Microbially Induced Carbonate Precipitation(MICP) method has been widely applied for soil reinforcement，but few researches on its applications in rock mass reinforcement had been reported. In order to explore the reinforcement mechanism of MICP method for rock joints，3D printing technology was used to prepare three groups of transparent resin artificial rock joints that had the same morphological characteristics as Barton?s standard profiles. Unidirectional non-cyclic grouting method was adopted for MICP tests in rock joints，and digital photography technology was used to collect real-time CaCO3 deposition images in rock joints，and on the basis of which the evolution of CaCO3 deposition during MICP process in rock joints was analyzed. From experimental results，it showed that CaCO3 firstly deposited and aggregated at the outlet corners，thus a CaCO3 deposition zone forming，and then it extended along the width direction of rock joint at the outlet. Furthermore，the CaCO3 deposition zone continued to extend toward the inlet and middle position of the specimen along the length and width direction，respectively. Finally，fully-deposited and partially-deposited CaCO3 zone were formed and CaCO3 effective deposition ratio was proposed to quantitatively represent the CaCO3 deposition zones in rock joint specimen under different grouting times. On this basis，it was obtained that the evolution law between CaCO3 effective deposition ratio and grouting time showed a three-stage trend which included initial deposition period，stable deposition period and accelerated deposition period. And an exponential function was proved to fit the evolution law well.

In order to reveal the deformation and rupture characteristics of wellbore surrounding rock in the energy storage area during deep geothermal energy mining，and to construct the failure criterion of circular ring granite，thestatic and dynamic mechanical tests of unidirectional compression in the ring plane were carried out. The test samples were treated by the methods of high temperature heating，heat transfer submerging andcyclic heating- soaking. In parallel，the rupture process of circular ring granite was investigated using high-speed photography and numerical simulation.The results show that the unidirectional static load-displacement curve of circular ring granite can be divided into three segments：up-concave-linear-like-post-peak failure，while the unidirectional dynamic load-displacement curve is similar to a parabola. When the heating temperature，immersion water temperatureand the number ofcyclic heating-soakingincrease，the static and dynamic peak load increases and the peak displacement decreases and both of them decrease occur in response to an increase in the inner bore diameter of the rock samples. The failure mode of the circular ring rock sample is tensile failure，and it is not affected by the type of unidirectional load. It is also found that the cracks all start occur from the inner ring wall of the rock sample in the direction of compression load.Finally，the evolution law of the accompanying energy of circular ring granite was revealed and on the basis of certain assumptions，the failure criterion of circular ring rock samples was established，and the rationality was verified by the test results.

The fracture characteristics and fracture mechanism of hard roof rock in coal mines are of key significance for the optimization of the artificial roof caving. Aiming at the hard roof coarse sandstone and gravel-bearing coarse sandstone in the Junger mining area of Inner Mongolia，the semi-circular bending samples of the rock were subjected to the loading rate of 0.35–3.78 GPa•m1/2•s－1 by using the split Hopkinson pressure bar. The dynamic fracture behavior and energy dissipation mechanism of rock under different loading rates are studied. The results show that：(1) under the impact，the fracture toughness of hard roof rock in the coal mine in the study area ranges from 0.76–3.36 MPa•m0.5. With the increase of loading rate，the fracture toughness of hard roof rock samples in the coal mine increases linearly，and the effect of loading rate on the fracture properties of hard roof rocks in the study area is significant. (2) At low loading rate，the fracture of hard roof rock is mainly simple tensile fracture，and the tensile cracks are formed parallel to the loading direction. Under medium and high loading rate，central tensile fracture and oblique shear fracture are formed in the roof sandstone. (3) With the increase of loading rate，the failure modes of hard roof rock changes from simple tensile fracture to shear-punch composite fracture，the degree of rock specimen breakage tends to be serious，and the number of fractures increases while the length decreases. (4) With the increase of loading rate，the energy absorption efficiency of hard roof rock samples during the fracture process is significantly reduced，which is disadvantageous to the realization of efficient rock breaking. (5) Due to the low loading rate，hydraulic fracturing can form a large range of rock fracturing under the same energy consumption，which is conducive to improving the fracture efficiency of hard roof in coal mine. However，due to the high loading rate，blasting has a limited range of impact crushing zone，which has certain limitations as a means of artificial roof caving of hard roof in coal mine.

The tar-rich coal reserves in northern Shaanxi are large，and its components contain more shale gas. At the same time，its internal fissures are few，dense and strong，and the underground mining process presents“three big and one fast”，which is easy to form large-scale roof hanging and other secondary disasters. There are many shortcomings in conventional measures to control roof dynamic disasters. Therefore，microwave radiation is introduced to make tar-rich coal samples with different moisture contents. Through microwave irradiation of tar-rich coal samples with different moisture contents，analyze the changes of physical and mechanical properties of coal samples under microwave irradiation，and the crack propagation law，the final failure form of coal samples and the fractal dimension based on the equivalent side length-mass of coal samples under microwave irradiation are studied. The experimental results show that：(1) Under the same microwave radiation condition，the energy accumulation and dissipation of coal samples are negatively correlated with the water content，and the average longitudinal wave velocity of tar-rich coal decreases by 4.22%，7.23% and 11.76% respectively，and the energy accumulation and dissipation are further reduced. (2) With the increase of water content，the failure mode of tar-rich coal gradually changed from compression-shear failure to tension-shear mixed failure. With the introduction of microwave radiation，the failure degree of tar-rich coal continued to increase，and the failure mode gradually changed from shear failure to columnar tensile failure. Compared with water，microwave has a stronger effect on coal sample reforming，and the participation of water makes the effect of microwave obviously improved. (3) With the increase of water content，the fractal dimension shows a decreasing trend，and the decreasing rate of fractal dimension is more obvious after microwave is introduced. Therefore，both of them can promote the decrease of fractal dimension. The progressive failure law of tar-rich coal under the interaction of microwave and water is revealed，which provides an effective reference for the mechanism of microwave and hydraulic fracturing，and provides basic theoretical support for roof dynamic disaster prevention measures.

