The stability of surrounding hard rock in large underground caverns always challenges its design and excavation under high geostress condition. A new cracking-restraint design method for caverns? stability optimization was proposed based on the summarization and practice of many underground caverns under high geostress condition. This method points out that the inner cracking of hard rock is the root factor for rock?s large deformation and failure. Taking the testing of rock mass break，excavation optimization for reducing the cracking scale and supporting reinforcement for restraining the cracking development as three basic factors and considering the way of restraining cracking of hard rock as the key issue ideology，optimization operations were synthetically carries out. A technical system for reducing or avoiding cracking scale，depth and degree of hard rock was proposed through improving the global excavation scheme. It is pointed out that，for the purpose of safety，efficiency and economy，rational selections of supporting parameters for rock bolts or cables and supporting time for surrounding rock help to restrain cracking of surrounding rock and to strengthen the integrality and the resistance of cracking surrounding rock，and make surrounding rock as a bearing structure for fully mobilizing its own bearing capacity to reinforce or build a load-bearing arch of surrounding rock. Applications in Laxiwa hydraulic station，Baihetan hydraulic station and Chinese Jinping deep laboratory indicate that the developed method is reasonable and useful.

In order to meet the special requirements of stability，compactness and capacity of high water pressure，a new concept of composite grouting，adopting composite material and process to form a functional composite structure and further to realize the dual effect of safety control and efficient water plugging，was proposed. A diffusion model of slurry vein was established，and the spatial distribution characteristics of the grouting range and the thickness of slurry vein and the influencing factors were revealed. A mechanical model of slurry vein skeleton and composite shell for evaluating the stability of the grouted region was established，and a determining method of macro-mechanical parameters was proposed. The main influencing factors of mechanical properties of the grouted region were analyzed，and a design method of grouting parameters was put forward. As a result，the whole process control of composite grouting can be realized. Based on the feature of composite grouting body functional structure，a technology of peripheral curtain grouting of tunnels was developed，and the water plugging rate，grouting region strength and overall stability were proposed as the evaluation indices of grouting effect. Compared with the full-sectional grouting method，the efficiency and reliability of the developed technology are significantly improved. Finally，the application of the composite grouting technique in the highly permeable area of F1 weathering trough of Xiang'an subsea tunnel in Xiamen was introduced，and it is shown that，by using the technology，the expected effect is achieved and the engineering safety is ensured.

Rock bolts have been extensively used as an effective reinforcement means of tunnels and mining engineering projects. The existing analytical method is only available for the mechanical analysis of the point anchored rockbolt in a circular tunnel. Based on the analytical function of a concentrated force at an arbitrary point in the surrounding rock of a deep buried elliptical tunnel，explicit solutions of stress and displacement were deduced and explicit expressions of stress and displacement subjected to multiple concentrated forces were also obtained based on the superposition principle. Considering the displacement caused by tunnel excavation，the linear equations for solving the axial force of the point anchored rockbolt were established according to deformation coordination conditions，and the axial force distribution of each bolt with or without a pre-tightening force was obtained. The analytical solution obtained was verified by ANSYS software. Finally，the influences of the stiffness，anchor length and pre-tightening force on the axial forces were discussed.

The uniaxial compression acoustic emission(AE) tests of dry and saturated marble were carried out to study the effect mechanism of water on crack propagation. The characteristic strength of samples was determined by AE method and volumetric strain(crack volumetric strain) method. The applicability of AE method for determining the characteristic strength was discussed，and the effect mechanism of water on the characteristic strength was analyzed combining statistical analysis results of dominant frequency of AE waveforms in the vicinity of the characteristic strength. The results show that the strength threshold of crack initiation determined by AE method is lower than that by macro volumetric strain method. AE method can be suitably used to determine the strength threshold of crack initiation for saturated rock，whereas it is not appropriate to determine the damage strength threshold. The normalized crack initiation strength of samples decreases and the normalized damage strength increases after saturation. Effect factors of water on the normalized characteristic strength are the intensity of the pore water pressure and the crack growth resistance. Near the moment of crack initiation，the effect of the pore water pressure is obvious and there are many micro-tensile failures inside the rock，which makes crack develop stably at a lower stress level. Near the moment of volume dilation，the effect of the pore water pressure is weakened along with the existence of the crack growth resistance，which makes unstable crack propagation occur at a higher stress level.

