Mining pressure occurrence is strong in longwall faces of deep-buried thick coal seams with weakly consolidated thin bed rock. The compression and damage of hydraulic supports happen frequently due to dynamic loads resulted from roof failure. In order to improve surrounding rock control of such longwall faces，adopting laboratory experiment，theoretical analysis and in situ measurement，the occurrence mechanism of the dynamic impact effect is analyzed and the determination method of the dynamic load is discussed. The results show that mining-induced fractures initiate within upper alluvium in the referred longwall face，and that upward and downward propagations of the fractures respectively lead to collapse of the alluvium and rupture of the main roof，leading to the development of a caving arc in the overburden. If the caving arc undergoes local instability，the new caving arc presents an asymmetric shape. In this case，the main roof fails in tension，exerting a static load on the hydraulic support. If the caving arc shows integral instability，the new caving arc presents a symmetric shape. The main roof fails in shear，exerting a dynamic load on the hydraulic support. Downward propagation speed of the fractures is so fast that it penetrates the interface between the alluvium and the bed rock inertially. The main roof becomes a cantilever beam with inertial cracks at the top edge，seriously deteriorating the load-bearing capacity. The times required for the fracture propagating to the vault and the foot of the caving arc are consistent. Before caving of the alluvium，strain localization is highest at the initiation position of the fracture，followed by the arc foot and the arc vault. Instability of the caving arc leads to quick transition of the gravity load of the caving alluvium to the deteriorated cantilever beam，resulting in shear stress concentration at the inertial crack tip. Accordingly，shear failure happens to the main roof，and the strain energy stored in the main roof is transformed to be kinetic energy of the broken block. Non-statically initiated block impacts the bottom immediate roof and the hydraulic support，resulting in dynamic loads. The boundary function of the caving arc is determined with upper-bound theory，and the methods for calculating the load exerted on the main roof and the strain energy stored in the main roof are moreover put forward. After that，the initial speed of the broken block and the impacting force of the main roof are achieved based on energy and momentum conservation principles. At last，hydraulic fracturing is applied to 14030 face of Zhaogu 2nd coal mine to release the strain energy concentrated in the main roof，which helps to prevent the occurrence of dynamic impact phenomenon.

Based on the statistical damage mechanics theory，a three-dimension damage model reflecting the characteristics of dilatancy was established. In the proposed model，load is borne by the undamaged part and the damaged part of rock. The deformation of the undamaged part of rock is elastic，while the deformation of the damaged part includes elastic and plastic deformations under the influence of the residual strength and the dilatancy angle. In order to adapt to the different post-peak shapes of the stress-strain curve，a new damage evolution equation is established by introducing the modified factor R in an exponential form into the Weibull distribution function，and a micro-element strength function is established based on the Mohr-Coulomb criterion. Parameters F0 and m of the model can be obtained from the peak point of triaxial compression test，and parameter k depends on the post-peak shape of the curve and can measure the brittleness of the rock. Applicability verification indicates that the theoretical calculation results of the statistical damage constitutive model are in good agreement with the conventional triaxial compression test results of pebbled coarse sandstone，siltstone and Ohya stone. Therefore，the model can accurately describe the strain softening，dilatancy characteristics，residual strength and elastoplastic strain evolution during the failure process of rock. Besides，the model can describe the anisotropic deformation characteristics of rock under true triaxial condition，and can reveal the damage mechanism of cohesive resistance weakening and frictional resistance strengthening.

