Swelling mudstone exhibits distinct physical behaviors of softening and expansibility when exposed to  water，which have a significant impact on the stability of engineering rock masses. In order to investigate the effects of hydration and expansion on the mechanical properties of mudstone，this study introduces the Weibull distribution statistical damage theory and the humidity stress field theory. The expansion strain of mudstone is used to represent its expansive behavior，while the influence of moisture content reflects the water weakening effect. A statistical damage constitutive model considering both hydration and expansion effects is developed. The model?s validity is verified by compression test results of mudstone specimens with varying water contents，establishing a quantitative relationship between the statistical parameters in the model and the water content. The effect of linear swelling coefficient，residual strength，confining pressure，proportional parameters and shape parameters on the mechanical response of mudstone is analyzed. The results demonstrate that：(1) The constructed statistical damage model effectively describes the mechanical response of mudstone under different water content conditions. The proportional parameters and shape parameters in the model are expressed as nonlinear functions of water content，influencing the peak strength and post-peak softening characteristics of mudstone，respectively. (2) Mudstone exhibits significant water weakening characteristics in terms of elastic modulus，peak strength and residual strength，with the degree of hydration significantly influencing the damage evolution process，making the mudstone microelements more susceptible to failure as the water content increases. (3) The linear swelling coefficient shows a negative linear relationship with the peak strength，and the swelling effect facilitates the transition of the rock to enter the post-peak softening stage. The residual strength determines the final bearing capacity after the peak，enhancement the post-peak deformation ductility. Moreover，increase of confining pressure，results in corresponding enhancements in peak strength and residual strength of mudstone，consistent with experimental observations，indicating the rationality and reliability of the proposed statistical damage constitutive model.

Based on the unified strength theory and non-associated flow rule，a whole-process analytical theory for the coupled deformation of deep circular tunnel surrounding rock and prestressed bolts(cables) system is derived，taking into account the strain softening characteristic of rock mass，the yield reinforced characteristics of bolts(cables) and the support timing. An analytical method for calculating the displacement difference of bolts(cables) is proposed，and the necessity of monitoring the elongation rate of bolts(cables) in high-stress tunnels is demonstrated：The displacement difference generated during the coordinated deformation of the bolts(cables) and the surrounding rock provides support resistance，thus the elongation rate safety margin standard can be used to assess the integrity and effectiveness of the support structure during the process of bolts(cables) action in real time. On the basis of verifying the rationality of the analytical theory through numerical simulation using Abaqus，the ground response curves(GRC) under bolts(cables) support with different prestressed，support timing，and intermediate principal stress coefficient are compared and analyzed. The results show that the bolts(cables) can significantly reduce the convergence of surrounding rock. With prestressed bolts support，the GRC exhibits a stepwise drop，which significantly and timely reduces the support force required for the equilibrium of surrounding rock. As the stress is gradually released，the active and passive bolts(cables) enter the stage of low-speed stress increase after yielding，and the GRC of surrounding rock under support of different prestresses gradually converge. The timing of support affects the starting point of the bolts(cables) function. The earlier the support，the more significant the displacement control effect，but it will also lead to a larger elongation rate of the bolts(cables). The intermediate principal stress coefficient reflects the self-bearing capacity of the surrounding rock，and increasing this value can improve the deformation control performance of the surrounding rock under bolts(cables) support as a whole，and reduce the elongation rate through the coupled function of the surrounding rock-bolts(cables) system. This study provides a theoretical and computational method for the analysis of prestressed bolts(cables) support and support structure safety in tunnel engineering，and can provide reference for convergence analysis of circular tunnels in underground engineering.