In order to study the mechanism of crack propagation in complete process and crack arrest behavior in set area between two holes，an ISCSC(improved single cleavage semi-circle specimen) configuration specimen was proposed. By using split Hopkinson pressure bar，the impact experiment was conducted with the crack propagation velocity detected by the crack propagation gauge. Meanwhile，the damage failure model combining principal stress failure criteria with crack softening failure criteria was introduced in the numerical simulation. With Experiment-Numerical method，the evolution law of rock crack dynamic propagation in complete process was investigated elaborately and the effect of two empty holes on crack propagation behavior was sophisticated demonstrated. The results show that the ISCSC configuration specimen could realize the crack arrested in set area and that the arrest zone can be predicted accurately. Two empty holes have huge influence on the behavior of crack propagation，restraining crack propagation velocity obviously. The interaction of the superimposed stress field between two empty holes and the tensile stress field of the crack tip could slow down the crack propagation speed sharply and even cause arrest when the running crack rushes into the set area between two holes. When the running crack goes across the set area between two holes，the crack propagation behavior could be influenced by inhomogeneity of material easier than before，which could cause crack deflecting and branching. It is also shown that numerical simulation outputs agree well with the results of experiment，confirming that ISCSC configuration specimen has great ability to be applied in researching the behavior of crack propagation in complete process.

The intersecting distribution of joints in rock mass makes the stress wave propagation complicated. In this paper，the propagation characteristics of stress P-waves across nonlinearly intersecting rock joints were studied by using theoretical analysis and numerical simulation. The propagation process of multiple reflected waves between two intersecting joints was analyzed using the time-domain recursive analysis method(TDRM) and the propagation equation was established combining the principle of superposition. The wave propagation process in two intersecting joints was simulated by UDEC. The comparison between the theoretical and numerical results shows that they are very close to each other. A numerical model was proposed for calculating the propagation of stress P-wave cross two sets of intersecting rock joints，and parameters studies were carried out. It is shown that the wave propagation is influenced by joint stiffness，joint distribution and incident wave frequency and that the transmission and reflection coefficients are different at different monitoring positions of intersecting joints. The theoretical method proposed in this paper，providing a new way for analyzing the propagation of stress waves in intersecting joints，still has some limitations. For complex conditions，the numerical simulation method can be adopted to study wave propagation across jointed rock mass.

On the basis of the load-transfer theory and Kelvin displacement solution，distribution functions of the axial force and shear stress of the GFRP anti-floating anchor rod body along the bolting depth under ideal conditions were deduced and verified through a pullout test for 2 GFRP anti-floating anchors with the same type. The test results show that the distribution curves of the axial force and shear stress are similar to the theoretical curves，which proves the practicability of the developed theory in solving the load-distribution function of the GFRP anchor rod body. Due to the unevenness of the anchorage body and debonding effect of the anchor，however，the test shear stress value is lower than the theoretical value and the main distribution range of the test shear stress is deeper. At the same time，the unevenness of the anchorage body and debonding effect of the anchor contribute to the phenomenon that the axial force decreases slowly and its disappearance depth is larger than the theoretical value. The theoretical distribution function of the shear stress was corrected by using the average shear stress attenuation method under the fixed debonding length and the method of moving down the elastic section，and the distribution function of the shear force was also amended through the functional relationship between the axial force and shear stress distributions. It is shown that the accuracy of the revised load-distribution curves is enhanced obviously.

In order to put forward an early warning method of roof cutting disasters with a large area caused by periodic fracturing of the main roof，the time-space relationship between periodic fracture of the plate structure of the main roof and rebound compression field formed by periodic fracturing in whole roof area was studied based on theoretical calculation，similarity simulation and engineering practice. The results show that，when the periodic fracture of the plate structure of the main roof with elastic foundation boundary occurs ahead of the coal wall，four zones including semi-ellipse rebound zone (I)，C-type compression zone，C-type rebound zone (II) and C-type compression zone will be generated in turn on the periphery of the fracture line. The rebound amount in the central region of rebound zone (I) in front of the fracture line is the largest，and the compression zone is located at the end region of the fracture line. The distance between the inner and outer boundary lines of the rebound zone (II) almost keeps constant，and the rebound amount in rebound zone (II) increases firstly and then decreases. The morphology of the rebound compression zone generated by the graded fracturing is obviously different from that generated by the one-off fracturing. The greater the fracture degree of main roof strata is，the larger the rebound amount of the plate structure of the main roof will be. However，the fracture degree of main roof strata has no obvious influence on the distribution form of the rebound compression zone. Due to that the rebound zone (II) encircles the entire “hanging roof area”，the rebound compression information generated by periodic fracturing of the main roof ahead of the coal wall can be detected in the two roadway regions and adjacent roadway regions. Furthermore，the correctness of the conclusions has been verified by similarity simulation experiment using the special high-precision displacement sensor and engineering practice. An early warning system of roof cutting disasters with a large area caused by periodic fracturing of the main roof，including one synchronization，two delays，two zones，two indexes and two controls，is formed.

