Due to the complex and diverse geological and mining conditions of a coal mine in Shandong Province，a method for the classification and evaluation of the rock burst was put forward. The risk and type of the rock burst were evaluated according to the stability and impact tendency influenced by the interaction of external stress and the surrounding rock. The external static and dynamic stresses were quantified using the model of three-zone structure loading. The total stress superposed with the tectonic stress was calculated approximately. The external stress acting on the different surrounding rock structure with the impact tendency yielded the rock burst hazard and impact type. The classification and evaluation method of rock burst based on this research accurately reflected the impact type and risk of the mining face，and provided a more accurate basis for the development of the control measures. The research results have been applied in the coal mine of Shandong energy group with good outcome.

The quality classification of rock mass is a basic geotechnical engineering issue. The classification of rock mass quality shows the uncertainty due to the fuzziness and randomness of the rock mass parameters. The effect of parameter uncertainty on the classification results is ignored in the existing classification model. The reliability method was thus introduced into the classification of rock mass quality，and a coupled model of Monte Carlo simulation(MCS) and technique for order preference by similarity to ideal solution(TOPSIS) was proposed，which can consider the effect of the parameter uncertainty on the classification. The model consists of two parts.
One part is to obtain the weight of classification system index with the game theory and to determine the limit-state equation of the reliability with the TOPSIS model，and the other part is to perform uncertainty analysis and to provide the final classification result based on the probability function. The TOPSIS model was tested with 25 sets of samples. The analysis results of the MCS-TOPSIS model indicate that the misjudgment ratio of the model is 0. The quality classification of the surrounding rock at Shuibuya underground powerhouse is examined based on the certainty and uncertainty methods using Matlab programs. The results demonstrate that it is feasible to use the MCS-TOPSIS model to classify the rock mass quality and the model has high accuracy and is easy to use.

The point-type sensors are widely used for monitoring the surrounding rock deformation in geo-mechanical modelling tests，but they can only obtain the strains at a few measuring points. Fibre optic sensing，as one rapidly developing distributed monitoring technology，can resolve this problem，but it cannot yet meet the requirement of high spatial resolution. This paper introduces one new OFDR(optical frequency domain reflectometry)-based sensing technology，and applies it in the geo-mechanical test modelling the excavation of shallow buried large diameter circular tunnel using the cross rock pillar method to achieve the continuous monitoring on the horizontal strains in different tunnel cross sections during excavation. Combined with the FEM analysis，the results show that the OFDR based sensing technology can accurately record the change of strain inside the geo-mechanical model during testing. It can reveal the deformation tendency of the surrounding rock when excavated using the cross rock pillar method，reflect the supporting effect of the cross rock pillar to the surround rock，and then guide the future tunnel excavation activities. The results are compared with the monitoring results obtained from the multipoint displacement meter after converting the strain-type results into the displacement-type results，and their deviations are within 10%. Generally，the OFDR-based sensing technology can be applied to the deformation monitoring in geo-mechanical modelling tests.

The spalling of hard basalt is one of the serious geotechnical problems in the underground powerhouse of the Baihetan hydropower station. The paper presented the general inner cracking process captured by the digital borehole camera and the detailed in-situ failure proofs during the unloading excavation. These study showed that the spalling，with the sheet and plate shape，happened not only to the intact basalt，but to the basalt with a few joints. Further optical scanning and scanning electron microscope observations indicated that the break surface of the spalling rock was rough and belong to the tensional failure mode. The field digital borehole camera observation in the underground powerhouse indicated that the basalt spalling had the characteristics of spatial discontinuous distribution，time-dependent increase of cracking depth，increase and decrease of crack?s width，obvious restraining effect of rock bolt and anchor cable. What?s more，the case study also indicated that the inner crack and surface failure of basalt related to each other，namely，the surface failure happened when the inner cracks developed sufficiently. These knowledge about the basalt spalling provided us not only the visual picture of basalt's break，but also a guide for disaster warning and supporting optimization in the deep rock engineering.

