The structural plane of rock mass shows obvious anisotropy, which directly influences the deformation characteristics, mechanical properties and seepage characteristics of rock mass. It is significant to conduct the anisotropic quantitative analysis of the structure surface. In this paper, the anisotropy characteristics of different genetic structure planes are analyzed by the common structural surface quantization parameters (joint roughness coefficient JRC, the average joint angle θ, and fractal dimension DB), and their influences on the shear mechanical properties are also studied. The results show that in the tensile structure plane, the values of JRC and θ along the direction of splitting are larger than the values of these parameters perpendicular to the splitting direction and fluctuated slightly with the change of the angle. DB fluctuated largely in the diagonal direction, and its value is related to profile length. In shear structure plane, the values of JRC and θ parallel to the splitting direction have no significant differences from those perpendicular to the splitting direction. However, DB changes greatly in the diagonal direction. When θ and DB are used to evaluate the anisotropy of the structure plane, there is no obvious difference in anisotropy coefficients of splitting fracture plane and shear fracture plane. While, when JRC is used as evaluation parameter, the anisotropy coefficient is quite different, which could better reflect the different characteristics of different structural planes. The peak shear load and normal displacement of shear fracture plane are higher than those of splitting structure plane. The shear displacements of the two structural planes are similar when the dilation angle reached the peak value, and the aperture distribution of shear fracture structural plane is relatively concentrated and generally larger. The aperture distribution splitting fracture plane is more dispersed.

The deep rock engineering is characterised by high ground stress and high head pressure. To study the permeability evolution of rock under high confining pressure and high pore pressure conditions, the seepage tests for the variable pore pressure were conducted on tight sandstone under different confining pressure conditions. The results show that within the studied confining pressure range (0～50 MPa), the permeability presents three different variation trends with the increase of pore pressure: rapid growth phase (confining pressure at 10～20 MPa), slow growth phase (confining pressure at 30～40 MPa) and constant phase (confining pressure at 50 MPa). During the unloading process of confining pressure, irreversible deformation occurs in the sample due to high confining pressure, which results in a significant irreversible permeability and hysteresis effect on the restitution of permeability. During the seepage test, volumetric strain and the permeability evolution have a good consistency. In the loading and unloading process of confining pressure, the sensitivity and recovery capabilities of permeability to stress under high pore water pressure are stronger than those under low pore water pressure. Polarising microscope images reveal the inherent mechanism of irreversible deformation during the confining pressure loading and unloading process: the mutual extrusion and movement of skeleton particles cause the compression of the original micro-fissures, the decrease or even collapse of the pores, resulting in the irreversible permeability. After the seepage test, the P-wave velocity increases, which indicates that the compactness of the rock is improved and has a good agreement with the change of the internal microstructure.

Under fast and slow excavation unloading rates, experiments were carried out on the surrounding rock specimens of the cement mortar to study the deformation law and acoustic emission characteristics of the rectangular roadway. The strain characteristics of surrounding rock and the evolution characteristics of AE impact count, energy and spectrum were obtained in this study. The test results showed that under rapid unloading, the strain release rate was high, and the deformation was unstable after unloading. However, under slow unloading, the surrounding rock stress was fully adjusted, which was conducive to the full release of strain, and the deformation developed relatively stable after unloading. Under the two unloading modes, the surrounding rock of the roof and the gang in the rectangular roadway were mainly subjected to the radial tensile deformation, while the surrounding rock of the corner mainly experienced the tangential compression deformation. As the depth of the surrounding rock increased, the unloading effect gradually decreased. The AE impact count and energy evolution characteristics of the two unloading rates were well correlated with the strain characteristics, revealing the development process of cracks and damages in the surrounding rock under excavation unloading. The precursor information of the main rupture of the surrounding rock can be referred to the increases of the width of peak frequency band and the number of the peak frequency of the high amplitude signal in a certain frequency band. Under rapid unloading, large pieces of flaking occurred around the roof and the gang. Under slow unloading, the through cracks perpendicular to the corners were generated at intervals around the roof and the gang, and the roof and the gang swelled obviously but didn’t fall off. The damage of the right-angle rock was small in these two states.

When natural gas hydrate is completely decomposed, the gas generated in this process makes the pore pressure increased rapidly and the effective stress decreases in energy soil, which leads to liquefaction failure of soil. At this time, the stress state and static liquefaction instability of deep sea energy soil slope can be simplified as the failure of gas-bearing soil under a constant shear stress drained or undrained stress path. Based on this, an improved gas tube method is proposed to prepare the gassy sandy soil samples, and a series of triaxial tests with constant shear stress path is carried out. The results of the 22 sets of experiments show that the gassy dense sand with the same void ratio has the same instability line under different cell pressures or different constant shear stress paths. The stress ratio during instability and volume strain increase with the increase of initial relative compactness. The regularity of saturation effect on the instability of gassy dense sand under the constant shear stress path is not obvious in both drained and undrained conditions, but the sensitivity of pore pressure (or volume deformation) of gassy dense sand to deformation decreases under undrained condition. After the constant shear stress path reaches the point of instability, the transient liquefaction bulging failure occurs in gassy dense sand under drainage condition and gradual shear failure occurs under undrained condition.

Clayey rock, an alternative medium for the geological disposal of high-level waste, is highly valued by many countries. For the clayey rock underground disposal repository, the excavation of the gallery damages the host rock and further induces the propagation of the internal fractures. During this construction process, on the one hand, the permeability of the host rock increases, which reduces its capacity for retaining radionuclides. On the other hand, due to the hydro-mechanical coupling effect, the internal fractures are gradually sealed as the clayey rock has good self-sealing properties. Then the fracture permeability may recover slowly until close to the original rock state after an extremely long time span. In this paper, the experimental studies are carried out to investigate the saturation process of clayey rock under different conditions by means of the resistivity measurements. The effects of damage degree and the saline solution on the saturation process of clayey rock are studied by measuring the equivalent resistivity. The results show that: (1) The equivalent resistivity decreases gradually with the increase of the saturation and finally tends to a steady value. (2) The equivalent resistivity is not only closely related to the saturation but also the internal structure of the clayey rock. The relation between the fissures and the resistivity distribution provides guidance to detect the fissures in the clayey rock by using the resistivity method. (3) The fracture becomes the preferential channel for the water flow in the clay rock. Due to the hydration expansion reaction between water and clay minerals, the fracture seals to a certain extent, which can be indirectly reflected by the resistivity test.

