The engineering scale of tailrace system at Xiangjiaba right-bank underground powerhouse is very huge. Restricted by the terrain and geological conditions，the design and construction face lots of difficult technological problems. According to this actual situation and by means of numerical calculation and physical model test，some advanced design plans such as tailrace tunnel with the ceiling height change and 2 adits merged to 1 tunnel，are adopted；and some special construction plans such as top arch lining first，then excavation down，and small holes in large holes，are adopted. Safety monitoring guides construction to ensure the safety of engineering. Deformation of surrounding rock gradually inclines to be stable after excavation. The maximum measured deformation at top arch is 13.25 mm，close to the theory value of 15.72 mm. The comparative result shows that the design parameters of excavation and support are reasonable；and the sequence and method of construction are successful.

Based on the results of cyclic loading and unloading tests of two kinds of deep marbles  and   from Jinping II hydropower station，an elastoplastic coupling mechanical model considering confining pressure effect is proposed with taking the following aspects into consideration：(1) Evolution of elastic parameters of marbles with internal variable under different confining pressures is studied；and the quantitative relationships among elastic modulus，confining pressure and internal variable are proposed. (2) On the basis of Mohr-Coulomb yield criterion，the variation of strength parameter with internal variable is put forward. (3) Evolutions of dilatancy angle of Jinping marbles with internal variable and confining pressure are analyzed considering non-associated flow rule；and the quantitative relationships among dilatancy angle，confining pressure and internal variable are proposed. (4) Finally，the proposed mechanical model is embedded in FLAC3D using C++ language，and used to simulate the conventional triaxial compression test results. It is shown that there is significantly better agreement between simulating results and test data，and the proposed mechanical model can reflect the main mechanical properties of marbles. Efforts of this paper can give an important reference for promoting numerical accuracy of deformation and stability for rockmass of deep engineering，especially for brittle rockmass with the characteristics of fracturing under small deformation.

In order to study the transmission law of P-wave across the dual nonlinear elastic rock medium with one set of joints，numbers of imaginary joints with small spacing and large stiffness were set in spatial domain. The nonlinear deformation BB model of rock joint was applied to certain joint location. Combined with the characteristics line equation of nonlinear wave，the time-domain numerical solution of transmitted wave from one-dimensional P-wave across rock with various numbers of joints was obtained. The computational program with finite difference method was developed. Then，the program was validated by using previous computation result；and the parameters were further discussed through simulation. The relationships between the parameters of P-wave and joints，joint number，joint spacing，the nonlinear coefficient of rock and waveforms of the first wave and the follow-up wave，transmission coefficient of the first wave，energies of the first wave and the follow-up wave were investigated. The study results show that when the transmission distance increases，P-waveforms distortion with larger amplitude and lower frequency occurs，while P-waves with small amplitude and low frequency are not sensitive to the nonlinear interaction of rock. Transmission coefficient of the first wave，energies of the first wave and the follow-up wave are influenced by joint spacing and nonlinearity coefficient of rock. When P-waves with small amplitude and high frequency cross the large number of joints，the joints showed the role of high frequency filtering and energy decomposition.

Water gushing in limestone breccia fracture zone is a complex geological disaster often encountered in tunnel construction. Compared with the general water gushing in fracture rock mass，due to the poor stability of surrounding rock and rock heterogeneity，gushing treatment in limestone breccias fracture zone is very difficult. For controlling the water gushing in breccias fracture zone with high water pressure and quantity in Zhongliangshan tunnel，water analysis and transient electromagnetic detection were conducted；and groundwater source and channel were analyzed. Based on this，drainage was done first to reduce the water pressure in surrounding rock，then grouting was carried out to strengthen shallow layer. The shallow layer grouting was divided into two parts，i.e. upper part and lower part. Curtain in deep rock was done to plug water. Plugging and drainage were combined in water gushing control. Those four measures formed a comprehensive treatment method. A good control effect was achieved through choosing adaptive grouting materials and matched technology. Surrounding rock deformation and water quantity were measured and analyzed to avoid rock instability induced by grouting pressure. The comprehensive water gushing treatment method well solved the problems during grouting process in breccia fracture zone and realized informatization construction.

