The pore structure of natural reservoirs perfroms a multi-scale assembly system of multi-geometry under the control of scale invariant for its various contributing factors. Its quantitative characterization is the key to accurately assessing reservoir static physical properties. And the meso-control mechanism of transport characters can be further effectively revealed. Recent research shows that fractal objects are dual-complexity systems，and they are composed of independent original complexity and behavioral complexity. Therefore，they are key to achieving quantitative characterization of pore structure，i.e. equivalent characterization of original complexity and unique definition of behavioral complexity. Thus，this paper systematically studied methods for characterizing complex pore structure and summarized their advantages and limitations. Following the definition of original complexity elements in fractal pore structures，we developed the pore-throat-solid-network-connectivity algorithm，and achieved equivalent characterization of any original complex types，i.e.，single/multi-scale，phase and type. With fractal topology theory，this research verified the unique definition of self-sameness，self-similarity and self-affinity in pore structures. Then，a unified characterization model of pore structure is constructed based on the concept of complexity assembly. The adaptability of the new model to the fine description of pore structures in natural reservoir is finally discussed beyond its fully verification. A theoretical and methodological system for quantitative characterization of fractal porous media.

In order to realize the safety and stability of the short arm beam roof structure in non-pillar mining with automatically formed roadway. The balance mechanism and dynamical evolution of the roof structure of the short-arm beam are analyzed，and the mechanism of compensating the support of the anchor cable is clarified. The Hoek-Brown strength criterion and the upper bound analysis method in plastic mechanics are used to analyze the caving failure mechanism of the surrounding rock of the short arm beam roof under the support of the anchor cable. Therefore，the calculation formula of anchor cable compensation support force of short arm beam roof in three stages of caving friction, dynamic pressure effect and roadway stability is deduced. In addition，a method for compensating the support force of a short arm beam roof in a self-forming roadway without coal pillars is developed. On this basis，the sensitivity analysis index is established and the influence of different parameters on the compensation support force of the anchor cable is analyzed. It is demonstrated that the surrounding rock stress，roof cutting parameters and roadway width are the main control factors for cable compensation support forces，with the surrounding rock stress being the most sensitive metric. Thus，the engineering suggestions for the stability control of short arm beam roof are put forward. The research results were applied in the transportation roadway of 5101 working face of N00 mining method in Xintai Coal Mine，and good effect of field application was verified.

To study the macro and micro mechanical characteristics and failure mechanism of cumulative damage of jointed rock mass under fatigue loading，cyclic loading and unloading tests of jointed sandstone with different upper stress ratios were carried out. The experimental results show that：(1) With the increase of the upper limit stress ratio，the hysteretic cycle spacing of jointed sandstone changes from two-phase sparse-dense to three-phase sparse-dense-sparse. (2) When the upper limit stress ratio is less than 0.90，the uniaxial compressive strength of jointed sandstone increases to different degrees after cyclic loading and unloading，and the value increases first and then decreases with the increase of the upper limit stress ratio. When the upper limit stress ratio is 0.80，the uniaxial compressive strength reaches the maximum. When the upper limit stress ratio is greater than or equal to 0.90，the failure of jointed sandstone occurs during the cycle，and the fatigue times decrease with the rise of the upper limit stress ratio. (3) The fatigue times of sandstone with different inclination angles follow the principle of 90°＞60°＞0°＞45°. Through comparative analysis of failure modes of jointed sandstone after cyclic loading and unloading，the main effect of different upper limit stress ratios mainly affect is the failure degree of samples，the higher the upper limit stress ratio，the greater the degree of fracture，while the primary effect of joint dip angle mainly affects the failure mode of the samples. The shear failure is the main failure mode of the 60°and 45°jointed sandstone samples，with the tensile failure of the 90° and 0° jointed sandstone samples as the main failure mode. (4) After using nuclear magnetic resonance(NMR) and scanning electron microscope(SEM) to test cycle and unloading joint sandstone porosity change after fatigue damage and mesoscopic structure characteristic，it is found the sample fatigue damage can be divided into three stages，slow fatigue-stability-accelerated fatigue，characterized by gap pressure filling-crushing-matrix mineral crushing clay minerals content. 

