods is valued respectively. The crack propagation path and fracture surface morphology are observed by optical microscope. Based on fracture mechanics, we give the calculation formulas of the rough undulating fracture surface of shale specimens. The reason for KIC value scattering of the tested shale specimens is analyzed; and the formation mechanism of rough fracture surface in the expansion process is explained using the principle of minimum energy dissipation. By comparing the KIC values of the two sample types, CCNSCB and NSCB methods yield KIC values of similar discreteness when notches are parallel to bedding planes. When notches are vertical to layers, KIC values from CCNSCB specimens is more consistent than that from NSCB. The ligaments of CCNSCB specimens are in favor of crack propagation, which counteracts the adverse influence caused by asymmetry loading configuration to some extent. Therefore, CCNSCB specimens are more suitable to test fracture toughness of anisotropic shale than NSCB.

Based on self-designed pressure-tension conversion device and the RMT150C rock mechanics test system, the direct tension tests of the bilateral asymmetric cracked rock-like plate specimen have been carried out with the digital speckle correlation method (DSCM); and then the tensile stress-strain curves, the evolution of the surface strain fields and the crack propagation modes are obtained correspondingly. The results show that the tensile stress-strain curve of rock-like specimen can be roughly divided into four stages: (1) The approximate linear stage, the prefabricated crack basically do not work, the stress increases rapidly with strain, and the specimen surface strain field distribution is mainly affected by the internal pores and particles. (2) The whole slowly increasing stage, the two prefabricated cracks and the pores and particles in the specimen affect the distribution of the surface strain field; and the stress increases with strain on the whole. (3) The short peak transitional stage, one prefabricated crack plays a decisive role in the distribution of the surface strain field. (4) The final failure stage, the crack initiation is located in the relatively concentrated area of the strain field, and which cause the specimen damaged. For the bilateral asymmetric cracked plate specimen under direct tension, one of the cracks will propagate first, and is away from and then close to the front crack, which have great significance for the study of the propagation law of multi-crack interaction under tension stress state by using numerical simulation method.

The mechanical response of the anchorage system under intermediate strain rate conditions is the key issue in the analysis and evaluation of the safety of the support structure when subjected to earthquake, considering that the bolt-grout interface is the weakest element in the anchoring system generally; its mechanical behavior under dynamic load are extremely important. Therefore, direct shear tests of bolt-grout interface are conducted under different levels of shear rate(0.06-30mm/min). The effects of shear rate on peak shear stress, shear strength parameters and normal deformation behavior under different normal stresses are analyzed detailedly. The test results show that under intermediate strain rate conditions, with the increase of shear rate, the peak shear stress first increase rapidly then almost keep constant, whereas cohesion and normal displacement show a change trend of first increase and then decrease. The test results can provide basic data for the dynamic response analysis of the anchorage system under intermediate strain rate condition.

Cycles simple shear test are carried out for coral calcareous sand from Xisha Islands and local siliceous sand under multistage normal stress; and the difference of shear properties and particle breaking properties of two kinds of sandy soil under multiple cycles is compared. Under cyclic shear, both sand samples exist relatively weak volume changes and staggered shear dilatation which make the axial displacement curve of the specimen fluctuating. Shear stress peak envelope in cycles simple shear test can be expressed as an ExpAssoc function. Shear stress is divided into synchronous phase and differential phase with the change of cycle period; and the number of cycles corresponding to two phase transition nodes decreases rapidly as the normal stress increases. During the synchronous phase, the shear stress of coral sand and siliceous sand is consistent, while during the differential phase, the shear stress of siliceous sand is significantly higher than that of coral sand. The shear stress difference between the two types of sand varies with the normal stress, with the shear stress of the siliceous sand can be up to 14.7% higher than that of the coral sand in maximum. There are significant differences in the particle breakage between coral sand and siliceous sand. The distribution of particle breakage in the full particle size range of coral sand is more balanced. By contrast, siliceous sand has a violent particle breakage within a certain particle size range with obvious inflection points in the grading curve. The shape of the hysteresis loops and its variation with the number of cycles have significant differences between siliceous sand and coral sand, which reflecting the difference in the shear properties of the two sand samples.

The ground movement caused by tunneling will induce extra deformation on adjacent buried pipelines, even damage. Research on soil-pipeline interaction indicates that higher soil stiffness will lead to a conservative bending moment. An equivalent linear method based on Winkler subgrade model is proposed for modifying soil modulus and evaluating the maximum bending moment for continuous pipelines affected by excavation. The method takes account of tunneling-induced soil nonlinearity by a stiffness degradation model, in which soil average deviatoric strains caused by green field displacement are calculated together with a multi-layer-disc elastic model in order to consider soil nonlinearity induced by soil-pipeline interaction. The validity and rationality of the approach is proved by comparing with elastic theoretical solution and centrifuge model test.