Analytical study on seepage field of the deep tunnel with asymmetric blocked drainage system has not been carried out at present. An analytical solution of the Laplace equation was derived based on the simplification of the studying area. With the PDE tools，the unknown but necessary boundary conditions were converted to the approximate inhomogeneous ones. These boundary conditions were homogenized with methods like conformal transformation in complex plane，transformation of coordinates，separation of problem for determining the solution of differential equation. The last inhomogeneous boundary condition was expressed as the sum of a family of orthogonal functions in Hilbert space. Finally，a solution of series for the seepage field were derived. The seepage flow field is similar to the funnel shape. The hydraulic head is higher in blocked side. And the further study shows that in most situations the sum of series converges quickly when the number of term in series greater than 50. The differences between the analytical and numerical results of the distribution of hydraulic pressure and seepage flux are only 4.28% and 4.05%.

The reason of taking the potential contact area of rock mass discontinuity(RMD) as the important factor of surface roughness evaluation was explained theoretically in order to obtain the evaluation index with a clear geometric meaning.   was put forward as a new evaluation index，which was associated with the mechanical properties. Two projection areas of the RMD surface were calculated，one was the projection of potential contact area on the plane which was perpendicular to the shear direction，the other was the projection of the whole RMD surface on the horizontal plane.   is the area ratio of the former to the latter. The three-dimensional(3D) geometry information of the RMD in the shear direction was embodied by  ，which was an anisotropic index. Based on the 3D laser scanning technology and Matlab programming，the 3D geometric model of the RMD was built and  was calculated. The computational process and anisotropy of   were presented via the engineering examples. A series of   of the RMD models built with different elaborate degrees were studied，and the results showed that   increased with the increasing of the elaborate degrees of models. The comparison between the results from Grasselli?s evaluation method and   method showed that these two methods are similar. Furthermore，a good relationship was established between   and the shear strength of the RMD，which laid the foundation for further study on the shear strength evaluation model of the RMD.

The safety of the heel of the concrete high arch dam is highly concerned during the initial impoundment. The microseismic monitoring system was installed for the first time in China at the high arch dam heel. The real-time monitoring of the micro-cracks was achieved in the heel zone of the Dagangshan arch dam during the initial impoundment. The deformation mechanism of the arch dam heel and its relationship with the microseismic activities were investigated. The P wave velocity was determined using the manual tapping test and was 4 300 m/s with the error of system positioning less than 8 m. The event waveforms were denoised. The automatic positioning results were manually verified for better accuracy. The results proved the feasibility of applying the microseismic monitoring technology in the large-scale concrete structures. During the initial impoundment period，the microseismic activities of the high arch dam heel were closely related to the water level of reservoir. The accumulation area of micro-cracks was transferred from the dam heel to the dam toe. The deformation of the toe area of dam increased and of the heel area decreased. The process of microseismic deformation of the dam heel zone revealed the inducement of the crack at the base corridor vault at the elevation of 940 m. The results can provide reference for the studies on the microseismic monitoring of concrete high arch dams as well as the dam working performances.

深部岩石的动力破坏，是岩石力学研究的一个热点问题。为模拟深部岩石动态断裂情况，选取一种花岗岩制备带10 mm预制裂纹的板状试样，开展含预应力条件下的岩板动态破坏行为研究。试件尺寸为305 mm×305 mm×10.5 mm岩板，在静态竖向预压的条件下，使用25 mm杆径的霍普金森压杆进行冲击试验。利用超高速摄影仪记录试样裂纹扩展的全过程，采用数字图像相关(DIC)技术分析试样的位移场及应变场，通过设置虚拟引伸计，获得预应力条件下岩板起裂时刻、裂纹长度、裂纹扩展速度及断裂韧性等动态断裂力学参量。研究结果显示：该岩板试件裂纹扩展速度可达到瑞利波速的0.57倍(～1000 m/s)，验证了采用花岗岩岩板测试的优势。在特定预应力条件下，岩板的裂纹扩展速率与动态断裂韧性具有明显的率相关性；特定冲击速度条件下，随着静态预应力的增加，裂纹扩展速度受到抑制，破坏模式由单一裂纹扩展向多条微裂纹扩展等复杂模式转变，甚至出现止裂现象。当气枪冲击气压103.43 kPa、静态预应力30 MPa时，裂纹扩展速度降为452.4 m/s，属于低速裂纹扩展范围。