To investigate the influence mechanism of early load damage on later mechanical properties of the cemented paste backfill，four different degrees of static load damage were applied to the backfill at ages of 3，7，14 and 21 d. After 28 d of maintenance，uniaxial compression tests，ultrasonic tests and electron microscopic microstructure scans were conducted to investigate the influence mechanism of early load damage on later mechanical properties of the backfill under three scales of macro-fine-micro. The results show that：the load damage had less effect on the late compressive strength of the backfill at ages 3 and 7 d，and the late compressive strength of the backfill increased under certain load conditions. The late compressive strength of the backfill at age 14 and 21 d was weakened. The late elastic deformation capacity of the cemented backfill at each age was strengthened. The quantitative relationship between the degree of load and the physical properties of the backfill was established based on the variation of wave velocity. It finds that there was a damage threshold and a repair threshold for the backfill at 3 and 7 d of damage age. With the degree of damage load increased，the internal structure of the backfill gradually expanded from a larger number of fine fissures to a single fissure，and the connecting material at the fissure section was mainly the hydration product C-S-H reticulated gel. At ages 3 and 7 d，there were a large number of incompletely hydrated cement particles inside the backfill，and the gel products produced at the later stage of maintenance were sufficient to fill most of the damaged fissures. Therefore，the damage had a less effect on its later compressive strength. While at ages 14 and 21 d，the incompletely hydrated cement particles in the backfill were reduced，and the gel products produced at the later stage were insufficient to fill the damaged fissures. Thus，the connection between the internal structural particles was poor，and the damage had a significant weakening effect on its later compressive strength. The results of the study can provide guidance for working with mine backfilling.

The evolution process of the magnitude and direction of three-dimensional mining stress is the key to reveal the damage and failure mechanism of coal pillar. The coal pillar between the fully mechanized top-coal caving faces was divided into upper and lower areas. There were four stages：roadway excavation-right longwall face mining-left longwall face mining-mining stability. The 3DEC numerical simulation method was used to analyze the full-cycle temporal and spatial evolution law of three-dimensional mining stress of coal pillar in these stages. The mapping relationship between the fracture structure of overlying strata，mining stress and displacement of coal pillar was revealed. Based on the simulation analysis results，the Mohr-Coulomb strength criterion was used to analyze the transformation form of Mohr stress circle of coal pillar and the relationship between stress circle and strength envelope. The failure width of coal pillar was determined to be about 8m. The results show that longwall face mining causes the three-direction principal stress direction of coal pillar to rotate greatly. An obvious two-cluster or three-cluster rule was showed in the three-dimensional principal stress data of coal pillar. The division points of the data clusters correspond to the time when the right longwall face is advanced to the survey line and when the mining of right longwall face ends. The obvious asymmetry in overlying fracture structure of coal pillar was caused by the different mining sequences of longwall face. The fracture line of the overlying strata is biased towards the longwall face which is mined later. As a result，the horizontal displacement of the measuring point on the left side of coal pillar is significantly larger than that on the right side of coal pillar. The full-cycle temporal and spatial evolution law of coal pillar mining stress and the mapping relationship between the fracture structure of overlying strata，mining stress and displacement of coal pillar lay the foundation for revealing the damage mechanism of coal pillar.