When full-length anchoring bolts were used to support roadways，the deformations of high-stress soft rocks caused complex changes in the internal force distribution of bolts. The work explored the bearing characteristics of full-length anchoring bolts，especially the evolution law of the mechanical properties of bolt bodies from normal bearing to critical and debonding bearing. The strength-softening and volume-expansion characteristics of the surrounding rock in the plastic stage were considered based on the secondary release displacement of surrounding rocks under the spatial effect of the excavation surface of the roadway. The interaction model of bolts and surrounding rocks was established under three typical working conditions of normal support，critical support，slip，and debonding to derive the analytical solution of the shear stress distribution of the axial force and the anchoring interface along the length of bolts. Besides，we systematically analyzed the effects of lagging support distance(support timing)，expansion coefficients，bolt lengths，residual shear strength，and pallet reaction force on the force distribution of bolts. The research results showed that：(1) The internal force distribution of bolts conformed to the neutral point theory under normal support conditions. The axial force of bolts rose rapidly from the orifice along the bolt bodies，and it exhibited exponential attenuation towards the hole bottom after reaching its peak at the neutral point. The shear stress of the anchoring interface quickly attenuated from the maximum value to 0 in the part from the hole top to the neutral point，and it first increased and then decreased along the bolt body. Shear stress on both sides of the neutral point was in the opposite direction. The axial force of the bolt and the shear stress of the anchoring interface both decreased with the increased lagging support distance and increased with the increased expansion coefficients and bolt lengths. (2) The neutral point of the bolt was moved to the hole top under the critical working conditions of support. Axial force reached its maximum at the hole top and quickly attenuated to 0 along the bolt body to the hole bottom. The shear stress of the anchoring interface was distributed in an arched manner. The shear stress at both ends of the bolt body was 0，and the direction pointed to the hole bottom，which had a significant compressive stress effect on surrounding rocks. The earlier support timing and the larger bolt length were conducive to the rapid improvement of the anchoring force of bolts under weaker surrounding rocks. However，the bolt body was easy to break near the hole top. (3) The debonding range at the hole top was positively correlated with the expansion coefficients and bolt lengths and negatively correlated with residual shear strength under slip and debonding. As the ranges of slip and debonding increased，the neutral point was offset to the hole bottom. The shear stress distribution of the anchoring interface evolved into a bimodal curve. Axial force concentration was significantly reduced，and effective compressive stress on surrounding rocks was significantly reduced. The slip and debonding of the anchoring interface greatly weakened the load transfer capacity of the bolt body，which hindered the anchoring capacity of the bolt. Stress causing cracks on the anchoring interface could be transferred to the tray in time if a tray was applied，which suppressed slip and debonding.

In order to solve the problem of the physical model preparation of highly fractured rock mass，a preparation method for physical model of highly fractured rock mass based on 3D printing was proposed by systematically reviewing the existing 3D printing preparation methods for fractured rock mass. The soluble 3D printing materials were screened out through the dissolution test. The physical models of highly fractured rock mass contained a fracture network were prepared using the soluble 3D printing materials，and the mechanical properties of the highly fractured rock mass model were verified by uniaxial compression laboratory test and numerical simulation test. The results show that the proposed method can generate physical models of highly fractured rock mass with excellent performance by first printing the physical model of fracture network with soluble 3D printing materials，next pouring the mortar and curing，and then dissolving the fracture material with solvent. The modified PVA material has excellent solubility，which can dissolve quickly under the conditions of pouring mortar，and the dissolved material can be used as filler for fractures. The dissolved material can prevent the disintegration of the highly fractured rock mass model because of the cohesiveness. Therefore，the modified PVA material is suitable for preparing physical models of highly fractured rock mass. The preparation method of highly fractured rock mass based on 3D printing has two outstanding advantages. Compared with the direct preparation method by 3DP(three dimensional printing)，the physical models have good simulation performance because of the use of conventional mortar as the main material，which has adjustable properties. Compared with the indirect preparation method by FDM(fused deposition modelling)，the influence of fracture material on the mechanical properties of the physical model is eliminated by using soluble 3D printing materials to print the fracture network. The proposed method based on 3D printing can prepare physical models of highly fractured rock mass with conventional mortar as the main material and containing a fracture network, in which the width of the fracture can be as small as 0.4 mm and the fractures have weak cohesion. The physical models can be widely used for physical simulation experiments on highly fractured rock mass，thereby expanding the physical simulation capabilities of fractured rock mass to highly fractured rock mass.

The seismic dynamic response of slope is a very complex problem，and the factors that affect the dynamic response of slope are various. In this paper，the dynamic response characteristics of anchor sheet pile wall under earthquake are studied by shaking table test. By observing the macroscopic failure phenomenon of the anchor sheet pile wall model after the earthquake，it is found that the trailing edge of the sliding body is easy to be damaged by tensile failure under the action of strong earthquake，and the damage accumulates continuously. When the peak acceleration reaches 0.9 g，the cracks at the trailing edge of the landslide are completely connected，which is 4 times that of 0.4 g. Through the analysis of the monitoring data of the monitoring points，it is found that the model is sensitive to the difference of seismic wave spectrum. The earth pressure on the back of the wall shows an irregular “inverted trapezoid”，peaking at about 10 cm below the top of the pile. Under EL-Centro earthquake excitation，the amplification effect of each measuring point changes linearly with the increase of PGA，and is scattered between 0.8 and 1.6，while under Wolong earthquake excitation，the amplification effect of each measuring point changes nonlinearly with the increase of PGA，mainly concentrated around 1.4. It can be seen that the acceleration amplification factor of the measuring point away from the anti-slide pile is much smaller than that of the measuring point near the anti-slide pile，indicating that the soil structure near the anti-slide pile is more complete.

Shazaoyuan granite masses is a key pre-selection area for high-level radioactive waste disposal in China. Outcrop joints widely distributed in the granite body are the channels for groundwater seepage and nuclide migration. On basis of previous outcrops survey and measurements，taking a single outcrop as an object，the circular window method was used to calculate the average trace length L and the number of unit area of the outcrop；the topological theory was used to calculate the number of connection nodes per unit joint，and the box counting method was used to calculate the fractal dimension D of the outcrop. Secondly，the linear correlation of plane characteristic parameters was analyzed，in which is positively correlated with L and D，and the coefficients are 0.418 and 0.612，while is negatively correlated with L and D，and the coefficients are －0.538 and －0.387.  and do not reflect the correlation，and the area density parameter of connected nodes of outcrop joints was proposed. Then，taking outcrops in the area as an object，based on location of outcrops，the Voronoi method was used to divide the rock mass. The regional plane characteristic parameter value = 13.54 m， = 0.095， = 2.93， = 1.19， = 0.25 obtained by the area weighting method. Finally，the regional distribution of parameters is presented by the quartile map，in which the regional distribution of is obvious，showing the characteristics that the southwest region is larger than the Northeast. The regional distribution of parameters ，L and D is similar，showing that the area is small in the middle and alternated around. The rock mass was screened by parameters ， and . The areas with“good”rock mass quality are located in the middle and east of the investigation area.

For water-rich tunnel in different construction stages under variable amplitude load disturbance of surrounding rock damage problem，by conducting graded loops and unloading test，analysis of loops and unloading stress-strain hysteresis curve，in the process of rock deformation parameters and macro fracture characteristics，revealing the grading loops and uninstall the deformation and failure regularity of saturated sandstone. The results show that with the increase of loading amplitude，the migration of hysteresis loop decreases first and then increases，the area of hysteresis loop increases step by step，and the axial strain of hysteresis loop develops as“sparse-dense-sparse”. The elastic modulus decreases step by step in the form of“sudden drop-slow drop-accelerated drop”，and Poisson?s ratio changes in the form of“step by step drop-relatively stable-rise”. The confining pressure increases the stiffness and deformation resistance of rock samples，the overall elastic modulus，the initial Poisson?s ratio，and the residual strain increase，but the weakening effect is obvious under the cyclic loading and unloading of the late yield section. The faster the loading rate is，the more obvious the load meshing friction effect is，the greater the average loading and unloading modulus is，and the less the irreversible deformation of the rock sample is，but the Poisson effect is not obvious. With the increase of confining pressure，the failure of sandstone changes from tension shear composite failure to compression shear failure；The smaller the load rate is，the more developed the main fracture is，the higher the penetration degree is，and the greater the scouring degree of the fracture surface is. The deformation and failure law of saturated sandstone revealed by the study has significant reference value for the deformation，damage and stability analysis of surrounding rock of rich water tunnel.

