With the continuous expansion of the scale of rock mass engineering and the increasing complexity of the occurrence environment，the phenomenon of rock joint shear slip causing rock bolt breakage is becoming more and more prominent. It is very important to recognize the shear characteristics and shear mechanism of bolted joints for the stability control design of rock mass engineering. In this paper，the effects of full anchor and end anchor modes on the macro and micro shear properties of rock joints and their mechanisms are systematically studied through shear tests and numerical simulation of anchored joints. The results show that the presence of anchoring agent can make the bolt play its“pin role”quickly in the full-anchor mode，while the bolt does not play its role until the shear displacement exceeds the gap between the borehole and the bolt in the end-anchor mode. Before the anchor rod fractures，the peak shear stress and breaking shear stress in the full-anchor mode are greater compared to the end-anchor mode. Under the same shear displacement，the number of cracks in the anchored joint is more in the full-anchor condition compared to the end-anchor condition. Under full anchoring method，the cracks are concentrated near the anchor rod，especially at the intersection of the anchor rod and the joint，while under end anchoring method，the cracks are distributed in the end bolted，the intersection of the anchor rod and the joint and the gasket. Under the same shear displacement condition，the shear stress of full-anchored bolt is much greater than that of end-anchored bolt，but its axial stress is mainly concentrated near the joint surface due to the restriction of anchoring agent. The axial stress of end-anchored bolt is fully mobilized and can effectively increase the normal stress of the joint after being transferred to the gasket. After the peak shear displacement，the deformation range of end-anchored bolt and full-anchored bolt increases continuously，but the deformation range of end-anchored bolt is significantly larger than that of full-anchored bolt.

The deep rock mass is in the environment of high water pressure and high ground stress，and its damage evolution characteristics are affected by the occurrence environment. Acoustic wave is widely used to characterize the damage cumulative evolution degree of rocks. In order to study the rule and attenuation mechanism of acoustic wave propagation of rocks under high water pressure and high stress，based on a self-developed high water pressure and high stress rock acoustic wave testing system，6 water pressure and 5 axial static stress levels were set to simulate the deep engineering environment，and acoustic wave propagation tests were carried out on red sandstone and limestone with large porosity differences. The selection method of the head wave was determined and the head wave was analyzed by the Fourier transform. The frequency domain transmission coefficient was defined，and the variation rules of the transmission coefficient，the centroid frequency and the quality factor were analyzed. The relationship between the wave impedance and the quality factor was explored and the empirical models of rocks frequency-domain attenuation were built. The empirical models of rock frequency-domain attenuation were built. The results show that the acoustic spectrum area and transmission coefficient of red sandstone firstly increase and then decrease with the increase of the water pressure，and the water pressure and transmission coefficient have Gaussian function relationship. While the two parameters of limestone first increase then change slightly with the increase of the water pressure. The transmission coefficient of two kinds of rocks both increase first and then decrease with the increase of the axial static stress. With the increase of water pressure，the centroid frequency of red sandstone decreases linearlyand the“frequency drift”phenomenon appears，while that of limestone increases first and then decreases slowly. With the increase of axial static stress，the centroid frequency of different rocks first increase and then decrease. With the increase of water pressure，the quality factors of the two rocks first increase rapidly and then decrease，but the degree of decrease are different，the red sandstone decreases significantly，and the limestone decreases slightly. When the red sandstone and limestone are in the compaction stage，the quality factor increases，and when the rocks reach the damage stage，the quality factor decreases. The research results provide a theoretical basis for exploring acoustic research methods of rock damage evolution under deep high water pressure environment.