The deformation and failure evolution characteristics of combination rock with weak interlayers are studied by using a CCD camera as observation method，and the deformation field under uniaxial compression is analyzed by the digital speckle method. Then the effect of the interlayer interaction is theoretically analyzed. The results indicate that the horizontal tensile strain localization zone first appears in the middle weak interbedded rock，and that，as the load increases，the localized zone develops towards the rock contact surfaces. Under the interlayer action，the upper and lower layers of rocks produce localized zones and appear vertical tensile cracks first，greatly reducing the compressive strength of the weak interlayer composite rock. The middle weak-strength rock is affected by the upper and lower layers of rock and undergoes tensile failure，resulting in the final failure of the specimen. After cracks appear in the upper and lower rocks，in the area to the left of the cracks，the restraining effect of the upper and lower rocks on the weak-strength rocks in the middle is weakened，causing the compressive strength of this part of the rock to drop suddenly and even failure. The theoretical calculation shows that，in a certain range from the interlayer contact surface，the compressive strengths of the upper and lower layers of rocks decrease while the compressive strength of the middle weak layer increases. The variation range of the compressive strength is related to rock mechanics parameters. The theoretical calculation also reveals that the compressive strength of the upper and lower layers of granite is reduced to 32.514 MPa，about 0.32 times of the initial strength and smaller than the compressive strength of the intermediate weak-strength rock，and hence，is the controlling factor of the compressive strength of the weakly interbedded rock. The compressive strength of the rock with weak interlayers obtained through model experiment is 33.91 MPa，which is consistent with the theoretical calculation result. It is observed that，during the experiment，the upper and lower layers of granite first appear cracks，indicating that their compressive strength is lower than that of the middle weak-strength rock，which is also consistent with the theoretical analysis. The results can be used as a reference for the occurrence mechanism and prevention of coal pillar rock burst.

In order to study the influence of the long-term strength change on the stability of the surrounding rock in deep roadways under the action of groundwater. The sandstone in Wanfu Coal Mine was taken as the main research object，and uniaxial compression test and uniaxial creep test were carried out with different moisture contents. It is found that the water content has an obvious softening effect on the rock strength and long-term strength. According to the viscoelastic strain law of isochronal creep curve，a viscoelastic modulus  was proposed，and the nonlinear softening laws of the viscoelastic modulus and the elastic modulus with the water content were obtained. A new nonlinear viscous dashpot element that can describe the accelerated creep behavior was proposed，by which an improved Nishihara model was developed based on the combination of the damage theory and the experimental results. The model was used to identify the parameters of the creep experiment results，and it is shown that the model has a good fitting effect on the experimental results，which means the model can better describe the mechanical behavior of each stage of creep. At the same time，it is found that the damage creep model parameters ，， have little difference under the same stress，and each parameter is affected by the creep stress. Specifically，has a linear relationship with ，while  and  have a negative exponential relationship with . Therefore，the creep state of rock can be reasonably analyzed according to the moisture content and different stress levels. Combined with the new long-term creep strength discrimination method，the developed model can provide a basis for the long-term stable use of roadways and the advance prediction of creep failure of roadways.

Direct shear tests on artificial joint specimens under different normal stress conditions were carried out. Based on the nonlinear characteristics of the experimental results，the linear Goodman shear model was modified，and a nonlinear full-scale shear model was proposed. Most parameters of the model can be obtained from experimental data. The new model can accurately describe the nonlinear relationship between the shear stress and the shear displacement during joint slipping. Referring to the method of determining tangential and normal coupling stiffness coefficients proposed by Saeb and Amadei，a new mathematical formula of the tangential coupling stiffness coefficient，which can describe the nonlinear characteristics of joint slipping，was deduced on the basis of the proposed nonlinear full-scale shear model. A novel incremental shear model was then established. The new model can simultaneously simulate the tangential and normal deformation behaviors of the joints. The incremental shear model was respectively solved by computer programming under the boundary conditions of constant normal load(CNL) and constant normal stiffness(CNS). The results obtained by the nonlinear full-scale model were compared with the available laboratory results，showing an excellent consistency and verifying the suitability and reliability of the proposed full-scale model. Considering both the CNL and CNS boundary conditions，the simulation results of the proposed incremental model were compared with the available laboratory results as well as those of the Saeb-Amadei shear model. The shear stress obtained by the incremental model shows better agreement with the experimental results. It is indicated that the proposed incremental model is more appropriate than the Saeb-Amadei shear model in describing the shearing behaviors of joints. The normal stress and normal displacement calculated by the incremental model are in agreement with the experimental results，indicating the proposed model can generally illustrate the normal mechanical behavior of joint shearing. Therefore，the proposed incremental model can predict both the tangential and normal deformation behaviors of the joints during the shearing process，which verifies the applicability and reliability of the incremental model under different boundary conditions.

