In order to study effects of the unloading rate on the dynamic characteristics and failure modes of deep rock，the improved SHPB test system combined with dynamic and static loadings，which can simulate the mechanical environment of deep rock excavations subjected to impact disturbance during high static unloading process，was used to carry out the frequent disturbance test under high axial pressure and unloading. The samples were applied by a complete cycle loading. Specifically，a sample was firstly applied with a given axial load referring to the uniaxial compressive strength of deep serpentine，then unloaded till to 50% of the axial load at a certain rate and at the moment，an impact load of 0.4 MPa was exerted，and finally the unloading process terminated. The test results show that the dynamic stress-strain curve of rock and its envelope have a stage of nonlinear development following a short straight line stage，which indicates that plastic deformation of rock specimen plays a dominate role during impact disturbance and unloading. The increase of the unloading rate leads to obvious delaying effect of rock specimen on the impact load，resulting in an increase of rock?s mean strength and the cumulative number of impact disturbance，and causing the interconvertible phenomenon of brittle and ductility. With increasing the pre-axial stress and the unloading rate，the fragmentation of damaged rock mass increases，and they lead to tensile and shear failures，respectively.

On the basis of the shear strength formulation arising from unified strength theory under plane strain conditions，unified solutions of the required cohesion and the safety factor of the backfill were derived for mine backfills with a high height-to-width ratio. Influencing factors such as the intermediate principal stress effect，the backfilling order and the back wall cohesion as well as the top surcharge were comprehensively considered in the unified solution. The solutions were simplified combining with an engineering case and applied to a specific example. Comparability analysis of the proposed solution was conducted, and parametric studies were also carried out. It was found that the proposed solution contains many conventional and new results and hence, has extensively theoretical value and good comparability. It was also shown that calculation formulas of mine backfills for two different objectives are both easy to use and choose in engineering practice. The influence of the intermediate principal stress effect，the backfilling order and the back wall cohesion on the calculation of mine backfills is significant，and effective usages of these three factors can generate an important economic benefit. Existing results available in the literature are conservative in comparison to the proposed result. The influence of the top surcharge cannot be neglected and should be evaluated for obtaining an optimal calculation of mine backfills.

Daguangbao(DGB) landslide，with a 3 m deep fragmented rock zone at 1.8 km long sliding surface，is a gigantic landslide triggered by 2008 Wenchuan earthquake. The fragmented zone formed due to historical tectonic motion and Wenchuan earthquake. Because of the unique and complexity，DGB landslide is wildly studied over the world. Based on 10 years? investigations，a geological model of DGB landslide was proposed. DGB landslide was a gigantic earthquake-induced landslide in carbonate strata and shear failure was triggered in a bedding fault. Shaking table model test was conducted with a weak layer simplified from the bedding fault. The results reveal that the deformations of the weak layer and the upper hard layer are discordant during vibration and the discordant deformation results in vibrating compression-tension or vibrating shearing pressure within the weak layer. It was concluded that rock fragmentation within the shear zone is ascribed to the discordant deformation response of the bedding fault and that the discordant deformation of the bedding fault and the corresponding rock dynamic damage trigger DGB landslide.