The basalt fiber reinforced polymer(BFRP) anchor rod has advantages such as lightweight，high tensile strength and excellent corrosion resistance. This study pioneers the application of BFRP anchor rods in the basement anti-floating of a coastal hospital. The ultimate pull-out tests were conducted on five full-threaded BFRP anti-floating anchor rods with different anchorage lengths and diameters. The failure modes of the anti-floating anchor rods were analyzed，and the load-displacement relationship of the anchor rod and the anchor body was determined. The distribution of the axial force and the shear stress along the depth of the BFRP anchor rod was investigated，and the failure mechanism of BFRP anchor rods was discussed. The research reveals that：(1) The ultimate pull-out capacity of both groups of BFRP anti-floating anchor rods exceeds 400 kN，fully satisfying the anti-floating requirements of the project. (2) With the increase in the anchorage length and the rod diameter，the ultimate pull-out capacity of the anti-floating anchor rods slightly increases，but the displacement of the rod also increases accordingly. (3) The axial stress of BFRP anchor rod is maximum at the hole opening and decreases with increasing the depth. The area of stress transfer extends approximately two-thirds of the anchorage length. It is limited to improve the pull-out bearing capacity of the anti-floating anchor road through increasing the anchorage length. (4) The shear stress in the BFRP anchor rod initially increases rapidly along the depth of the anchorage，and then gradually decreases after reaching a peak near the anchorage depth of 0.75 m. The peak shear stress increases with increasing the load level. The results of the study provide a foundation for the application of BFRP anti-floating anchor rods.

The high temperature and high stress conditions pose great challenges to the efficient exploitation of deep and ultra-deep oil and gas. To investigate the differences in the effects of real-time high temperature and heat treatment on the mechanical properties of reservoir rocks，using a self-designed multi-field coupling test system，real-time high temperature and heat-treated triaxial compression tests were carried out on carbonate rocks in Tarim Oilfield，Xinjiang. Under the two test conditions，the evolution of rock strength，deformation，failure modes，and mechanical parameters were analyzed. The results show that：(1) As the temperature increases，the critical confining pressure of brittle-ductile transformation of carbonate rocks under real-time high temperature decreases，while the critical confining pressure of rocks after heat treatment increases. (2) The elastic modulus of carbonate rock decreases with increasing temperature under both experimental conditions；the Poisson?s ratio exhibits different patterns of variation；additionally，the exponential function can be used to describe the elastic modulus and Poisson?s ratio at real-time high-temperature. (3) The fracture angle decreases with increasing confining pressure. Compared to room temperature，the fracture angle of rocks exhibits litter variation in real-time temperature，however，there is a trend of increasing after high temperature. (4) Compared to rocks after heat treatment，the influence of real-time temperature on the volumetric strain and dilatancy stress of rock is more obvious. This study contribute to our knowledge of how temperatures affect the mechanical properties of deep carbonate reservoirs under the influence of high temperatures and provide a theoretical basis for the productive and safe extraction of deep oil and gas.

To study the coupling mechanism of seepage and heat transfer in high-temperature rough rock fracture and to improve the efficiency of geothermal energy extraction，lattice Boltzmann method the double distribution functions were applied to deal with the evolution of seepage velocity field and heat transfer temperature field separately. Considering the effects of fluid temperature on its kinematic viscosity and thermal diffusion，a numerical model was proposed to simulate the coupled process of seepage and heat transfer in rough rock fracture. And the accuracy of the model was verified according to a classic example. Based on the proposed model，the effects of rough fracture surface and dynamic evolution of fluid physical parameters on the coupling mechanism of seepage and heat transfer were analyzed，and the relationship between the roughness of fracture surface and the performance indicators of geothermal extraction was discussed. The results show that the obstruction effect of the rough fracture surface increases the inertial pressure drop and reduces its seepage velocity，which makes the heat transfer between water and rock more sufficient，and the water temperature is higher at the outlet. Neglecting the influence of fluid temperature on its kinematic viscosity seriously overestimates the flow velocity，and significantly underestimates the thermal breakthrough time. As the roughness of the fracture surface intensifies，its thermal breakthrough time gradually increases，while the heat production power shows a decreasing trend. When the fractal dimension of fracture surface is 1.079 8，its thermal breakthrough time increases by 191.49% compared to the smooth fracture，and the heat production power is only 44.36% of that of smooth fracture. In addition，when the pressure drops are the same，the smoother the fracture surface is，the higher the heat recovery rate obtained within the same time. However，due to its shorter heat breakthrough time，the heat recovery rate is significantly reduced when the thermal breakthrough occurs.