The acoustic emission(AE) and wave propagation in granite under uniaxial compression were measured with the ultrasonic wave and AE synchronous monitoring devices. The stress thresholds were determined with the macro-micro methods firstly. Then evolution of AE and wave propagation during different phases were studied. The result shows that the evolution of micro cracks is related to the macroscopic deformation closely. As the cracks propagate mainly along axial direction under uniaxial compression，the axial stiffness is less sensitive than the nonlinear lateral deformation to the crack initiation and coalescence. The slope variation point of the instantaneous Poisson's ratio coincides with the stress thresholds. Crack initiation stress determined by AE monitoring is smaller than that by the macro strain methods. However，the initiation of micro crack is accurately reflected by AE. The temporal and spatial hypocenter distribution of AE events was refined based on the measured variation of velocity，which depicts the localization of the cracks or their propagation well. Because the amplitude and energy of AE signals emitted at different stages differ greatly，the variations of the characteristic parameters related to the crack propagation are different，especially after the crack damage stress. The outburst increase of AE energy before rock failure can be a precursor to catastrophic damage. At the initial compaction stage，the ultrasonic velocity and amplitude increase with the axial stress. However，the increasing rate decreases gradually. The lateral velocity reaches the peak near crack closure stress and remains constant in a certain later stage. Meanwhile，velocities along the other directions keep increasing. With the increase of the angle to the radial direction，the increment and the stress corresponding to the decreasing point of acoustic velocity increase gradually. The influence of damage development on ultrasonic velocity lags behind that on the AE events.

The coefficients of gas diffusion，concentration flow，initial migration strength and attenuation are the mechanical characterization of the pore structure and quality characteristics in coal matrix. In order to investigate the mechanism and to quantify the ability of gas migration in coal seam，a mathematical model about gas concentration and diffusion rate was established based on the Fick′s law and mass conservation equation. The method of variable separation was employed to solve the equation. The coefficients of gas diffusion and gas concentration flow were proposed with the data iterative method. The gas diffusion experiments were carried out for four kinds of coal samples. The results indicated that the mass increment of gas emission had a negative exponential relationship with the test time. The higher the coal rank is，the greater gas quality growth will be. The gas diffusion velocity and the attenuation coefficient were controlled by the pore structure and micro components of the coal matrix. There were obvious differences between the four coal species. The permeability varies linearly with the diffusion coefficient and parabolic with the flow coefficient. The flow coefficient and diffusion coefficient increase with the increasing of coal rank.

In this paper，the mitigation strategy of Landslide K227 was summarized，and the numerical simulation and optimization of the mitigation stages of the upper，middle and lower parts of the slope were conducted. The results of the comparison of the field monitoring and simulation data guided the process controlling of slope construction，which achieved the target of safety，orderliness and control at all the stages of the construction and no hidden risks. The global safety factor 1.10 was suggested to be the threshold value to define the slope stability under the comprehensive conditions due to the need for stability control of super-high cut slope and their structural durability in the whole construct process. The backfilling at the toe of the slope was imperative to ensure the present stability during the construction of the super-high cut slope. The timing and opportunity to adjust the similar temporary safety precautions should be prudently determined. Planning in advance and installation in time of two rows of anti-slide anchor piles were important to control the reduction of stability and the development of towing deformation in up-rear part of slope，to keep the safety of construction process and to make the remediation successful. There are various potential failure mechanisms in the treatment to super-high cut slope with the transformation of local and global deformation of slope. Therefore，multiple plans are supposed to be simulated and adjusted in order to maintain the compatibility of local and global deformation. The passive mode of the design adjustment due to the slope failure need be to transformed into the active one of simulating the slope deformation in advance，which can control the secondary disasters during the period of construction of cut slopes.

The failure mechanism of the internal rock bridge of the high-steep rock slope is complex. It is important to study the failure of central locking section and the failure mechanisms of slope. The rock bridge was formed by prefabricated cracks at the ends of the rock simple in order to represent the tensile failure in the trailing edge of slope and shear failure in the toe of slope. The conventional triaxial loading test and triaxial loading-unloading test were carried out on three rock bridges of different lengths. The characteristics of stress-strain curves，strength-deformation and the crack propagation types under two types of stress paths were analyzed，and the mechanism of crack propagation was discussed based on the fracture mechanics. The results of test show that the peak strength of specimens and the corresponding strain increased with the increasing of confining pressure and rock bridge length. The peak strain and peak value of rock bridges specimen under the triaxial loading-unloading are greater than those from the conventional triaxial loading test. The “burst failure” and “post-peak rise” characteristic appeared in the stress-strain curve，and the stress-strain curves of some specimens show the “double peak ” phenomena. There are five types of crack propagation in the rock bridge specimens：the coalescence rock bridge，the coalescence specimens upper end-face，the inward circumferential failure，the outward circumferential failure and the coalescence specimens lower end-face. The tension cracks and shear cracks are generated at the tip of the lower joint of rock bridge specimen where the stress concentration occurs. Most of the crack initiation angles are between 40° to 50°. The lab test revealed that the failure mode of locking section in rocky slope was a multi-stage process.