Under conditions of seismic action or any other mutation stresses, the soil of the liquefiable foundation can lose its strength and stiffness rapidly due to the liquefication, resulting in the loss of the bearing capacity. The traditional anti-liquefaction measures mainly focus on the ground treatment, while the open-hole pipe pile provided in this paper has both anti-liquefaction and bearing capacity. Firstly, the liquid flow in the holes of the pipe pile is assumed to meet the Poiseuille equation, and the equal strain assumption is applied. Then we derive the analytic solution of the pore pressure considering both radial and vertical flows under the time-varying load, combined with the stress concentration phenomenon of the pipe pile composite foundation. Furthermore, considering the pore pressure accumulation under cyclic loading, the analytical solution is improved by using the empirical model of pore pressure development. Based on the analytical solution, this paper analyzes and compares the development of pore pressure of the open-hole pipe piles, gravel piles, undrained piles and natural foundation. Thus, the results indicate that the open-hole pipe pile has the best drainage capacity. The factors such as the modulus ratio of pile and soil and the radius ratio have important influence on the development of pore pressure. The higher the modulus ratio of pile and soil is, the smaller the radius ratio is, and the faster the pore pressure dissipation rate is. The influence of open-hole coefficient on the development of pore pressure is not obvious. The load frequency only affects the peak value of initial pore pressure and has little influence on the rate of pore pressure oscillation attenuation.

Water injection is an important means to increase the production of tight sandstone reservoirs, which is widely used in tight oil and gas exploration. However, long-term water injection changes the physical and mechanical properties of formation rocks and further affects the production of oil wells. Comparison experiments were carried out on the same formation cores with water injection for 15 years and without water injection to explore the microscopic mechanism of the effect. The differences of elastic mechanics parameters, mineral composition and microscopic structure of the formation rocks before and after water injection were obtained through experiments. After the long-time water injection, the mineral composition and internal structure of rock were changed. Especially the loss of clay minerals in the form of cement and fillers caused a decrease in the cohesion among the rock particles and an increase in the porosity. After long-time water injection, clay minerals and calcite content decreased, the fillers and cements between rocks particles reduced, the small pores developed into large pores. Thus, the mechanical properties of sandstone were weakened and the deformation capacity increased.

Energy pile is a relatively new foundation technology for extracting the shallow geothermal energy from surrounding rock and soil mass when transferring the load of the upper building, which poses a new challenge for the design and safety service of pile foundations. In the view of the practical application of energy piles, this paper focuses on two key scientific issues of heat transfer performance and bearing performance of energy piles. The main research problems related to energy piles are introduced from the following four types of research: heat transfer of energy piles, structural response characteristics of energy piles, bearing performance of energy piles, and load transfer mechanism of energy piles. On this basis, the applicability of current heat transfer model of energy piles, the bearing characteristics of single pile and pile groups under heat exchange, bearing performance and structural safety under long-term operating conditions are discussed. Finally, future research on energy pile engineering is prospected. The analysis results are significant for ensuring structural safety and developing the shallow ground energy rationally.

The debris flows are recognised as a major threat to bridge piers located in mountainous gullies, especially in the areas of the active seismological and hydrologic region in Southwest China. It is important to build the dynamic evolution model and quantitatively describe the dynamic process of debris flow impacting bridge pier. In this study, all of the large-scale laboratory tests are conducted by using large multi-functional debris-flow simulation system. The main objectives of our experiments are to find the correlation between impacting pressures and variable factors including velocity, flow depth, and dimensionless characteristic parameters of fluid mechanics and to obtain the dynamic behaviour of bridge pier under the impact of debris flow. The experimental results and dimensionless analysis show that the dynamic process is mainly controlled by two dimensionless numbers of Froude number (Fr) and Reynolds number (Re). Generally, the dimensionless impact pressure is the function of Fr for the low-viscosity debris flows, while for the high-viscosity debris flows, it is the function of both Re and Fr. Different types of debris flows present significant differences in both the peak impacting pressure and impacting power spectrum. Under the same bulk density, the low-viscosity debris flow has greater impact energy than that of the high-viscosity debris flow. In addition, various types of debris flows are essentially distinguished by the critical Fr line. To provide technical support and scientific basis, we analysed the impact signals of different types of debris flows and discussed the mechanism of impact model.

Rainfall is the most important factor in triggering the landslide. To reduce the loss of life and property caused by the landslide disaster, the early warning system against landslides becomes one of the best choices. Based on the principle of elastic wave propagation and the characteristics of deformation and failure of rainfall-induced landslides, this paper proposes to use the elastic wave velocity to detect the changes in soil moisture content and displacement on slope surface. The bender elements and ceramic disk, incorporated in a triaxial apparatus, are used to measure the S-wave and P-wave velocities in soils subjected to water infiltration. The device allows water to infiltrate into the soil from the pedestal to simulate the process of rainfall infiltration into the soil. The moisture content, deformation and elastic wave velocity are simultaneously measured during the tests. Besides, the rainfall model tests are carried out. Based on the triaxial model tests, this study reveals the process of rainfall-induced landslides, the evolution of elastic wave velocity, and the coupling relationship among the wave velocity, water content and deformation. The results show that the elastic wave velocity decreases slowly with the increase of water content, but decreases sharply with the increase of deformation, indicating the initiation of the instability. We also interpret possible mechanisms of the reduction of elastic wave velocity caused by water content and deformation. This paper provides a new method and reliable basis for an early warning system for rainfall-induced landslides and slope failures.

Nuclear waste continuously releases the decay heat after it being stored in the disposal repository. For the safe operation of the disposal repository, it is necessary to accelerate the decay heat to dissipate to surrounding rock. A good solution to solve this problem is to improve the thermal conductivity performance of buffer layers. In this study, the natural graphite powder was mixed into Na-bentonite as backfilling material, which can exert both of their advantages: fast heat conduction for graphite and isolated function of buffer materials. A series of tests, including swelling pressure, free swelling ratio, permeability and thermal conductivity, was conducted on the graphite-bentonite mixture with different graphite contents (Rg = 5%, 10%, 15%, 20%, 30%, 40%) and different granularities (297, 150, 74, 44 μm). The hydro-mechanical-thermal performance of mixtures showed that the added graphite improved the thermal conductivity significantly, and its influence degree depended on the graphite content, initial water content and dry density. Based on parameters of hydro-mechanical-thermal performance, it was found that the optimum graphite content was about 15%?20% (Wt.), and the graphite with a particle size of 150 μm or 74 μm was more beneficial for the optimum requirements. The pore-size distribution curves of the compacted mixture showed that too large or too small graphite particles were conducive to form macropores easily with the same graphite content. The reason is that as the natural graphite particles are flat and a majority of bentonite particles or agglomerates are smaller than graphite, they are formed in the point-edge contacted mode. Especially for mixtures compacted relatively loose, there are a large number of pores at the contact interface between bentonite and graphite. Moreover, graphite is hydrophobic with a low capacity for adsorbing water molecules. Hence, water can easily pass through the surface of the graphite sheet, even after the bentonite is swollen by soaking sufficiently.