In order to investigate the effect of high temperature dehydration on physical and mechanical properties of natural gypsum rock，standard rock samples contained different crystal water were prepared at 220 ℃ within a certain time and tested with scanning electron microscope，ultrasonic wave and conventional triaxial compression. The influence of the dehydration time on physical and mechanical behaviors of gypsum rock，including microstructure，porosity，longitudinal wave velocity，conventional triaxial compressive strength，elastic modulus，peak strain，cohesion and friction angle，was analyzed. The results are showed as follows. High temperature effect on gypsum rock is an extreme complex physical and chemical process. Gypsum rock can be obviously weakened by high temperature dehydration. With increasing the dehydration time，the crystal structure and shape of gypsum rock change gradually and the numbers of micro-cracks and micro-voids increase gradually，which leads to the deterioration of the physical and mechanical properties of gypsum rock. The dehydration amount，the apparent density and the porosity are nonlinear with the dehydration time. The dehydration rate of gypsum rock is larger within 6 hours while decreases within 6 to 24 hours. P-wave velocity of gypsum samples decreases to some extent due to high temperature dehydration. The damage factor decreases linearly with the porosity within 6 hours but changes little after 6 hours. The deformation characteristics of gypsum rock under triaxial compression are influenced by the confining pressure and the high temperature dehydration time. The influence of the dehydration time on the deformation parameters of gypsum rock samples including the elastic modulus and the deformation modulus is far greater than that on the confining pressure within 4 hours，but the confining pressure has little influence on the elastic modulus and the deformation modulus. With increasing the confining pressure and the dehydration time，the brittleness of the specimens decreases but the plasticity increases. Triaxial peak strength of the samples increases monotonously with the confining pressure，which accords with Coulomb strength criterion. The strength of gypsum rock material is negatively correlated with the dehydration time without considering the influence of the confining pressure. The failure mode of gypsum rock samples has no direct relationship with the confining pressure and is more complex with longer dehydration time.

Dynamic caustics test and ABAQUS numerical analysis method were used to study the dynamic fracture behaviors and the stress field distribution of burst cracks at the end of single cylinder and double cylinder blastholes with different spacings at simultaneous initiation. The law of crack propagation at the end of blastholes was investigated. The results show that，compared with single hole explosion，the stress field produced by double cylinder blasthole explosion superimposes between the blastholes，which makes the radial cracks more easily form between the boreholes and increases the breakage degree between the blastholes. The propagation velocity and the stress intensity factor of the cracks at the end of single hole are between the inner and outer ends of the double holes. In the vertical direction near the end of the double cylinder blasthole，the compressive stress between the blastholes play a dominant role，which inhibits the relative propagation of the explosive cracks in the adjacent blastholes. The smaller the blasthole spacing，the earlier the crack arrests and the shorter the propagation length. In the far area outside the end of the double cylinder blasthole，the superposition action of explosive stress waves between and outside the holes is characterized by alternation change of tension and compression at t = 0—90 us，and then appears in tension mainly. The blasting crack at the outer end of the blasthole has a large curvature degree and has a short stage from crack arrest to re-initiation. The smaller the hole spacing，the earlier the curvature occurs and the earlier the transition from crack arrest to re-initiation. The crack length has no significant change，but it is larger than the crack length at the end of single hole.

In order to find out the large deformation mechanism of tunnels with small intervals through squeezing soft rock stratum and to propose the control technology of large deformation of surrounding rocks，the influencing factors，the deformation law of the surrounding rock and the mechanical characteristics of the lining structure were studied by theoretical analysis，numerical calculation and field test. Results show that the large deformation of the tunnel is resulted from the coupling effect of multiple factors such as high geostress，steeply dipping strata，low surrounding rock strength and approaching construction. The unloading disturbances of the rear tunnel exerts a bias load to the preceding tunnel on one hand，and on the other hand，results in the bending damage of the surrounding rock of the preceding tunnel near the central rock pillar suffers outwards the tunnel，including the decrease of the displacement of the preceding tunnel's side wall near the central rock pillar，the transformation of the force state of the initial support in the arch and the increase of the tensile stress of the secondary lining in the arch and the inverted arch. According to the surrounding rock?s deformation and the support force condition，the small interval tunnel is divided by the influence degree of proximity construction，which can be used as the basis for the dynamic adjustment of the control measures and the engineering analogy. The construction process should be controlled strictly to avoid the secondary lining?s end of the preceding tunnel lying behind the excavation working face of the rear tunnel，and other measures such as adjusting the shape of the tunnel section according to the stress distribution characteristics，changing the bolt angle according to the characteristics of the rock mass and protecting the central rock pillar according to the proximity disturbance condition should also be taken into account.