The difference between the mechanical properties of rock mineral components is a key factor affecting the macroscopic friction behavior. Based on the target test method，the indentation mechanical properties of sandstone minerals are tested under eight normal loads，and the scratch friction properties of these minerals are studied under basically stable normal load. The results show that as the normal load increases，the deformation parameters(hardness and elastic modulus) of hard-phase minerals exhibit a negative indentation size effect，while the indentation size effect of deformation parameters of soft-phase minerals is not obvious，and the comprehensive basic stable normal load for the four minerals is determined as 8 mN. Under the stable normal load，as the scratch length increases，the friction force of quartz and albite in the hard-phase minerals increase rapidly and then remain stable，while the friction force of calcite and chlorite in the soft-phase minerals both increase rapidly and then slowly. Statistical calculations show that the average elastic recovery rates for the four minerals are 13.29%，15.81%，35.91% and 42.28% respectively. Further combined with the analysis of microscopic mechanism，it is found that dislocation creep and dislocation evolution of minerals are the key factors affecting the indentation size effect and scratch stick-slip behavior respectively. The above research results provide reference significance for the study of correlation between macro and micro mechanical behaviors of rocks.

Tunnels in cold regions are generally affected by freeze-thaw action，and is prone to damage and debonding along the interface between concrete lining structure and surrounding rock，which seriously affects the construction quality and safe of tunnel engineering operation. In order to improve the bonding strength and frost resistance of the tunnel surrounding rock-spray layer interface，the surrounding rock-spray layer interface is simplified into a rock-concrete binary body. The cement-based interfacial agent is developed for improving the adhesion and frost resistance of the surrounding rock-spray layer interface. A comparative test of the bonding strength and frost resistance of the sandstone-concrete interface was carried out before and after the spraying of the cement-based interface agent. The test results show that：(1) The main chain fracture parallel to the silicon-oxygen tetrahedron in the rock-concrete interface caused by freeze-thaw action is the core reason for the decrease of the bonding performance of the rock-concrete interface. (2) Through the test and development，the optimal mix ratio of cement-based interfacial agent suitable for improving the interfacial adhesion and frost resistance of tunnel spray layer in cold regions is proposed as follows∶cement∶water∶silica powder∶silane coupling agent∶polymer cementitious material(water-based acrylate peritoneal gel + bamboo liquefied phenolic resin) = 10∶4.4∶0.8∶0.2∶1∶0.5. (3) Due to the polymer hydration of the cement-based interfacial agent，the 'root pile' effect generated at the interface of the spray layer expands the degree of plugging on the contact surface between the rock and the concrete. At the same time，the chemical bonding of the silane coupling agent enhances the mechanical bite force between the interfaces. The coupling enhancement of the two improves the bond shear strength and splitting strength of the rock-concrete interface. Through comparative tests，it is found that after 30 freeze-thaw cycles，the shear strength of the rock-concrete interface can be increased by 109% compared with the untreated sample，and the bond splitting strength is increased by 78%. (4) The silicon-oxygen bond produced by the hydrolysis and condensation of siloxane in the cement-based interfacial agent is adsorbed on the hydrophobic layer formed at the rock-concrete interface，which inhibits the expansion of the interface water-rich zone；the silicon gel generated by the combined reaction releases heat by phase change，which reduces the freeze-thaw damage of the rock-concrete interface and inhibits the initiation and propagation of cracks at the rock-concrete interface. (5) The developed cement-based interfacial agent itself has good frost resistance，especially in the freeze-thaw environment of －10 ℃–10 ℃，it can effectively improve the adhesion and frost resistance of the surrounding rock-spray layer interface. This paper provides a new solution for the thickening and frost resistance treatment of tunnel surrounding rock-spray interface in cold region.