Although the application of 3D printing technology in physical modelling in rock mechanics is still at the preliminary stage of exploration, its reproducible production of specimens with complex internal structures is impossible for the conventional test method. At present, 3D printing technology is difficult to be applied in physical modelling in rock mechanics. The reasons are caused by the low strength of 3D specimens that is even lower than the weakest existing rock and the strong ductile behaviour of the 3D printed specimens. The main objectives of this study are to explore the effects of the drying time after printing and binder saturation level on the strength of the 3D printing specimens during UCS tests and Brazil disk split tests. Based on the test results, the study puts forward a set of optimum printing parameters, which can greatly enhance the strength of 3D printing specimens and reduce their ductile behaviour in the test. By changing the inclined angles of the printing layers, the specimens can be used to simulate the anisotropy of natural bedding joint rock. The results show that as the inclined angles increases, the uniaxial compressive strength of the 3D printing specimens decrease first and then increase, showing a U-shape trend. Besides, the tensile strength shows an obvious anisotropy with changing the printing directions. The results are similar to the previous results of natural bedding joint rock. The findings of this study verifies the feasibility of 3D printing technology in the experimental study on rock mechanics.

With the rapid development of the transmission line project in western China, the problems of the tower foundation uplift become prominent. It is necessary to solve the failure model of rock and the calculation method of ultimate uplift bearing capacity urgently. The centrifuge model test results are used to analyze the failure model of rock, load-displacement curve, axial force distribution and friction resistance curve of piles. According to the test results, after the failure shape of rock is non-dimensionally processed and fitted, a unified function description form is obtained. On this basis, the limit equilibrium method is used to derive the calculation method of ultimate uplift bearing capacity of the rock-socketed pedestal pile overburden soil, and the calculation method is simplified. The integral calculation value and the simplified calculation value are compared with the results of the centrifugal model test. The results show that the failure model of the soft rock is trumpet-shaped surface, which can be described by a unified power function. The results of the simplified calculation method are in good agreement with the results of the centrifugal model test. Therefore, the method proposed in this paper provides a reference for the uplift design of tower foundation in the western mountainous area.

By using the self-developed shear-seepage coupling test device for coal rock, experiments were carried out on similar materials containing structural surface sandstone to obtain shear-seepage coupling properties under different filling degrees. The results show that under constant water pressure, the larger the filling degree is, the smaller the peak shear stress of similar materials is, the larger the normal displacement is and shear shrink phenomenon is observed, and the larger the peak flow rate is within a certain filling degrees range. The flow change during shearing is mainly controlled by the cracks generated in the filling. The larger the shear displacement is, the more the fracture develops, and the greater the flow is. The normal displacement has a certain influence on the flow rate change, but with the increase of the filling degree, the influence becomes smaller. With the increase of filling degree, the fragmentation degree of filling materials gradually increases. The small filling degree is mainly controlled by the crack opening degree, while the large filling degree is mainly affected by the normal force. Due to the softening effect of permeate water, the wear degree of the structural surface slowly decreases.

According to the similarity criterion, the freezing model tests were carried out on Beijing sand-gravel stratum to study the expansion rule of the temperature field of the multi-row-pipe partial horizontal freezing body under the effect of seepage. Three factors were mainly investigated, including the length of water surface, downstream flow length, and thickness of the multi-row-pipe partial horizontal freezing body. The results show: 1) the temperature in the central part of the horizontal freezing body develops fastest and is the lowest, while the temperature in the upper part develops slowest and is the highest. 2) Percolation gradually makes the columns of the permafrost lap in the upstream direction from the downstream face to the upstream face. Moreover, the upstream and downstream temperature fields are no longer symmetrical. In the late stage of freezing, the back surface is in the shape of a sloping roof. 3) The effect of seepage on the horizontal frozen body progressively increases with the increase of seepage velocity. During the active freezing period, the freezing front expansion velocity of the last frozen soil column and the average development speed of the horizontal freezing body in the upstream direction are both in a squared and negatively correlated relationship with the seepage velocity. When the seepage velocity exceeds 14.1 m/d, the frozen soil column does not overlap, which is the limit flow rate of the model test. According to the theory of equivalent trapezoidal algorithm, the development of the horizontal freezing body can be easily evaluated by the average temperature formula of the multi-row-pipe partial horizontal freezing body under seepage. The research results can provide the basis for the basin-shaped freezing construction of large-flow velocity stratum.

The rock is highly fractured with low strength and poor self-stability in the diversion tunnel of water transferring project from Hongyan River to Shitou River. Due to the large deformation of the soft rock tunnel, a series of special problems such as TBM jamming occurs during tunnel construction. This paper is aimed to analyze the effects of sample composition and clay mineral content on the disintegration through X-ray diffraction and the disintegration test. In addition, the deformation and failure characteristics and creep properties of rock mass under different stress conditions are studied through a series of uniaxial compression tests, triaxial compression tests and the triaxial creep tests, respectively. The test results show that the surrounding rock is softened, because the clay minerals (33.49%) like montmorillonite and illite of the rock are sensitive to water. The sample has a large plastic compression deformation, and its stress-strain curve presents a strain-hardening type but no obvious peak intensity. The large deformation mechanism of the soft rock tunnel is analyzed, and a new support technology for installing polyurethane buffer layer between surrounding rock and lining is proposed based on the experimental studies and on-site monitoring data. The rationality of the proposed support technology is also verified through the numerical calculation. The results show that the polyurethane buffer layer can absorb the deformation pressure of the surrounding rock, and avoid the dislocation of segment caused by stress concentration, which can greatly reduce the failure zone of the lining. Research results of this study provide significant references for the tunnel design and construction as well as long-term stability analysis.