Due to both the distance between constructions and the distance between construction and high-steep slope are quite small，grasping the stability of foundation rock and mutual effects between constructions accurately is crucial to the feasibility of design scheme. Four key problems concerning stability of foundation rock of Aizhai suspension bridge are summarized. Comprehensive approaches to investigate the bridge foundation rock masses are introduced，as well as main geological defects，the stability analysis and monitoring results of foundation rock masses during construction stage. The geological conditions exposed during excavation，stability analysis and monitoring results show that comprehensive survey approaches are indispensable to fully understand the geological conditions of rock masses. The stability problems of Aizhai suspension bridge focus on the high-steep slopes of two banks. Design load never causes significant deformations；and mutual effects between constructions are not obvious. The stability of rock foundations can be guaranteed if the high-steep slopes are reinforced appropriately. The tower-beam-separation design and the arrangement of constructions are feasible. The studies of foundation rock stability give support to the innovation in structural design. Tunnel-type anchorage can generate very huge pull-resistance capability caused by gripping effect from surrounding rock masses. Because the tunnel-type anchorages used in large suspension bridges at home and abroad are limited，and the researches on rock mechanics problems of surrounding rock masses of tunnel-type anchorage are not deep enough，the bearing capacity of tunnel-type anchorage may be seriously underestimated.

Using self-developed meso-shear test equipment for coal or rock containing gas，tests of meso- characteristics of crack?s evolution of coal subjected to direct shear load under different gas pressures，were carried out to reveal general law of crack?s evolution and influence of gas on crack?s evolution. The results show that initial cracks nearby shear plane crazed firstly when at small angle to the direction of shearing. The principal displacement fracture is formed by transfixion of series of declined cracks(mostly from bottom left corner to top right corner) at various angles to the direction of shearing. Extension of these declined cracks increases as gas pressure increases. From shear load-shear displacement curves，and comparison analysis between level of cracking load Pk and level of transfixing load PG，conclusion was obtained that coal damaged to failure after crack craze more and more quickly as gas pressure increases because of fragmentation caused by gas. The angles of cracks show that cracks originated from non-crack area have small angles to the orientation of shear load；and mean angle decreases with the increasing gas pressure. The finally formed principal displacement fracture didn?t parallel to the orientation of shear load，a certain angle existed.

To explore the rockburst prediction principle and applied technology by microseismic method，in mine with high precision microseismic monitoring equipment，the continuous rock crack in mining process on site is monitored and analyzed with laws of rockburst induced by mining and self-made rockburst prediction software MapRAS. The result shows that deep diffusion of rock microcrack induced by mining at roof and floor is the main reason for the occurrence of rockburst. It is proposed that the deeply damaged of roof and floor induced by mining is an important factor in rockburst nucleation. The function and algorithm for identifying rupture damage depths of roof and floor by using microseismic data are established. Analysis displays that between damage depths of roof and floor exist linkage and there is corresponding to cycle breakage of roof key layer，as well as its after-effect，which reflects the loading and unloading processes of roof-floor. Most of the rockbursts in Huating coal field are roadway floor rupture. The engineering test indicates the method has higher prediction performance and good application effect.

Ordinary silicate cement grout is one of the most commonly used grouting materials，of which transport and diffusion laws have become one of focus of geotechnical engineering fields. Diffusion laws of cement grout in planar fracture were researched systematically by model experiment and numerical simulation. Based on the theory of fluid dynamics，action mechanism of the grout diffusion patterns and pressure distribution laws influenced by movement of groundwater were analyzed. Through comparing the experimental and numerical simulation data，the transport and diffusion mechanism of cement grout in the hydrodynamic and hydrostatic conditions were studied. According to the study results，under the hydrodynamic condition，pressure of cement grout decreases rapidly from the grouting hole；and the pressure decreases extremely at the direction opposite to water flowing. At the same time，there are limits of diffusion space and distance opposite to the water flowing direction. Some suggestions were put forward to improve traditional grouting techniques.