According to the regional landslide features，an evaluation index system developed based on the characteristics among different types of landslides，can make landslide susceptibility evaluation more scientific and accurate. Taking Wanzhou district of Three Gorges Reservoir as an example，the regional landslides were divided into steeply inclined strata landslides and gently inclined strata landslides based on geological situation，landslide spatial distribution and characteristics. Twelve index factors including elevation difference，slope angle，aspect，plane and profile curvatures，stratum lithology，water distribution，geological structure，highway，stratum dip，rainfall and weak interlayer containing montmorillonite were obtained to build the basic evaluation system，and a weighted frequency ratio model(WFR) was proposed to perform regional landslide susceptibility evaluation based on the logistic regression(LR)-fuzzy analytical hierarchy process(FAHP) method(LR-FAHP). A susceptibility evaluation index system for different kinds of landslides was built up by sorting the importance of all index factors and calculating their weights，and susceptibility level prediction of regional landslides was performed based on GIS platform. The results indicates that，compared with LR，FAHP and FR models，WFR model can promote the evaluation accuracy by 4%‐9%，proving that the LR-FAHP method is a good method for calculating the weight of evaluation index factors. It is also shown that the success rate and the prediction rate of susceptibility evaluation by WFR model with landslide classification reach 79.2% and 79.6% respectively，which are respectively better than those by WFR model without landslide classification. The model can provide a reliable approach for building up evaluation index system and regional landslide susceptibility.    

The slate with foliations exhibits significant anisotropies in terms of physical and mechanical properties. Brazilian splitting tests were carried out considering two factors such as the foliation angle and the loading direction，and the three-dimensional structure effects of foliation planes were studied in depth. The results show that the three-dimensional structure effects of foliation planes have a significant influence on the mechanical strength and failure characteristics of slate and that the variation trends of Brazilian splitting strength with loading direction are obviously different at different foliation angles. When the foliation angle ranges from 0°to 15° or from 75°to 90°，the three-dimensional spatial effect of the fracture surface is not obvious and the macroscopic cracks on both sides of the disc have certain similarities. When both the foliation angle and the loading direction are in the range of 30° to 60°，however，the fracture surfaces present a three-dimensional spatial distribution due to the coupling effect of the two factors and the macroscopic cracks formed on both sides of the disc exhibit an approximately anti-symmetric positional relationship. The energy storage capacity of slate in Brazilian splitting tests is negatively correlated with the foliation angle but positively with the Brazilian splitting strength. It is also revealed that the foliation angle and the loading direction respectively have more significant effects on the Brazilian splitting strength and the fracture pattern，and that，with increasing the foliation angle，the anisotropy ratios of the Brazilian splitting strength and the energy show an increasing trend. The research results can provide a reference for the analysis of tensile mechanical properties of transversely isotropic rocks.

The wells at different positions have different production laws in the inclined coal seam, which is different from the flat seam. In order to enhance coalbed methane(CBM) recovery efficiency in the inclined seam， the well type and well pattern arrangement for the inclined coal seam were studied considering the effect of gravity differentiation. According to the characteristics of different structural positions of the inclined coal seam and combining gas-water distribution and well production laws，the well type and well pattern arrangement methods were optimized and verified by numerical simulation. The results show that the horizontal wells should be located at the top of the coal seam at the high position of the structure and along the inclined direction of the coal seam at the flank with the heel or the toe of the horizontal well lying at the bottom of the coal seam, and that vertical wells or T-shaped wells can be used in the low position of the struture. The well density should be increased at the high and low positions，and reduced at the structural wing. In anticline coal seam，umbrella-shaped well pattern is adopted. In monoclinic coal seam，well pattern can be arranged along the contour line of the coal seam，and the well row spacing increases gradually from both the top and the bottom to the wing.