Under the effect of repeated lifting and lowering of the reservoir water level, the rock mass in the dissipated zone is in the soaking-air drying circulation state, which deteriorates its mechanical properties significantly. Thus, the deformation and stability of the bank slope are directly affected. Considering the soaking-air drying cycle and water pressure changes, the water-rock interaction tests were carried out on the sandstone of the bank slope in the Three Gorges Reservoir area. Scanning electron microscope (SEM) was used to analyse the effect of water-rock interaction on the sandstone microstructure. The degradation process of sandstone under the action of the water-rock was simulated using PFC2D discrete element software. The results showed that the degradation effect of water-rock on sandstone mechanics was significant. It was found that the elastic modulus and uniaxial compressive strength generally showed a steep and slow deterioration trend, and the deterioration effect was particularly obvious in the first six times of immersion-air drying cycle. Under the action of water-rock, the microstructure of sandstone gradually changed from a dense pore-type cementation structure to the irregular cellular structure, which caused the deformation of sandstone and the degradation of strength characteristics macroscopically. Through the analysis of PFC2D discrete element simulation, it was found that under the action of water-rock, the strength of internal particles and the bond strength between the particles of rock decreased gradually, the heterogeneity of rock increased, strain localisation features under load increased progressively, and the overall bearing capacity reduced slowly. Moreover, the failure mode gradually transformed from the typical tension damage into a shear failure.

Due to environmental pollution, the underground structure gradually deteriorates, which causes severe long-term stability problems of the underground structure. In this study, the immersion erosion tests were first carried out on concrete specimens by soaking in the 50 g/L Na2SO4 solution, 50 g/L NaCl solution and landfill leachate containing 50 g/L Na2SO4 + 50 g/L NaCl, respectively. Then the gas permeability under different confining pressures, chloride permeability and mechanical properties of the eroded concrete specimens were studied. The results show that the permeability coefficient of the specimens after immersion in different solutions is closely related to the confining pressure. Under the same erosion time, the permeability coefficient gradually decreases with the increase of confining pressure. The permeability of the specimen under continuous immersion by landfill leachate increases linearly with the time of erosion, and the lower the confining pressure is, the greater the rate of the increase is. While the permeability of the specimens exposed to Na2SO4 and NaCl solutions decreases first and then increases. Generally, under immersion in three kinds of solutions, the permeability sensitivity of specimens to confining pressure is improved. The uniaxial compressive strength of the specimens after exposed to different solutions is divided into two stages: linear increase and slow decrease. However, the strength of the specimen exposed to landfill leachate is the lowest. The elastic modulus also presents a similar pattern. At the same erosion depth, the free chloride content of the specimen after the landfill leachate erosion is 20%?50% lower than that of the specimen after the erosion of the NaCl solution. In addition, the erosion degree of the concrete specimen by the chloride ions in the landfill leachate is lower than that of the concrete specimen by the NaCl solution. Compared with uniaxial compressive strength and chloride diffusion coefficient, the gas permeability changes the most obviously by the erosion, which is more suitable for evaluating the long-term stability of the concrete structure. The research results can provide a theoretical basis for the long-term stability analysis of underground structures under corrosive environment.

Since the slide of expansive soil slope is generally characterised by time-dependent properties such as chronicity and gradualness, triaxial unloading creep tests are carried out on the expansive soil specimens by GDS stress path triaxial apparatus. The test results show that the creep curve of expansive soil only shows transient deformation and attenuation creep with low deviatoric stress. When the deviatoric stress reaches a certain value, the creep curve also exhibits attenuation creep, steady creep and accelerated creep, and the velocity in the accelerated stage is nearly constant, different from common soil. Meanwhile, isochronous stress-strain curve of expansive soil indicats that its creep process has nonlinear characteristics, and the nonlinear degree is related to creep time and stress level. When the creep time is longer and the stress level is higher, the degree of nonlinearity is higher. Based on the nonlinear rheological theory, a new nonlinear four-element creep model is presented, in which the standard linear body is connected in series with a nonlinear clay pot. The proposed model can describe the evolution of the axial strain of expansive soil with time under constant confining pressure and triaxial compression stress. According to triaxial compression creep test results of expansive soil, the parameters of the proposed model are inversed by using curve fitting method．The theoretical curves accord well with the test curves, which indicate that the proposed model can describe the creep property of expansive soil. Furthermore, critical failure stress can be obtained based on the creep model. As the confining stress decreases, the ratio of the critical failure stress to conventional shear failure stress decreases, which indicates that creep likely happens on the expansive soil layer closer to slope surface.

To solve the common problem of uneven settlement of highway, this paper proposes a new technology for composited embankment by combining the replacement load shedding with reinforcement. In the new technology, the polyvinyl chloride (PVC) pipes are used to replace the embankment fill, which can not only reduce the self-weight load of the embankment but also exert the reinforcement of the circular tube at the same time. Thus, the additional stress of foundation is decreased, which controls the ground subsidence correspondingly. To verify the control effect of the technology on the uneven settlement of subgrade, a series of large-scale comparison model tests is carried out on the composited embankment and untreated ordinary embankment. Combining the settlement calculation theory and the measured results, the control mechanism of uneven settlement by the composited method is analyzed. The results provides a theoretical basis for the design and calculation theory of reinforced embankment and light replacement embankment.

Based on the upper bound theorem of limit analysis, the stability of the three-dimensional reinforcement slopes was investigated by using the pseudo-static analysis method under the horizontal and vertical seismic forces. Both uniform reinforcement and triangular reinforcement patterns were considered, and analytical expression was derived to calculate the required critical reinforcement strength to prevent the failure of reinforced slopes. The validity of this method was verified by comparing with the results of existing literature, and the effects of the ratio of slope width to height and horizontal and vertical seismic force coefficients on the stability of three-dimensional reinforced slopes were discussed. The results show that with the increase of the ratio of slope width to height, the critical reinforcement strength of the slopes increases under seismic forces, but the changing rate gradually decreases. When the ratio of slope width to height is larger than 10, the critical reinforcement strength of the 3D slopes is similar to that of the 2D cases. With the increase of horizontal seismic force, the critical reinforcement strength of 3D slopes increases nonlinearly. While, with the increase of vertical seismic force, the value of the critical reinforcement strength increases approximately linearly. In addition, with the increase of slope angle, the effect of vertical seismic force on the critical reinforcement strength becomes more significant. The changing rule of the critical reinforcement strength under two reinforcement modes is consistent. Moreover, the stability values of triangular reinforcement mode is always smaller than that of uniform reinforcement mode, and is more conducive to maintaining the stability of the slopes. Finally, some engineering suggestions are proposed for practical projects.

This paper conducted a series of electro-osmotic consolidation experiments on marine clayey soils collected from the coastal region in Liaoning Province. The effect of the electrode materials, such as the steel, copper, aluminum and a new composite electrode, on electro-osmotic consolidation was investigated. The consolidation efficiency was analyzed through the experimental results including the effective potential, current, dewatering amount, velocity of dewatering, energy consumption, water content and bearing capacity of the consolidated soil. The new composite electrode, which consists of the carbon fiber, plastic drainage board and steel plate, takes advantage of each material. Thus, the fracture of the steel is solved after the current flows through the steel, and the electrode erosion is reduced. The experimental results demonstrated that the strength of the consolidated soil increased significantly by using the new composite electrodes, and the soil area with the strength of larger than 160 kPa accounts for 75%. In the experiments, severe erosion of the electrode mainly occurred at the anode. According to the erosion ratio of the anode, the erosion amount of the composite electrode was less than that of the metal electrodes. The new composite electrode improved the consolidation efficiency and reduced the cost of the electrode.