On the basis of reasonably simplified practical tunneling conditions，from meso-level structure of rock mass，the 2D model of rock chipping process induced by tunnel boring machine(TBM) disc cutters was established using particle discrete element method. The dynamic response mechanism of rock fragmentation induced by two cutters was studied；and the relationships of cracks，penetration and cutting force of rock mass were obtained. The optimum cutter spacing under common cutting depths was simulated，from which the relationship between cutter spacing and specific energy consumption under different cutting depths was analyzed. Then，the corresponding experiments were carried out to verify the rock dynamic fragmentation characteristics and optimum cutter spacing. Finally，the field TBM performance was taken to corroborate the conclusion. The results show that：(1) The change of cutting force with penetration is in good consistence with the jump crashing of rock；and the failure of rock follows the Griffith theory. (2) The breakage of rock mass is shear failure under small cutting depth，while the breakage of rock is caused by tensile stress under large cutting depth. When the cutting depth equals to 10 mm，the specific energy has obvious inflection point at the cutter spacing of 100 mm. The specific energy is achieved minimum at the cutter spacing of 60 mm when the cutting depth equals to 6 mm. The crack can?t penetrate rock when the cutting depth is less than 2 mm.

In order to understand the damage properties of different ages concrete under multiple impact loads systematically，the impact compression tests of 5 early ages concrete were conducted with a large diameter split Hopkinson pressure bar. The damage properties were analyzed by the statistical damage theory based on Weibull distribution to systematically study the damage law of concrete induced by repeated impact loads. The results show that，under the impact condition of 75% critical incident energy，the first time impact could improve the compressive strength of each age concrete. Then，the compressive strength and deformability become weaker with the increasing impact times. The damage-strain curve of concrete displayed different damage properties with the growth of ages. The sensitivity of damage to incident energy decreased. There was no obvious changes of cumulative damage when sample was broken as the age increased，almost at 1.00. However，the peak damage decreased logarithmically as the age increased. Peak damage at stable age indicated that the damage properties can be presented by the statistical damage model based on Weibull distribution.

The scale effect of rockfill exists objectively and is influenced by many factors. The existing test results conducted by different researchers show different and even reverse trends. By employing the stochastic granular discontinuous deformation method(SGDD) considering particle breakage，the mesoscopic mechanism of rockfill scale effects is studied，and attempting to explain the reasons leading to different test results. This research mainly focuses on the effects of degree of compaction control standard and particle properties on scale effects of rockfill. The simulation results show that particle shape and grading have great influence on compaction capacity of rockfill，so the degree of compaction controlled by relative density is much more reasonable. With the increasing of maximum particle size，the uniformity coefficient of rockfill increases；particles provide a higher degree of interlocking and bring about a higher initial tangent modulus. The scale effects on rockfill strength is much more complicated，which is related with scaling method，degree of compaction control standard and particle?s own properties. The shear strength of rockfill comes from shear dilation，particle breakage and particle rearrangement. Under the influences of external factors，these three mechanisms of action will eliminate and replace each other. The final response depends on which factor is dominant. The attempt to find a universal model to describe the properties of scaled rockfill and to extrapolate the mechanical parameters of prototype rockfill is rarely practical. The research aimed at specific rockfill can be conducted.

Based on energy theory and marble test of unloading confining pressure before peak strength under high stress，the whole process of strain energy conversion is researched，including absorbing strain energy for axial compression，dissipating strain energy for plastic deformation and cracks propagation，expending strain energy for circumferential deformation，storing and releasing elastic strain energy. The mechanism of strain energy conversion for marble specimens? damage evolution is revealed. The elastic strain energy stored is more than strain energy dissipated before the peak；and the quantity of strain energy dissipation can be significantly increased only near the peak. The stress quickly drops companying with elastic strain energy being rapidly released and strain energy fast dissipated for plastic deformation and fracture expansion after the peak. The rate of strain energy conversion obviously increases with the increasing unloading rate whenever before and after the peak，especially more intensely after the peak. The influence of initial confining pressure on the rate of strain energy conversion is closely related to unloading rate；and the rate of strain energy conversion clearly increases with the increasing initial confining pressure when the rate of unloading is faster；but the change is not obvious relatively when the rate of unloading is slower. The increasing initial confining pressure significantly enhances elastic strain energy storage before the peak. The rate of elastic strain energy release is far larger than that of strain energy expenditure for circumferential deformation；and the strain energy absorbed for axial compression is almost equal to that dissipated for plastic deformation and cracks propagation. So，the hard rock often presents the characteristics of tensional fracture or rip with the orient proximately perpendicular to unloading orientation，even rock burst appears. The mechanism of strain energy dissipation and release for marble damage and fracture under rapid unloading and high stress is that the elastic strain energy stored is more than the strain energy dissipated before the peak；and the elastic strain energy is quickly and largely released and dissipated after the peak；and companies with expending the strain energy for relatively fast confining tensile deformation towards unloading orientation.