Due to the wave-load and tidal load, granular soils, such as sand, often suffers from long-term cyclic deformation. Cumulative strains of five different granular soils under different loading conditions are analyzed by using the fractional calculus, and its there exists a fractional strain rate for granular soils subjected to repeated loads. Unlike the traditional integral strain rate which is varying with the load cycles, the fractional strain rate remains constant for a given loading condition. To investigate the physical origin of the fractional approach, fractal breakage theory of granular soils is used. It is found that the fractional strain rate has a strong connection with the corresponding fractal dimension of a given granular soil. It decreases with the increase of the fractal dimension.

The proper design of underground powerhouse support is the key engineering technique to guarantee the safe construction and operation of underground works. By regression analysis of surrounding rock bolting parameters of 20 underground powerhouses with a span of 19.2 m to 32.5 m, this paper puts forward the empirical formula of the relationship between the supporting intensity of the anchor bar, strength-stress ratio and workshop span, and the relationship between the supporting intensity of the prestressed anchor, strength-stress ratio and workshop span. The research results show that, when the strength-stress ratio is less than 3.0, the supporting intensity of the anchor bar of the surrounding rock increases significantly; and the supporting intensity is the function of strength-stress ratio with -2 singularity; when the strength-stress ratio is greater than 3.0 and less than 6.0, the supporting intensity of surrounding rock is in the nonlinear transition zone; when the strength-stress ratio is more than 6.0, the supporting intensity of surrounding rock tends to be constant.There exists a negative correlation (power exponent function) between the supporting intensity of prestressed anchor and the strength-stress ratio, and when the strength-stress ratio is less than 4.0, the supporting intensity of prestressed anchor increases significantly. The paper also puts forward the concept of the bolting index and the corresponding calculation formula, and finds that the bolting index of the anchor bar and the prestressed anchor of these 20 powerhouses are all distributed around 1.0. Therefore, the bolting index of practical engineering support design should reach 1.0 to ensure a reasonable support intensity.

In order to explore the stress and deformation characteristics of widened embankment which directly built on soft ground under static loading, a self-designed and self-made model test system is adopted. A series of model tests are carried out on this test system. By changing the value of the differential settlement and the layers of geogrid, variation characteristics of the soil stress in the old and new widened embankments are studied. The test results show that the vertical stress in the soil of both new and old sections of widened embankment increases with the load increase. The vertical stress decreases at first, then increases and finally decreases along the depth direction under the influence of the filling slope of embankment and the underlying foundation with lateral restraint. The differential settlement of the widened embankment built on soft ground has significant influence on the vertical stress at the junction between the old and new roads, the vertical stress in this area increases with the differential settlement, while the vertical stress in the old road is rarely influenced. Vertical stress and settlement of the embankment can be obviously reduced when geogrid reinforcement layers are laid at both the top and bottom of the widened embankment. Compared with non-reinforced embankment, the settlement on the top surface of embankment reinforced with 2 layers of geogrid can be reduced by 62% at most, which shows the geogrid reinforcement has a good control on the settlement of embankment built on soft ground.

To study swell-shrink fissure evolution rule of expansive soil in the natural rainfall and evaporation process, wetting-drying cycles tests, and CT scanning tests have been done. The three-dimensional reconstruction of soil CT images and the extraction of fracture information are carried out using Matlab software. The relationship between three-dimensional space cracks and wetting and drying cycles is studied from qualitative and quantitative dimensions. The relationship between soil’s fracture in three dimensional space and d wetting-drying cycles are studied from the qualitative and quantitative dimensions. Qualitative studies have found that the development of fractures begins at the weak spots such as initial pores and microcracks within the soil; and thus extends to form fracture surfaces and fissure bodies; and finally forms a complex three-dimensional fracture network. As the wetting-drying cycles progresses, the area and volume of the fracture gradually increase; and finally tend to stability. Quantitative studies have found that the distribution of fracture area along the axial direction of the sample has obvious periodicity. As the wetting-drying cycle proceeds, the period gradually decreases, and the amplitude A increases first and then decreases. The development of fissure is divided into three stages: i.e, fissure gestation period, fissure rapid development period and fissure steady development period; and fissure development mainly occurs during fissure development period. The approximate relationship between radial fracture area, axial height, and cumulative dry shrinkage volume change is obtained. The fracture volume is defined as a function of the Logistic function. It can predict the development and distribution of fissures in the sample, and can provide references for the permeability characteristics of fissured expansive soil and the study of the overall and local stress and strain.

The geocells are widely used in the reinforcement and diseases treatment of subgrade bed of road or railway. And the reinforcement effect of geocells is significantly affected by different geometric dimensions. Nine different types of geotextiles, combination of weld distance of 340, 400, 680 mm and height of 0.10, 0.15, 0.20 m, and traditional method of sand replacement are applied to treat subgrade subsidence. Then dynamic stress attenuation law in different treatment experiments is analyzed. The test results show that with height increased 0.01 m, dynamic stress decreased more about 0.6%-1%; and the attenuation decreased by about 5% for augmenting 100 mm of weld distance. On the whole, geocell is better than traditional treatment method; as dynamic stress attenuation is faster, stress distribution is more balance and subgrade strength is higher. Finally, design theory of replacement thickness called allowable stress design method is proposed on the basis of field test results, which considering subgrade stress level, dynamic stress attenuation law of different treatment and the allowable bearing capacity of subgrade. A theoretical design method for replacement thickness design is provided.