The probability distribution characteristic parameters of geotechnical strength indices are necessary for determining the standard values of geotechnical strengths，analyzing reliability and evaluating risk. Existing method using in-situ data has the problem of insufficient information due to small samples. Based on Bayesian theory，in this paper，it is proposed that the probability characteristic parameters of geotechnical strengths obey a 2D Joint Prior Distribution，and a posterior distribution function and an equation for calculating the maximum posteriori estimator were deduced. Taking the cohesion and internal friction angle of mudstone and sandstone from Wanzhou for example，the hyper-parameter of the Prior Distribution Function was obtained based on the sample of means and variance of geotechnical strengths from different projects and consequently，the Prior Distribution Function of the cohesion and internal friction angle of mudstone and sandstone in Wanzhou was determined. By using the field data of an actual project，the posterior distribution and the maximum posteriori estimator of the probability characteristic parameters of mudstone and sandstone strengths were determined，and the standard values of the cohesion and the internal friction angle were calculated. Comparison with conventional methods shows that the new Bayesian method containing the information of historical and field data is more scientific and reasonable.

To reveal the generation mechanism and variation law of friction resistance between the outer wall of a large section of concrete pipe string and the surrounding rock during construction via ultra-long-distance rock pipe jacking，the shear friction behaviors and mechanical mechanism between sandstone and concrete pipe string wall under seven complex contact conditions were investigated through large-scale direct rock shear tests. The results show that the optimal values of the average friction coefficient for all test results are obtained by only considering bentonite slurry contact condition. In the later stage，the average friction coefficients at the contact surface can be higher than the initial values by 50%–70%. Among them，the average friction coefficient for a combination of extra-pipe in-situ debris，bentonite slurry and sand-laden waste slurry reaches a maximum value. The jacking force needed for stuck pipes was predicted based on the test results and the modified empirical formula, which is identical to the field-monitored value. Finally， a temporary intermediate jacking station(TIJS) method for solving the pipe stuck problem was proposed based on the law of jacking force transmission loss. It is pointed out that the focus of reducing in-situ pipe-rock friction resistance should be placed firstly on controlling the extra-pipe sediment to prevent the formation of high-viscosity mixture that leads to an increase in the friction resistance of the pipe wall and a decrease in the effective injection volume of bentonite slurry. Besides，it is also necessary to ensure a sufficient grouting volume outside the pipes.

Permafrost slope supporting structure with frame ventilation anchor pipes has both ventilation cooling and anchoring functions. In order to promote the application of this structure in engineering，its cooling effect was studied. Firstly，the heat exchange mechanism between the ventilation pipe and the soil was analyzed，and a formula for calculating the heat flux of the pipe wall under the influence of the wind speed was obtained. Then，a radial heat transfer model of the ventilation anchor pipe was established，and an evaluation index of cooling effect of radial frozen front expansion was obtained by taking the heat flux density of the pipe wall as the anchor pipe boundary condition adopting the perturbation method. Meanwhile，another evaluation index of cooling effect of thawed depth variation on the axial slope under the supporting of ventilation anchor pipes was obtained based on the energy conservation law. In addition，the cooling effect of the ventilation anchor pipe was simulated with the self-developed finite element program and verified combined with the theoretical results. The results show that the heat exchange action of the pipe wall is the superposition of convective heat transfer and evaporative heat dissipation and that the ventilation anchor pipe has a good cooling effect which is greatly affected by the open porosity of the pipe wall. It is also indicated that the evaluation indexes can comprehensively evaluate the cooling effect of the ventilation anchor pipe. The research results can provide a theoretical basis and guidance for the design of the structure.