In order to study the influence of size on damage and failure of cemented gangue backfill body(CGBB)，cube specimens with sizes of 70.7，100，150，200 and 300 mm were prepared for uniaxial compression test. The acoustic emission(AE) and resistivity values of specimens during loading were monitored，and the micro morphology of the specimens was observed by scanning electron microscope. The damage evolution and failure mode of CGBB with different sizes were discussed. The results show that the uniaxial compressive strength of CGBB decreases with increasing the size，and the failure mode of CGBB gradually changes from splitting failure to shear failure with increasing the size. The smaller CGBB shows stronger AE activity in the initial compaction stage than in the post-peak failure stage. The sudden change of AE ringing and the stable stage of resistivity can be used as the precursor to judge the failure of CGBB. According to the test results，a calculation formula of size effect law of the compressive strength of CGBB and a damage constitutive model of CGBB with different sizes were established，which can provide reference for the design of backfill body in structural backfill.

In order to study the influence of freeze-thaw(FT) cycles on the dynamic tensile properties of sandstone，a 50 mm split Hopkinson pressure bar(SHPB) was used to conduct dynamic Brazilian splitting tests on sandstone samples after different FT cycle numbers(0，20，40，60，80 and 100) under three loading rates(344.72，371.991 and 431.761 GPa/s)，and the change of the cores in the samples due to FT cycles were detected by a nuclear magnetic resonance system The damage characteristics，dynamic tensile strength and energy evolution of sandstone caused by FT cycles and loading rate are analyzed. The research results show that the FT sandstone degradation model satisfies an exponential function. As the number of FT cycles increases，the porosity and the degree of fracture increase，while the dynamic splitting tensile strength decreases. The degradation rate is the fastest after 80 FT cycles. The increase of the loading rate will weaken the degrading effect of the FT cycles on the sandstone and delay the half-life. The increase rate of the maximum absorbed energy caused by the rising of the loading rate decreases with increasing the damage degree. Meanwhile，the maximum absorbed energy decreases with the number of FT cycles in an exponential form while has a good positive correlation with the dynamic splitting tensile strength. The research results can provide a theoretical basis for the study of the failure mechanism of rock mass engineering in cold regions.

The triaxial compression tests of coal rock under quasi-static strain rate were carried out by using MTS815 test system，and the failure characteristics and energy evolution law of coal rock were analyzed. By using energy dissipation theory to determine the damage stress，a brittleness index reflecting the pre/post-peak mechanical behavior was established based on characteristic stress to analyze the brittleness traits of coal rock under different strain rates and confining pressures. The results show that stress-strain curves of quasi-static triaxial coal rock have obvious stage characteristics. As the confining pressure increases and the strain rate decreases，the post-peak stress drop declines，failure mode transitions from tensile failure to shear failure，and the brittle failure characteristics of coal rock are gradually weakened. According to the irreversible damage in coal rock due to energy dissipation，the dissipation energy rate is defined as the ratio of the dissipation energy to the total strain energy，and the minimum of the curve of the dissipation energy rate is determined as the damage stress point. Comprehensively considering the degree of crack propagation in pre-peak and stress drop in post-peak，a brittleness index Bstress of quasi-static triaxial coal rock is established with the combination of the damage stress，the peak stress and the residual stress. Bstress decreases as the confining pressure increases and the strain rate decreases，indicating that the brittleness of coal rock is weakened. Comparing with other brittleness indexes，it is found that Bstress can better depict that the brittleness of coal rock is promoted by the strain rate and restrained by the confining pressure. Further analysis of the dispersion degree of each brittle index under the same group of parallel tests is carried out by using the coefficient of variation，finding that the dispersion of Bstress is minimal and it is more reasonable to characterize the brittleness of triaxial coal rock under quasi-static strain rate.

The correlation between the stability of coal specimens during the whole process of deformation and damage with the evolution of deformation localization was studied by uniaxial compression test method. A kind of coal was selected as the test piece，and the deformation localization evolution of the specimens was observed by digital speckle correlation method. The tensile displacement and rate，the sliding displacement and rate and the shear stress displacement of the deformation localization band，as well as the energy evolution of the surrounding rock during deformation，were analyzed. The results show that，in the process of deformation and failure of coal and rock，the reduction of the bearing capacity of coal and rock is caused by the abrupt changes of tensile and sliding displacements in the deformation localization band of coal and rock，that the overall stability of coal and rock at the macro level is related to both the equivalent stiffness and the shear stress reduction of deformation localization band，and that，in the process of specimen instability，the deformation energy release and the stress release of the surrounding rock are not synchronized，that is，the stress release lags behind the deformation energy release of the surrounding rock.