Dynamic stability analysis of slopes is a difficult problem in the field of geotechnical engineering. In order to apply the vector sum method(VSM) in dynamic stability analysis of a three-dimensional slope，a method which combines VSM with dynamic finite element method was developed，and an example of a three-dimensional uniform slope was analysed. The method was used to analyse the dynamic stability of two typical talus deposits. The dynamic analysis of the slope shows that the terrain has great effects on the dynamic response of the three-dimensional slope and that the absorption effect of talus deposit on the seismic wave is pretty obvious. Under the action of earthquake scale 6.5 (the peak acceleration is 0.2 g)，the average safety factors of talus deposit Q1 and Q2 are 1.47 and 1.23 respectively，while the minimum values are 1.33 and 1.18 respectively. The slope was thus considered stable under this seismic load.

Mechanism of gob-pillar interaction for subcritical panels was studied against Zhenchengdi coal mine through theoretical analysis，physical modelling，numerical modelling and field observation. Different panel layouts were found to lead to the different shapes of panel and coal pillar. The gob behavior has the significant influence on the stress distribution and failure of the coal pillar which should not be ignored in the numerical modelling. The width of limit equilibrium zone of coal pillar is derived. When a slice of multiple longwall slices of a coal seam is being mined，the mining height is reduced leading to the reduction of the width of the limit equilibrium zone，and so are the high seam longwall mining and split-level longwall mining(SLM) due to their elevating section. The angle of break plays an important role in gob-pillar interaction. The angles of break were obtained and were used for numerical modelling. An expression for the panel width L，the span of the uppermost key stratum L1 and the angle of break θ is obtained. The numerical modelling shows that the more load the gob bears，the less the abutment pressure and vice versa，which is the result of the gob-pillar interaction for subcritical panels. The abutment pressure，stress concentration factor and failure zone were larger and the elevation of failure zone was lower if the influence of gob was not taken into account. According to the mechanism of gob-pillar interaction for subcritical panels，the air intake way was set under the gob edge(with roof along the gob rather than rib) in the least stressed zone in the entire panel system，and the air exit way was arranged along the roof，as such，the ground control problems for both gate roads are solved.

The present paper focuses on the study of a project called as Hetaojing tailings pond to store fine grained tailings，which is located in the active seismic area of Zhongdian—Dali. The intensity of 8 degree is specified in the design. The feasibility of upstream embankment method for tailings pond with the similar characteristics was investigated. In order to analyze the seismic response and the static and dynamic stability of the tailings dam，an integrated approach was applied，consisting of the embankment model test，geotechnical engineering test，theoretical analysis and numerical simulation. The results show that the static and dynamic stability of tailings dam in Hetaojing tailings pond can be improved to meet the requirements of national codes by means of constructions of a high starter dam，appropriate drainage and fitting the slope with rocks，which confirms the feasibility of upstream embankment method with the appropriate earthquake resistant construction for fine grained tailings pond in seismic area theoretically. It was also found that due to the generation and growth of dynamic pore water pressure，the dynamic safety factors of tailings dams fluctuated and decreased gradually during the earthquake. The excessive permanent deformation is one of the major seismic disaster forms for the fine grained tailings dam. The insufficient length and height clearance of the safety beach makes the overtopping more likely to occur after earthquake. Furthermore，the causes of the characteristics of fine grained tailings dam including the particle size grading，the shallow phreatic line and the gentle beach face were analyzed in mesoscopic view.