In this study, we perform a series of oedometric tests on saturated sand-clay mixtures with five different sand contents at high pressure using a self-designed high-pressure oedometer. The evolutions of compressibility and permeability and their dependency on mineralogical compositions during compaction process were investigated. Experimental results showed that the compression curve (e-lgP) of the saturated sand-clay mixtures transfers from an exponential function to a hyperbolic function with the increase of sand content. However, the compression curve (e-P) plotted in normal coordinates presents a linear evolution for all the sand-clay mixtures when the consolidation pressure is above 8.1 MPa, and its slope depends on sand content. The concept of optimum sand content is used to describe the minimum void ratio at a certain value of consolidation pressure. The optimum sand content varied continuously from 75% to 30% following the increase of consolidation pressure. Furthermore, it was founded that the relationship among void ratio, consolidation pressure and sand content follows the uniform power function for all the mixtures studied. An exponential correlation is proposed to describe the correlation between the permeability coefficient and void ratio, which can further reveal the influence of sand content on hydraulic conductivity. Overall, the effects of consolidation pressure and sand content on the compressibility and permeability of the sand-clay mixtures were analyzed from the perspectives of skeleton structure and pore features of sand-clay mixture. The correlation between the skeleton structure and sand content of sand-clay mixtures was further confirmed by SEM microphotograph observations.

The purpose of this study is to establish a modified Yin’s double-yield-surface model based on the ratio of bioenzyme-based soil stabiliser, which can accurately describe the physical and mechanical properties of the bioenzyme-treated expansive soil. A series of drained triaxial shear tests was carried out to study the evolution laws of stress-strain, the elastic deformation, yield surface shape, dilatant yield surface, and failure line equation relating to the content of bioenzyme. Moreover, the effect of the bioenzyme content on the parameters of the Yin’s model was analysed. Finally, the bioenzyme content was introduced as a correction factor for the modified Yin’s double yield surfaces model. The results show that the bioenzyme can effectively improve the mechanical properties of the treated expansive soil. The modified Yin’s double-yield-surface model can well describe the constitutive relation of the bioenzyme-treated expansive soil. The theoretical calculation results of the modified Yin’s model show good agreement with the experimental results. Besides, the parameter determination method of the modified model is consistent with Yin’s original model.

To study the damage characteristics of sandstone pore structure under freeze-thaw cycles, five rock specimens were selected to conduct 100 freeze-thaw cycles, and the pore structure of sandstone was measured by nuclear magnetic resonance technology (NMR). The mesostructure characteristics such as T2 spectrum distribution and sandstone porosity were obtained under the freeze-thaw effect. According to the distribution of pores, the pore size was divided into three categories: mini-pores, meso-pores, and macro-pores. Meanwhile, the diffusion electric double layer theory was used to analyze the distribution of pore water with different pore sizes. The results show that as the number of freeze-thaw cycles increases, the T2 distribution of NMR shifts to the right and the porosity of the sandstone increases. At the same time, some minerals are dissolved in the pore water under the water-rock effect, which causes the ion concentration to increase in the pore water and results in a large number of secondary pores within the rock. With the increase of pore size, the bound water content in the pores gradually decreases, and the bound water content of small pores is much larger than that of macro-pores. At a low temperature, the free water freezes before the bound water, and the increase of ion concentration of bound water in small pore is lower than that of macro-pores, which leads to a difference in ion concentration. As a result, the water molecules in the small pores migrate to the macro-pores and the damage rate of small pores is much smaller than that of macro-pores. Therefore, the mini-pores continuously deteriorate under the effect of water-rock interaction and the frost heaving pressure; the macro-pores are rapidly developed and expanded under the frost heaving until the macroscopic damage of the rock samples.

To solve the consolidation problem of vertical drains under vacuum preloading, this study mainly considers three types of radial permeability coefficient of soil (including the constant distribution pattern, the linear distribution pattern and the parabolic distribution pattern) in the disturbance area and the resistance of vertical drains changing with time. The mathematical model is established. The analytical solution is used to derive the consolidation problem of vertical drains under vacuum preloading considering the variation of radial permeability coefficient due to construction disturbance. Based on this solution, the calculation program is compiled, and the consolidation curve of vertical drain considering the influence of various factors is drawn. The results show that the change rate of drain resistance greatly affects the average consolidation degree. In the three models studied in this paper, the consolidation rate is the fastest when the permeability coefficient shows a parabolic change, while the consolidation rate is the slowest when the permeability coefficient maintains constant.

Microbial induced carbonate precipitation (MICP) technology mainly uses carbonates formed by microbial life activities and environmental reaction to repair rock and soil. This paper is to study the effect of this technology on improving the impermeability and strength of fractured rock. The repair tests on fractured sandstone were carried out by using Bacillus Pasteurii. Meanwhile, the repaired fractured sandstone was tested under unconfined compression, nuclear magnetic resonance and scanning electron microscope (SEM). The repair effect and mechanism of Bacillus Pasteurii on the fractured sandstone were analyzed. Research shows that Bacillus Pasteurii has good repair effect on fractured sandstone. The longer the repair time is, the better the repair effect of Bacillus Pasteurii is. After 42 days of repair, the porosity of fractured sandstone decreased by 36.41%, the impermeability increased by 94.62%, and the compressive strength increased by 30.52%. The reason for the better repair effect of Bacillus Pasteurii is that the calcium carbonate induced by Bacillus Pasteurii can cement the filler and the sample, and greatly reduce the porosity of the sample, and improve the homogeneity of its internal pore structure.

Collapse is one of the major disasters in the construction of mountain tunnels. Because there are many factors affecting the collapse, and the weight of each factor varies greatly, even some factors are unnecessary or redundant. At present, the commonly used evaluation methods not only fail to screen these unnecessary or redundant factors, but also rely too much on expert experience and subjective evaluation to determine the weight, resulting in low accuracy and poor reliability of risk assessment results. Based on this, considering the advantage of rough set theory in data mining, index screening and importance computation, the risk assessment of mountain tunnel collapse is constructed as the decision information table of rough set. However, in the engineering experiment, it is found that the attribute reduction and weight calculation based on the traditional dependency degree can not meet the requirements, and there is a problem that the weight of calculation is zero or the reduction result is too much and can not be taken out. In view of the above problems, a method based on conditional information entropy is proposed, which introduces conditional information entropy into the definition of attribute importance and weight. At the same time, the most important conditional attributes are taken as the starting point, and attributes are gradually added to realize attribute reduction. The method established in this paper can not only extract the main influencing factors from a large number of influencing factors, but also eliminate the relatively redundant or unimportant factors. At the same time, it can calculate the objective weight of each factor. Then combined with fuzzy comprehensive evaluation method, the risk evaluation model of mountain tunnel collapse based on rough set and conditional information entropy is established and successfully applied to the Xiucun tunnel. It shows that the model is reliable and practical, and provides a new research idea for the risk assessment of mountain tunnel collapse.