To study the failure mode of reef limestone under impact load，static mechanical tests are performed on two types of reef limestone and several terrigenous rock. And the stress-strain change laws of the rock samples under different impact pressures were analyzed using the split Hopkinson pressure bar system(SHPB). And explore the dynamic mechanical properties of reef limestone under three cycle impact loads with LS-DYNA numerical simulation software. The results show that the static mechanical properties of reef limestone are close to those of gypsum，far less than those of terrigenous rocks. And the reef limestone has a certain residual strength after failure. However，under dynamic impact load，the reef limestone has an obvious compaction stage. And its dynamic compressive strength will increase significantly with the increase of strain rate. In addition，when the cyclic impact load is small，the stress-strain curve of reef limestone sample is closed or open type under the first and second impacts，but it becomes open type under the third impact. When the impact load increases to a certain value，the stress-strain curve of reef limestone sample under different cyclic impact times is open type.

In order to study the seismic cumulative deformation effect(SCDE) of tunnel lining in landslide area reinforced by double-row piles，the shaking table test is conducted for the first time based on an actual engineering case to test the acceleration and dynamic displacement response data of double-row piles and tunnel lining under different probability levels of seismic action. The internal correlation mechanism of the deformation- frequency-energy evolution characteristics of the tunnel lining during the whole process of slope disaster is established. An analysis index of plastic deformation degree of tunnel lining under seismic wave excitation-plastic effect coefficient(PEC) is proposed，and the applicability of PEC to analyze plastic deformation of tunnel lining is verified by Arias strength( ) from the perspective of the energy transfer characteristics. Based on the fast Fourier transform(FFT) method，the influence mechanism of the seismic wave frequency components on SCDE and local deformation of the tunnel lining is discussed. The results show that PEC fully takes into account the plastic deformation characteristics of the tunnel lining and has a clear physical meaning，which can more clearly reflect the degree of plastic deformation and SCDE of the tunnel lining than the peak tunnel displacement(PTD). The seismic cumulative deformation evolution process of tunnel lining and the regional response characteristics of the particle spatial position are systematically revealed by the comparative verification analysis of   peak strength ratio( ). The results of the frequency domain analysis show that the low-frequency and high-frequency components of the seismic waves play a controlling role in the overall and local deformation of the tunnel lining，respectively. The dynamic deformation response of tunnel lining in the landslide area reinforced by double-row piles is a progressive cumulative evolution process. Obtaining a better understanding of the SCDE of the tunnel lining can provide a scientific basis for the identification of the seismic damage status and appropriate seismic reinforcement.

In order to study the mechanical properties and tensile-shear failure mechanism of soft and hard interbedded rock masses，the specimens with different layer dip angles and layer thickness ratios using a physically similar simulation method and conducted uniaxial compression tests were prefabricated，and the following conclusions were obtained：(1) the peak strength and Young?s modulus of the specimens decrease first and then increase with the increase of the dip angle . They decrease with the increase of soft-hard layer thickness ratio k. (2) Due to the local shear slip along the bedding plane，the stress-strain curves of specimens with a dip angle of 30°–45° have a large stress abrupt drop point at the early stage of loading. This is a unique multi-peak characteristic of the stress-strain curve of soft and hard interbedded rock masses. In addition，compared with the existing laminated rock failure modes，a new failure mode was found，that is，soft strata compression damage and hard strata tensile damage across the bedding plane. (3) Using a method of crack image extraction，the rose distribution map of crack characteristic evolution on the samples surface is given for the first time under different dip angles and thickness ratio k. At the same time，the failure mechanism of tensile and shear cracks and the distribution proportion of cracks were studied，along with the influence on the specimen?s failure mode. It is believed that the dip angle controls the crack propagation direction，and the thickness ratio k determines the proportion of tensile-shear failure. Shear slip along the layer，tensile fracture in the hard layer and crushing failure in the soft layer are the three main factors leading to the deformation and failure of the samples. When the bedding plane dip angle is around 30°–45°，the shear slip occurs at the bedding plane and the shear cracks increase. When the dip angles are near 0° and 90°，tensile failure occurs in the through layer or along the layer direction，and the shear cracks decrease.

In order to explore the influences of joint roughness coefficient JRC，seepage solution and confining pressure loading on the seepage characteristics of limestone rough fractures，the distilled water and sodium sulfate solution were selected as seepage solutions to carry out limestone fissure seepage tests under different conditions. The evolution mechanism of seepage characteristics of limestone rough fracture under different roughness and seepage solutions was revealed by combining the morphological characteristics of the fracture surface before and after the tests. The results show that the fracture seepage flow rate，equivalent hydraulic gap width and permeability show a trend of rapid decline，slow decline and basically stable change with the increase of seepage time. Under the same seepage solution and stress condition，the larger the JRC of fracture surface is，the smaller the permeability is. With the increase of confining pressure，the fracture seepage flow and permeability decrease continuously. Compared with distilled water，the fracture surface of the sample corroded by sodium sulfate solution becomes coarser，JRC of each fracture surface increases by 3.31%–36.61%，and surface roughness parameter increases by 0.10%–1.05%. The research results can provide theoretical support for the estimation of fracture permeability and leakage of fractured rock mass.

In order to explore the effect of water temperature on the thermal shock process of granite at high temperature，based on the heat shock heat transfer theory，the constant temperature convection heating experiments with different heat source temperatures were designed and conducted. Through theoretical derivation and data analysis，the following conclusions were obtained：(1) high temperature granite in unboiling water thermal shock cooling，temperature gradient and thermal shock rupture decrease with increasing water temperature. When thermal shock cooling in boiling water，the temperature gradient and thermal shock rupture are significantly greater than in the case of thermal shock in unboiling water at any temperature. (2) The experimental results prove that the convective heat transfer coefficient of boiling water is greater than that of unboiling water by more than one order of magnitude. When the high temperature granite is cooled by thermal shock in water(0 ℃–100 ℃)，the effect of the dramatic change of convective heat transfer coefficient due to boiling on thermal shock is significantly greater than that caused by temperature difference and thermal conductivity of rock material. (3) In engineering，it is more economical，energy efficient and effective to enhance or avoid thermal shock rupture by changing the convective heat transfer coefficient of fluid medium rather than changing the material thermal conductivity and temperature difference. This study contributes to the fine characterization of thermal shock rupture of rock materials and also provides guidance for engineering involving thermal shock rupture.

The high-speed long-distance landslide is a landslide disaster with extremely strong destructive force. Its typical movement feature is that the landslide mass is transformed into debris particle flow after the instability. It is a typical progressive failure process from continuous to discontinuous. This study is based on the continuous discontinuous element method，and then the particle element method is introduced. The sliding body with large displacement and deformation is calculated by discrete element method，and the sliding bed with small deformation and displacement is calculated by finite element method. A high-precision three-dimensional geological disaster model is established based on the topographic and geomorphologic data of the landslide area. In the calculation process，the strength reduction caused by friction and collision in the sliding process of rock mass is considered，and the disaster range is analyzed numerically. By comparing the simulation results with the field investigation data，it is determined that the calculated accumulation shape and range of the sliding body are in line with the actual situation. Based on the energy and velocity monitoring data，two high-speed remote landslides were quantitatively analyzed.