The failure range and the stability of a bedding rock slope are often affected by the construction disturbance. The bedding slope of Huaping at Jinshajiang bridge connecting the Huali highway was studied in the paper. The results of the in-situ survey，geomechanical analysis and simulation revealed the structure and failure mode of the slope. The model test was carried out under the different combinations of abutment and horizontal loadings，and mechanical analysis was performed. The results indicate that critical horizontal load of different schemes vary from 1.89 to 3.15 kN and that relative limit horizontal seismic accelerations vibrate from 0.134 g to 0.208 g. With the exception of working condition of 100 years seismic fortification criterion，other seismic conditions of Huaping bank slope all meet the revised criterion of 0.105 g(50 years)and 0.144 g(100 years). During model test process，sensitivity and stability rank of monitoring datum are surface force and displacement，inner stress and strain. Sensors? cost-benefit ratio ranks are force-measure ring，centigrade indicator，mini soil pressure cell and strain gage.

The waterproof partition coal pillars are divided into the plastic zone，the elastic core zone and the hydraulic fractured zone on the basis of the existing reasonable structural division of coal pillars. The width of the plastic zone is derived with the application of limit equilibrium theory，the parabolic strength theory and the method of separation of variables. The width of the elastic core zone is derived adopting the semi-inverse method with the consideration of mine pressure and hydraulic pressure effects and the selection of unified strength theory. The width of hydraulic fractured zone is determined considering the infiltrating and softening effects of water. The comparisons with the results from previous typical models for each zone confirm the reasonability of the model.  The monitored structures of inner coal seam with the ultrasonic probing technique also verify the correctness of the model. The method was applied to the design of the waterproof partition coal pillar in Dongjiahe coal mine for the secure and high-efficient production of the coal mine.

The frequencies of traffic loading vary with various factors such as traffic speed. Currently there is no unified understanding in the load frequency effects on the long-term behavior of road base under the cyclic traffic loading. In order to investigate the effects of loading frequency，a series of large-scale cyclic triaxial tests on the Unbound Granular Materials(UGMs) under saturated drained condition were conducted with GDS large-scale cyclic triaxial apparatus(LDCTTS). The influence of loading frequency on the long-term performance of UGMs was investigated systematically under various stress paths. The experimental results showed that the loadings with higher frequency resulted in a larger accumulated volume contraction during the stage of densification，and consequently the UGMs reached a higher rebounding modulus. The accumulated axial strain of UGMs was also different under the loadings with different frequencies. At the stage of densification of UGMs，the loadings with the higher frequency led to higher accumulated axial strain when the cyclic stress ratios were high(ζ = 3，5)，while the loading frequency effect was minimized when the cyclic stress ratio was low(ζ = 1). After the UGMs reached the stable deformation stage，the loading frequency had almost no influence on the accumulated axial strain. This study has revealed the dynamic behavior of UGMs under the cyclic loading with different frequencies. It is found that the effects of loading frequency on the long-term performance of road base can be greatly reduced by controlling the cyclic stress ratio in the UGMs to a low level. This study can be served as reference for the accurate prediction and control of road post-construction settlement.

Peaty soils are generally viewed as“problematic”soils for their high organic matter content，high water contents，low bulk density，high compressibility and low strength characteristics. The long-term accumulative behaviour of peaty soils subjected to traffic loads was studied through a series of cyclic triaxial compression tests on the samples retrieved from the site nearby Caohai on the northern side of Lake Dian. The variables including the confining stress level，the amplitude of dynamic stress and the static deviatoric stress were taken into account in this study. It was found that the tested samples were typical peaty soil，which had the initial water contents of 181.5%–259.3%，the initial densities of 1.10–1.22 g/cm3，the organic contents of 34.7%–44.2%. The organic matters were highly decomposed. Both the amplitude of dynamic stress and static deviatoric stress had the distinct influences on the developments of permanent axial strain and pore water pressure. The larger amplitude of dynamic stress or the static deviatoric stress accelerated the developments of the permanent axial strain and pore water pressure. The development of permanent axial strain was faster when a lower dynamic stress and a larger static deviatoric stress were applied，in contrast to the case that a larger dynamic stress and a lower static stress were applied. The initial confining stress level appeared to have a little effect on the development of permanent axial strain，while it had a significant impact on the accumulation of pore water pressure. In addition， an empirical relation between the accumulative plastic strain and loading cycles was presented based on the relationships between the permanent axial strain rate and loading cycles under dual logarithmic coordinates as well as the previous studies.