In order to improve the similarity between freeze-thaw model and the prototype, the concept and calculation method of similarity ratio of freezing index and laboratory correction coefficient are put forward. The loess in Harbin is taken as the experimental material; and the average temperature of this area between the year of 2010 and the year of 2012 is linearly simplified. Based on the differential equation with the heat conduction with phase transition, a freeze-thaw cycle model test is carried out for a specimen with a density of 1.60 g/cm3 and a moisture content of 20 % under the constraint of geometry, temperature and time scale by using the similarity theory. The K value of the laboratory correction coefficient is determined as 1.13 and the similarity ratio of the freezing index CI is determined as 1:102.5 so that another freeze-thaw experiment is conducted after an optimization of the temperature control time in the freeze-thaw stage. By comparison, the maximum frozen depth value of the optimized model is 21.33 cm, which is close to the predetermined model value 20 cm and the difference is 6.65 %; and the optimized freeze-thaw period is reduced from 108.14 h to 84.53 h. Therefore, it is reasonable to optimize the duration time of temperature controlled at different temperature controlling stage by using laboratory correction coefficient K and freezing index similarity ratio CI in freezing-thawing model. The ensured that the freeze depth are more similarity to prototype in the geometrical scale and time scale; at the same time reduced the duration time of a freeze-thaw cycle significantly.

In order to investigate the influence mechanism of the long-term strength of cemented tailings backfill(CTB) with different filling interval times(FITs) and solid contents(SDs). The uniaxial compression strength(UCS) test was carried out by using two layered CTB specimens with three SDs of 70%, 72% and 75%, four FITs of 12, 24, 36 h and 48 h. And the mechanical properties and its failure forms were investigated. The results show that: (1) The peak compressive strength of CTB decreases with the increases of filling interval. When the FIT is fixed, the UCS value increases along with the SD, and the peak compressive strength and filling interval are polynomial. (2) During the loading process, four stages of the compaction, line elastic, crack propagation and failure development are shown. With the extension of interval time, the failure forms of CTB may represent as the tension failure-shear failure transition-shear mixing damage. The conclusion can provide a useful reference for the strength design and stability control of CTB.

The natural characteristics of hydraulic fill for land is one of the important factors that cause its frequency to be struck by lightning. Based on the theoretical analysis, laboratory test and numerical simulation, the electric shock characteristics of hydraulic fill in Guangxi Beibu Gulf are studied; and then its response rule to the external electric field is explored. Based on the theory of Archie resistivity model and the formula of dielectric constant of soil, the electric shock model of hydraulic fill is proposed; and the main factors affecting the response law between soil and electric field are dry density, water content and salt content. Then the electrical shock test shows that breakdown strength of hydraulic fill has a logarithmic relationship decreasing with the water content and dry density, and the exponential relationship decreasing with salt content. On this basis, combined with the numerical simulation results, it is found that the higher the water content, dry density and salt content, the greater the electric field inside the dredger fill, the more remarkable of the impact field on the dredger fill, and the stronger the response to the external electric field. Among them, the influence of water content and salt content is the main.

For ultra-deep reservoir, the higher formation temperature and fracturing pressures lead to the limitation of pumping equipment in hydraulic fracturing. The paper focuses on the breakdown pressure and acoustic emission(AE) monitoring in large-scale hydraulic fracturing laboratory experiment with 762 mm×762 mm×914 mm in cement sample size by cycle and general injection. The test results show that: (1) Initiation pressures can be reduced on cyclic injection relative to general injection. Cyclic injection can bring about fatigue, which like the behavior of rock under uniaxial and triaxial cyclic loading. (2) For spiral perforation completion wellbore, the hydraulic fracture initiation only starts from the weakest perforation. Once the fracture is initiated, the other perforation holes are hard to reopen. The fracturing distance and cluster spacing should be chosen reasonably in hydraulic fracturing, to optimize the efficiency of reservoir stimulation. (3) The occurrence of the Kaiser effect before fracture initiation is the result of pore fluid diffuse to rock and cause the local rise in pore pressure, the failure modes can still be represented by Mohr circle. The results of the law of fracture propagation in cyclic injection, which is of great significance for the development of new fracturing technology.

Based on the ultimate bearing capacity tests at field site, comparison and analysis between compression and uplift is conducted for pressure-static and post-grouting micropile. A study is carried out in virtue of the Q-s curves to investigate the influence of pressure-grouting process and grouting volume ratios on the bearing capacity and ultimate pile side friction. The pile-soil interaction mechanism and uplift ultimate state is discussed; and then the uplift factor λ and the ultimate uplift displacement are suggested. The results show that compared with micro steel-pipe piles, the ultimate bearing capacity of pressure-static and post-grouting micropiles have been enhanced in soft foundation, especially for the uplift bearing capacity.