In order to explore the dynamic fracture behavior of rock materials under different bedding angles，the dynamic fracture impact test were carried out on three kinds of notched semi-circular bend rock specimens in 30°，45°，60°，75° and 90° bedding angles using the split Hopkinson pressure bar impact loading system. The stress wave and energy propagation law，stress response characteristics and dynamic fracture toughness of the three rock specimens under different bedding angles conditions were studied. DLSM numerical simulation software is used to assist analysis，which proves that the simulation method can be well applied to the study of rock dynamic fracture behavior. Stress wave propagation images and crack tip stress field images are used to analyze the stress wave transmission law of specimens，and explain the mechanism of dynamic fracture toughness changing with the bedding angle. Combined with kinetic energy and failure curves of the model，failure characteristics of rocks under different bedding angles are summarized. The results show that the change of bedding angle will affect the effective reflection area of the stress wave，and thus affect the transfer law of reflected wave and transmitted wave，resulting in the change of the energy ratio of each part. The three kinds of rocks have different failure characteristics，but their dynamic fracture toughness is affected by the bedding angle，and precracking and tensile failure are more likely to occur at small bedding angle，leading to the reduction of specimen strength. The simulated stress wave propagation image explains the transreflectance law of stress waves at different bedding angles，while the stress field image of crack tip reflects that the dynamic fracture toughness is related to the occurrence of premature failure in the specimen. With the increase of the bedding angle，the larger the kinetic energy consumed by the fracture of the specimen，the more uniform the failure.

The extra-high arch dam has the characteristics of three high and one strong. It exhibits complex, diverse and time-varying deformation behavior in long-term operation. Among them，the time-varying characteristics imply the evolution of dam system safety. This is of great significance to the service of engineering health. The specification clearly states that the deformation behavior of extra-high arch dams needs to be specifically studied. In this paper，the deformation time-varying characteristics of typical extra-high arch dams in China are analyzed. Then，based on the differences presented by the time-varying effects，the influencing factors and formation mechanism of the aging deformation of the ultra-high arch dam are analyzed in depth. Next，consider that the aging deformation is generated by the superposition of multiple factors and cannot be directly monitored. The aging deformation is regarded as a state vector，the measured deformation is used as the observation sequence，and the trend term of wavelet decomposition is used as the state sequence. A time-sensitive deformation separation method for ultra-high arch dams based on state-space model is proposed. Finally，the discriminant index of time-varying effect is proposed. This enables dam safety judgments from a time-varying perspective. The overall evolution law and trend of the aging deformation of ultra-high arch dams can be revealed, and the healthy service performance of the dam can be diagnosed.

In order to explore the damage and deformation characteristics of the tunnel structure across the landslide area under the action of earthquake，the seismic performance of the tunnel structure was improved by using the damping layer，the shaking table contrast test of the shock absorption optimization design of the tunnel under the main sliding surface was carried out for the first time. According to the dynamic response law of tunnel structure acceleration，an energy identification method based on Hilbert-Huang transform(HHT) and marginal spectrum was proposed to discuss the seismic damage deformation characteristics of tunnel structure，and the validity of this method was verified by peak Fourier spectrum amplitude(PFSA). The results show that：(1) The changes of seismic Hilbert spectrum and marginal spectrum energy can be used to identify the overall and local deformation of tunnel structure. The peak Hilbert spectrum interval of the tunnel structure has seismic wave frequencies of 15–17 Hz，while the peak marginal spectrum interval has seismic wave frequencies of 10–30 Hz. (2) The effect of the damping layer is obvious under the action of low intensity earthquake，but with the increase of earthquake intensity，the effect of the damping layer decreases，and the damping layer has a great influence on the spatial distribution of Hilbert spectrum peak, but has little influence on time and frequency. (3) The tunnel structure is firstly damaged by progressive cumulative damage in the arch region，and with the increase of seismic intensity，the damage site develops to the arch foot and elevation arch region，showing the continuous effect of spatial coupling deformation of regional damage and failure. (4) The seismic Hilbert energy of the high frequency component(＞30 Hz ) mainly causes local damage of tunnel structure，and the marginal spectral energy of the low frequency component(10–30 Hz) amplifies the seismic response of the surface slope. (5) Compared with the Hilbert energy spectrum, the marginal spectrum represents a certain Hilbert spectrum in each intrinsic mode function. It has rich frequency components and high recognition degree，which can clearly reflect the energy transfer and local seismic damage characteristics of the tunnel structure. The research results can provide a theoretical reference for the prediction of deformation damage mode of tunnel-landslide and the design of tunnel seismic mitigation technology in high seismic intensity areas.