It is a frequently used method in three-dimensional(3D) slope stability analysis based on the stress field of slope obtained by finite element computation. The factor of safety is defined as the ratio of resisting force and driving force along the specified slip surface. The analytical solution of 3D simple slope is compared with the numerical solutions obtained with this proposed method. The calculating results show that the Poisson?s ratio of material has some influence on the factors of safety obtained with this method and stress distribution. The factor of safety calculated with this method is in full agreement with the analytic solution when the Poisson?s ratio is close to 0.5. Finally，this method is applied to a high rock slope. The calculating results are well comparable with the factors of safety obtained by strength reduction technique.

An automatic method for determining mode I stress intensity factors(SIFs) and crack tip positions of rock specimens from displacement fields obtained by digital speckle correlation method(DSCM) is proposed. Notched semicircular disk granite specimen under three-point bending are employed for determining the mode I SIFs and the displacement fields around crack tip which are measured by DSCM. Nonlinear displacement field equations with unknown parameters are solved by Newton-Simpson method. The research results show that mode I SIFs，crack tip positions and crack propagation length can be determined accurately from the components of displacement fields；and the characters of rock fracture and crack propagation are revealed. The present method settled the problem of determining stress intensity factors and crack tip position simultaneously in rock fracture testing；so the fracture parameters of rock can be calculated.

Joint roughness coefficient(JRC) has influence on the deformation，failure and seepage properties of rock mass discontinuities；and the measurement and estimation of JRC are always focal，but difficult problems in the field of rock mechanics. The majority of the current research methods which have been based on the analysis of two-dimensional(2D) profiles rather than three-dimensional(3D) surface topography lead to erroneous results. On the other hand，the existing 3D evaluation methods only depend on the geometry data，but the anisotropy properties of JRC are ignored. Therefore，a new representation method for 3D JRC based on the brightness area percentage(BAP) was proposed. Firstly，with the help of laser scanning technique，the 3D digital model of rock fracture surfaces was established. Secondly，a light source was simulated；and there would be some brightness and shadows produced on the model surface. In addition，the simulated results were saved as picture format. Thirdly，in order to obtain the value of BAP of each specimen，the image recognition technique was introduced and the brightness area in the picture was identified. Lastly，combination with the results from formula proposed by R. Tse and D. M. Cruden and taking the direction of shear or seepage into account，an empirical formula was found between BAP and 3D joint roughness coefficient(JRC3D). Taking the data of Yujian River Reservoir project for example，the experimental results show that：(1) In the case of equal light source angle，generally，JRC3D are positive proportional to BAP. (2) A comparative analysis of results from different incidence angles was performed；after an extended evaluation，35°–70° was chosen as the most appropriate incidence angle. (3) The evaluation formula for relationship between BAP and JRC3D based on the engineering data of Yujian River Reservoir was derived. The predictions(17.20，17.40，17.17) of JRC3D made with this equation agreed well with the results(16.47，16.81，16.69) obtained in equation proposed by R. Tse and D. M. Cruden.

In order to study the frost deformation of rock under subfreezing temperature，strains of dry and saturated rock samples at low temperature were tested by strain gauge method. The result proves that dry rock samples behave as linear elastic characteristics during one freeze-thaw cycle，while the deformation of saturated rocks experienced four stages as follows：thermal contraction stage，frost expansion stage，thawing contraction stage and thermal expansion stage，and the residual strains were evident. Based on the test results，frost expansion deformation of moist rock at low temperature was analyzed. Ultimately，the conclusions were applied to a tunnel in cold region and the frost deformation characteristics of tunnel is studied. Besides，the distribution of unfrozen，freezing and frozen zones under certain frozen condition are sketched.