In order to explore the cyclic impact dynamic characteristics and crack propagation law of coal under different initial gas pressures，the cyclic impact test of coal under different initial gas pressures is carried out by using the combined dynamic and dynamic loading test system of coal-rock containing gas，and the dynamic stress-strain curve of gas-bearing coal under cyclic impact load is obtained. The relationship between coal dynamic parameters and initial gas pressure under cyclic impact is analyzed，3D visualization and fine quantitative characterization of crack propagation process before and after cyclic impact of gas-bearing coal are realized by CT scanning technology. The results show that：(1) the dynamic stress-strain curves of gas-bearing coal under cyclic impact load are basically similar，which are divided into three stages：linear elastic stage，plastic stage and unloading stage. The dynamic parameters of coal under impact load decrease with the increase of the initial gas pressure，and the greater the initial gas pressure，the stronger the gas weakening erosion effect. (2) Based on the fracture slices extracted by CT scanning and the reconstructed 3D fracture results，it is shown that annular parallel cracks and axial splitting through cracks exist in the impinged coal. The crack propagation process can be effectively and quantitatively characterized by two-dimensional and three-dimensional fracture characteristic parameters of gas-bearing coal，and the characteristic parameters are proportional to the initial gas pressure. Under high gas pressure environment，the fracture network in coal body is more complex，the connectivity is higher，and the instability failure is more likely to occur. (3) Based on theoretical analysis，the causes of strength damage and deterioration of coal body are revealed from the perspective of gas erosion and internal stress wave propagation of coal body. Combined with the damage effect of gas and dynamic load on coal body，the causes of strapping failure of cyclic impact coal body under the action of gas are discussed. The research results are helpful to enrich the dynamic theory of gas-bearing coal and have a certain theoretical reference significance for the prevention and warning of coal and gas outburst disaster in mine.

为了研究深部回采煤巷开挖扰动引起的围岩径向梯度损伤特征，以平顶山十一矿深井工程为背景，对现场煤样开展不同围压条件下三轴压缩试验和三轴损伤试验，结合三轴压缩轴向应力–应变曲线研究煤样的变形特征；利用MATLAB软件识别并分析三轴损伤煤样的破裂特征。结果表明：轴向应力达到屈服强度后，煤样出现明显的应变软化特性，峰值应力与残余强度随围压呈线性增长，利用M-C强度准则计算出煤样黏聚力c = 10.19 MPa，内摩擦角? = 27.26°。煤样表面裂纹对轴压敏感度较高，轴压越大，煤样表面裂纹越复杂，围压的增加在一定程度上可以抑制表面裂纹的扩展，但最终都会向剪切破裂面发展。基于岩石损伤变量服从Weibull分布的特点，理论推导了常规三轴下的煤样损伤软化本构模型，结合三轴损伤煤样应力–应变变化关系，采用线性拟合方法对模型参数F0和m进行修正，最终得到了修正的煤样损伤软化本构模型，并基于试验数据验证了修正模型的可靠性。此外，在修正后的煤样损伤软化本构模型基础上对弹性区、塑性软化区以及破碎区围岩应力、应变的关系式展开讨论，建立了一种巷道围岩径向梯度损伤程度的计算方法。

To evaluate impacts of gas pressure on permeability and slippage effect of gas hydrate bearing coal，the permeability was measured for gas hydrate bearing coal under different gas hydrate saturations，particle sizes and gas pressures，by using triaxial testing machine for coupling action of stress，seepage and chemical effect. Then，the relationship between the gas hydrate saturation and the slippage effect was quantified by combining with the secondary permeability correction equation. Furthermore，the slippage effect was quantitatively evaluated on the permeability. The results show that：(1) The permeability of gas hydrate bearing coal exponentially decreases with the increase of the gas pressure with a reduction between 14.6% and 66.4%，and the permeability variation can be divided into two stages，including accelerated decrease stage and stable variation stage. (2) The permeability change rate and the gas pressure sensitivity coefficient are introduced to evaluate the sensitivity of the permeability of gas hydrate bearing coal to the gas pressure. The permeability change rate and the gas pressure sensitivity coefficient respectively increase and decrease rapidly with the increase of the gas pressure，if the gas pressure is less than 1.50 or 1.625 MPa，indicating that the sensitivity of the gas pressure is significant. (3) The hydrate saturation has significant influence on the slippage effect and the slippage factor decreases with the increase of the hydrate saturation. (4) The influence rate of the slippage effect on the permeability of the gas hydrate bearing coal ranges from 30.1% to 98.2%，and the influence rate of the slippage effect exponentially decreases with the increase of the gas pressure. The results can provide experimental reference for hydrate method application in coal and gas outburst prevention.