The flat top cave is one of the most typical cave shapes of the North Grottoes. The interface strength of the sedimentary layer on the top of the flat top cave is low and easy to weather and crack. In order to effectively improve the effect of grouting bonding and reinforcement for roof cracking diseases，sintered stone and sandstone powder were selected as the main materials，mixed with different concentrations of organosilicon-modified acrylic acid solution and different contents of glass microbeads to configure the slurry to test its flow properties，basic physical mechanics indexes，micromorphology and adhesive properties. It is found that the wave speed，flexural resistance，compressive resistance and bonding tensile strength are all significantly improved，and the shrinkage rate and density are reduced that the slurry fluidity and pourability met the requirements by adding 0%–1.0% concentration of silicone-acrylic or 0%–0.5% content of glass beads. Microscopic experiments show that the sintered sintered stone generates -CaO•SiO2•nH2O，2CaO•Al2O3•SiO2•nH2O and CaCO3 through hydration and gasification reactions，which improves the strength of the slurry. Changed to a compact lamellar shape，the glass microbeads can be filled in the original larger pores of the slurry，which enhances the continuity of the slurry. The sintered stone and sandstone powder are 1∶1，mixed with 0.5% silicone-acrylicand 0.25% glass microbeads，and the indicators are the best. It has broad application prospects in the grouting bonding of cracks between the roofs of flat top cave in sandstone caves.

An indoor splitting test was carried out to investigate the rock breaking effect which is influenced by the pre-cutting slot at borehole with an electro-hydraulic servo dynamic and static universal testing machine and some cube granite rock specimens. The directional control effect and the maximum splitting force at the moment of breaking were studied specifically in the test under different arrangement modes of pre-cutting slot，such as the setting or not，the direction(inclined slot along the diagonal direction and straight slot parallel to the upper surface boundary of specimen) and the length. Several experimental results were obtained as follows. (1) The pre-cutting slot can effectively control the initiation and propagation of crack and the extension direction of breaking surface，and can significantly inhibit the generation of secondary cracks. (2) Compared with the inclined slot，the straight slot can achieve better breaking directional control effect because it is less affected by the free surface. (3) The length of the pre-cutting slot possesses an obvious promotion effect in guiding the crack propagation and controlling the extension direction of the breaking surface，and this effect is positive correlation with the length of the slot. (4) The pre-cutting slot can reduce the maximum splitting force，and the maximum force shows a monotonically decreasing trend with the increase of the length of the slot. The above experimental conclusions will provide important practical guiding significance for improving rock breaking efficiency in non-blasting directional control rock splitting in the future.

The efficient production method of tight sandstone reservoir in Tanhai block of Jidong oilfield is volume fracturing of deviated wells. The bidirectional deformation along the horizontal maximum principal stress direction and the vertical stress direction leads to the complex fracture morphology. The distortion interface is easy to form sand blocking phenomenon. Therefore，it is of great significance to clarify the law of fracture propagation in deviated wells. Based on the large-scale true triaxial hydraulic fracturing physical simulation experiment，this paper studies the influence law of horizontal stress difference，well inclination angle，azimuth angle and phase angle on the fracture initiation characteristics and propagation morphology of deviated well. The results showed that：(1) the fracture morphology of deviated well after fracturing can be divided into single fracture surface，double wing parallel fracture surface，multiple fracture surface and complex fracture surface. (2) Under the low horizontal stress difference coefficient，the number of perforation hole initiation is more. On the contrary，only the perforation hole with a small angle to the direction of the horizontal maximum principal stress starts to crack. (3) There are fewer fracture initiation points in 20° or 80° wells，while there are more fracture initiation points in 40° or 60° wells. The degree of fracture distortion increases first and then decreases with the increase of inclination angle. (4) When the azimuth angle is greater than 80°，the fracture initiation pressure increases，and the fracture morphology is mainly multiple fracture surface and complex fracture surface. (5) The increase of perforation phase angle leads to the increase of fracture initiation pressure. With the increase of hole spacing，the communication between holes becomes weaker，leading to the generation of secondary spreading fractures. It is suggested that the well trajectory design of formation with large horizontal stress difference should adopt large well inclination angle，small phase angle and small azimuth angle. It can effectively reduce the fracture initiation pressure and distortion degree，so as to solve the problem of sand blocking in site construction.

To break through the limitation of long-term dependence on limited test data for estimating the ground shock power of underground explosion，based on the systematic review of the research results at home and abroad，this paper systematically analyzed the coupling mechanism of ground shock and crater effect of large equivalent underground explosions，theoretically revealed the law of volume of underground explosion damage zone and coupling ground shock energy，the theoretical calculation method and conversion relationship of equivalent coefficient，ground shock energy coupling coefficient and ground shock stress coupling coefficient are established. Finally，the calculation methods of shock stress and particle velocity under different buried depths are systematically given，and the accuracy of the theoretical model and calculation formula under the conditions of chemical explosion and nuclear explosion is verified by field test and model test.

The physical mechanism of ice-rock debris flow?s super fluidity and super impact damage remains unclear. In this study，the motion and impact process of ice-rock debris flow with varying ice contents were qualitatively studied through laboratory experimental model tests. The evolution characteristics of flow velocity，flow depth，impact height，and impact force with ice content were analysed. The influence of ice content on the fluidity and impact characteristics of ice-rock debris flow was clarified. The ice content increase leads to a decrease in the internal friction angle of the ice-rock debris flow. Simultaneously，the flow velocity，flow depth，and impact wall height of the ice-rock debris flow increase, enhancing its fluidity. As the ice content increases，the dynamic indicators of the ice-rock debris flow also increase，while the density decreases. This results in a characteristic pattern where the maximum impact force of the ice-rock debris flow initially increases and then decreases with increasing ice content, reaching its peak at 40% ice content. Theoretical analysis suggests that the impact force of the ice-rock debris flow can be calculated by summing the dynamic and static components of the impact force.

In view of the lack of effective theoretical prediction models for surface subsidence caused by the operation of groups of salt caverns for gas storage，this paper studies the surface subsidence caused by cavern shrinkage of gas storage through the influence function method. The numerical simulation method is used to study the influence function method，including the variation law of the volume transfer coefficient of single cavern and the influencing factors of double cavern. A surface subsidence prediction model based on cavern group effect correction is established using the influence function method. Combined with the engineering experiment of Jintan gas storage，the modified surface subsidence prediction model is used to analyze the subsidence above salt caverns，and a surface subsidence early-warning threshold based on the safety of cavern volume shrinkage is proposed. The conclusion shows that the influence function method can effectively calculate the surface subsidence caused by the shrinkage of the salt cavern. During the operation period of the salt cavern gas storage，the volume transfer coefficient is between 0.6–0.8，and it continuously increases with the increase of the volume shrinkage ratio of the gas storage. Applied to engineering examples，the recommended early-warning threshold for surface subsidence during the operation period of the salt cavern gas storage is that the cumulative value does not exceed 200 mm.