Interlayer staggered zones at Baihetan hydropower station are characterized as loose structures, poor water-physical properties, weak mechanical properties and large spatial distribution. The weak structural surfaces in the surrounding rock of underground space determine the deformation and failure of the surrounding rock mass. Based on a large number of geological exploration and experimental results of interlayer staggered zones in the Baihetan project area, they are divided into joint zones, lining zones and muddy zones. The formation mechanisms, macrostructural and microstructural features, mineral compositions, water-destructible properties and shearing mechanical properties in the C2 and C4 zones are studied. It is concluded that the interlayer staggered zones are mainly tectonic genesis, and the differences in clay mineral content, microstructure and hydrologic properties are obvious in different sub-zones. The shear mechanics curves of the interlayer staggered zones presents an ideal elastic-plastic. In the end, we analyze the effect of geological characteristics of interlayer staggered zones on the engineering rock mass during construction. Three main failure modes block collapse, shear slip, and seepage failure in the surrounding rock mass of underground powerhouses and caverns are observed.

Energy pile functions as the bearing capacity of upper load and energy transfer of shallow ground temperature, which becomes one of the most important issues for engineers. However, there is relatively little research on the thermal-mechanical coupling characteristics of energy pile in the pile-raft foundation. One new buried pipe type of energy pile was proposed in this study, in which the bottom end of the acoustic tube was connected as the heat transfer tube. Field tests on the thermal response characteristics and the stress of the raft affected by energy pile were carried out under the operation of the single energy pile in the pile-raft foundation. The temperature and stress of the pile and the stress of the raft were accurately measured. The results showed that the heat transfer efficiency of the energy pile (single U-shaped buried pipe, the effective depth of 12.8 m, pile top depth of 5.5 m) was about 80?90 W/m under the experimental conditions. The tensile stress of the raft on the top side was found during heating without dead load condition, which should be considered during the structure design.

Currently, there is a lack of information on the theory and practice of the relatively new tunnel-type anchorage for suspension bridges. Firstly, the safety control indexes commonly used in tunnel anchorage engineering are summarized from two aspects of anti-draw bearing safety and anchorage deformation control. Then the research methods are analyzed for the bearing capacity and deformation characteristics of tunnel-type anchorage, respectively. Finally, the achievements of more than 10 tunnel anchor projects in the project team for the past 20 years are summarized. It is concluded that the deformation of the existing and under construction tunnel-type anchorages are generally in the order of millimeters, and the overload stability coefficient of the anchorage is usually greater than seven under tens of thousands of tons load of the main cable. It shows that the existing and under construction tunnel-type anchorages have a sufficient safety margin, and the design of tunnel-type anchorage can be optimized to a certain extent. At the same time, it is pointed out that the current proposed deformation control standard of tunnel anchor is based on the bridge structure and does not take into account the restrictions on the deformation of materials such as anchor body itself and surrounding rock. The bearing capacity of tunnel anchorage summarized in this paper is mainly from the bearing capacity of anchor concrete and surrounding rock system, without considering from other factors such as the strength of steel strand material. The conclusions in this paper have their specific conditions and scope of application, and further research on the bearing mechanism of tunnel anchor system is required.

After the landslide enters the creep deformation stage, it is usually difficult to carry out the investigation and management of the landslide in a timely manner. A reasonable early warning system becomes an important means for effectively reducing landslide hazards. This paper first determined that the key early warning criteria for stepwise landslide induced by rainfall: previous rainfall, current rainfall, and displacement rate. Moreover, one rainfall process is introduced to define the rainfall interval for landslide monitoring, and the warning process is divided into two modes of the previous-current rainfall and the current rainfall. Then the least squares method is used to define the failure inflection point and the stability inflection point on the displacement deformation curve of the stepwise landslide. Thus, the deformation acceleration interval of the landslide is determined to solve the previous rainfall, the current rainfall and the displacement rate threshold. Finally, taking the Wangjiapo landslide as an example, this paper designs the five-level progressive early warning system under two modes. The results show that: (1) the time interval of a rainfall process constituted by the previous rainfall and the current rainfall is 7 days; (2) the displacement rate threshold of Wangjiapo landslide is 20 mm/d; (3) in the mode of the previous-current rainfall, the previous rainfall threshold and the current rainfall threshold of the Wangjiapo landslide are 10 mm and 15 mm, respectively, and the rainfall threshold of the Wangjiapo landslide under the current rainfall mode is 25 mm.

In this study, the Que’er moutain tunnel in the project of No. 317 national highway was investigated, and the frost heaving force of the moraine stratum at the entrance of the tunnel was measured in-situ by the self-designed test method. Meanwhile, the thickness of the freeze-thaw circle and frost-heaving force in the cold region was obtained by combining the numerical simulation and the theoretical calculation. Based on the frost heaving stress measured inside and outside the lining structures, the axial force, the bending moment distribution, and variation law of lining structure were calculated and compared with the existing research results. The results show that moraine stratum in the cold region, as the regular seasonal frozen soil in the plateau, are significantly affected by low temperature, and the thickness of freeze-thaw circle is about 2 m under low temperature for 22 hours. The frost heaving pressure is 19.8?158.3 kPa by frost heaving force calculation, while it is 40?240 kPa from the in-situ measurement. Besides, the smallest frost heaving pressure is found at the arch foot, while the largest value is at the inverted arch. The changes and distribution rules of the stresses inside and outside the lining structures in the moraine stratum are complex and different under the freezing and thawing conditions. The axial force and bending moment of the lining in the frozen state are fan-shaped and butterfly-shaped distributions, respectively. Compared with related research results, the in-site testing method is more reasonable, and the results are more accurate.