In order to explore the influence of fracture characteristics index on crack initiation pressure in vertical well and solve the problem of theoretical calculation about vertical well initiation pressure. First of all, the vertical well initiation pressure model is established based on the principles of fracture mechanics and elastic mechanics, considering the characteristics of primary fractures and fracturing fluids. Secondly, the influence of primary crack characteristics on initiation pressure is analyzed quantitatively; meanwhile, proposing the concept of "crack characteristic index control coefficient T" and deriving the mathematical expression of T. At last, sensitivity analysis of the primary crack characteristic parameters is made for the initiation pressure. It is concluded that the most sensitive factor affecting the initiation pressure is the crack width b. When b is in the range of 100-700 μm, the fracture characteristics of the formation have the practical significance for the initiation pressure, which solves the problem of the choice of fracturing target layer. The results show that: The influence factors of vertical well initiation pressure are related not only to the mechanical properties of the source rock, the stress field, the fracturing fluid properties and the well size, but also the width, length, density and roughness of the crack. Especially the small fluctuations in the width of the crack will cause vertical wells crack pressure changes. According to the actual geological prospecting data and fracturing construction data of the 5 test wells in Jiaozuo mining area, the vertical well initiation pressure is calculated and verified. It is found that the actual initiation pressure is in good agreement with the calculated results. It is shown that the theoretical model has some guiding significance for the actual control of the vertical well initiation pressure.

The direction, magnitude and distribution of in-situ stress are important factors affecting the deformation and failure modes of underground engineering. It is difficult to carry out a lot of measuring test work in the engineering area; the measured results may be of great discreteness. Therefore, it is one of the effective methods to introduce the numerical analysis method and mathematical theory to analyze the in-situ stress field synthetically. This paper is based on the Xianlushan water dispersion tunnel that planned to across the active Longpan-Qiaohou fault, and aims to solve the problem of large discreteness of directional results in measured results. Qualitative understanding of the direction of in-situ stress field is firstly obtained by theoretical analysis and numerical simulation with the existing understanding of the tectonic stress field in China. Based on the test results, the quantitative understanding of the direction and magnitude of the in-situ stress field is obtained by the inversion of the three-dimensional in-situ stress field based on the multiple linear regression. The preliminary results obtained demonstrate that the movement form of Longpan-Qiaohou fault (F10) is mainly consists of normal sliding in conjunction with minor strike sliding. With its influence, the direction of the maximum principal in-situ stress is approximately parallel or small angle intersecting with the trend of F10. The regressed maximum principal in-situ stress for the rock mass near the tunnel will be 13-19 MPa; and the corresponding intermediate principal stress will be 11-16 MPa; and 9-13 MPa for the minimum principal stress. The stress level is relatively high, and presents a trend that > > ( and are the maximum and minimum horizontal principal stresses respectively). F10-1 and F10-2 become the control boundary of the in-situ field, and the stress level between the F10-1 and F10-2 is obviously smaller than the upper and lower rock mass, i.e. 9-10 MPa for the maximum principal in-situ stress, and 7-10 MPa for the minimum principal stress. The maximum principal stress direction of in-situ stress intersects with the longitudinal axis of tunnel with an angle of about 60 degrees, which has a negative impact on the stability of the tunnel.

Seismic stability of Huaping bedding slope of Jinshajiang River bridge in Huali Expressway is studied. Safety factor, slip surface and scope of width 900 m and height 450 m are suggested by Janbu-simplified method based on slide. Safety factors and deformations of seven kinds of seismic working conditions such as horizontal acceleration being 0.00g, 0.10g, 0.15g, 0.20g, 0.25g, 0.30g and 0.35g are respectively computed by strength reduction method of finite elements on basis of Phase2D using quasi-static method, simulated object being model test. After curves of safety factor or defromation and horizontal acceleration of different seismic load conditions are compared with each other. The results show that: (1) Safety factor near to 1.0, the deviation is least, otherwise the deviation and discreteness increase, which is caused by disunity of limit condition defined by the two methods. Critical horizontal acceleration done by safety factor is 0.20g. (2) Fail mode presented by shear strain is bridge pier being tensile-shear fail, sliding in T2 tuff stratum and horizontally sheared out in front. Sensitivity order of deformation response in slope is horizontal displacement more sensitive than vertical displacement than shear strain. Limit value done by deformation evolution is 0.15g-0.20g, corresponding horizontal displacement being 10.2 mm. These are all proved by model test. (3) Finally, the critical horizontal acceleration of Huaping bedding slope comprehensively being 0.2g, safety factors of exceedance probability being 10% for 50 years and that of exceedance probability being 2% for 100 years are respectively 1.2 and 1.1. Huaping slope is safe under current seismic fortification criterion. In practice, safety factor considered material strength reserve is often selected as evaluating indicator of slope stability; but a strong operability and warning displacement considered deformation mechanism is selected for engineering safety monitoring. So, slope stability needed to be estimated by safety factor combined with critical displacement.