The study of damage and failure of rock is of vital significance in the stability evaluation of rock engineering. Based on thermodynamic principles，the plastic constitutive model and hardening law are introduced into the framework of classical phase-field damage model. The damage evolution equation is driven by the plastic dissipation energy，during the plastic hardening stage and post-peak softening stage. In this way，a novel elastoplastic phase-field damage model for rock is established and its numerical implementation is given. The simulation results and analytical solutions of the phase-field homogeneous response are compared. The accuracy and reliability of the model under the plastic-damage coupling effects are verified. Then，two-dimensional and three-dimensional crack propagation in rock is simulated by the proposed model. The plastic shear damage and failure process of rock samples with pre-existing notches are studied. The simulation results are in good agreement with the existing experimental observations. By means of the proposed model，the complex propagation path of cracks in rock can be automatically and accurately tracked. Meanwhile，the damage evolution law of rock and the coupling effects between plastic deformation and non-local phase-field can be effectively described. The model can be further applied to simulate the damage failure and analyze the stability of rock in practical engineering.

Single，first mining coal seam gas extraction are in situ extraction，which is the key and difficulty of coal mine gas extraction. Compared with the conventional gas reservoirs，the mechanical state response of coal seam during extraction is more complex due to gas adsorption，and its evolutionary law and control mechanism on permeability are still unclear. Therefore，in this paper，the evolution of in-situ coal seam permeability and mechanical state during gas extraction were studied under different stress field conditions，and the control effects of multiple stresses on permeability were discussed. Results show that：(1) The coal seam horizontal stress and vertical strain decline slowly at first and then rapidly during the process of gas extraction. The changes in mechanical state with respect to pore pressure satisfies a linear relationship，while this behavior related to gas adsorption can be well described using a Langmuir-like equation. On this basis，a mechanical state model of in-situ coal seam was established considering the coupling effects of geo-stress，pore pressure and gas adsorption. (2) The permeability does not change significantly with vertical geo-stress，but shows a significant downward trend under the action of horizontal geo-stress. This is mainly attributed to the fact that there is a direct mechanical effect between coal seam cleats and horizontal geo-stress，but not with vertical geo-stress. The mechanical state in the horizontal direction plays a major role in controlling the evolution of permeability. (3) During in-situ coal seam extraction，the permeability increases slowly first and then rapidly with the decrease of gas pressure，reaching the maximum value when the gas is completely extracted(final state). However，when only pore pressure is applied，the permeability shows a trend of slow decline. (4) Both pore pressure and gas adsorption control the evolution of permeability by changing the effective stress and the internal interaction between coal matrix and cleats，of these，gas adsorption plays a major controlling role. In the current stress-dependent permeability models，the effective stress is simply used to represent the coupling effect of pore pressure and gas adsorption on the coal seam permeability，but the internal interaction between the coal matrix and cleats is ignored.

During cavern leaching in layered salt rock of China，the falling blocks formed by interlayer collapse may collide with the leaching tubing. The falling blocks are deposited on the cavern bottom to form accumulation characteristics. Therefore，laboratory experiments of free-falling homogeneous aluminum blocks in water were carried out using photography，in order to study the free-falling motion behavior of typical interlayer blocks. Based on the repeated block-falling experiment，distribution characteristics of block-falling points were preliminarily analyzed，and the probability of blocks colliding with the leaching tubing was qualitatively evaluated. The results show that：(1) The motion behavior of the free-falling block in still water can be divided into four types：steady falling，zigzag motion，tumbling motion and chaotic motion. (2) The motion behavior of free-falling blocks is greatly affected by its own geometric size ratio(such as length-to-width ratio，thickness-to-width ratio)，and is sensitive to initial conditions(such as initial angle). (3) For blocks with a thickness-to-width ratio of not more than 0.2 and a length-to- length ratio of not less than 2 falling in the cavern，there is a high probability of colliding with the leaching tubing. The research results may be expected to be applied to optimize the simulation software of cavern leaching，so that the shape prediction of salt caverns is more in line with the engineering reality，and the accident of leaching tubing broken by the block is reduced.