Based on wave theory and superposition principle，the spatial variation of motions caused by incident seismic waves was investigated by taking the oblique incident plane primary wave in semi-infinite space as a study object in this paper. According to the wave superposition pattern of particle motion，the half-infinite space was divided into superposition and separation domains. An analytical expression of the border line of two spaces was given and the control parameters of the border line were studied based on the dimensionless superposition range coefficient. The spatial variation and polarization characteristics of particle motion in different spaces were studied. The result shows that the border of two domains is determined by separation lines of arbitrary two waves of incident P wave(PI)，reflected P wave(PR) and reflected SV wave(SR). An implicit equation was given to obtain the critical angle which controls the border. It is shown that the border is respectively determined by the separation lines of PR and SR，PI and PR，and PI and SR in the cases of the incident angle less than the critical angle，the incident angle larger than the critical angle and the amplitude of PR equal to zero. There is a one-to-one correspondence between the polarization angle of particle motion on the surface and the incident angle. In superposition and separation domains，the polarization characteristic of particle motion is in consistent with the seismic wave when the particle motion is contributed by one single wave，but changes with time when particle motion is contributed by different waves.

The rockfall attenuator system aims at preventing rockfall hazards by controlling the rockfall trajectory and attenuating the rock impact energy. In order to study the energy dissipating performance of the system，the laboratory rockfall impact experiment was conducted，a multiposition distributed counterweight method was put forward based on the net deformation analysis，and a numerical model was built to study the performance of the system under high-speed rockfall impact and to simulate the protecting process of the system against the rockfall impacting  simultaneously or continuously. The research results show that the multiposition distributed counterweight method obviously improves the protection performance of the system. The attenuation rates of the rockfall velocity and the kinetic energy increase by 20.02% and 21.56% at most respectively. The counterweights at different positions on the net improve the protection performance of the system differently. The closer the counterweight to the falling position，the more obvious the improvement. Meanwhile，by using distributed counterweight method，the high-speed rockfall impact and simultaneous/continuous rockfall impact can also be defended successfully. The research results can provide a reference for the design and engineering application of the rockfall attenuator system.

In order to research the outburst mechanisms of rock cross-cut coal uncovering，the outburst rock mass，stress environment and physical phenomena in rock cross-cut coal uncovering were analyzed，and a analytical model for the shape of the coal plastic zone and its induced outburst mechanism of rock cross-cut coal uncovering was established according to the butterfly-shaped failure theory of coal rock. The study results show that there is a butterfly-shaped promotion in the size and the shape of plastic zones s of rock cross-cut coal uncovering，and that the size of butterfly-shaped plastic zone is highly sensitive to the changes of the principal stress ratio and the strength of the coal rock mass. When the ratio or the strength reaches a critical condition，a slight increment would result in a massive expansion of the plastic zone. The outburst mechanisms of coal and gas induced by the butterfly-shaped mutation of plastic zones in the process of cross-cut coal uncovering were revealed. A butterfly leaf plastic zone forms within a very short time due to the changes of the principal stress ratio and the strength of the coal rock mass，which triggers a sudden release of both the elastic energy and the gas energy in coal rock and then，a coal and gas outburst accident. A computer replay of the 6.20 extraordinarily prominent case of Hongling Coal Mine was carried out，and the calculated shape and scope of the butterfly-shaped promotion in the coal body are in good agreement with the prominent cavity shape and the outburst coal volume in the disaster case. The research provides a new idea for investigating the occurrence mechanism of rock cross-cut coal uncovering.

Soft soil foundations are repeatedly subjected to periodic vibration and time intermittence during the subway operation period. The mechanical characteristics of soft soils in intermittent periods will affect their long-term dynamic characteristics，but most of previous researches on the dynamic characteristics of soft soils under traffic loads neglected the effect of time intermittence. Considering different dynamic stress levels and coupling effects of different vibration times and intermittence times，a series of undrained continuous-stopping vibration triaxial tests were designed to study the long-term pore pressure and deformation characteristics of the undisturbed K0 consolidated marine soft clay under uncontinuous subway loads. By comparing with the continuous vibration tests，it was found that the intermittence has a significant effect on the dynamic characteristics of the soft soil. Due to the change of the dynamic characteristics during the intermittent period，the maximum residual pore pressure and strain of the soft soil after loading stabilization decrease obviously，and the number of vibrations required to stabilize the pore pressure and the strain decreases while the time increases. Based on the test results，the mechanism of time interval effect and the influence of intermittence time on dynamic characteristics of soft soil were analyzed in depth. It is shown that the further adjustment of the internal structure of the soft soil during the intermittent period reduces the elastic aftereffect pore pressure and the strain that fail to recover in time during the vibration period，and that the partial pore pressure and the strain repeatedly occur in the vibration period，which makes the calculated residual pore pressure and strain are far greater than those resulted from the continuous vibration. Under the same condition，the longer the intermittence time is，the greater the pore pressure and the strain response of the soft soil are weakened，the smaller the maximum residual pore pressure and the strain are，and the longer the time required to enter a stable period. This study has a positive significance for calculating the long-term settlement of soft soil foundations under subway loads.