The stability of rock and soil under unfavorable geological conditions has attracted wide attention in underground space engineering. A 3D mesh model reconstruction method of unfavorable geological structure based on CT detection technology was proposed to establish a reliable analysis model for evaluating the stability of rock and mass. In this method，a 3D visualization model of the elastic-wave velocity was obtained by performing numerical simulation of elastic-wave CT detection and block Kriging interpolation. The peak value formula is used for material threshold segmentation，and the 3D mesh construction and material property mapping are used to form a 3D grid model in the target region. Comparison between the reconstructed 3D grid model and the original model shows that the simulation degree of the reconstructed model is as high as 91.44% and the absolute error of the volume fraction is 3.33%. Field test of elastic-wave CT detection was carried out for the bridge foundation location area，and the 3D mesh model of the region was reconstructed and verified by coring. The simulation degree is greater than 84.31%，and the absolute error of the volume fraction is less than 2.45%. The method has high modeling accuracy and can accurately reflect the spatial distribution state of bad geological bodies，and hence，has important scientific significance for evaluating the stability of poor geological structure.

Aiming at the serious damage of water supply canals in expensive soils in the high cold region of northern Xinjiang，the triaxial tests under the unidirectional action of wetting-drying and the cyclic action of coupling wetting-drying and freeze-thaw were performed to investigate the influences of freeze-thaw process on mechanical properties and damage evolution law of expensive soils. The stress-strain behavior，the elastic modulus and the effective shear strength index were obtained under different cycles and the influence factors were discussed. Based on the basic theory of damage mechanics，a damage variable was introduced to evaluate the coupling effect of wetting-drying and freeze-thaw processes，and the strength and modulus damage process were also discussed. The test results show that，under a low confining pressure(?3 = 100 kPa)，the stress-strain behaviors of samples are affected considerably by the cycle numbers and that the morphological difference of different stress-strain curves decreases with increasing the confining pressure. A comparison of the elastic modulus and the effective shear strength index of samples under different test conditions indicates that the freeze-thaw process in the coupling cycle of wetting-drying and freeze-thaw has significant influence on the attenuation of the elastic modulus and the effective cohesion but limited effect on the effective internal friction angle. The damage of soil under a high confining pressure is mainly caused by wetting-drying process，while the damage effect of freeze-thaw process under a low confining pressure is more obvious.

The construction of a series of reclamation islands on coral reefs in South China Sea is a strategic project of China. These reclaimed lands on the top of coral reefs mainly consist of calcareous sand. Previous studies have confirmed that coral calcareous sand could generate creep deformation under long term constant loading. As the foundation material of all kind of structures built on reclaimed coral reefs，the creep behavior of calcareous sand will definitely affect the long-term subsidence of these structures. Therefore，it is highly necessary to investigate the long-term creep characteristics of the coral calcareous sand from South China Sea. A series of tri-axial drained creep tests were performed with the samples from a coral reef island in South China Sea under the confining pressure of 100 kPa to investigate the creep characteristics of calcareous sand. The experimental results indicate that the creep of the calcareous sand is an attenuated and steady type. The curves between the creep strain and the time in double logarithmic coordinates are all straight lines under different stress conditions and can be described by a power function. It is found that，in the case of the same dry density of the calcareous sand, these straight lines corresponding to different creep deviatoric stresses are basically parallel with each other and  the slopes of the straight lines are hardly affected by the creep deviatoric stress. It is also revealed that the trend of volume change of calcareous sand samples at the creep stage is mainly controlled by the process of that the volume contraction of calcareous sand samples is finished or not under shearing before the beginning of the creep stage. The research results show that Mesri creep model can effectively describe the stress-strain-time relation of the coral calcareous sand and that the final creep strain of the calcareous sand is highly linearly related to the stress level q/(?1－?3)f. Particles gradation tests before and after the creep test indicate that the creep of the calcareous sand under a low confining pressure is mainly attributed to the slipping，shifting and rearrangement between soil particles.