In order to study the three-dimensional fracture evolution characteristics of the main roof between adjacent coal seams，a mechanical model for the periodic fracture of the main roof plate structure with special-shaped load and elastic foundation was proposed to analyze the fracture position，fracture type and fracture pattern of the main roof. Moreover，spatial stability of the fracture structure was analyzed to discuss the instability conditions of the right-angle trapezoidal block and its response to the key factors. The results were as follow：(1) The fracture characteristics of the main roof are directly related to the distribution of the overlying load. When the  load is uniform，an“O-X” shaped fracture appears on the main roof，which forms an isosceles trapezoidal block and two arc triangular blocks. When the roof is subject to a single peak load formed by boundary coal pillar and goaf，an“O- ”shaped fracture appears on the main roof，which forms two right-angle trapezoidal blocks and two arc triangular blocks. Meanwhile，when the roof is subjected to a bimodal load formed by isolated coal pillar，the fracture pattern of the main roof takes an“O- ”shape，thereby forming a crushing zone between the right-angle trapezoidal blocks. (2) According to the instability criterion of the fracture structure，instability forms of right-angle trapezoidal block include sliding instability and rotation instability，and each form can be divided into overall instability and one-side instability. (3) As the overlying load(q) increases，the sliding instability coefficient(K1 and K2) decreases，while the rotation instability coefficient(K3 and K4) increases，indicating that the increase of load(q) is not conducive to the safety of surrounding rocks. The law of the fracture width(w) is consistent with the overlying load(q). However，when the fracture width reaches a certain threshold，the sensitivity of block stability decreases. As the cycle weighting interval(l) increases，the sliding instability coefficients(K1 and K2) and the rotation instability coefficients(K3 and K4) increase，indicating that the increase of the weighting interval simply induces rotation instability. As the mining height of the lower coal seam(m2) increases，the corresponding sliding instability coefficients(K1 and K2) decreases，and the rotation instability coefficients(K3 and K4) increases significantly at the end of the rotation，indicating that the increase of the mining height adversely affects the main roof stability. (4) Field ground pressure monitoring and borehole detection verify the rationality and reliability of the mechanical model and theoretical analysis.

To investigate the de-bonding failure mechanism of the full-length anchorage system and achieve the purpose of constructing high-quality anchor solids. A mechanical model of the bolt-anchor interface was established. The three stages of bolt pulling and sliding lead to the expansion of the anchor ring crack，and the changes of circumferential pressure at the bolt-anchor and anchor-rock interfaces with bolt sliding were analyzed. The locations of the maximum axial force and shear stress were deduced，and the de-bonding failure mechanism of the bolt-anchor interface was revealed. The criteria for de-bonding failure at the bolt-anchor and anchor-rock interfaces were proposed and verified by engineering examples and experiments. The results show that the de-bonding failure of the bolt-anchor interface is in the order of adhesion，mechanical interlocking and friction when the surrounding rock is deformed. The circumferential pressure of the surrounding rock directly affects the peripheral induced circumferential pressure for complete cracking of the anchor ring's radial cracks，and the tensile strength of the anchor determines the interface at which anchor de-bonding occurs. The bolt-anchor interface is de-bonded when the tensile strength of the surrounding rock is greater than the tensile strength of the anchor ring. The anchor ring cracks at the maximum axial tension of the bolt and de-bonds to opposite sides. When the tensile strength of the surrounding rock is less than the tensile strength of the anchor ring，the anchor-rock interface is de-bonded，or the surrounding rock is dislodged. The de-bonding of the anchor-rock interface starts from the bolt loading end and moves to the end of the bolt. How the pullout-resistant anchorage force acts is related to the intact form of the anchor ring，i.e.，bonding and mechanical interlocking when intact，partial bonding and mechanical interlocking after crack initiation，and frictional action after complete fragmentation. The de-bonding of the bolt-anchor interface of the full-length anchorage system fails with the neutral point shift in a cyclic diffusion de-bonding pattern.