The advanced support pressure produced in the mining process is an important factor leading to the development，expansion and penetration of fault fracture zones. Grouting is an important means to control the stability of surrounding rock. In order to analyze the reinforcement effect of grouting on surrounding rock near fault fissure zones under stress disturbance，disturbance rule of surrounding rock in fault fissure zones under stress disturbance and reinforcement mechanism of grouting were studied in this paper，by using similar material simulation tests to obtain surrounding rock collapse，displacement change data and stress change data，and numerical simulation tests to obtain damage nephogram，shear stress curve and other parameters. The results show that the advanced support pressure disturbance caused by mining is a dynamic evolution process as the working face advances. This stress can induce the development and expansion of fault fracture zones，and the stress value of the fault fracture zone increases as it is closer to the working face location and the stress concentration at the end of the fault fracture zone is obvious. As the distance between the excavation surface of the working face and the fault structural surface decreases，the disturbance of advanced support pressure causes uneven distribution of damage in fault fracture zones；Grouting makes the fault more stable and results in the hanging and foot walls more tightly bonded，reducing the barrier effect of the fault on stress. Grouting effectively inhibits the development and expansion trend of fault fracture zones，making them difficult to activate，thereby reducing the trend of fault slip.

To investigate the evolution characteristics of stress and rock structure under high stresses，a testing method for the evolution of the in-situ stress was studied based on the rheological recovery method，which can monitor the disturbed stress in surrounding rock. Based on the weak reflection fiber grating technology and time division multiplexing principle，a large deformation sensor was developed and a real-time monitoring method for rock structure was developed. Further，the distribution of the fractured zone，damage expansion zone and continuous deformation zone under excavation and unloading conditions of deep roadway was studied. The distribution characteristics of stress and the range of damage expansion zone under polar coordinates were derived. The bearing capacity considering the coupling effect of surrounding rock and support was further analyzed，and the proper intervention timing of each support measures was proposed. Subsequently，the intervention timing of support measures such as pre-tensioned bolt，steel support，shotcrete，pre-tensioned cable and deep grouting for different grades of surrounding rock was studied. And the step-wised combined support technology for intervention of rock structure was studied. Support measures should be conducted at a proper timing during the evolution of structure. Pre-tensioned bolt should be applied as early as possible after excavation to restore the normal stress on the roadway surface. Shallow grouting can be carried out when Rr extends to approximately 2Rb/3. Pre-tensioned cable should be installed before the damage expansion area(Rf) exceeds the primary support range of bolts(Rb) and the action range of cables(Rc)，which is favorable for releasing high pressure and hindering rapid expansion of the failure zone. The intervention timing of deep grouting can be implemented when of the fractured zone(Rr) expands to approximately 3Rc/4.

To explore the characteristics and mechanism of pillar burst at engineering sites，this paper uses cubic red sandstone to carry out pillar burst experiments under the condition of four-faces unloading and uniaxial compression conditions. The process of rock failure，acoustic emission(AE) characteristics，velocity field characteristics，debris characteristics and energy evolution characteristics were obtained. The results show that the failure process of uniaxial compression and pillar burst is similar，but the failure modes are different. The unloading process will aggravate the damage，and the higher the confining pressure，the greater the damage caused by unloading. The debris of uniaxial compression is massive and plate-shaped，while the debris of the pillar burst is long strips. The ejection velocity increases first and then decreases，reaching the peak at the moment of the burst，and the maximum velocity increases with the increase of the confining pressure. The distribution range of the AE spectrum is different，the spectrum is concentrated at 300–350 kHz when the confining pressure is low，and the spectrum is concentrated at 150–200 kHz when the confining pressure is high. The waveform energy of uniaxial compression distributes in complex multi-frequency bands，while the waveform energy of pillar burst distributes in single frequency band，and there is a good correspondence between different frequency bands and crack types.