The construction of mountain tunnel can not completely avoid the large deformation disaster. After tunnel invasion, the improper timing of the deformed first liner replacement will not only delay the construction period, but also possibly cause the secondary damage, such as tunnel collapse. Taking the collapse event of Anqicun No. 1 tunnel in Yunnan Province as the background, after the large deformation of the tunnel and the application of the temporary steel support, the stress curve and the stress-deformation relationship of the rock and support are analyzed based on the convergence-confinement principle. The influence of different treatment timing on the stress of rock and the failure of rock block and joint in large deformation tunnel is analyzed using the discrete element software 3DEC. In this model, the deformed first liner is replaced when the settlement of the tunnel reaches 70%, 75%, 80%, 85%, 90%, 95% and 100% of the final displacement(the displacement when the deformation rate less than or equal to 0.2 mm/d). Then, the stress distribution, the amount of rock destruction and the area of joint failure are statistically analyzed. The results show that when the displacement of the vault settlement reaches 90% of the final displacement, the rock stress is almost as same as it reaches 100%. After the deformed first liner replacement completed and the tunnel become stable, the joint destruction area when replace in 90% is less than replace at 100%, and the rock failure amount are almost the same as replace at 100%. Therefore, the treatment can be carried out before the displacement reaches the final displacement. This research can not only improve the safety of large deformation treatment process, but also greatly reduce the treatment time, which has important reference value for research and construction.

For the backfill horizontal movement of gob-side entry retaining in deep mine, the characteristics of horizontal movement of backfill in deep mine with compound roof are analyzed; the horizontal pressure of backfill suffered from gob caving gangue based on elastic foundation beam theory and friction force between backfill and roof(floor) are calculated; based on the condition of 1115(1) working face tail entry in Guqiao mine of Huainan mining area which is typical condition of gob-side entry retaining with compound roof in deep mine; and then the mechanical model of backfill is established; the backfill horizontal movement expression of gob-side entry retaining with compound roof in deep mine is obtained. The results show that: (1) Due to the development of the compound roof fissure, it has a good flow ability after the collapse; it is easy to produce horizontal squeezing force on the filling during the rotation of the key block, and the given deformation of key block can be absorbed by compound roof which leads to the backfill is not easy to insert the bottom; therefore, the backfill is more prone to shift to roadway under the condition of gob-side entry retaining with compound roof in deep mine. (2) Theoretical calculation displacement of backfill is 0.536 m; the field measured displacement is 0.55 m; the results verify the correction of researches. According to the characteristics of backfill horizontal movement, the supporting scheme that increasing the friction factor by using shear bolts between backfill and roof(bottom) and setting isolation piles near the backfill in gob to isolate the backfill and gangue are proposed.

In the case of reverse inclined layer-like slope failure mechanism and stability analysis, due to the general good stability of the system, the intensive study is not very much in terms of its failure mechanism and stability. A gentle reverse inclined layer-like rock slope formed by several volcanic eruption cycles is introduced, and the tilt of layered rock slope as the research object, based on the finite element analysis of the displacement vector diagram, reveals the slope deformation failure mechanism and stability of the control elements; The stability is evaluated by using limit equilibrium method and vector sum analysis method. Using strength subtraction analysis regularity of plastic zone, it reveals time space law of the development of the slip surface. The results show that: (1) The similar layered rock slope is the tilting of the potential failure mode is shear-tension, sliding surface morphology of approximate folded line, slope through the tuff interlayer and strongly weathered rock mass, the trailing edge passes through the steeply dipping structural surface. (2) The limit equilibrium method and vector sum analysis method of comprehensive evaluation show that the stability of shallow slope stability does not meet the requirements of the engineering stability; stability of deep satisfies the stability requirement; and the safety factor of 3 D vector sum is greater than 2 D; this is caused by 3 D effect. (3) The spatial development sequence of the sliding surface reveal by the expansion of the plastic zone is sliding surface 4, sliding surface 5-3. The technical route and analysis scheme of this paper can be used to evaluate the stability of the gentle reverse inclined rock slope.

The advantages and feasibility of Beidou high-precision satellite positioning technology applied to the deformation monitoring of airport high fill engineering are introduced firstly. Then a deformation monitoring system based on the Beidou satellite positioning is designed for airport high fill engineering. In this deformation monitoring system, high-precision satellite positioning is realized by using the carrier phase difference technology. With the 4th generation mobile communication technology, deformation monitoring data is transmitted to the cloud server. This realizes automatic remote monitoring. For the purpose of making the power supply stable, solar panel and colloidal battery are used in the high fill airport deformation monitoring system. In order to determine the daily measurement time of monitoring equipment, a test is designed to study the relationship between Beidou satellite vertical measurement precision and positioning time. The test results show that the vertical precision of Beidou satellite static relative positioning is above 3.6 mm when the daily positioning time is 60 minutes. This precision meets the standard of airport high fill engineering deformation monitoring. And if the monitoring time is continued to increase, the precision will have little improvement. Use timing switch to set up monitoring equipment arranged in airport working 70 minutes automatically every day.