The liquefaction evaluation methods are basically characterized by the relationship between the critical liquefaction curve and the depth of the soil layer. However, the comparative analysis shows that the critical curves of the existing liquefaction evaluation methods have different performance modes and even qualitative opposite. In this paper, based on the Seed-Idriss model, the theoretical solution of the effect of soil depth on the liquefaction potential was derived, and the general relationship between the depth of the soil layer and the critical liquefaction value was put forward. Meanwhile, the variation trend and general rules for liquefaction critical curves were obtained. The results show that with the increase of soil depth, the increasing rate of horizontal shear stress is faster than that of liquefaction resistance of soil layer. Moreover, the liquefaction potential and critical liquefaction value have positive correlations with the depth of the soil layer. The critical value increases nonlinearly with the soil depth, which means that the liquefaction potential increases drastically in the shallow layer, but gently in the deep layer. In the CPT liquefaction evaluation of the national standards in China, it is reported that the critical liquefaction value has a decreasing relationship with the soil depth, which is qualitative error and needs to be corrected. In some existing liquefaction discriminant formulas, the critical value increases linearly with the depth of sand layer, which is qualitatively correct, but the model needs to be improved. The results of this paper can provide a theoretical basis and reference for the development of liquefaction evaluation methods and the future revision of national and professional standards.

The pile-soil shear displacement has a significant influence on the development of negative skin friction of piles. Based on current research, a calculation method of plie-soil shear displacement was established by the monitoring results of the pile strain and the soil settlement in the field test. This method was used to analyze the monitoring data of pile and soil in the shallow middle layer, and then the shear displacement of pile and soil was determined to be 4?5 mm under the condition of free pile top in the test. However, the negative skin friction was unavailable to reach its extreme value when the shear displacement of deep pile and soil did not reach the above value. In addition, according to the development characteristics of negative skin friction, its calculation in the specifications was improved by considering both the vertical effective stress of soil around piles and the pile-soil shear displacement. The negative skin friction calculated by this improved method has a good correspondence with the test results. The obtained dragload can achieve a safe, economical effect, which can offer references for engineering design.

In this study, a scheme of jacking framed bridge with loading was proposed based on the concept of unload-load balance. Taking a highway under Beijing-Shanghai high-speed railway as an example, the deformation and control technology of its piers were also studied. The results show that the highway is excavated at a depth of 10 m under the high-speed railway bridge, and the excavation volume is nearly 100, 000 square meters. The uplift deformation of the high-speed railway is effectively controlled by adopting the scheme of the jacking framed bridge with loading, in which the monitoring and loading measures of the soil heap on the top of the framed bridge, under the bridge and in the framed bridge are carried out. After three months of operation, the cumulative maximum differential settlement of adjacent piers is 2.7 mm, which meet specifications with a margin of 46%. Rail inspections reveal that the regularity of ballastless track satisfies operational requirements. Through comparative analysis, the compressive modulus of silty clay in the numerical model can be determined under the stress state of experimental P0 - P0 + 100 kPa (P0 is the soil self-weight stress), and the unloading modulus can be 3?5 times of the compressive modulus.

The sustained releasing heat of spent fuel has important impacts on the mechanical and seepage fields of the surrounding rock in high-level waste disposal repositories and its long-term stability. Generally, the thermal parameters of surrounding rock depend on the mineral composition, porosity and pore fluid of rock. To the multi-field coupling analysis of high-level radioactive waste geological repository, it is necessary to determine the values of thermal parameters accurately. Through the meso-mechanical analysis, the method was established to obtain the effective thermal parameters of the surrounding rock, including heat capacity, thermal conductivity coefficient, and thermal expansion coefficient. Based on Biot theory for porous media, a thermo- hydro-mechanical coupling model was built, and then its numerical simulation method of surrounding rock in the high-level radioactive waste repository was proposed. Finally, through the multi-field coupling software of COMSOL Multiphysics, the proposed numerical simulation method was verified using the in-situ test data of thermo-hydro-mechanical coupling in surrounding rock in the Mont Terri high-level waste underground laboratory in Switzerland. The simulation results agreed well with the experimental results. The evolution law of the thermo-hydro-mechanical coupling process was also discussed. The research results can provide a scientific basis for the safety assessment and site selection of high-level radioactive waste repository in China.

In this paper, both physical tests and numerical simulation were conducted to study the dynamic response characteristics of the tunnels with horseshoe cross-section under high-speed train loads. Based on time domain and frequency domain analysis, the frequency response function (FRF) and peak particle acceleration (PPA) are used as evaluation indicators. Under the train vibration loads, the dynamic response of tunnels is analyzed at the speeds of 300 km/h and 350 km/h in the physical tests, respectively. The numerical model is developed by FLAC3D to study the dynamic response of the tunnel under moving loads of high-speed train. Results show that the dynamic response of the tunnel is not attenuated in the circumferential direction as the distance from the vibration source increases. The tunnel response shows a clear attenuation from the inverted arch to the arch. However, there is an increasing trend from the arch to the vault. The test results also show that dynamic response of the horseshoe cross-section tunnel is greater than dynamic response of the circular tunnel, and the average difference is about 3.8 dB in frequency range of 40?200 Hz. It indicates that the tunnel cross-section greatly affects the dynamic response of the tunnel, which should be considered in design. Furthermore, the PPA of the tunnel is the largest at the inverted arch under single-point excitation load. The peak acceleration is the smallest at the tunnel dome. The PPA of the tunnel at monitoring points shows obvious periodic effect under moving train loads of high-speed train. The PPA reaches the highest value when the train travels at the monitoring section. The PPA of the tunnel under moving train loads shows a clear amplification compared with tunnel response under the single-point excitation load. Therefore, it is important to consider the effect of moving trains when studying the tunnel dynamic behaviour under train induced vibration loads.

On the basis of the time-domain wave method coupling the explicit finite element method with the viscous-spring artificial boundary condition, the input seismic motion was converted into the equivalent nodal force acted on the viscous-spring artificial boundary condition. For the three-dimensional (3D) fault site, the free-field response of the 3D field model was obtained by solving the seismic response of the equivalent two-dimensional field model, and the free-field response was converted into the equivalent node force of the 3D model. Subsequently, the oblique-incidence input method of P waves was proposed for the 3D fault site in the study. The precision of the present approach was verified by half-space numerical examples. Finally, the proposed method was applied to investigate the influence of fault on the seismic response of a long lined tunnel through fault subjected to P waves. The numerical results indicate that the seismic response of tunnel lining near the fault is amplified greatly. The tunnel is in the complex stress state of tensile, compression and shear under P waves. The seismic response increases with the weakening of the mechanical properties of the fault, and the depth of fault also influences the seismic response of the tunnel. With increasing the incident angle of earthquake waves, the axial force and bending moment of the tunnel lining near the fault increase first and then decrease. However, the shear force gradually decreases with increasing the incident angle.