A large number of disasters caused by reservoir landslides are in the form of impulse waves in western China. If all landslides that may generate waves are prevented and controlled by current specifications，the economic cost is huge. Taking Shuipingzi #1 landslide in Baihetan reservoir as an example to carry out application demonstration in this paper，a three-dimensional physical prototype model experiment was constructed with a geometric scale of 1∶150，and landslide energy reduction and wave descent experiments were carried out to find more economical landslide-induced impulse wave risk reduction solution. Physical test shows that under extreme conditions of the impounding water level with 825 m above sea level combined with a VIII-degree earthquake，the landslide would slide into Baihetan reservoir with the maximum speed of 7.37 m/s，and the maximum generated wave amplitude would be 7.59 m. The maximum runup around Xiangbiling community is about 3.5 m above the ground，which would seriously threaten the safety of the riverway with the length of more than 4.5 km and the safety of Xiangbiling community. As the removal volume increases from 10×104 m3 to 47.9×104 m3，the effect of reducing energy and wave becomes evident. Wave making energy transmitted from landslide decreases by about 94.8%，and the maximum wave amplitude and the maximum runup around the Xiangbiling decreased to 4.35 m and 1.73 m，respectively. The area with the impulse wave larger than 1 m is only distributed in the landslide course and the opposite bank of Jinsha River，and the risk of landslide-induced impulse wave decreases sharply. Based on this，this study proposed and discussed the feedback design mentality and the realization method of the safety margin of landslide-induced impulse wave risk reduction engineering design，which using the hazard degree of landslide-induce impulse wave as a measurement indicator，and recommended a risk reduction design scheme that can greatly reduce the economic cost of Shuipingzi #1 landslide treatment. The design mentality of risk reduction prevention for landslide-induced impulse wave is a useful supplement of landslide control specification，which has yet to be further developed and promoted.

In order to study the response relationship between the vibration signal with drilling and the geomechanical parameters of the rock mass，and to perceive and predict the uniaxial compressive strength of the rock accurately and quickly，a research on the prediction of uniaxial compressive strength of the rock based on the vibration signal with drilling was carried out. Based on indoor drilling experiments of four types of raw rock(coal) specimens，namely granite，limestone，sandstone and coal，the GA-BP neural network model was constructed by combining Fourier transform and vibration signal noise reduction methods，and the prediction performance of the model before and after the noise reduction，as well as the models with different noise reduction methods，were compared and analyzed. The results show that there is a responsive relationship between the vibration signal with drilling and the uniaxial compressive strength of rock，and the uniaxial compressive strength of rock can be predicted by using the vibration signal while drilling. The GA-BP neural network prediction model using Adobe Audition software to denoise the vibration signal has a determination coefficient R2 of 0.838，a root mean square error of 7.063 MPa，and an average absolute error of 5.347 MPa. The results are better than the original prediction model and the general noise reduction method prediction model. Compared with the original prediction model，the prediction accuracy of the optimal noise reduction model is improved by 6.3 %，the root mean square error is reduced by 1.954 MPa，and the average absolute error is reduced by 1.621 MPa. There are some differences in the prediction effect of different lithology in the same prediction model. The GA-BP neural network prediction model of noise reduction signal has excellent prediction ability for uniaxial compressive strength. The method can provide a basis for the measurement of rock mass geomechanical parameters while drilling.

In order to reflect the compressive shear failure mode of rock in the process of compression，and to solve the problem that the original multi-scale rock damage mechanics constitutive model cannot describe the shear weakening，a new nonlinear mesoscopic damage-plastic coupling constitutive model is established in the framework of multi-scale rock damage mechanics by introducing local Mohr-Coulomb plastic yield function. The analytical solution of the constitutive model under conventional triaxial compression is derived，and the calibration method of all parameters of the constitutive model is given. The optimized semi-implicit decoupling algorithm is used to write the constitutive model into LS-DYNA material library，and the convergence and calculation speed of the algorithm are verified by unit test. The triaxial compressive mechanical properties of limestone are simulated by using the proposed meso-mechanical damage model. The numerical simulation results are in good agreement with the experimental data. The influences of the constitutive model parameters on the peak stress，peak strain and brittle-ductile transition of rock are obtained by the sensitivity analysis of constitutive model parameters. The established constitutive model does not need to introduce additional hardening/softening functions，significantly reduces the number of model parameters，and the parameters have a strict calibration method. The correlation flow law can be used to accurately describe the axial，transverse and shear nonlinear mechanical behavior. The convergence of the optimized semi-implicit decoupling algorithm is good，and the calculation process of the compiled LS DYNA solver is stable，and the calculation speed is significantly faster than that of the traditional phenomenological model of rock，which is of great significance for the practical application of the constitutive model.