The cyclic loading test，repeated shear test and scanning electron microscope(SEM) technology were used to study the dynamic characteristics and microcosmic damage mechanism of loess and mudstone in Tianshui area. The dynamic elasticity moduli of loess and mudstone increase nonlinearly with the increasing of confining pressure and are inversely proportional to the damping ratio. When the dynamic shear stress ratio is larger than a certain value，the soil sample fails after the loading cycles reaching a certain number. With the increasing of shearing cycles，the shear strength decreases and finally achieves the residual strength. But with the increasing of confining pressure，the soil occlusion and shear strength increase. The static shear which makes the particles finer belongs to the particle shear trituration mode. The soil particles arranges more smoothly with regular orientation and the inter-particle pores become tight. Under the cyclic dynamic loading，the particles experience the shearing-grinding with the increasing of shear amplitude. The soil particles arranged more smoothly，and the inter-particle pores decreased obviously. The shear plane is shown to be hardened and impervious.

In the past，the stress-strain curve of rock and soil can only be described by using the different mathematical models according to its morphological type，and the description of corresponding volume deformation curve is very rare. In order to realize a unified mathematical model for the description of different stress-strain curves and volume deformation curves，a new nonlinear model called as the composite power exponential model(CPE model for short) is presented by analysing the characteristics of power function and exponential function. The determining method of each parameter is also proposed. The structural loess is studied experimentally and the curves of measured stress-strain and the volume deformation from triaxial tests with different water contents and different confining pressures are fitted by CPE model. The variation law of each parameter is analyzed. For unsaturated undisturbed loess，the CPE model of stress-strain curve of strain softening which considers water content and that of strain hardening which considers confining pressure are obtained respectively. The CPE model of volume deformation curve of shear contraction which considers confining pressure is obtained，too. The calculated curves using the above CPE models are compared with the measured ones. The result shows that the CPE model has extensive adaptability and high accuracy，which can describes the stress-strain curves of softening and hardening of different degrees and the volume deformation curves of shear expansion or shear contraction. The CPE model provides a unified mathematical model for stress-strain curves and volume deformation curve of different forms.

The magnitude of the lateral earth pressure against wall depends on the wall movement. The soil behind a wall approaching the active or passive earth pressure state from initial state is considered as the shearing process of soil sample in the simple shear test. The geometric relationship between the shear strain of soil and the wall displacement，the equilibrium equation between the earth pressure and the shear stress of soil，and the constitutive relationship between the shear strain and the shear stress of soil were used to derive the expression of the wall displacement with lateral earth pressure. The wall displacement reaching the limit state of earth pressure increases with the ultimate shear strain of soil and the scope of failure zone. The required displacement decreases with k0(rest earth pressure coefficient) from the initial to the active state，but increases with k0 from the initial to the passive state. The relationship between the wall movement and the lateral earth pressure macroscopically describes soil stress-strain behavior. The calculated displacement required to reach the active state for the cohesionless and cohesive soils are about 0.6‰–15.0‰ of H，and to reach passive state which are about －0.5%–－5.9% of H，where H is the height of the wall. The estimated wall displacement-earth pressure curves agree reasonably with the model test results from the relevant literatures.

When tunnel passes through a self-weight collapsible loess stratum，lining structure of loess tunnel may be destructed by the additional collapse deformation of loess upon water immersion. In this paper，the surrounding pressure of loess tunnel，the characteristics of the self-weight collapse deformation of collapsible loess tunnel foundation，and the destruction of lining structure caused by the collapse deformation of foundation are discussed. Firstly，a calculation method for the additional stresses of foundation soil under the surrounding pressure and weight of lining structure and under soil self-weight stress of both sides of tunnel was proposed. The collapsible compression stress is obtained by the additional stresses adding the soil weight under foundation. Secondly，the relationships between the structural index and physical index，between the structural index and structural yield stress，and between the ratio of void ratio to initial void ratio and the ratio of compressive stress to structural yield stress were used to establish a calculation method for the collapsible coefficient and self-weight collapsible coefficient of loess by comparing the confined compression curves of loess in natural moisture content and in saturation. According to the fact that the loess at the different depths has the different threshold values in the region with thick layer of self-weight collapsible loess，the self-weight collapsible deformation of the site and the collapsible deformation of the tunnel foundation are derived. Finally，the different collapsible deformations of tunnel foundation，the stress fields and plastic region of lining structure were analyzed numerically. The larger the settlement difference is，the more extensive the range of plastic region is. Three grades of collapse deformation of tunnel subgrade，0–5，5–10 cm and more than 10 cm are proposed according to the control standard of railway bed.