Analysis of surface deformation caused by underground mining in metal mines can provide guidance for the mine safety production and prediction of surface deformation. Taking Chengchao iron mine, Hubei province, in China, for example. Through the investigation of underground mining situations and the analysis of monitoring data by GPS, leveling and three-dimensional laser scanning. The relationship between the mined-out area and the movement and break lines, the relationship between underground mining and settlement funnel expansion and the relationship between underground mining and displacement of measuring points are discussed. The results show that the expansion of movement and break lines in the western mining area mainly concentrated in the northeast, east and southeast direction from the year of 2006 to 2017 due to the -325, -342.5, -358, -375.5 m and -393 m level mined-out area expand continuously to the east, and a new funnel center developed in the east of the settlement funnel, and the funnel curve of the settlement funnel gradually shows two funnel centers. The displacement of measuring point just above the mined-out area is directly controlled by the underground mining. When the orebody below the measuring points is explored, the deformation of the measuring points will be accelerated obviously. However, the displacement of measuring points in the vicinity of the mined-out is affected by many factors. Based on the monitoring results, the caving process of overlying rock masses is analyzed. However, the mechanical models of rock masses around the mined-out area are established, and the deformation law of monitoring points is explained. The results can provide references for other similar metal mines.

The evaluation method of lining sharing surrounding rock pressure in composite lining structure is one of the important research objectives in tunnel engineering. In this paper, an evaluating method of lining sharing surrounding rock pressure based on back analysis of monitoring displacements is proposed. Using the monitoring displacements and the lining casting time, the residual deformations of initial support are first determined; and then by useing finite element back analysis, the stresses of surrounding rock and initial support can be obtained; therefore the both of pressures behind the initial support and the lining are calculated. In order to show the applicability of the proposed procedure, the comparison of the in-situ observed and calculated is carried out for a newly built railway tunnel in which the lining is casted after 95 days in the initial support is closed. The pressure behind the lining is calculated to be about 0.04-0.06 MPa; and the ratio of lining sharing surrounding rock pressure is about 13 %-16 %. The results show that the proposed method can be useful for the design of composite lining structures.

In current researches, although the calculation method of the foundation pit enclosure structure based on p-y curve has considered the actual situation for which the inside soil of the foundation pit may enter into the plastic state, it has not considered the lateral displacement of the retaining wall when the internal bracing is erected, which starts working after the retaining wall has occurred the initial displacement. In view of the above-mentioned shortcomings, this paper presents a calculation model of the foundation pit enclosure structure based on p-y curve, considering the initial displacement of the retaining wall where the internal bracings erect at the time of bracing. The finite difference equations and methods for lateral displacement calculation of enclosure wall are established; and then the rationality of the proposed method is verified by case studies. Theoretical analysis and case studies are all shown that the calculation method of the foundation pit enclosure structure based on p-y curve is reasonable.

The sewage sludge-municipal solid waste (MSW) mixed landfill is one of the ways of sewage sludge disposal. The dry density parameter of the sewage sludge and MSW mixture have important influence on the strength and stability in landfill. The compaction tests on the mixture are conducted under different compaction energies and sewage sludge contents conditions to study the compaction characteristics. The results show that compared to MSW, the dry density of the mixture is increased by 2.74%-32.50%, improving the compaction characteristics of MSW. The dry density increases with the increase of compaction energy; and a hyperbolic model can be used to express this relationship. The physical meanings of model parameters are also analyzed. The variation laws of model parameters are discussed. It is found that varies from 0.373 to 0.750, and that varies from 1.958 to 2.158. The dry density increases with the increase of sewage sludge contents; and this relationship can be described by a logarithmic model. The variation laws of model parameters are also discussed. It is also found that b varies from 0.331 to 0.776, and that c varies from 0.052 to 0.164. Comprehensively utilizing these two models, the dry density parameter of the mixture can be predicted; the workload of testing can be reduced; and the theoretical basis can be provided for the design and analysis of the landfill site. The compaction evaluation method and the compaction mechanism of the mixture are analyzed. According to the variation trend of the dry density, the mixture is judged whether densification.

A new type anchor cable with double anchor is developed to explore endurable and anchoring effect of anchorage system in the slope of high embankment and deep cut slope. Based on its structural design, anchorage mechanism and structural characteristics, the stress model and calculation method are analyzed. The endurable and anchoring effect of the double anchor cable anchorage are analyzed through indoors contrast analysis experiments. Experimental results indicate that: (1) The outer anchorage section played an effective and dual-function anchorage role. (2) Double anchoring section system is able to effectively avoid the prestress loss caused by anchoring failure (3) Compared to the traditional cable, the new type anchorage system is able to realize self-locking function, and demonstrated characteristics of high safety, reliability. Accidents by sudden catastrophic failure of anchor cable can be effectively avoided. Thus, high effectiveness-cost ratio is realized in the long term. (4) The engineering cases show that, the failure of outside anchor head and prestress loss of free section can be effectively inhibited, when the outside solid length of Carboniferous rocks formation sandstone, mudstone and dark gray limestone, with interbedded strata are not less than 8 m, These experimental results can be used as a valuable reference for the correct analysis of the mechanism and engineering design of the new double anchor cable.