To improve the design approach of anchor plate supporting slope，the calculation formula of anchor plate size is proposed according to the internal balance of slopes，and the formula of the safety factor of unsaturated anchor plate supporting slope is obtained through the variational method combining limit balance method. By using transient seepage to simulate rainfall conditions，the variation rule of the slope safety factor with the rainfall time is obtained，and the internal mechanism of the slope safety factor variation is analyzed. The results of safety factor are compared with the results of the existing methods by 4 examples，and the rationality of the suggested formula is verified. The effects of the rainfall intensity，seismic conditions and anchor plate supporting conditions on slope stability and sliding surface are analyzed. The results show that heavy rainfall and earthquakes will significantly reduce slope stability. Horizontal and vertical seismic forces will lead to deeper sliding surface，while vertical downward seismic forces will lead to shallower sliding surface. The proposed approach can not only calculate the safety factor of saturated and unsaturated slope，but also calculate the safety factor of slope under transient seepage and steady seepage，and has strong applicability. In order to facilitate the engineering application，by comparing the slope safety factor when the anchor plates are arranged at different vertical spacing，the vertical 3m spacing arrangement of the anchor plate is given as engineering suggestion. A simple method for the size design of anchor plate is presented. The size of anchor plate obtained by the simple design approach is much lower than the existing empirical design size.

In order to study the mechanical properties and failure characteristics of the coal-rock combination with different stiffness ratios，coal samples and rock samples with different elastic modulus were combined to construct composite coal-rock samples for tests. Uniaxial compressive tests were carried out to evaluate the response of the combined samples including the macro and micro failure characteristics. The debris of coal samples was collected after test to quantify the spacial and scale distribution characteristics. The ejection process of the debris during failure was recorded using a high-speed camera and then used to analyze the ejection parameters such as the volume，velocity，momentum and kinetic energy of the debris which were then used to quantitatively evaluate the damage intensity of coal samples with different stiffness ratio combinations. The deformation characteristics of the loading process are obtained by using the strain gauge pasted on the surface of the sample，and the energy evolution is calculated by combining the load data recorded by the testing machine. The impact failure mechanism of the middling coal sample of the combined sample is analyzed from the energy perspective. The research findings are as follows：(1) Impact failure occurs to middling coal samples of combined samples，and the rock is compressed during the loading stage to accumulate elastic strain energy. When the coal sample is damaged，more than 90% of the accumulated energy releases to work on the coal sample with the rebound deformation of the rock，leading to the impact failure of the coal sample. (2) The axial deformation of composite specimens is a comprehensive deformation of rock and coal samples. The axial deformation of coal samples is relatively constant at peak strength，and the difference in axial deformation of composite specimens under different combination modes mainly depends on the rock. The axial strain of rock at peak strength decreases with the increase of elastic modulus. (3) As the elastic modulus of the rock decreases，the pre peak deformation increases in an inverse proportional function，the accumulation of elastic strain energy increases，and the post peak energy release rapidly increases，leading to a nonlinear intensification of the coal sample failure intensity as the elastic modulus of the rock decreases. (4) The nonlinear characteristics of parameters such as axial strain of rock at peak strength and failure intensity of coal samples with respect to the evolution of rock elastic modulus in composite samples are prominent：when the elastic modulus of rock and coal samples is at the same level，the response of each parameter to the change of rock elastic modulus is significant；When the elastic modulus of rocks is significantly higher than that of coal samples，the response of various parameters to the elastic modulus of rocks weakens.

End-anchored prestressed anchor cables，as an effective and economical reinforcement method，are widely used in rock support applications. Shear failure for the free section of end-anchored anchor cables is a common failure type of anchor cables in engineering practice. Its failure mechanism differs from that of full length anchoring cables，which requires further in-depth research. By using the research methods of laboratory test，theoretical analysis and numerical simulation，the characteristics of shear failure in the free section of anchor cables were clarified，and the mechanical mechanism and micro-evolution laws of shear failure in prestressed anchor cables were revealed. The study showed that the shear action on joint surfaces caused coupled growth of axial and shear forces inside the anchor cable，and the steel strands at the fracture exhibited both tensile and shear failure modes. The axial force and shear force in the anchor cable at the inflection point were positively correlated. Based on the combined tensile-shear failure criterion，the mechanism of shear failure in anchor cables was well explained. During the shear process，there were both tensile stress concentration area and tensile-shear composite stress concentration area. Shear damage on the surface of the outer steel strands of the anchor cable resulted in earlier failure，and the evolution law of internal forces in the anchor cable confirms that shear failure in the anchor cable was a combination of tension and shear failure. The research results provide a reference for the development of anchor cable support technology.