Offshore turbines are often supported on large-diameter steel pipe monopoles. There is a significant effect of soil-added-resistance force caused by the rotation of the pile section of laterally loaded large-diameter steel pipe piles. The impact of the soil-added-resistance force on pile lateral capacity should be taken into account. A modified Winkler foundation beam model was proposed to model the lateral bearing loads of large-diameter steel pipe piles，in which the soil and the pile are respectively modeled by nonlinear springs and C1 beam elements considering the shear deformation. Assuming that the secant stiffness of the soil load transfer curves inside a pile element is linear，finite element formulas were deduced to develop a coupling method which can take into account the soil-added-resistance force caused by the rotation of the pile section，and a corresponding program was written. Two case studies were performed to verify the coupling method developed in this paper，and their computed results were compared with those obtained by the p-y method only considering the lateral nonlinear springs? effect. The results show that the coupling method can better predict the laterally loaded characteristics of the large-diameter steel pipe pile. The closer the deformation of the large-diameter steel monopile is to the rigid rotation，the more obvious the soil-added-resistance force caused by the rotation of the pile section. On the contrary，the soil-added-resistance force can be ignored while the deformation of the large-diameter steel pipe pile is close to the flexible deformation.

In order to analyze the influence law and mechanism of dry-wet circulation on the mechanical properties of earthen archaeological site，the dry-wet circulation test was carried out by using the self-made stratified sampling test device. The test lasted as long as 15 months. The samples which were prepared for microscopic test and triaxial drainage shear test under low stress conditions were from the soil column after a certain number of dry and wet cycles. Triaxial drainage shear test results show that the strain softening characteristics are enhanced significantly when the soil experiences the first dry-wet circulation. As the number of dry-wet cycles continues to increase，the strain softening decreases gradually on the whole. The cohesion c and deformation modulus E0 also increase significantly after one cycle，and then gradually decrease. The strength and deformation parameters of soil show the law of nonmonotonic change under the action of dry-wet circulation. It was suggested that mechanical parameters of dry-wet circulation after stabilization under low stress level should be used for the shallow damage restoration project in earthen archaeological sites. Combined with the mercury injection test results，It was concluded that the main reason of the nonmonotonic change law is that the volume of intra-aggregate pore decreases after one cycle and then the volumes of intra-aggregate，intragranular pores and intergranular pores increase at the later stage of circulation. The dry-wet circulation effect of silt mechanical properties may be mainly controlled by the uniform shrinkage and local failure of clay "three-dimensional grid structure" in silt，which is essentially different from that of clay. The research can provide technical basis and theoretical support for the preventive protection and reinforcement of earthen archaeological site.

Aiming at the problem of unclosed freezing wall in seepage fields，a coupled control equation of seepage field and freezing temperature field was established based on the heat transfer theory of porous media and Darcy?s law，and the interaction mechanism between the two fields was discussed. According to the similarity theory，a model test system for the frozen double-row-pipe with plum blossom arrangement under percolation was built，with which a orthogonal test aiming at main factors affecting the formation of frozen wall in high velocity percolation layers was conducted. For comparison，another test with frozen single-rowed pipe was carried out subsequently. The results show that，for double-rowed pipe freezing，the groundwater velocity，the hole spacing and the salt water temperature are，respectively，the primary factors affecting the thickness of the upstream frozen wall，the frozen wall intersecting time，and the downstream frozen wall thickness and average temperature. It is also indicated that，when groundwater velocity ranges from 5 m/d to 25 m/d，the thicknesses of upstream and downstream frozen walls of double-rowed pipe freezing are respectively larger than those of single-rowed pipe freezing by 62.6%–151.8% and 3.7%–33.8%，and at the same time，the intersecting time and the average temperature of the frozen wall decrease by 7.1%–91% and 12.1%–103.9% respectively. The limit velocity of the frozen wall intersecting under different conditions was obtained based on the nonlinear regression between the frozen wall intersecting time and the groundwater velocity. Finally，effective countermeasures for frozen engineering under seepage were put forward，which provides a significant reference for the design and construction of similar frozen engineering.