Spraying cement mortar is often used in the construction of supporting structures in clay rock tunnels. The debonding of the interface may induce serious geology hazards. Taking the cement mortar-clay rock(C-C) binary as the research object，the shear and tension tests of the interface are carried out. Meanwhile，the influence of the initial moisture content of clay rock on the cohesive strength of the binary is analyzed. According to the macroscopic failure mode and microscopic pore characteristics of the binary，a method to determine the thickness of the interfacial influence zone is given. A new numerical model of C-C binary is proposed，which can simulate the effect of the interfacial influence zone. Finally，the debonding process of eccentric compression binary was taken by the new numerical method. The results show that：(1) In shear or tension tests，the failure face of the mortar-clay rock binary is located in clay rock near the interface，which is a weak zone of the binary，namely the interfacial influence zone(IIZ). (2) The shear stiffness Ks and residual friction coefficient k are independent of normal stress and decrease with the increase of water content of clay rock. (3) The infiltration and solidification of cement slurry will cause the swelling and shrink of clay rocks near the interface，which will produce a large number of initial micro-cracks in the interfacial influence zone. Based on the special pore characteristics of the interfacial influence zone，the thickness of the zone can be identified and measured by computer tomography(CT) and digital image processing technology. (4) The new interface cohesive model considers the bonding effect in the normal and tangential direction and the friction of the interface at the same time，which can simulate the stress-displacement relationship of binary accurately. (5) When the interface stays in an eccentric compression state，the debonding load decreases with the increase of the angle between the load and the interface normal. Therefore，the support structure of the eccentric compression tunnel is more prone to debonding.

Based on the propagation theory of elastic waves in frozen saturated porous and single-phase elastic media，the energy transfer problem of plane-S-wave incidence at the interface between elastic and saturated frozen soil media is studied. According to the boundary conditions at the interface and using the Helmholtz vector decomposition，the theoretical expressions for the transmission and reflection amplitude ratio and energy rates are derived. The energy rate of S-wave incidence at the interface between elastic and saturated frozen soil media is investigated numerically in relation to the incident angle，incident frequency，cementation parameters，porosity，saturation and contact parameters. The results show that the energy rate of the transmitted P1，P2，P3，S1 and S2 waves increased with the incident angle increased，and the reflected P waves disappear and the transmitted P1 and S1 waves show a significant pulse under the critical angle. The energy interaction rate between transmitted waves only decreased with saturation increased and increases with the remaining parameters. The energy rate of the transmitted S1 wave accounts for more than 90% of the total energy rates of the transmitted and reflected waves，and the energy rate of transmitted S1 waves will be increased with the various parameters increased. In addition，the incident frequency，cementation parameters，porosity and contact parameters have a significant effect on the energy ratios coefficient.

In order to study the dynamic response and failure mechanism of mountain tunnel across fault zone and portal section under earthquake，a large-scale shaking table test was designed and carried out according to the Kangding—Zheduoshan tunnel project. Through this test，the dynamic response and failure mechanism of tunnel lining under different surrounding rock conditions were compared and analyzed. The research results show that：in this shaking table test，the acceleration，dynamic earth pressure and strain responses of tunnel lining were mainly affected by the surrounding rock conditions. The quality of surrounding rock around tunnel lining is poor，and its seismic response is strong. Under the action of three-dimensional seismic wave，the PGA amplification coefficient of tunnel lining decreases gradually with the increase of seismic wave amplitude，and the difference between dynamic earth pressure and strain increases gradually. The tunnel lining is under eccentric stress，and the conjugate 45° of cross section is the main stress direction. In addition，the longitudinal failure of lining structure develops from the portal to the deep surrounding rock，and each section of lining has the same failure mechanism. The failure process develops from“inverted arch→arch foot→arch shoulder→arch crown”. By comparing and analyzing the final failure modes of tunnel lining，it is found that the seismic damage of lining structure in portal section and fault zone section is more serious，and the seismic damage of substructure is obviously more serious than that of superstructure. Therefore，in the same tunnel project，it is necessary to pay attention to the seismic fortification of the mountain tunnel across the fault zone and the portal section，and focus on the seismic design of the lining inverted arch，arch foot and other parts.