Carbon storage is an effective way to reduce CO2 emissions and mitigate environmental problems such as global warming. The porosity and permeability characteristics of storage reservoir are the key factors to determine the efficiency of CO2 storage，among which one important mechanism is the weakening of calcite cementation by acid erosion，and it is therefore necessary to carry out the researches on weakly cemented sandstone sensitive to acid. This study developed a prepare method of acid-sensitive weakly cemented artificial sandstone，conducted the deformation analysis of acid-sensitive weakly cemented sandstone during acid erosion process，and investigated the change laws of sandstone permeability before and after acid erosion. Firstly，based on the response surface experimental method，the effects of different urease activity，concentration of cementing fluid and concentration of skim milk powder on the strength of acid-sensitive weakly cemented artificial sandstone were studied，and a regression model considering multiple factors was established. Secondly，the acid erosion seepage tests of acid-sensitivity weakly cemented artificial sandstone under different stresses were carried out to analyse the deformation of sandstone during acid erosion：During acid erosion，the sandstone strain increases linearly with the acid flow，and the cementation weakening induced by acid erosion seepage can make the sandstone shrinkage strain exceed 4%. Finally，the change of sandstone permeability before and after acid erosion was studied：The permeability reduced by 70% under high confining pressure. The study reveals the acid erosion characteristics of weakly cemented sandstone，which has a certain guidance on CO2 geological storage project.

In order to explore the strength，deformation and damage characteristics of the roof sandstone damaged by blasting load under different confining pressure conditions，triaxial compression tests were carried out on three sandstone specimens with different damage degrees by triaxial loading system，and the microstructure of the specimens with different damage degrees was obtained by electronic digital microscope. The effects of blasting load damage and confining pressure on the strength，cohesion，volume strain，fracture morphology and microstructure of sandstone specimens are analyzed. The results showed as follows：(1) Compared with the undamaged specimens，the damage degree of vibration damage and blast damage specimens at 0 MPa perimeter pressure is 5.53% and 18.87%，respectively. The peak stress，cohesion and internal friction angle of undamaged specimens are higher than those of vibration-damaged specimens and blasting damaged specimens. The blasting load causes obvious deterioration of sandstone strength，and the damage degree of blasting damaged specimens is higher than that of vibrating damaged specimens. (2) The peak stress of specimens with different damage degrees increased linearly with the increase of confining pressure，and the existence of confining pressure limited the deformation of specimens，and the deformation degree of specimens subjected to confining pressure was smaller when they reached the same stress. (3) The ultimate volume strain of the undamaged specimen at 0 MPa confining pressure is 1.65 and 1.46 times that of the vibration-damaged specimen and the blasting damaged specimen，and 1.85 and 1.49 times that of the vibration-damaged specimen and the blasting damaged specimen at 10 MPa confining pressure. The whole homogeneity and bearing capacity of undamaged specimens are higher，and the deformation degree of undamaged specimens under load is greater. (4) With the increase of confining pressure，the fracture degree of the specimen decreases first and then increases，and the specimen shows multiple failure modes of shear failure，tensile failure and compression failure co-existing. A large number of new joints，cracks and faults are generated in sandstone damaged by blasting load at the mesostructural level，and the damage degree in the blasting damage area is higher than that in the vibration damage area.