In order to study the excavation response of deep underground engineering rock masses under high temperature and high-pressure conditions，a true triaxial rheological test system of the“two rigid and one flexible” type was independently developed for carrying out experiments on rocks under high temperature and high pressure. The system mainly includes two rigid stress loading components respectively for applying maximum principal stress() and intermediate principal stress()，a flexible stress loading system for applying minimum principal stress()，a temperature servo control system and some extensible parts. The rigid loading force in the directions of  and  is up to 2 000 kN and the maximum pressure of the flexible loading in the  direction is 70 MPa. The system is designed for a standard rock sample with three edges respectively of 50 mm×50 mm×100 mm，and can perform various types of high-temperature stress loading tests such as true triaxial，creep，and cyclic loading and unloading. The system was used to study the strength and deformation characteristics of Beishan granite under high temperature(60 ℃，100 ℃，150 ℃，200 ℃) and high pressure(= 30 MPa，= 20 MPa) true triaxial loading conditions，and the true triaxial creep behaviour of Jinping marble under high-temperature conditions. The results show that the peak strength and elastic modulus of Beishan granite first increase and then decrease with increasing temperature，and the turning point appears at 150 ℃. The true triaxial creep curve of Jinping marble at 80 ℃ obviously exhibits the attenuation creep，stable creep and accelerated creep process. The system provides a new effective method for characterization of the true triaxial mechanical properties of rocks under coupled high temperature and high-pressure condition.

In order to obtain the seepage characteristics of the protected layers under repeated mining，this paper summarizes the stress path of the protected layers as three stages of loading，unloading and recovery，and carries out simulating repeated mining seepage tests by a self-made gas injection and displacement gas tester to analyze the seepage law of two types of intact and fractured coal samples. The results show that the more the mining times，the more obvious the permeability changes，and the unloading stage is the main stage of permeability change. The stress sensitivity of two kinds of coal samples decreases along with increasing the mining times in the loading stage，while increases with increasing the mining times in unloading and recovery stages. The stress sensitivity of the intact coal samples under the first and second mining is greater than that of the fractured coal samples，while the stress sensitivity of the fractured coal samples under the third mining is greater than that of the intact coal samples. The first and second mining is the compaction stage of two types of coal samples，and the third mining is the permeability increasing stage. The permeability increasing effect of the third mining is greater than that of the first and second mining，and the permeability increasing effect of repeated mining on the fractured coal samples is greater than that of the intact coal samples.

The gap between the segment and the surrounding rock in shield TBM tunnels is backfilled with pea gravel and then grouted to form backfill. The backfill and its state have an important impact on the mechanical characteristics of the tunnels. In order to find out the influence law of the backfill layer on the stress and deformation of tunnels，the mechanical characteristics of shield TBM tunnels in construction are analyzed through field test in this paper，and the following conclusions are drawn. When the backfill layer is in a loose state，the constraints and supports of the surrounding on the segments are limited，and the segments cannot provide enough support for the surrounding rock. As a result，the surrounding rock is prone to deformation and collapse，and the structural stress，opening，staggering and surface settlement of the segments will increase significantly. The stress system of the surrounding rock，the segment and the backfill layer is gradually stable after the backfill layer is grouted and consolidated. The volume of the pea gravel behind the segments has an important effect on the force and deformation of shield TBM tunnels in construction. The smaller the filling volume of the pea gravel is，the more obvious the stress concentration is，and the greater the opening，staggering and surface settlement of the segments are. The volume control standard of the pea gravel behind the segments should be formulated in the construction of shield type TBM tunnels，and the grouting time should be selected according to the volume control standard and the volume of the pea gravel filled behind the segments.