为了准确识别不同围压条件下岩石加载过程中的峰前特征应力，在GCTS RTX–3000试验机上对砂岩标准试样进行围压分别为0，10，30，50和70 MPa的假三轴试验，采用超声波测试系统和声发射采集系统同时监测，获得砂岩加载过程中超声波波速的变化规律和声发射定位事件的分布特征，提出一种能够从声发射采集的数据中屏蔽超声波干扰信号的方法。结果表明：试样纵、横波波速随着围压的增加呈二次函数关系，随着轴压的增加呈现增长–平稳–下降的变化规律，横波波速总是先于纵波波速出现下降趋势，横波相较于纵波对损伤更加敏感；对比体积应变、声发射、超声波和动态弹性参数的变化规律，能够准确判定试样的峰前特征应力，闭合应力对应横波波速上升结束时刻，起裂应力对应横波波速开始下降时刻以及动弹性模量的拐点，损伤应力能够通过纵波波速开始下降、声发射信号快速上升时刻和体积应变的拐点共同确定；声发射定位能够直观反应试样的破坏模式，低围压条件下，试样发生劈裂–剪切混合破坏，高围压条件下，试样发生剪切破坏。该研究有助于准确识别岩石受载时的峰前特征应力，深入了解不同应力条件下岩石的损伤特征，对深部地下工程岩体的稳定性评价有重要的理论意义。

In order to study the effects of loading strain rate and supercritical CO2 on the mechanical properties of coal rock，uniaxial compression experiments of un-soaked and supercritical CO2 soaked coal rock are carried out under different quasi-static strain rate(10－5，10－4，10－3，10－2 s－1) loading. The energy signals during the loading process are recorded by acoustic emission monitoring system. The uniaxial compressive strength，elastic modulus，failure mode，energy evolution and AE characteristic parameters of the tested coal rock are studied from the perspective of strain rate effect and ScCO2 soaking weakened mechanism. The results show that：(1) With the increase of the loading strain rate，the compressive strength and elastic modulus of the un-soaked and supercritical CO2-soaked coal rock increase at first and decrease later. Under the loading strain rates of 10－5 and 10－2 s－1，the deterioration of mechanical properties of coal soaked in supercritical CO2 is more obvious. The uniaxial compressive strength of coal rock is reduced by 28.66% and 34.98%，and the corresponding elastic modulus is reduced by 35.50% and 27.68%，respectively. (2) The failure mode of un-soaked supercritical CO2 coal rock is mainly in the style of the X-shaped conjugated shear failure，while the failure mode of the supercritical CO2 soaked coal rock changes from inclined shear failure to vertical splitting tensile failure with the loading rate increase. (3) Both the loading strain rate and ScCO2 have effects on the mechanical properties of coal and rock. They also affect the elastic strain energy stored in the tested coal rock. It can be proved from the measured acoustic emission signal which characterizes the energy release during the failure process of the coal rock. This study is not only meaningful for revealing the variation law of mechanical properties of the supercritical CO2-soaked coal rock under different loading rates，but also helpful for understanding the coal rock deformation and fracture characteristics during fracturing of coal reservoirs.

In order to solve the surrounding rock support problems in rapid heading faces with heading and anchoring integration，taking the headgate in No. 2 Coal Mine of Huangling Mine as the engineering background，based on the field investigation of heading technology current situation，the idea of partitioned parallel anchoring is proposed，and the partitioned parallel anchoring technology in rapid heading face is systematic studied through numerical simulation and engineering practice. Numerical simulation results show that the surrounding rock stress of the entry is redistributed during excavation，the stress peak is about 3 m in front of heading face，the rock mass within and around the entry contour begin to deform at this position. The entry shallow rock strata within 2 m behind heading face are still in three-dimensional stress state，the surrounding rock deformation and damage amplitude are small at the initial stage of entry formation. The surrounding rock stress tend to be relatively stable at the position about 7 m behind heading face，while the surrounding rock deformation and failure tend to be relatively stable at the position about 8 m behind heading face. The stress state，the principal stress magnitude and direction in shallow rock of entry roof are changed fundamentally，and the principal stress in shallow rock of entry side is decreased significantly after excavation. On this basis，the mechanism of partitioned parallel anchoring is proposed：the surrounding rock near heading face should be anchored timely to form a local anchoring system within the range where the shallow strata of entry roof still have a certain vertical stress，the shallow strata of entry side still have a certain horizontal stress，and the deformation and damage of surrounding rock are small，at the same time，the remaining bolts and anchor cables are quickly installed in the relatively stable area behind heading face to form an integral anchoring system. Combined with the actual mining conditions，the partitioned parallel anchoring scheme is proposed，the effect of partitioned parallel anchoring is demonstrated by numerical simulation，and the heading cycle operation technology and parallel anchoring technology are determined. Practice shows that the partitioned parallel anchoring technology ensure the smooth implementation of rapid heading with heading and anchoring integration，the average monthly footage is increased by more than 124%，the parallel operation time is increased to more than 50%，and the heading efficiency is significantly improved. The stress of anchoring system is reasonable，the surrounding rock deformation is small，and the entry is stable as a whole，which provides effective alternative to control the surrounding rock in rapid heading faces with heading and anchoring integration under similar conditions.