In order to reduce the deformation of tunnels located in broken surrounding rock with high ground stresses，the advantages and disadvantages of different types of bolts(cables) are analyzed. Combined with model test，a new type of prestressed pipe-cable(PPC) structure for tunnels is developed. This study introduces the bearing mechanism of the new developed PPC structure and sets up a coupling mechanical bearing model based on the PPC structure by theoretical analysis. Furthermore，the bearing effect of PPC structure is systematically analyzed. Finally，the reliability of the new structure is verified by field test. The research results indicate that the PPC structure can reinforcement the rockmass by grouting and forming a bearing structure. More importantly，the PPC structure can amplify support capacity. The PPC structure，it is important to adopt grout to improve the mechanical parameters of surrounding rockmass，but adjusting the row spacing between adjacent PPC to improve the bearing capacity of surrounding rock is more direct and efficient. Further analysis indicate that the reasonable thickness b1 of the shallow prestressed body is about 0.8 times of the tunnel radius r0，and the reasonable thickness b2 of the deep prestressed body is 1.44 times of tunnel radius，which can provide theoretical basis for the parameter design of the PPC. The field test shows that the prestressed pipe-cable support can effectively improve the stability of soft and broken surrounding rock，and can provide reference for similar projects.

Sandstone grotto temples are subject to varying degrees of weathering damage when exposed to freeze-thaw cycles. This study focuses on the North Grottoes in Gansu，employing a multi-faceted approach based on the coupled relationships of numerous environmental factors. Large-scale sandstone weathering simulations were conducted in a sophisticated multi-field coupling laboratory under conditions emulating snowfall-temperature variations. The findings reveal that repetitive snowfall-temperature fluctuations induce freeze-thaw cycles，causing significant microstructural changes in the sandstone. At the microscopic level，freeze-thaw cycles result in the nearly complete dissolution of surface sandstone cementation. Internally，the sandstone exhibits a degradation characterized by a predominant contact-type cementation breakdown，accompanied by a noticeable increase in pore volume and size. Macroscopically，there is a discernible augmentation in the depth of moisture infiltration，coinciding with a progressive expansion of damaged regions and an intensification in the severity of observed deterioration. Surface manifestations include warping，detachment，deepening discoloration，and widening of cracks. Mechanically，there is a gradual decline in strength. Moreover，a categorization of five distinct response-sensitive zones was established based on different sandstone rock types. This classification sheds light on the progressive cumulative weathering mechanism of sandstone under the influence of snowfall-temperature fluctuations.

The mud pumping disease under multi-stage/multi-frequency train loading-wetting coupling seriously affects the normal operation of railways，and its mechanism is still unclear. The model test study on the mud pumping particle migration and dynamic characteristics in ballasted track subgrade under multi-stage/ multi-frequency train loading-wetting(MSC-W/MFC-W) coupling was carried out. The test results show that under the unsaturated state，there is no significant particle migration phenomenon in the two working conditions，the accumulated axial deformation under the MSC-W working condition is more significant than that under the MFC-W working condition；Under the saturated or near saturated condition，the two working conditions result in significant mud pumping phenomenon by the driving force of dynamic pore water pressure. The mud pumping degree，fine particle layer displacement and ballast fouling index under MFC-W working condition are significantly higher than those under MSC-W working condition；Thus，special attention should be given to the prevention and control of subgrade mud pumping during the speed-raising reconstruction of the existing railway with frequent rainfall.

The microstructure of sand-structure interface would evolve due to resulting in the state dependence of its stress-displacement behavior. A series of monotonic and cyclic interface direct shear tests on the sand-steel interface under constant normal stiffness(CNS) and constant normal load(CNL) conditions were carried out，where the evolution of the microstructure within the interface was analyzed using high-resolution image identification technique. It was found that different extents of interface dilatancy occurred under monotonic tests with CNS and CNL. Higher extent of dilatancy and microstructure evolution took place under CNL，where the particle probabilistic entropy increased with the shear displacement. When subjected to cyclic shearing，the interface with initial state under the critical state line exhibited contraction and dilatancy alternately. As the load cycles increased，the microstructure within the interface evolved，with an alternately increase or decrease in the particle probabilistic entropy，which resulted in an overall contraction of the interface. Thus，microstructure evolution influences the interface dilatancy. To capture these phenomena，a microstructure-dependent dilatancy state line was proposed，based on which a nonassociated kinematic hardening elastoplastic model for sand-structure interface was developed. The model had 12 parameters，which can be all determined from laboratory test. Simulations of the test data revealed that the model can reasonably capture the dilatancy and softening behaviors，etc.，of the interface，especially the strong contraction behavior under cyclic loads.