At present，there are few tests and constitutive models on the mechanical properties of limestone under dissolution. In order to reveal the influence of dissolution on the deterioration of mechanical properties of limestone，a constitutive model suitable for describing the deterioration of mechanical properties of limestone under dissolution was established. Firstly，based on the results of uniaxial compression tests of limestone under dissolution，the mechanical properties of limestone are deeply analyzed，and the results show that the elastic properties and strength properties of limestone are affected by dissolution and plastic characteristics. Secondly，based on the strain softening model，the deterioration model of mechanical properties of limestone under dissolution(DLDM) was established from three aspects：elastic increment rule，yield criterion，and flow rule. Then，the method of FLAC3D-machine learning was used to obtain the specific change law of limestone mechanical parameters(elastic modulus，cohesion，internal friction angle) with dissolution action and equivalent plastic strain. Finally，the rationality of the DLDM model was verified by comparing the existing experimental values with the calculated values. The validation analysis indicates that the calculation results of the DLDM model are consistent with the uniaxial compression test results of limestone，Therefore，the deterioration evolution law of elastic modulus and strength parameters during the failure process of limestone can be accurately described. Besides，the theoretical basis for the stability analysis of surrounding rock of underground engineering in karst strata is provided.

Non-Darcy seepage experiments of broken rock mass were carried out under high hydraulic gradient. The influence mechanism of non-Darcy flow characteristic and critical hydraulic gradient was revealed with different porosity and gradation of rock mass sample. Considering the influence of the porosity and Talbot gradation coefficient，the calculation models of the non-Darcy flow coefficient，linear and non-linear term coefficients of Forchheimer?s law were established. By piecewise analyzing the relation curve of pressure gradient and flow rate with Darcy?s law，the non-Darcy equivalent hydraulic conductivity was proposed，and the non-Darcy equivalent seepage model was established. The results show that the experimental data were highly compliant with Forchheimer?s law. The critical hydraulic gradient was changed from 125 to 183. Because the influence of inertia force, the critical hydraulic gradient was reduced with increased porosity and the number of coarse particle of rock mass sample. The non-Darcy flow coefficient，linear and non-linear term coefficients of Forchheimer?s law have negative exponential with porosity and reduced power relationship with Talbot gradation coefficient. The non-Darcy equivalent hydraulic conductivity have negative exponential relationship with hydraulic gradient and decided by the pore structure of rock mass sample. The established non-Darcy equivalent seepage model was highly agreement with Forchheimer?s law. The established model possessed fewer calculation parameters and could adapt to the coexistence and interconversion between Darcy flow and non-Darcy flow.

Aiming at the problem that the roof fault of the mining roadway is prone to activation and roof deformation under the influence of mining. With the background of the roof crossing fault fracture zone of return laneway in 201 working face of Ruineng Coal Mine. Theoretical analysis, numerical simulation and field measurement were used in this study. Which contains the influence of principal stress deflection induced by mining activities on the risk of fault activation，the characteristics of the mining stress deflection in front of working face，the principal stress deflection characteristics of the roadway roof fault plane and the roof stability. The results showed that the mining stress deflection caused the transition from the tangent state to the secant state of the stress Mohr circle of the fault plane and the rock strength curve，which increased the risk of slip instability of the fault plane. The risk evaluation coefficient k of fault plane activation covering the ratio of normal stress to shear stress was obtained by theoretical derivation. The influence range of advance disturbance of working face was 25 m，the principal stress deflected obviously in the range of 2 m in front of the working face and 4m on the side of the coal wall of the roadway，and the deflection angle was greater than 60°. The principal stress deflection of shallow fault plane within 2 m of roadway roof was significantly affected by the mining disturbance of working face，and the significance decreased with the increase of distance from working face. The shallow part(k＞1) of the overlying roof of the roadway along the fault dip belonged to the fault activation risk area，and the deep part  (k＜1) belonged to the stable area. The risk of fault activation risk zone decreased exponentially with the increase of distance from working face along fault strike. Within 5 m in front of the working face，it belonged to the high risk area. Within 5–20 m，it belonged to the general risk area. Within 20– 25 m，it belonged to the low risk area. The risk of fault activation in the mining stage of working face had a significant influence on the deformation of roadway roof. With the increase of distance from working face，roof deformation in high risk area＞general risk area＞low risk area. Based on the risk of fault activation and the stability of roadway roof，the reinforcement support scheme during mining was given.

When tunnelling in soft rock under high in-situ stress，obvious time-dependent deformation of surrounding rock is often observed，and the deformation can cause serious damage and cracking of the secondary lining. To reduce the ground pressure of the secondary lining induced by time-dependent deformation，a compressible layer is suggested to construct between the primary support and secondary lining. Filling material of the compressible layer should have high compression capability to absorb the time-dependent deformation. In this study，the yielding support used polyethylene foam(density is 90–100 kg/m3) compressible layer and U steel ribs was applied in a tunnel excavated in sandy mudstone and glutenite in northwest China. According to the field observations and numerical results，the performances of the yielding support were analyzed. The results showed that because U steel ribs were connected by the friction connections，the maximum monitoring stress of the U steel ribs is only 140 MPa，which was much lower than that of the H steel ribs. The polyethylene foam layer has great compression capability，and can absorb the time-dependent deformation of the surrounding rock efficiently. According to the monitoring results，the maximum circumferential compression stress of the secondary lining was 13.0 MPa with average value 6.2 MPa，which is lower than the design compression strength of the secondary，indicates the high performance of the compressible layer.

It is practically important for geomechanical modeling and wellbore stability analysis to obtain Biot coefficient of transverse isotropic shale accurately and efficiently. The dynamic and static Biot coefficient and elastic stiffness coefficient of marine-facies Longmaxi black shale in the South Sichuan Basin are investigated by using acoustic measurement and conventional triaxial compression in this study. The main results are as follows：The dynamic and static elastic stiffness coefficients，Young?s modulus both increase with confining pressure，and the dynamic value is higher than the corresponding static value. The value of Young?s modulus parallel to bedding is higher than that of perpendicular to bedding. However，the dynamic and static Poisson?s ratio has no significant rule with the increase of confining pressure and the change of bedding. In addition，the dynamic and static Biot coefficients decrease with confining pressure. And the Biot coefficients perpendicular to bedding are higher than those parallel to bedding. On the other hand，the static Biot coefficients are higher than the dynamic results. Finally the fitting analysis shows that there is a linear conversion relationship between dynamic and static Biot coefficients and Young?s modulus，respectively. The obtained anisotropic characteristics of Biot coefficient and the dynamic to static conversion relationship play an indispensable role in the geomechanical analysis in drilling and completion of shale.

Large-scale cataclastic bedding rock landslides are prevalent in the Three Gorges reservoir area, and they continue to displace and deform, posing a significant threat to residents，the Yangtze River channel, and even the Three Gorges Dam. This paper analyzes the characteristics and inducing mechanism of landslide deformation under the dynamic action of reservoir water，rainfall，and groundwater，using multi-factor comprehensive process analysis and quantitative analysis methods based on GPS monitoring data，survey data，and hydrometeorological data of Tanjiahe landslide. The results indicate that：(1) the decrease of reservoir water level will induce the landslide deformation，on the contrary，while the rise of reservoir water level can inhibit the landslide deformation. During the fluctuation of reservoir water level，continuous heavy rainfall will aggravate the landslide deformation. (2) During the flood season and storage season，rainfall is conducive to raising the groundwater level. The previous monthly rainfall reaches more than 129 mm，the groundwater level of QSK2 has a fluctuation process，during which the hydraulic power leads to significant landslide deformation. (3) The heavy rainfall on the first day did not cause any landslide deformation. However，after two days of continuous rainfall，the groundwater level of QSK2 rose to a critical value of 242.4 m，which led to severe landslide deformation. As the local groundwater level dropped from its peak value of about 245 m to the critical value of 241 m，the landslide deformation trend weakened. (4) During the fluctuation of QSK2 groundwater table，the higher the uplift height of groundwater table (≥2.85 m)，the average groundwater table(≥242.1 m)，the peak value of groundwater table(≥244.0 m)，and other related parameters，the more severe the landslide deformation tends to be. On the contrary，when the groundwater level is lower，the landslide generally tends to be more stable. The research results can be referenced for analyzing the inducing mechanism，monitoring and providing warning，as well as emergency treatment of cataclastic bedding rock landslides.