Skarn samples from the Chuanyandong orefield of Wengfu phosphate mine，taken as the research object，were placed in the self-designed device for 49 days with four humidity ratios(70% RH，80% RH，90% RH and 100% RH) and measured at certain intervals for obtaining the porosity，mass and size. Then，uniaxial and triaxial compression tests，electron microscope scanning and X-ray diffraction were subsequently performed to analyze the variations in micro structure，mass loss and corrosion depth. Simultaneously，the response features of the strength，deformation and mechanical parameters were also discussed. The results show that the structural porosity positively relates to the placing time under high-humidity conditions. The dense layered crystal morphology tends to be flocculent，accompanied with the generation of micro fissures，and the width of these fissures increases with time. Higher humidity ratio frequently causes larger variations in porosity，mass and size. The change rate reaches the fastest initially and levels off over time. The uniaxial compressive strength under 100% RH condition decreases by 35%，compared to that of 70% RH condition after the placement for 49 days. Under 90% RH condition，the accumulated decrease ratio of the uniaxial compressive strength is 46%. The decrease ratio slows with time. In addition，the cohesion and the internal frictional angle also decrease with time，while the cohesion is more sensitive to the high-humidity environment than the internal frictional angle. The proposed strength model，considering the corrosion law under high-humidity ratios，agrees well with the laboratory results. The chemical corrosion under high-humidity conditions，involving dissolution，hydration and disintegration，impairs the friction between particles，weakens the mechanical strength，causes the transition from shear failure to tensile failure and finally accelerates the damage of the skarn pillars.

The core-wall rockfill dam is an uncertain system affected by many complicated factors. It is of great significance to research the evaluation and early warning method of the service reliability of core-wall rockfill dams from the point of uncertainty for the scientific evaluation of the safe state of the dams in service and the improvement of dam risk management level. Lack of data on some uncertain parameters and dependence of the probability distribution functions on experience make the traditional probability reliability evaluation approaches difficult to be applied. The analytical method of non-probabilistic reliability is applied to the analysis of the service state of the core-wall rockfill dams，and a non-probabilistic reliability calculation model of the core-wall rockfill dams based on dimension proportional factors is constructed after probing into the representation model of uncertain parameters. A method for formulating the deformation safety multi-point comprehensive early warning index of the core-wall rockfill dams is presented based on non-probabilistic reliability，which combines with the grading standard of the non-probabilistic target reliability index. The reliability of a core-wall rockfill dam in service is evaluated and the multi-point comprehensive early warning index of deformation safety is developed by using the developed method. An engineering example shows that it is feasible to apply the non-probabilistic reliability evaluation and safety early warning method to the deformation safety analysis of the core-wall rockfill dams.

The traditional elasto-plastic models cannot consider the non-coaxial plastic deformation of soils when simulating the bearing capacity of foundations. In this paper，a non-coaxial plastic model was established by introducing the modified non-coaxial theory into the sub-loading surface model，and the model was embedded into ABAQUS software through the user material subroutine interface. Then，the model was used to predict the bearing characteristics of clay foundations with different degrees of over-consolidation. The results show that，when the non-coaxial plasticity is considered，the predicted maximum settlement increases with decreasing the non-coaxial plastic modulus，and that the influence of the non-coaxial plastic modulus on the simulation results is related to the over-consolidation degree of foundation soils. In addition，decreasing the non-coaxial plastic modulus to the shear modulus will have a relatively significant effect on the predicted maximum settlement. Therefore，when the actual non-coaxial plastic modulus is less than the shear modulus，the influence of the non-coaxial plastic deformation should be carefully considered in foundation engineering to ensure safety.

In order to alleviate serious soil cracking in the dredged slurry reinforced by electro-osmosis method，the polypropylene fiber is added to the dredged slurry to improve the effect of electro-osmosis treatment. Through 16 groups of indoor electro-osmosis model tests with three kinds of fiber length of 6，9 and 12 mm as well as five mixing ratios，the drainage，the current intensity and the potential value in the electro-osmosis consolidation process were monitored. The water content and the vane shear strength were measured before and after testing. The improved effects of the length and the mixing ratio of the polypropylene fiber on the electro-osmotic solidification of dredged slurry were explored. The test results show that the polypropylene fibers with different lengths and different mixing ratios have significantly different effects on electro-osmosis. The polypropylene fiber added to dredged slurry can effectively inhibit the cracks in the soil during the process of electro-osmosis and increase the drainage efficiency. The test group with a fiber length of 9 mm and a blending ratio of 0.3% has the best effect. Compared with the electro-osmosis consolidation of dredged slurry without fiber，the drainage and the cross-plate shear strength increase by 31.6% and 87.5%，respectively. Adding fiber will increase the soil integrity，inhibit current attenuation and reduce the surface cracks of the soil，showing that the improvement effect is very significant.