Stability analysis of roof wedge is an important means to assess the risk of tunnel roof instability，and uncertainty analysis methods are widely applied in the field of geotechnical engineering. For the low computational efficiency caused by the high nonlinearity of the real function of the wedge，the linear response surface function was used to approximately replace the function of wedge. At the same time，upgrading the selection of sampling points in traditional response surface method，a reliability method for tunnel roof wedge was proposed based on vector projection response surface method. Then，the traditional RSM was improved(IRSM). Basing on a classical failure model of wedge，the effectiveness of the method was verified. The influence of parameter variability，probability distribution type and correlation on tunnel stability were systematically discussed. The results show that the accuracy and efficiency of the proposed method is higher than first order reliability method and Monte Carlo simulation. IRSM can not only ensure the accuracy，but also avoid the gradient solution of complex nonlinear performance functions，greatly simplify the calculation process and significantly improve the efficiency. The uncertainty of rock and soil mass parameters has a significant impact on the failure probability of tunnel roof wedge. The uncertainty of rock and soil parameters has a significant impact on the failure probability of the tunnel roof wedge. The variability of effective friction angle and the positive correlation between joint effective friction angle and semi-apical angle have the most remarkable effect on the failure probability. It is recommended that the coefficient of variation COV = 0.2 should be the threshold for selecting the probability distribution.

In order to investigate the deformation characteristic and failure mechanism of deep-buried clay tunnels in urban，the similarity model test was conducted in this paper. The full-section excavation apparatus of tunnels was used in the model test. The displacement，ground pressure and strain devices were adopted to explore the tunnel mechanical responses under different buried depths. The failure modes of the tunnel lining were analyzed，and the effectiveness of model test was verified by numerical simulation. The results indicate soil cracks induced by compression-shear stress are distributed above the tunnel face after tunnel is excavated. The uneven longitudinal settlement of soil is induced by excavation，and the settlement near the entrance of tunnel is the most significant. Under the buried depth of 50–500 m，the soil settlement decreases with the increase of the depth，and the attenuation magnitude of the ground pressure in the vertical direction is greater than that in the horizontal direction. The ground pressure is the most significant at the tunnel invert，followed by the right tunnel waist and the crown. The left tunnel waist has the smallest ground pressure. The bearing capacity of the tunnel lining reaches the limit when the buried depth is 150 m. The damage of the right part of the lining is more severe than that on the left part under asymmetric loads，and the convergence deformation of the lining is similar to“horizontal egg”shape. The convergence of the tunnel crown at the entrance of the tunnel is the most significant，while the largest horizontal expansion occurs at the end of the lining. The test results reveal the interaction between the surrounding soil and tunnel structure of deep-buried clay tunnel. It will provide references for the safety of deep-buried metro tunnel construction.