Subsoil vibration induced by metro train arriving at or leaving station is a special vibration with vast vibration sources. In this study, the train vibration source is simplified to the cylindrical vibration source to study vibration characteristics and different vibrations caused by metro train arriving at and leaving station. On the basis of wave theory, the wave field expression in soil space is obtained by wave function expansion method. Secondly, the reflection law is used to deduce the propagation direction of different types of reflection waves. Thirdly, according to Graf addition formula and the Bessel function transformation, the wave field expression is converted into a uniform coordinate system, and undetermined coefficients are solved by boundary conditions of large circular arc surface. Finally, according to vibration superposition in frequency domain, the wave field expression of the moving vibration source is established during the whole train arriving at or leaving the station. The validity of cylindrical vibration source calculation method is verified by comparing the theoretical calculation results of ground vibration frequency spectrum with its actual monitoring results. In addition, low-frequency vibration characteristics are more obvious when the train arriving at or leaving station. Parameteric analysis shows that both the maximum starting acceleration and initial braking speed increase with increasing the vertical vibration response.

In-situ testing and laboratory testing are two common methods for determining rock and soil mechanics parameters, but there are certain limitations of both methods. The rationality of the parameter selection greatly affects the effectiveness of design calculations and numerical simulation results. The support vector machine method shows obvious advantages on the theoretical basis and solving algorithm. To guarantee the rationality of rock and soil mechanics parameters, the support vector machine method is applied to conduct invert calculations of the rock and soil mechanics parameters. Firstly, the kernel function of the support vector machine is constructed using wavelet analysis theory, and then the support vector machine model parameters of Morlet wavelet, Mexico wavelet and RBF function are optimized using particle swarm optimization(PSO). Finally, the nonlinear mapping relationship between the inversion parameters and the displacement values is established through the wavelet support vector machine model. Based on the orthogonal test and uniform test, this study designs the rock and soil mechanics parameters, which need invert calculation. Meanwhile, by combining the calculation and analysis results through finite element software, the learning samples and the test samples are obtained. After the initial data is compared with the predicted results from the calculations of the Morlet wavelet, the Mexico wavelet, and the RBF function, respectively, it is found that the prediction result of the Morlet wavelet kernel function is more reliable and effective than those of the other two methods. The relative error between the calculated value and the actual monitoring value is no more than 8.1%, when parameters predicted by the Morlet wavelet kernel function are input into the Midas model to calculate the final settlement of the building. The research results show that this method presents good application value in the inverting calculation of geotechnical engineering parameters, and provides a new idea for the determination and verification of rock and soil mechanics parameters in the future.

Quantitative description of fluid flow and solute transport properties of crossed fractures is a fundamental issue for understanding the characteristics of fracture networks. This study is aimed to simulate the fluid flow and solute transport through three-dimensional crossed fractures. The morphological data of the natural rock fracture surface was first obtained via a three-dimensional profilometer, and then a reconstruction technique was employed to generate the corresponding three-dimensional crossed fracture model. The Navier-Stokes equations were solved to simulate the fluid flow and solute transport through the intersection by assuming the solute transport satisfying the Fick’s law. Comparing the simulation results of the rough-walled model with the parallel-plate model, it was found that the surface roughness had a significant influence on the distribution and flow state of the fluid through the intersection. The results obtained from different inlet and outlet configurations showed that the geometry of intersection greatly affected the solute mixing process. These results revealed that the widely accepted parallel-plate model led to remarkable errors in the assessment of solute transport behaviour in fractured rock masses, especially the intersections. Therefore, it is necessary to establish modified models to improve the accuracy of the assessment in future studies.

The uncertainty in the grain-based model, such as grain shape, size and spatial distribution, has a significant effect on the reliability and reasonability of numerical simulation for rocks. Based on the Voronoi model in UDEC, two modified Trigon models were proposed and realised through the built-in programming language FISH. Meanwhile, the effects of grain shape, iteration and random seed on the macroscopic response and failure mode of the coal sample were analysed in uniaxial compression test. The results showed that the effects of iteration and random seed on uniaxial compression strength and deformation of coal samples depended on the grain shape. For the two Trigon models, the influences of iteration and random seed were similar. However, for the Voronoi model, the influence of random seed was greater than that of iteration. Furthermore, the type, number and development of cracks were mainly affected by the grain shape. The failure modes of the coal sample were determined by the grain shape, iteration and random seed. Hence, the reliability of numerical simulation in the UDEC grain-based model can be improved by considering the real grain shape, grain size and spatial distribution of rocks.

A large number of non-rock failure signals are usually obtained by microseismic monitoring. At present, these kinds of signals are mainly identified and filtered by manual experience, which consumes much precious time and seriously affects the efficiency of disaster prevention and rescue. By analysing massive microseismic signals, we find that the STA/LTA algorithm can roughly characterise the amplitude and frequency of waveforms after the real-time triggering of signals. The R values of the rock failure signals and the non-rock failure signals are different in the delayed position. Therefore, a real-time recognition algorithm for the microseismic signal of rock failure is proposed. The new algorithm is applied to three projects, including the underground powerhouse of the Baihetan hydropower station, the deep stope of the Hongtoushan copper mine, and the deep stope of the Ashele copper mine. The accuracy rates of the identification of rock failure events are 85.98%, 92.45% and 91.06%, respectively. The accuracy rates of the filtering of non-rock failure events are 72.06%, 83.11% and 49.87%, respectively. It is of great significance that the algorithm makes it possible to automatically analyse and predict rock engineering disasters based on microseismic information of rock failure.

An accurate microseismic (MS) source location method is the foundation of MS monitoring technology for stability analysis of rock mass, and the first-arrival travel time calculation method is one of the important factors determining the precision of MS source location. An improved linear interpolation algorithm based on the fast marching methods (FMM) and LTI ray tracing is introduced to obtain relatively accurate first-arrival travel time in complex rock masses. Moreover, this improved algorithm is verified by the uniform velocity model and the Marmousi model. On the basis of travel time calculation, Runge-Kutta method, a single-step high-precision method in the numerical algorithm of ordinary differential equations, is introduced to calculate the ray propagation path. Besides, its rationality is verified in the uniform, stratified and hollow rock mass model established by us. Finally, using the least-squares method as the objective function, the MS source location is achieved by obtaining the optimal node that makes the objective function taken the minimum value. In the Marmousi model with underground caverns established by us, the location errors for the pre-set source points are 1.41, 1.00, 2.83, 1.41 m and 1.41 m, respectively. It is verified that the method in this paper can achieve relatively accurate location in the complex rock mass and provide a new idea for improving the accuracy of microseismic location in the engineering rock mass.