In the process of slurry balance shield excavation, the thrust force is difficult to determine and the fluctuation is complicated. In light of this problem, the resistance in the process of shield advance is analyzed systematically; and then the component and calculation method of the resistance are determined. The calculation formula of friction between shell and surrounding soil is modified. And the composition and working principle of slurry water balance shield thrust system are analyzed. Basing on the static model of shield thrust, a single degree-of-freedom dynamic model is established. According to the principle of energy conservation, the equilibrium differential equation of the system is established; and then the formula of nonlinear kinetics is derived. Based on the above formula, the change trend and fluctuation of shield thrust are summarized and the optimal distance of hydraulic jack is put forward in the process of propulsion. Through the comparison and analysis of the measured data of the thrust force of the Yangtze section of the tunnel at Wuhan metro line 8. It is proved that the formula can be used to calculate the dynamic thrust load of the lining accurately, which is of great importance to the analysis of the internal force of the lining structure.

Derivative is not defined at the edge corners of yield and plastic potential surfaces based on the generalized Hoek-Brown strength criterion and numerical singularity has been caused there. Smooth transitions with circular surface only satisfy the first derivative continuity; the second derivative is still undefined on the edges; so that the consistent tangent modulus can not be calculated correctly there. The implicit solution of nonlinear equilibrium equations in finite element method(FEM) with Newton-Raphson method is unable to achieve full quadratic convergence. C2 continuous rounding of yield and plastic potential surfaces in the π-plane has been introduced; so that the surfaces can be second-order continuous derivative on the edges; and the consistent tangent modulus matrix can be calculated accurately. Subroutine UMAT for the generalized Hoek-Brown linear elastic-perfectly plastic constitutive model has been coded with FORTRAN in ABAQUS software. Numerical examples are used to verify the correctness of the proposed method.

The problem of three-dimensional crack propagation is analyzed by the numerical manifold method(NMM) and the corresponding program with C++ is produced. By fully taking advantage of NMM in the area of discontinuous deformation analysis, the concepts of level set(LS) and Heaviside function in the extended finite element method(XFEM) are not required to be used. The result obtained from NMM is used to analyze failure state of each crack tip line. The exiting nonlocal crack tracing method and triangle tracing method are simplified and extended; and then a new tracing method is proposed to determine the final crack face. A block with a horizontal penny-shaped crack under tensile loading is simulated. The results show that the 3D crack propagation simulation based on NMM is feasible. After the simplification and extension, the shortcoming of original algorithm is overcome. The numbers of new crack tip line and new crack face are greatly reduced; and the influence of mesh on new crack surface is reduced; therefore the computational efficiency can be improved and the application can be expanded.

We combine the analytical solution of displacement for arbitrary-shaped tunnel in anisotropic media with the intelligent algorithm—differential evolution(DE) to investigate the displacement back analysis for horseshoe tunnel excavated on an anisotropic plane in transverse isotropic rock mass. The conclusions about parameter sensitivity, parameter unique identifiability and measuring line arrangement are obtained. In identifications, the high accuracy results for parameters can be obtained by DE algorithm. The parameter unique identifiability is not only related to the sensitivity, but also the combination type. When the vertical in-situ stress and the angle of isotropic plane are given, the maximum amount of uniquely identified parameter is 5. When the amount of identified parameter is equal to or bigger than 4, the combinations that cannot be uniquely identified will exist. When the amount of identified parameter is equal to or less than 3, any parameter combination can be uniquely identified with high accuracy.

A numerical model based on finite difference method(FDM) in FLAC3D is proposed to simulate the fracture of nonuniform rock materials. Weibull distribution is introduced to describe the distribution characteristics of elastic modulus and uniaxial compressive strength in each mesoscopic element which exhibits elastoplastic strain softening mechanical response. Then, this numerical model is used to investigate the effect of the mesoscopic nonuniformity and mesostructure on the macroscopic properties of numerical specimens under uniaxial compression. The results show that: (1) With the improvement of mesoscopic nonuniformity, the nonlinear characteristics of the numerical specimen gradually weaken and the brittleness gradually increases. Besides, the macroscopic peak strength and elastic modulus are linearly increased with ln(m) and 1/m respectively. Meanwhile, the failure mode of numerical specimens changes from plastic flow failure to shear failure and further to tensile failure. (2) When the mesoscopic nonuniformity indices keep constant, the mesostructure or mesoscopic elements space arrangement is the main factor that determines the fluctuation of rock mechanical behavior. Both the near-peak and post-peak phases of the stress-strain curve are sensitive to the spatial arrangement of the mesoscopic elements; but the pre-peak phase is opposite.