A series of direct shear tests on unsaturated silt with a water content of 18.3% during freezing and thawing were conducted，and the phase composition of pore water was measured by NMR during the shear process. Effects of the unfrozen water content and the ice content on mechanical properties of the tested silt were analyzed. The results indicate that the freezing process of unsaturated silt can be divided into super-cooling stage            ＞－1.15 ℃，no phase change)，rapid freezing stage(－1.15 ℃–－2 ℃) where 76% of the pore water freezes，and stable freezing stage(＜－2 ℃) where the unfrozen water content only decreases by 7%. The cohesion changes significantly with the temperature during the process of freezing and thawing while the friction angle varies slightly. The change of the shear strength of silt occurs primarily within the stable freezing stage，where the cohesion increases by 123.5% and the friction angle decreases by 12%. For the rapid freezing stage，the cohesion only ascends by 38.5% and the friction angle has no obvious change. It can be concluded that，within the rapid freezing phase，the freezing of the pore water drives the matrix suction to increase，which results in increasing of the cohesion，while that，within the stable freezing phase，the increase of the cementation strength between ice and soil particles leads to a rise of the cohesion. When the ice content changes slightly，the shear strength of frozen silt is mainly controlled by the cementation strength between ice and soil particles which depends on the thickness of the unfrozen water film. The decrease of the friction angle within the stable freezing phase is mainly caused by the force acting on the particle skeleton generated by volumetric expansion of the pore water upon freezing.

The shear strength of soil would be deteriorated by moisture migration and the accompanying phenomenon during freeze-thaw process. For the prevention and treatment of freeze-thaw diseases in expansive soil engineering，it is necessary to ascertain the degradation effect of moisture migration on the shear strength of expansive soil. By simulating real freeze-thaw boundary conditions，the moisture migration experiments of expansive soil under the axial freezing and bidirectional thawing action were carried out，and direct shear tests were conducted. The moisture field，temperature field and vertical deformation of expansive soil were monitored during the test. The research results show that the moisture migration quantity is influenced by the freezing temperature gradient，and that the expansive soil during freezing-thawing shows frost heave and thawing settlement characteristics and the thawing settlement is slightly larger than the frost heave. The variation of the shear strength has a high consistency with the water content redistribution along the depth direction. For specific performance，the shear strength of frozen soil attenuates when the water content increases，while the shear strength of unfrozen soil increases mildly with decreasing the water content. The variations of shear strength indexes and moisture field redistribution also show a high consistency along the depth direction. Specifically，shear strength indexes decrease when the water content increases. The attenuation degree of the cohesive force is significantly greater than that of the internal friction angle. The decrease of the cohesive force is the main reason of freeze-thaw deterioration the shear strength for expansive soil.

The modified primary compression index of municipal solid waste(MSW) is an essential parameter for predicting waste settlement，evaluating landfill capacity and planning landfill process. Two groups of large-scale model experiments and six groups of column compression tests were conducted to investigate the primary compression behavior of MSW，and a modified primary compression index model was proposed. It is found that the modified primary compression index increases with increasing the moisture content or the compressible component content but decreases with rising the dry unit weight. A mathematical model for predicting the modified primary compression index was proposed taking the water content，dry unit weight and compressible component content into account，and the model was developed to predict the modified primary compression index with varied burial depths. Comparison between the model and the testing data of borehole samples from Qizishan landfill in Suzhou was carried out，which indicates that the model fits well the test data and performs better than the models documented in literature. An example illustrates that it is beneficial to take the variation of the modified primary compression index with burial depth into consideration in accurately planning the landfill process or/and assessing the landfill capacity of MSW landfills.

For shallow tunnels in sand or some poor blocky rock masses with a very low cohesive，effect of the partially mobilized arching on the calculation of the overburden pressure is still not well understood. a modified approach，different from previous limit equilibrium methods that calculate the vertical loading by the assumption of the trace of the principal stress，was proposed taking into account the distribution of the rotation angle of the principal stress，the variation of the slip surface and the friction angle mobilized on the slip surface. The average lateral stress coefficient and the distribution of the vertical stress above the tunnel were analyzed by the modified approach and were compared with those obtained by previous limit equilibrium methods. The modified approach was verified by numerical simulation and experimental results，and the partially mobilized arching effects were analyzed. The results show that，after tunnel excavation，the vertical stress within and outside of the range of the slip surface decreases and increases respectively，and that the shear stress near the slip surface is mobilized to prevent the soil above the tunnel from slipping. The average lateral stress coefficient is a function of the soil friction angle and the friction angle mobilized on the slip surface. The partially mobilized arching effects  on the average lateral stress coefficient can be ignored when the soil friction angle   is low. It is also shown that the ground arching effect   calculated by the modified approach and previous methods are all insensitive to within a range of . The insensitivity of  to is not only affected by  but also affected by the partially arching effect . The lower the friction angle mobilized on the slip surface，the more distinct the insensitivity is.