Based on integrating the theories and methods of multi-discipline，the research on formation mechanism and dynamic stability of Jingu landslide，a high-speed and long-run-out landslide induced by Wenchuan earthquake，was conducted. In the aspect of qualitative study of engineering geology，the formation mechanism of Jingu landslide was analyzed after comprehensive investigation involved in topography，lithology，tectonics and earthquake，as well as hydrogeology. As a result，the evolutionary stage of Jingu landslide was divided into two closely-linked phases. First，the upper sliding body was separated and thrown across the river standing at the toe of landslide. Second，the lower part of the slope was developed into a secondary landslide by the scratch from the upper body. On the other aspect of rock and soil mechanics quantitative study，three tasks were performed as follows：(1) Based on the fast Lagrangian analysis of continua in 3 dimensions(FLAC3D) dynamic analysis and a multilayer particle swarm optimization technique，a self-made parallel searching program was utilized to locate the non-circular critical slip surfaces of the landslide and its corresponding time-histories of dynamic factor of safety，of which frequency characteristics were revealed by spectrum analysis. (2) Based on the comparative study of two potential failure modes，the cluster #2 of slide surfaces is more possible to dominate the whole failure and trig the secondary landslide of slope?s lower part. (3) By aerodynamics calculation，long-distance throwing of upper sliding body is entirely possible. Comprehensive studies have shown that the quantitative analysis results of rock and soil mechanics are consistent with the engineering geology qualitative analysis results. The four prerequisites of the development of Jingu landslide were summarized as follows：poor mechanical properties，high position of shear crack，open terrain in lowering direction and enough initial velocity.

Acoustic emission(AE) technique was employed to measure the AE signals of coarse-grained granite and fine-grained sandstone with prefabricated square holes or circular holes under uniaxial compression test. AE time-space evolution characteristics during failure process were studied based on simplex locating algorithm. AE activities characteristics，AE energy release rate and spatial correlation length were also analyzed. The results show that the three-dimensional location of AE events directly reflects the process of initiation，propagation and evolution of microcracks and the stress redistribution within the specimens. For specimens that the distance of prefabricated holes is same with the prefabricated hole size，located AE event are clustered in the central of specimens；and shear failure occurs in the center area of specimens. The AE activities of granite with coarse and heterogeneous grains isn?t much stronger during the whole loading phase；while the AE activates of sandstone with thin and homogeneous grains isn?t enhanced until the later period of loading. Before the failure of rock，microcracks coalescence into large scale cracks，which result in AE activates weaken and AE energy release rate increases；during this phase，many AE signals are superimposing，which induces the AE quiet period and blank area of located AE events occurred. During rock fracture process，long-range correlations are established by redistribution of stress field，which cause the spatial correlation length obviously increasing before rock failure and reach its maximum value when rock failure.

According to the reality of bedded rock salt and clay interlayer for underground oil or gas storage carven in China，considering the existing interface element between salt rock and weak interlayer，the interface element taking nodal displacement and pore pressure as degree of freedom，is used to simulate the initiation，propagation and fluid seepage of weak layers resulted from hydraulic damage. Based on the fluid-solid coupling theory of porous fluid diffusion and deformation，the coupled damage model of dual media for salt rock with formation interlayer is established. This model can depict the crack propagation process and reflect the seepage flow of interface. Then，some numerical simulations are carried out to analyze the seepage and crack propagation characteristics of high pressure fluid on interface between salt rock and clay. The results show that the fluid pressure decreases along the interface element direction and the aperture of the opened fracture is fan-shaped during the leakage process of high-pressure fluid along cavity surrounding rocks. It is concluded that the effects of interface seepage on pressure distribution are very important. For the tightness and stability of the oil and gas repository，the inner pressure of oil or gas repository should be controlled to avoid the oil and gas leakages on the interface for salt rock with interlayer.

Three nodal triangular elements，of which velocity variables vary linearly，are often used in limit analysis of finite element upper bound solution. However，this low-order element has deficiency in simulating the shear and plastic zones occurred in failure mechanism of rock and soil masses. Based on predecessors? research，the six nodal triangular elements which have quadric changes of variables were introduced into finite element upper bound solution；and velocity discontinuities were also set between adjacent elements. The formulated model with this quadric element was a linear programming and can be used to analyze stability problems of the soil which obeys Mohr-Coulomb yield criterion. The formula of finite element upper bound theory was deduced and its calculating program was compiled. Using two typical calculating examples，the influences of linearization of yield criterion and velocity discontinuities additional variables on calculation results were investigated. The results obtained by six nodal triangular elements were compared to those of three nodal triangular elements. It was indicated that the calculation precision of results were improved by using six nodal triangular elements with equivalent number of elements. However，for the problems that failure zones were not remarkably constrained and velocity discontinuities line playing an key role，the favorable results can also obtained by using three nodal triangular elements.