In order to study the bearing characteristics and landslide thrust of large-diameter anti-slide piles in the treatment of revived accumulation landslides，based on the Treatment Project of H1 landslide at the Jiangdingya of Zhouqu County，steel bar stress gauges and concrete strain gauges were respectively arranged at the middle and corners of the front and back sides to sliding surface of the three large-diameter anti-slide piles，and earth pressure cells facing the sliding surface are arranged outside the retaining walls of the anti-slide piles. In this way，the long-term monitoring results were analyzed. The results show that：(1) The large-diameter anti-slide piles present good mechanical properties and have many extreme stress points on the front and back sides to the sliding surface. The design of anti-slide piles in the treatment of revived accumulation landslides should not be directly calculated by the current way；(2) In the section of large diameter anti-slide piles，the stress of the steel bar in the middle and corner along the width direction is not equal. The maximum tensile stress on the steel bar in the middle part of the front side to sliding surface can reach 2.4 times of the stress on the steel bar in the corner. It is not suitable to adopt the method recommended by the current code directly in the design of anti-slide pile in the treatment of resurrected accumulation body landslide；(3) The pile bending moment calculated according to the measured results has several extreme points，and the shear force of the anti-slide pile has multiple zero points，which indicates that there are multiple sliding surfaces in the revived accumulation landslide. The positions of the primary and secondary sliding surfaces should be considered in the subsequent landslides treatment project；(4) The distribution form of landslide thrust monitored by the earth pressure box is different from that of the code，and the resultant value is 1/3 of that calculated by the code. The resultant value of landslide thrust retrieved from the monitoring steel stress is half of the calculated result of the method recommended by the design code；(5) The pile-soil interaction of large diameter anti-slide pile in landslide control of multi-stage surface revived accumulation body is complicated，and the internal force of pile body calculated by design code is too large. The research results can provide scientific basis for the landslide treatment of this kind of revived accumulation body.

To overcome the deficiency of the current “step-type” landslide displacement prediction model，a new model is proposed to characterize the features of “step-type” landslides under the combined effects of rainfall and reservoir water level. The model first uses the Nishihara creep model to fit the trend term displacement of the landslide，and then obtains the step displacement through the sliding step identification method based on the adaptive Genetic Algorithm and the step displacement extraction method based on the Moving Average Algorithm. After the step displacement is extracted，the influencing factors of rainfall and reservoir water level are analyzed and selected，and the optimal comprehensive index of rainfall and reservoir water level under the best correlation is obtained utilizing the Particle Swarm Optimization(PSO) algorithm. Finally，the LOF(Local Outlier Factor) Algorithm is utilized to remove outliers of the data set，and the ADASYN(Adaptive Synthetic) Algorithm is utilized for oversampling. After binary classification by the Grasshopper Optimization Algorithm optimized Support Vector Machine(GOA-SVM)，the classification and prediction of landslide step displacement are realized. Taking the Baishuihe landslide as an example of “step-type” landslides，the data of monitoring point ZG118 in the typical step period from June 2003 to August 2009 are selected for research. The prediction results show that the overall prediction accuracy of the data set is 72.73%，the prediction accuracy of the step displacement data set is 100%，and the prediction accuracy of the data set without step displacement is 66.67%，It indicates good prediction performance. When rainfall and reservoir water level become the dominant factors of the occurrence of step-type landslide steps，this model provides new ideas and exploration for the prediction of such landslides.

The shear behavior of the contact interface between frozen soil and pile is an important basis for establishing the frost jacking calculation model of piles in frozen soil regions. A series of negative temperature direct shear tests of frozen sand soil and concrete with different ice film thickness at the contact interface were carried out to analyze the influence of the ice film thickness on the shear mechanical deformation characteristics of the interface. Combined with multiple regression method，a trilinear shear constitutive model with multiple factors was established. Based on the shear-displacement method，the trilinear shear constitutive model is introduced to establish a theoretical calculation model for the frost jacking behaviour of single pile during the process of unidirectional freezing of seasonal frozen soil，and an example is analyzed. The results show that the ice film thickness has a significant effect on the shear behavior of the interface，and the relationship between the peak shear strength and the residual shear strength and the ice film thickness can be approximated as hyperbolic functions. The shear constitutive model can better reflect the effects of interface temperature，normal stress and ice film thickness on the shear behavior of frozen soil-concrete interface. Some pile-soil interface will slip during the freezing process of the soil around pile，and the peak position of tangential frost heaving force moves downward with the development of frost depth. The thickness of ice film has significant influence on the frost jacking effect of pile foundation. The frost jacking force does not increase linearly with the increase of frost heaving ratio，which is mainly affected by the shear strength between pile and frozen soil.