Through the field survey，multi-phase remote sensing data analysis，surface displacement monitoring，indoor test and numerical simulation analysis，the run-off slope in Wudu District，Bailongjiang River Basin，Gansu Province was taken as an example to conduct a deep discussion about the development characteristics，activity characteristics，formation and evolution process of the landslide，and the safety of unstable blocks in the run-off slope landslide source area was scientifically evaluated and predicted. The results showed that：(1) run-off landslide was a large accumulation landslide in a high place，which was formed by the coupling effect of multiple factors，with a volume of 188.35 × 104 m3. It can be divided into three sections：the upper potential slip source area，the middle narrow flow area，and the lower siltation accumulation area，whose evolution was overall characterized by multiple stages，multiple layers，and progressive retrogression. Each slide body is characterized by the creep-tensile pattern and push deformation. (2) Under the conditions of different and uncoordinated landforms，the formation process of run-off landslide was dominated by active neotectonic movement and based on the disaster strata prone to slip，while the continuous deterioration of rainfall，the seismic cracking effect of historical strong earthquakes and the creep effect of faults were the main factors of landslide instability.       (3) According to the stability calculation，it can be known that the landslide was basically in a stable state or an unstable state，and there were still different degrees of deformation and damage in several parts. After using River-Flow2D software to simulate the start and movement process of the upper potential slip source area under extreme rainfall conditions，it was shown that the maximum sliding distance was 810 m，the maximum velocity could reach 33.5 m/s，and the maximum accumulation thickness was 26.7 m，with the total accumulation volume of about 121 × 104 m3，forming a local river blockage disaster chain. This research can provide a scientific basis for the prevention and mitigation of such high-level landslides in the basin.

To calculate the influence of the uplift deformation of the foundation pit bottom on the longitudinal deformation of the underlying tunnel, the calculation model of foundation pit excavation deformation is established. A cooperative tunnel model of rotation and staggered platform deformation is adopted. Based on the virtual image technique，the formulas of longitudinal deformation of the underlying tunnel caused by the excavation of the foundation pit are derived. Three sets of typical cases were selected for calculation and analysis. The B-W and B-P methods are compared to verify the correctness of the calculation method. Moreover，the influence of four factors，namely the maximum uplift of the pit bottom，the excavation width and depth of the pit and the buried depth of the tunnel are analyzed. The results show that there is a positive correlation between the maximum uplift value of the foundation pit bottom and the maximum uplift value of the underlying tunnel. As the excavation width of the foundation pit increases，the uplift value and uplift range of the tunnel increase accordingly. The buried depth and the uplift value of the underlying tunnel show a nonlinear decreasing law. The longitudinal deformation of the underlying tunnel can be effectively controlled by reducing the uplift deformation of the pit bottom and the pit excavation width along the tunnel axis.

High-strength layer at the bottom of foundation is treated as rigid layer to determine ultimate bearing capacity of strip foundation. Failure modes of strip foundation under the action of ultimate load become extremely complex when it is restricted by the rigid layer at the bottom of foundation. Under this scenario，ultimate bearing capacity of foundation is derived using limit analysis，slip line or other numerical methods，which is less likely to obtain quantitative failure modes. In this paper，the finite element upper bound method with rigid translational motion element is adopted to conduct systematic analysis. The upper bound solution reflected by curves and the slip line failure modes for bearing capacity factor Nc related to the cohesion is mainly discussed. The related factors such as the thickness of soil layer，the internal friction angle of soil mass and the finite friction of foundation at the interface are studied. The results show that the changes in Nc and the correction Kc influenced by rigid layer are not prominent with varying friction angle and thickness of the soil layer when the thick foundation is above the rigid layer. However，for thinner soil layer，the Nc and Kc increase sharply with the increase of internal friction angle of soil mass and the decrease of soil thickness. Furthermore，for the thinner soil layer，the friction conditions of contact surface between strip footing and foundation has a significant influence on the failure modes. In other words，the decreasing roughness of the bottom of the foundation makes the Nc smaller. It is significantly  different from the one free from the restriction of the bottom rigid layer. Finally，the conversion relationship between the ultimate bearing capacity coefficient of the foundation Nc and Nq is verified through the analysis using the finite element upper bound method with rigid translational motion element.