With the large-scale development of underground space，the hazards induced by leakage of groundwater and sand in excavations occur frequently. DEM-CFD method was adopted to simulate the process of this kind of hazard. The microscopic parameters of soil and fluid were determined based on laboratory tests，biaxial model of the particle flow code and seepage model. A numerical analysis model was developed to research the laws of ground movement，ground loss and ground stress field due to the leakage of groundwater and sand. Two typical strata including water-rich sand stratum and water-rich sand layer overlying clay stratum were considered. The results show that，for the water-rich sand stratum，the leakage of groundwater and sand induces a settlement trough on the ground surface outside the excavation，the maximum value of ground surface settlement is proportional to the soil mass loss ratio，and the leakage of groundwater accelerates the ground loss and results in the concentrated movement of ground towards the leakage point. It is also indicated that，for the water-rich sand layer overlying clay stratum，there exists a critical soil mass loss ratio leading to the crack of the ground surface，and the thicker the clay layer，the greater the critical soil mass loss ratio is. Furthermore，the ground around the leakage point could be divided into hollow area，loose area，main tensile stress area and complex stress area. The results of the research provide a reference for the hazard control and delicacy management during the leakage of groundwater and sand in excavations.

In unsaturated expansive soil regions，ground upheaval threats the safe operation of high-speed ballastless railway. To reduce or eliminate the ground upheaval and to cut down the engineering investment of high-speed railway，a long-short micropile structure considering atmospheric influence depth of unsaturated expansive soil foundations was proposed on the basis of the traditional micropiles. In accordance with several basic assumptions，an upheaval calculation methodology of expansive soil foundations reinforced by long-short micropiles was derived based on the analysis of working mechanics and stress path. Field tests of swelling-shrinkage responses of an expansive soil foundation under the subgrade bed of Yun-Gui high-speed railway were performed，and key design parameters were investigated. The results show that long-short micropiles can significantly reduce the upheaval of expansive soil foundations by about 60%. The ground upheaval can be reduced or even eliminated by increasing the pile diameter of long-short micropiles，reducing the pile spacing，optimizing the elevation of the railway line or appropriately increasing the pile length. Based on analysis of parameter sensitivity，influence weight ratio and pile setting scheme，a design principle of long-short micropiles to control ground upheaval under ballastless track subgrades in expansive soil regions was proposed，namely that small pile diameter and small pile spacing is recommended to reinforce expansive soils under ballastless track subgrade，that the length of long micropiles should be slightly larger than the critical pile length and not less than the atmospheric influence depth，and that the length of short micropiles should be greater than the depth of soil layer affected by atmosphere dramatically.

In order to overcome the difficulties such as the spatial variability of correlated multi-parameters and the implicity of limit state equations in the reliability analysis of soil slope stability，a moment method based on the layered discrete random field of soil parameters was presented. According to the local average process theory and the vertical variation of soil parameters，a layered discrete random field model of soil parameters was proposed，in which the soil parameters within each soil layer are regarded as random variables and the spatial variability of the soil parameters in adjacent layers is described by variance functions. The reliability function of soil slope stability was simplified as a reduced-dimension function of soil parameters，and the reliability of the slope stability was calculated by the four-order moment method. Comparisons among the proposed method，MCS and the multi-random response surface method using slope examples were performed and a good agreement among them was illustrated.