Recycling construction and demolition waste(CDW) in the construction of transportation infrastructure can benefit from various environmental，economic and social aspects. The gradual accumulation of permanent deformation of the granular structural layer under traffic loading may lead to rutting，cracking，and other diseases of the pavement，thus reducing its service life. In this paper，the plastic deformation characteristics of coarse-grained soil filler recycled from CDW under different stress states were studied by repeated-load triaxial tests，and the influence law of particle breakage state on plastic deformation and critical dynamic stress was investigated by designing five different graduation specimens. The prediction models of accumulated plastic strain and critical dynamic stress were established based on the measured data，which can comprehensively consider the particle breakage state and stress level. The test results show that the axial accumulated strain of recycled aggregates gradually decreases with the increase of confining pressure or the decrease of dynamic stress amplitude；the increase of particle breakage weakens the ability of specimens to resist plastic deformation. The established accumulated plastic strain prediction model overcomes the dispersion of the parameters of the accumulated plastic strain calculation model under different gradation conditions. The empirical equation for the critical dynamic stress based on the shake-down theory provides a theoretical basis for the reasonable assessment of the dynamic stability of the recycled coarse-grained soil filler under the action of traffic load.

Solid-liquid two-phase flow generally occurs during natural disasters，such as debris flows and avalanches. To address the shortcomings of current numerical methods，this study developed a two-layer two-phase smoothed particle hydrodynamics(SPH) method by combining soil constitutive equations and considering the complex interaction mechanism between the solid and liquid phases. The simulation of soil-water interaction with large deformation is performed using unified governing equations under the framework of the continuous medium theory，revealing its practical feasibility for researching large-scale debris flows. The accuracy and reliability of the developed numerical method for modeling the liquid and soil motion，as well as the interaction of soil-water are verified through a numerical example of saturated soil collapse in air，which approximates actual debris flows. The sensitivity analysis of fluid viscosity，effective grain size of soil mass，initial void ratio，and other parameters was conducted. Meanwhile，different percolation models for the soil-water coupling are compared. The results suggest that the proposed two-layer two-phase SPH method in this paper is reasonable and effective for simulating the soil-water coupling with large deformation. Notably，the environmental liquid and soil parameters significantly affect the results. When the Reynolds number of the particles is large，percolation models are essential for correctly simulating the interaction between solid and liquid and capturing the interface between the two phases. The investigated results in this paper are of significance for understanding the solid-liquid interaction mechanism in debris flows as well as disaster prevention and mitigation engineering.

Studying the operation performance and reinforcement mechanism of prestressed subgrades under train loads can provide technical references for engineering design. In this study，a 1∶5 scale model test was performed to explore the effect of the train axle load and the prestress on the acceleration response of the subgrade，and a three-dimensional dynamic finite element model of the prestressed subgrade was then established to analyze the distribution characteristics of the acceleration field and the prestress reinforcement mechanism. The results show that：(1) Under the action of the cyclic train loading，the peak and trough of the vertical acceleration of the subgrade fluctuate in a small range，and their mean value can be used to reflect the long-term vibration degree of the subgrade. (2) At the shoulder of the subgrade，the peak vertical acceleration linearly increases with increasing the train axle load and exponentially decreases with increasing the prestress，and an empirical model is then established to describe the relationship among the peak acceleration，the train axle load and the prestress. (3) The peak vertical acceleration exhibites a highly correlation with the prestress level，and the acceleration significantly attenuates while propagating along the transverse and depth directions of the subgrade. Therefore，the zones around the lateral pressure plate is significantly affected by the prestress comparing with the inner zones of the subgrade. (4) The horizontal prestress could alleviate the vertical vibration of the subgrade，and the core zones of the subgrade can be effectively enhanced by adjusting the prestress level and increasing the subgrade slope rate. The research findings can provide references for further understanding the reinforcement mechanism of the prestressed subgrade.