A coupled discrete-continuum simulation incorporating three-dimensional aspect is performed to analyze pile penetration process in layered media. A particle numerical simulation program is used to consider the sand near pile as interacted particles by discrete element method(DEM). The sand away from pile are simulated as continua. Binding module of FLAC3D and PFC3D is developed；and the contact between the finite elements and the particles at boundary edges follows the principles defined in the DEM. In comparison with other numerical simulations and centrifuge tests，it is shown that the coupled discrete-continuum simulation can give a proper macro-microscopic description of pile penetration process. There exists ultimate pile tip resistance in the process. Overlying weak layer has a light influence on ultimate pile tip resistance. The penetration displacement in layered media is much shorter than that in pure sand when the pile tip resistance reaches ultimate value. After analyzing the variation of macro-microscopic parameters of soil at pile tip in detail，some conclusions are drawn as follows：(1) The sand particles under pile tip is gradually compacted with vertical movement instead of rotation. (2) The sand particles contacting with the pile skin vertically move with penetration instead of rotation. (3) The sand particles strongly rotate influenced by dilatation and vertically move，which causes the trend of ramming downward.

Combining the slope geological hazard control engineering in the repairman group living community of Changting branch of Highway Administration Bureau of Longyan city，Fujian province，firstly，the shear strength indices of the slope soil are obtained through back analysis by using ABAQUS program. Secondly，a lot of real large-scale three-dimensional(3D) finite element models in different design cases of anti-slide piles are established in supercomputer. Then，the relationships between the safety factors of soil slopes and pile lengths，as well as pile diameters，pile spacing，are obtained by using 3D strength reduction FEM. And the bending moment diagrams of the piles are also obtained. Meanwhile，the distribution laws of earth pressure surrounding the anti-slide piles are revealed. It is illustrated that because of the existence of soil arching effect，there are differences between earth pressure surrounding the anti-slide piles and that with laterally crown loading piles located in horizontal strata. At last，based on comprehensive comparison of a large number of test computation cases，the optimal design case of anti-slide piles is obtained. The method can be for references in the design of anti-slides piles for large and medium scale slopes(landslides).

The deformation and shear strength of anisotropic granular materials are dependent on the shearing direction or the orientation of principal stress relative to the bedding plane. In order to investigate the shear strength properties of any shear plane for anisotropic granular materials，an improved direct shear apparatus was designed，with which the ψ of Fujian standard sand defined as the angle of shear plane with respect to the bedding plane can be changed in the whole range of 0°–180°. The characteristics of the improved direct shear apparatus is that its walls are independent and demountable，thus the apparatus can be assembled according to different needs；and some top and side surfaces can be opened. By using the improved direct shear apparatus，direct shear tests are conducted on Fujian standard sands with the variation of ψ from 0°to 180° at intervals of 15°. The experimental results show that the plane with the minimum peak internal friction angle is achieved at the angle of ψ from 0° to 90°. After that，the peak internal friction angle increases with the increasing ψ. However，the plane with maximum peak internal friction angle is not the plane perpendicular to the depositional plane(ψ = 90°)，but that with ψ ≈105°. The planes related to the maximum and minimum peak internal friction angles are dependent on the anisotropy degree of materials.

Intact loess and remolded loess are combined for modeling. The centrifugal test is carried out to study the stability and deformation mode of the high sticking slope of collapsible loess in the states of natural moisture content and saturation. According to the results，in the state of natural moisture content，the stability of high sticking slope of collapsible loess is good；and consolidation deformation of sticking slope is the leading factor for high sticking slope deformation. The amount and rate of deformation after construction are large at early stage yet small at later stage；and the thicker the sticking slope thickness，the larger the settlement after construction and the longer the demand time of deformation completion. The thickness of sticking slope has a linear relation with settlement after construction. In the state of saturation，sticking slope consolidation and loess collapse cause the settlement of high sticking slope. If the settlement deformation is too large，the slope may crack along the weak zone formed by water penetration. The intensity of collapsible loess decides the stability of high sticking slope. The slide surface from soil damage passes through collapsible soil；and its location depends on the intensity difference between collapsible soil and its adjacent soil. When the interface between collapsible soil and its adjacent soil forms a weak layer caused by large intensity difference；the interface is definitely a part of slide surface；and the interface with lower intensity is firstly damaged. Moreover，the soil at the top of slide surface is in a typical translation sliding mode. On the contrary，the slide surface is approximately in circular arc；and there is a filter layer with a certain thickness between slide surface and interface.