A new type of rock landslide failure mode in red bed area，lateral drag landslide，is proposed after detailed field investigation and mechanics analysis of Fengyan village landslide in Yilong County，Nanchong City，Sichuan Province. During the movement of the main sliding body of the landslide in the heavy rain，the dragging force will be generated along the sliding direction of the contact zone of the boundary on both sides，which will lead to the dragging deformation of the slope on both sides. The longitudinal length of landslide is smaller than the transverse width and the surface lateral deformation shows obvious strong and weak zones. Firstly，the slope structure conditions，lithologic composition conditions，free face conditions and external triggering conditions which must be had for the occurrence of the drag landslide are systematically studied and identified. Then on the basis of the comprehensive force analysis of landslide，the three-dimensional stability evaluation model and criterion of main sliding body and dragging body are established. Finally，in order to prevent the subsequent deformation and failure mode of the drag landslide，the paper puts forward some suggestions on surface drainage and groundwater dredging，supplemented by appropriate retaining engineering. The research findings have certain guiding significance for the prevention and control of red bed landslide.

In order to study the disintegration evolution characteristics of mudstone under water and different stress paths，scanning electron microscopy，high-energy CT and triaxial servo press were used to explore the fractal dimension variation law of microscopic particle structure，microscopic pore number，macroscopic disintegration and failure fragmentation，and reveal the cross-scale failure mechanism of mudstone. The results show that：(1) The particle size and morphology of pyrite and kaolinite in mudstone are different，and the primary pores will become water seepage channels. With the increase of water content，the deterioration of kaolinite structure leads to the widening of water seepage channel and the increase of microscopic pore fractal dimension. (2) The number of large pores increases and penetrates，and natural disintegration of mudstone occurs. The fractal dimension of disintegration block is between 1.26 and 1.77，which is larger than that of pore fractal dimension. The damage fragmentation fractal under loading and unloading is greater than that under natural disintegration，reflecting the damage superposition effect of external force. (3) The fractal dimension of fragmentation under loading and unloading is all partitioned. Before the characteristic water content，the fractal dimension of the block is negatively correlated with the strength，but it is positively correlated with the strength after exceeding the characteristic water content. The inflection point of the fractal dimension can be used as the demarcation point of the influence of water content and stress. At this point，the influence of water on the main fracture surface reaches the peak. (4) The unloading stress path affects the failure characteristics and morphology of water-bearing mudstone. The low-water-content mudstone exhibits brittle failure，and the high-water-content mudstone exhibits plastic failure. The tensile failure increases，and the fragments are mostly“flaky”.

Grouting is not only an effective method to address the high stresses and large deformations of surrounding rock in deep mining，but is also a key technology for green and low-carbon mining. Accordingly，this study conducted uniaxial compression tests on grouting reinforcement with different negative pressure pressures to explore the reinforcement effect of negative pressure grouting. It analyzed the effects of slurry flow effect of porous media on the mechanical properties of grouting and solid. Moreover，we investigated the relations of the physical parameters，specimen?s strength，deformation in different samples under different negative pressures and examined the sample failure modes drawing the following conclusions based on the present compression test results. First，the effect of the four forces on the negative pressure grouting results in the reinforcement mechanical properties being affected by four factors as the actual situation of the broken rock mass differs from the theory. Secondly，as the negative pressure is increased，a triple change in the water-cement ratio，porosity，and doping of the specimen occurs. The density of the specimen shows a trend of first increasing and then decreasing，exhibiting a three-stage character，with the porosity of the specimen continuing to decrease. Thirdly，the stress-strain curve of the specimen reinforced by negative pressure grouting shows four stages of change of which the strength and elastic modulus of the specimen showed a trend of first a rise and then a decrease，while the mean curve of the axial strain shows a first decrease and then a rise. It can be determined that the negative pressure of 60 kPa is the threshold value of negative pressure grouting reinforcement. Then，the difference between negative pressure grouting pressure makes the internal structure of the specimen different，and finally shows three types of failure modes. Finally，the negative pressure grouting process is affected by four factors. It is necessary to take into account not only the hydration reaction of the slurry，but also the characteristics of the liquid bridge at the solid-liquid interface，and at the same time the pore changes and vacuum dehydration effects during the grouting process. The results are of great reference to improve the grouting reinforcement process and provide a theoretical and experimental basis for clean，efficient and stable coal mining.

The pressure varies greatly in the depletion stage of abnormally high-pressured gas reservoir(AHGR)，and the peak pressure in the alternating injection-production stage cannot reach the original formation pressure after AHGR was reconstructed into underground gas storage(UGS)，which makes conventional methods not applicable to its geomechanical evaluation，thus leads to a lack of systematic evaluation method. In order to ensure the safe and efficient operation of UGS that reconstructed from AHGR，the X abnormally high pressure gas reservoir was selected as the study object，and both of its reservoir pressure field at the end of depletion and the stress and strain fields obtained from geomechanical numerical simulation were selected for data interactive transmission. Then，the dynamic coupling model of trap in-situ stresses and reservoir seepage is established. Finally，using the method of combining finite difference and finite element，the 4D geomechanical characteristics of trap geological body were evaluated systematically and accurately by regard the trap of UGS as the basic evaluation unit. In the end，the 4D geomechanical evaluation method，which can provide effective support for the evaluation of the UGS reconstructed from AHGR，is established.

The deformation and failure characteristics of layered soft rocks are related to their occurrence，and the horizontal stress significantly affects the stability of the surrounding rocks of layered soft rock tunnels. In this paper，based on 3D printing technology，the deformation and failure characteristics of tunnel surrounding rocks under different horizontal stress conditions are studied through model tests，in which horizontal lateral pressure coefficient and time-dependent deformation of rock mass were considered. In addition，the distribution law of strain field disturbed by layered soft rock tunnel excavation is obtained. The research results are as follows. When the lateral pressure coefficient is less than 1.4，the effect of layers on surrounding rock deformation is more significant；the compressive strain of the surrounding rock is unevenly distributed along the perimeter of the tunnel；the failure mode of the surrounding rock is shear sliding failure along the soft layer. When the lateral pressure coefficient is greater than 1.4，with the increase of the horizontal stress，the distribution of the compressive strain of the surrounding rock is deflected along the direction perpendicular to the horizontal stress；the compressive strain increases and the excavation disturbed zone expands rapidly；the failure mode is layer shear slip combined with bedrock compression-shear failure. After tunnel excavation，the compressive strain of the surrounding rock rapidly grows over time in the pre-deformation period and continues to expand along the layer and the direction perpendicular to the layer to the deeper part of the surrounding rock. The orientation of surrounding rock failure after layered soft rock tunnel excavation is closely related to the horizontal stress and the stratigraphic occurrence. The orientations vary significantly under different horizontal stress conditions. The local strengthening and overall stabilization of the surrounding rock should be integrated during tunnel timbering design.