The design methods of scale model test based on traditional dimensional analysis theory，when applied to multi-medium coupling dynamic model design，are faced with some problems，including a large gap between theoretical calculation results and actual test conditions，failure to satisfy the dynamic characteristics of each substance and difficulty in realizing the similarity of contacting and coupling interaction between substances. To solve these problems，the separation dimension analysis theory is proposed，and a system similar design method for model test is established based on the theory. The developed method is then applied to the similar design of shaking table model of soil-underground pipe gallery dynamic interaction. The soil-underground pipe gallery system is divided into four sub-systems of soil，underground pipe gallery，contact surface and seismic wave according to its overall characteristics. The contact mechanism of soil-underground pipe gallery is studied，and the parameters controlling the sub-system characteristics of the contact correlation effect between substances are proposed. The similar materials are prepared to ensure the similitude of contact coupling interaction，and the four sub-systems are separately designed based on their respective characteristics. In order to explore the degree of simulation between the system similar design method and the traditional similar design method，the prototype and the models of the underground pipe gallery are respectively designed by different similar design methods，and the shaking table tests of the prototype and the models are carried out. The test results show that compared with the traditional similar design method，the system similar design method has no obvious advantage in the simulation of the acceleration response of the underground pipe gallery structure but has obvious advantages in the simulation of the strain response of the underground pipe gallery structure，which can accurately reflect the true law of the prototype.

Soil desiccation cracking is a common natural phenomenon. The initiation and propagation of cracks can significantly weaken the structure and integrity of the soil，leading to engineering disasters. In order to study the influence of the layer thickness and the temperature on the crack morphology of Chongqing silt，physical test，XRF test，XRD diffraction test，desiccation cracking test and scanning electron microscope test are carried out. Subsequently，based on digital image processing technology，fractal theory，etc.，the quantitative characterization of the crack morphology is realized. The results show that Chongqing silt is a high liquid limit clay，whose particle morphology presents a dispersed structure and irregular particle clusters，and that the cracks mostly present the forms of three way junctions such as T and Y shapes，and the soil clods divided by the cracks are mostly in the forms of triangles，polygons and sectors. Under the corresponding temperature condition，the number of nodes，the number of cracks，the total length of cracks，the number of clods and the total area of clods all decrease with increasing the layer thickness，while the total crack area，the surface crack rate，the surface crack ratio，the average length of cracks，the average width of cracks，the average area of clods and the maximum area of clods show an increasing trend with the layer thickness. In addition，the frequency distribution of the crack length conforms to a LogNormal function. It is also indicated that the fractal dimension tends to increase slowly with increasing the layer thickness while has a good exponential relationship with the average crack width，and that，under the conditions of the corresponding layer thickness，the distribution range of the crack length shows a decreasing trend with the temperature. The crack morphology of Chongqing silt is multi-scale，including macro-cracks，meso-cracks and micro-cracks. The multi-scale cracks in the soil greatly weaken the engineering properties of the soil.

It is difficult to directly solve the time-domain impulse response function of foundations in complex sites. Establishing the high-precision conversion relationship between the frequency domain dynamic stiffness curve and the time domain model of the foundations is a hot issue of current concerns. Based on the traveling wave superposition principle and considering the singularity of the dynamic stiffness，the Nakamura model that transforms the frequency domain dynamic stiffness to the time domain impulse response function is improved. The repeated phase angles and the singular terms in the classic Nakamura model often lead to unstable numerical results. In order to solve these problems，the reasons for the repeated phase angles are analyzed，the distribution law of the repeated phase angles is revealed through formula derivation，and a simple and feasible micro-adjustment method is proposed to avoid the occurrence of the repeated phase angles，making the improved method more robust. In addition，due to the singular terms contained in the frequency domain dynamic stiffness，it is impossible to use the numerical Fourier transform to directly convert to the time domain. The strategy of stripping the singular terms and fitting only the conventional terms enables the time domain impulse response function to achieve a higher fitting precision. Taking the analytical solutions of a cavity in an elastic full space and a semi-infinite rod in an elastic half space as examples，it is verified that the improved method can obtain a high-precision time-domain impulse response function and improve the calculation stability. A case study illustrates the applicability of the improved method in engineering application.