The debris flow is a worldwide geological disaster, and has been widely and deeply investigated over the years. Most studies of the geomaterial are focused on the instability mechanisms before the failure and the fast propagation after the failure, separately. This paper attempts to simulate the consistent process of a debris, using a continuous approach. The initiation, propagation and deposit stages of the debris flow are modeled using a constitutive model. The visco-elastoplastic constitutive model with solid-fluid transition is briefly presented and used in the study; and the corresponding physical parameters are carefully calibrated. Two failure mechanisms induced by increasing gravity and decreasing suction are discussed; and the definition for the interface between viscous and elastoplastic layers is explained. Finally, the consistent simulation of the debris flow is performed; and the impact effect against a retaining wall is heuristically studied.

Considering Hansob’s seepage flow law and the Merchant’s rheological model, a one-dimensional rheological consolidation model of soft clay under cyclic loadings is established, which is described by using two variables, the excessive water pore pressure and the vertical strain . The rheological consolidation equations are solved by using FlexPDE software; and then the results are compared to those of existing literature to verify the reliability of the numerical solutions. Meanwhile, the behaviors of soil during rheological consolidation are investigated and the effects of the Hansob’s flow parameters, the parameters of Merchant’s rheological model on rheological consolidation are analyzed and discussed in detail. The results show that the average degree of consolidation in terms of the excessive water pore pressure and that associated with settlement vary predictably with the cyclic loading, and the maximum value of is larger than that of at the same time. Further, when the loading cycles are very big, may reach the final cyclic steady-state while the peak value of increases with the cycles due to the rheological effect. Moreover, the peak values of and both decreases with the increase of the parameters m and of Hansob’s flow model. The peak value of decreases with increasing the rheological model parameter F, while the peak value of is on the contrary. Further, the peak values of and both decrease with the increase of the rheological model parameter . The average degree of consolidation under cyclic loadings is in a circulation state all the time, which never reaches 100%, and it is smaller than that under ramp loading.

This paper investigates the soil behavior and adjacent building settlement disturbed by the installation of diaphragm wall. This investigation is carried out by the numerical software FLAC3D; and in this simulation, the UBCSAND model is adopted for the modelling. The feature of strain strengthen in this model is able to characterize the soil behavior at shallow depth. The trench excavation, cage reinforcement, concreting, and concrete hardening, involved the installation of wall panel is carefully simulated. The results show that: Thanks to the hardening model, the soil movement at the shallow depth is well simulated. At the depth smaller than 20m below the ground surface, the trench excavation caused a significant soil movement. The movement decreases with the depth and it maintains tiny in deep soil. The cage reinforcement and concreting alleviates the trend of the movement. During the concrete hardening, the soil movement tends to be stabilized. A project of diaphragm wall in Suzhou is re-examined by using the new model. The numerical results are consistent with the in-situ measurements.

In order to accurately measure the tensile strength and deformation characteristics of rock specimens under different confining pressures, a series of technological modifications are carried out with material testing machine MTS815, which is mainly used for rock triaxial compression test, on the one hand, a set of test machine piston and three-axis chamber with the interlocking device, so that the original can only provide compression load testing machine MTS815 can also provide accurate axial tensile load; the other hand, the design and development of a multi The degree of freedom of rock specimen triaxial tension fixture, to solve the rock and other brittle materials in the stretching process is difficult to always maintain the technical problems. On this basis, a complete set of test techniques is proposed to realize the complex triaxial direct tensile test of various rock specimens in the range of 0-140 MPa confining pressures. The results show that the test apparatus and the test method can fully carry out the rock triaxial tensile test under different confining pressure conditions; and the corresponding test results are obtained. The results show that the test specimen and the test method can carry out the triaxial tensile test on the shale specimen with the supporting equipment and test method, also triaxial tensile test curve is obtained. The results show that the shale has different failure characteristics and failure modes under low confining pressure and high confining pressure. Under the low confining pressure, the shale is still characterized by brittleness.

There is still a theoretical defect in interpretation and judgment of karst morphology and filling state in karst cave detection using electromagnetic wave computed tomography. In order to solve practical problems in the detection, on the basis of finite-different time-domain(FDTD) algorithm, a numerical CT detection model is established using Matlab. A perfectly matched layer(PML) and a perfect electric conductor(PEC) are set at the boundary of computation model to prevent electromagnetic wave getting into the model again after it passed through the boundary. Simulation and experiment results show that: (1) When the electromagnetic wave passes through karst cave, it refracts at the cave boundary. And within the cave, the phenomenon of reflection, diffraction, and obstacle gain occur. Energy attenuation of electromagnetic wave is mainly caused by refraction. (2) When the cave filled with water, the reflection makes a part of the electromagnetic wave remains in the cave inside, this part of wave reflects and diffracts repeatedly inside the cave. (3) After electromagnetic wave passing through the cave, the disturbance of the waveform is mainly caused by the reflection phenomenon and the electromagnetic wave trapped inside the cave. (4) We have to consider the influence of the filling type, water content and other factors when the electromagnetic wave absorption coefficient changes in karst caves. At last，the tomography data obtained in practical detection are judged and interpreted according to the simulation results. By comparing the interpretation of tomography with previous investigation data, the accuracy of the simulation results and the reliability of the application of electromagnetic wave CT technology in detecting karst caves are validated. This research provides a reference and a theoretical basis for interpreting and judging tomography results in the future.