To explore the static compression behavior and damage evolution characteristics of the“rigid-flexible combination”surrounding rock support structure，a new type of green and sustainable“rigid-flexible combination”support strucature was initially established with a high content of rubber-cement composite material as the energy-absorbing cushioning material in the energy-absorbing lining structure. Monotonic compression and cyclic compression tests were carried out on the combination specimens of“rigid-rigid：rock(sandstone) like material (RLM)-normal cement mortar(NCM)”，“rigid-flexible：RLM-rubber cement mortar(RCM)”and“flexible-rigid：RCM-high performance supporting concrete(HPSC)”. The static compression behavior and damage characteristics of the specimens were compared and analyzed from the aspects of the stress-strain curve，deformation，modulus，energy，damage evolution，and failure state. The influence of the rigid-flexible ratio on the compressive mechanics and damage characteristics of combination specimens was further discussed. The results show that，under the same test conditions and loading modes，compared with RLM-NCM，the peak stress of RLM-RCM and RCM-HPSC decreased by 86.2% and 82.8% respectively，and the maximum loading deformation modulus of RLM-RCM and RCM-HPSC decreased by 78.7% and 72.9%，and the maximum cumulative elastic strain energy of RLM-RCM and RCM-HPSC decreased by 81.4% and 78.6%，respectively. The failure degrees of RLM-RCM and RCM-HPSC were obviously smaller than that of RLM-NCM，RLM-RCM and RCM-HPSC mainly occurred the ductile compression-expansion failure of RCM，while RLM-NCM mainly occurred the overall brittle compression-shear failure. RCM improved the elastic deformation and ductile-plastic deformation capabilities of the combination structure，provided the RLM compression flexible deformation space，and helps to avoid a large amount of energy accumulation of the combination structure caused by the RLM extrusion，thus reducing the risk and intensity of dynamic instability of the combination structure. Based on the Lemaitre equivalent strain principle，the pre-peak-post-peak two-stage damage constitutive model established by Weibull statistical distribution theory and Lognormal statistical distribution theory can accurately predict the stress-strain relationship of rigid-rigid combination specimens and rigid-flexible combination specimens under cyclic loading.

In order to study the influence of artificial freezing method on the deformation and damage of surrounding rock unloading，the stress change path of surrounding rock is simulated，and the lateral unloading mechanical test and acoustic emission signal monitoring are carried out under different conditions. The results show that the characteristics of total crack number，tensile crack number，cumulative AE count and cumulative AE count of tensile crack are basically the same with time for sandstone under different lateral unloading conditions. The increasing point(point A) of lateral unloading deformation rate of rock sample can be used as fracture warning. The peak stress of lateral unloading of sandstone after freezing is increased by 2.3–3 times. With the increase of initial confining pressure, the tensile action of frozen rock sample is enhanced，the lateral unloading rate is increased，and the tensile crack is reduced. The initial confining pressure and lateral unloading rate of frozen rock sample increase，the peak stress increases，and the failure becomes more severe. Under the same conditions, lateral unloading of rock samples accounts for 52%–72% of the triaxial compression capacity. The damage model is established according to the number of lateral unloading tensile cracks. The model results are very close to the test results before the peak stress，which can characterize the damage fracture characteristics of frozen sandstone under lateral unloading.

This study aims to improve the evaluation accuracy of collapse susceptibility in Guangdong Province using an intelligent analysis model. To this end，7 171 collapse data and 13 basic environmental factors in the province are collected，and the problem of massive data processing is solved by batch and block methods. Random Forest model(RF) and the coupled Frequency Ratio-Random Forest model(FR–RF) are used to carry out 1∶50 000 accuracy evaluation of collapse susceptibility. The performance of the model is evaluated by the receiver operating curve and the susceptibility distribution characteristics. The evaluation results were compared with those of traditional evaluation methods(Analytic Hierarchy Process(AHP)，Frequency Ratio(FR) and Coupled Frequency Ratio-Analytic Hierarchy Process(FR–AHP)). The results show that：(1) The 13 basic environmental factors have no significant correlation，and they all have a high degree of contribution. Topographic relief，elevation and annual average rainfall are the most important environmental factors affecting the occurrence of collapses in Guangdong Province；(2) The very high and high susceptibility areas are mainly distributed in the northeast，central and southwestern regions；(3) Among the five models，the prediction accuracy of RF is the highest，with an AUC value of 0.884，followed by FR–RF(0.860)，FR–AHP(0.797)，FR(0.794) and AHP (0.601). The uncertainty of the susceptibility index of RF and FR–RF is low. Except for AHP，all four models can be used to obtain reasonable evaluation results of collapse susceptibility，and RF has been found to be the most suitable method to evaluate the collapse susceptibility of Guangdong Province. Overall，the performance of the intelligent analysis method is better than that of the traditional evaluation method. This study can be considered as a reference for the evaluation of collapse susceptibility in large-scale low-altitude areas.

The transfer coefficient method is the original limit equilibrium method of analysis utilized in China for calculating the sliding thrust force of landslide. Due to its straightforward and pragmatic calculation，it finds extensive application in landslide prevention and treatment engineering. However，this method exhibits limitations for complex sliding bodies with an angle greater than 10° between adjacent slices，often resulting in significant calculation errors. Based on the sliding direction of slope，the slope sliding thrust can be transferred along the sliding direction rather than along the bottom of the slices，and the improved transfer coefficient method was proposed. The calculation results of a landslide with a circular sliding surface and a landslide with a gently tipping polyline sliding surface indicate that the proposed method exhibits a safety factor error of 3.73% when compared to the strict limit equilibrium M-P method. Additionally，the curves for sliding thrust of the proposed method are completely consistent with those of the transfer coefficient method，and its curve of the angle for sliding direction is gentler than the standard method，which verifies the rationality of the proposed method in conventional slope stability analysis. Furthermore，the analysis results of a landslide with a complex polyline sliding surface indicate that，the error of safety factor between the transfer coefficient method and M-P method is 21.66%，while the relative error is 6.83% for the proposed method. Moreover，the sliding thrust of the proposed method is slightly greater than that of the standard method. These findings demonstrate that the proposed method is suitable for determining the sliding thrust of the complex landslide，which can be used as an extension and supplement of the transfer coefficient method，providing an effective design basis for landslide prevention and treatment engineering.

To investigate the deformation and strength characteristics of expansive soils after suction loading and unloading，this paper uses an improved true triaxial apparatus for unsaturated soil to realize the suction loading and unloading process，and conducts the true triaxial shear tests under different middle principal stress parameter b value on intact expansive soils. The hydraulic variation characteristics after suction loading and unloading and during the shearing process，as well as the change characteristics of volumetric strain and strength are studied. The results show that compared with those without suction loading and unloading，the void ratio，the degree of saturation and volumetric strain of expansive soil experienced wet-dry path increase，and the shear strength decreases，while the void ratio and the degree of saturation of expansive soil experienced dry-wet path decrease，the shear strength increases，and which have a greater strength and a smaller volumetric strain when it experienced greater suction. The cohesion increases with an increase in the middle principal stress，and the internal friction angle decreases with an increase in the middle principal stress. Under different values of b，the water contents of expansive soils without suction loading and unloading，experienced wet-dry path and dry-wet path(smaller suction) decrease with an increase in generalized shear strain，and the degree of saturation increase with an increase in generalized shear strain，and both water content and degree of saturation decrease with an increase in b value. The water content of expansive soil experienced dry-wet path(larger suction) increases with an increase in generalized shear strain. When b = 0，0.25 and 0.5，the degree of saturation first increases to the peak value and then decreases to the stable value. When b = 0.75 and 1，the degree of saturation first increases rapidly and then slowly increases to the stable value.

In order to explore the shear characteristics of saline soil-concrete interface under cyclic loading，a series of monotonic direct shear tests，cyclic direct shear tests，and post-cyclic direct shear tests were carried out through large-scale dynamic direct shear apparatus. The effects of 5 salt contents(0%，1%，2%，3%，4%)，3 shear displacement amplitudes(3，6，9 mm) and 3 shear frequencies(0.25，0.5，1 Hz) on cyclic shear characteristics of saline soil-concrete interface were analyzed，and the changing laws of interface shear strength under different salt contents before and after cyclic loading were also compared and analyzed. The results showed that when the salt content was 0%，1%，2% and 3%，the obvious decrement of the peak shear stress was shown in the initial cycles，and slightly increment in the subsequent cycles. When the salt content was 4%，the interface peak shear stress firstly increased to maximum shear stress at cycle number of 16，and then decreased with the increase of cycle number. During the shearing process，the change of the shear dilatation was mainly concentrated in the first ten cycles. As the number of cycles increased，the value of dilatancy reduced. The interface shear stress increased under the cyclic loading with larger shear displacement amplitude and higher shear frequency. Compared with that in monotonic direct shear tests，the interface shear strength after cyclic direct shear tests was improved. The effect of salt content on interface strength was attenuated by cyclic shearing.

It is of great significance to study the microstructure of soft soil for engineering construction. In order to investigate the microstructural characteristics of soft soil in Zhuhai，a series of mercury intrusion porosimetry (MIP) tests were conducted for soft soil samples. According to the test results，the pore diameter of soil is distributed in the range of 3 nm–338  ，the total pore volume is 0.2–0.3 mL/g，and the average pore diameter is 50–85 nm. The pore characteristics curves of soil samples show a single-peak distribution pattern. With the increase of depth，the pore volume of the soil gradually decreases，the dominant pore size gradually decreases，and the soil pore size is more concentrated. The effect of stack pre-pressure on soft soil is significant，the total pore volume can be reduced by 15%，and the porosity can be reduced by 10%. According to the cumulative mercury injection percentage curve，there are obviously two turning points，the microscopic pores of soft soil in Zhuhai can be divided into micro-pores(＜10 nm)，small pores(10–360 nm) and large pores(＞360 nm)，of which large pores account for about 4% and micro-pores account for about 5%.

Freeze-thaw cycles are an important reason for the deterioration of expansive soil mechanical properties in north Xinjiang. In this research，freeze-thaw cycle tests were carried out using a self-designed unidirectional environmental boundary loading device. On this basis，volume measurement，unconfined compressive strength，and scanning electron microscope tests were carried out. The characteristics of volume changes and mechanical properties of expansive soil at three different compaction degrees(90%，95% and 100%) were investigated. The evolution law of mechanical strength deterioration and microscopic pore development was quantitatively analyzed by grey relational analysis. The effect of pore change characteristics on the unconfined compressive strength of soil under freeze-thaw cycles was discussed. The tests results showed that the volume change of specimens gradually changed from shrinkage to swelling with the increased compaction degree. The hardening properties of expansive soils weakened with increasing compaction，and freeze-thaw cycles promoted the softening of stress-strain relationships. The unconfined compressive strength of the specimens was significantly reduced after the first freeze-thaw cycle，with attenuation amplitude from 56.07% to 67.54% after seven cycles. Freeze-thaw cycles also attenuated failure strain and resilient modulus to varying degrees. The correlation between the surface porosity and the unconfined compressive strength attenuation rate was 0.779–0.882，and the corresponding weight reached 0.467–0.471，with an excellent linear relationship. The study results provide a reference for constructing and maintaining expansive soil projects in north Xinjiang.

High-frequency radial and circumferential transverse wave interferences，and transverse inertia effect are the three key factors influencing the readability of the low strain integrity test signal. So far，the analytical solution capable of reflecting the coupling effect of these three factors has not yet been found. Modified Rayleigh-Love rod model is proposed to realize the true 3D strain wave propagation simulation across the pile-soil system. The corresponding analytical solution is derived through Laplace transform，variable separation，and inverse Fourier transform. Based on the proposed model，the formation mechanism of the high-frequency transverse wave interference and the oscillations after the reflected signals are revealed. Meanwhile，some mainstream high-frequency interference elimination methods are compared. The main conclusions can be summarized as：(1) With the increase of the pile radius，the main components of the interference transfers from the circumferential transverse wave to the radial transverse wave；(2) The pile whose radius lies between 0.2–1.0 m is more vulnerable to high-frequency interferences；(3) Arranging the signal receiving point perpendicular to the excitation position or using the signal superposition method can both better reveal the reflected signal，but the signal superposition method has a better performance on eliminating the high-frequency interferences.

PC pile is an innovative pile consisted of steel pipe pile and steel sheet pile，and each individual pile are connected with each other via locking joints. PC pile has advantage of lower environmental impact，quick construction efficiency and recycle utilization，which was frequently applied as retaining structure in deep excavations. However，systematic studies of the deformation mechanism of the PC piles retaining structure in deep excavation are rarely reported and not well understood. In this study，a cantilevered excavation model test was designed and carried out according to the similarity principal. The whole excavation process from initial state to retaining structure failure was simulated in this experimental test. The strain of pile shaft，lateral displacement at the pile top，ground surface settlements，lateral earth pressure of pile shaft，the bending moment of the pile，displacement field behind PC pile were continuously measured during the whole process of excavation，respectively. The pipe pile models and sheet pile models were manufacture by using 3D printing technology. The excavation model test was conducted in dry sand. The experimental results show that，PC pipe model piles manufactured by the 3D printing have a good precision. During the whole process of excavation，a triangular settlement shape was observed at the ground surface. As excavation went deeper，an apparent slide failure plane appeared behind the PC piles，which is about 59 degrees to horizontal plane. When excavation depth increases，PC piles change from independent supporting state of each single pile gradually to an entire enclosure structure. A “S”shaped distribution of the bending moment was observed along the sheet piles and pipe piles shaft and the deflection of both piles were quite similar to cantilever beam subjected to distributed loads. The ratio of the bending moment between pipe pile and sheet pile is approximately equal to the ratio of the bending stiffness of two piles. In cantilevered excavation，the safe installation ratio of PC piles is suggested from 2 to 2.5. The sectional shape of the PC piles affects the distribution of the earth pressure against the wall. At supported side，the earth pressure on the protruding side of the PC piles retaining structure was larger than that on the denting side when the deformation of PC pile was small. The earth pressure at the protruding side was generally smaller than that on the denting side，when a large deflection occurs in PC piles.