Steel bolts were used to reinforce the underwater soft rock slope of the Yangtze River-to-Huaihe River canal project. In order to study the influence of existing detection methods on the bonding state of steel bolts in soft rocks，insitu test was carried out. The results show that the effective anchoring depth increases with increasing the load exerted on the bolt. The degree of bond damage at the interface of the bolt body is positively correlated with the magnitude of the load，and compared with the load，the loading number has minimal effect on bond damage. Longer loading time of incremental graded load will result in greater increment of the elastic elongation of the bolt under the same magnitude of the load，indicating that the degree of bond damage at the interface of the bolt body is positively correlated with the time during which the graded load is maintained. The plastic displacement at the end of the bolt is generated during the unloading process，which comes from the relative displacement at the interface between the bond body and surrounding rock and is mainly affected by the method of unloading. The faster the unloading speed is，the greater the plastic displacement is. The plastic displacement is positively correlated with the time during which the incremental graded load is maintained. Combining four different detection methods for the bond damage characteristics，a more scientific testing method for detecting the anchoring state of reinforcement bolts in soft shaly sandstone was proposed.

In order to study the freeze-thaw damage of porous rock caused by moisture migration inside the pores (cracks) during the freeze-thaw process，the pressure-suction equilibrium state of the film water was analyzed，and it was found that the main role of the liquid pressure is to offset and balance the net suction. The conversion coefficient λ between the pressure variable and the suction variable was given，and it was pointed out that the surface adsorption force comes from the difference between the net suction force and the offset factor λPLy. Based on the capillary theory，the freezing temperature equation of pore water was derived，and the stress state of film water in the frozen large pores was given. Besides，for the “main-side branch” pore structure with poor frost resistance，a capillary-film moisture migration unit model was established，and the stress distribution，migration direction and migration path of the characteristic pores were given. The research results show that the net suction and liquid pressure of the film water inside the frozen main pores are the largest. The net suction force drives the capillary water and film water in the secondary pores and micro-pores to migrate to the main pores，while the increase of the liquid pressure leads to the crack expansion and structural damage of the main pores. Finally，Taking the Jurassic-Cretaceous silty soft rock as the test object，particle analysis，scanning electron microscopy and low field-nuclear magnetic resonance tests were carried out to analyze the mineral composition，pore structure and pore distribution of siltstone，and the correctness of the capillary-film moisture migration unit model was verified according to the change characteristics of T2 spectrum during the freeze-thaw process.

In order to appropriately understand the dynamic mechanical behavior of sandstone sampled by roof cutting non-pillar mining method in deep coal mines under some special conditions including high geo-temperature，high hydraulic pressure and high ground stress，the impact compression test under thermal- hydraulic-mechanical coupling condition is carried out using a self-developed triaxial dynamic impact mechanics testing system. The dynamic stress-strain characteristics and the correlation between the dynamic deformation modulus and the loading rate，as well as the dependence of the peak stress/strain on the loading rate，the axial and confining pressures，the hydraulic pressure，the temperature and the absorption energy， are investigated，and the micromorphology of sandstone fractures after testing is examined by scanning electron microscopy(SEM). The results reveal that both the peak stress and the peak strain of siltstone proportionally increase with increasing the axial pressure，the confining pressure，the hydraulic pressure and temperature，accompanied a tendency from brittleness to ductility，and that the deformation process siltstone can be divided into four stages including compaction deformation，elastic deformation，plastic deformation and failure. With increasing the loading rate，the dynamic deformation modulus gradually increases and then decreases with a critical value of 136 GPa. It is also found that the axial and confining pressures，the hydraulic pressure and the temperature have significant enhancement effect on the mechanical properties of sandstone under dynamic loading. Moreover，the absorption energy of siltstone increases linearly with increasing the peak strain，and the crushing deformation is proportionally correlated with the absorption energy.

A magnitude Ms 7.0 earthquake struck the Jiuzhaigou World Natural Heritage Park，in Sichuan province，Southwest of China on August 8，2017，and trigged abundant coseismic landslides in the scenic spot. Due to 3 strong rainfalls，dozens of debris flow hazards occurred in the national park after the earthquake. Field survey，sampling test and comparative analysis were used to research the damage models of the debris flow mitigation engineering completed from 1984 to 2016. In total，there are 11 mitigation systems of debris flow gully suffering from partial damage such as Keze gully，Rize 1st gully，Rize 2nd gully and Shuzheng gully，and the engineering of Xuan gully near the Xiajijie lake. Striking of the earthquake the mitigation engineering would trigger a coseismic damage，mainly affected by topographic conditions and engineering structures. As the formed conditions changed，it also caused an indirect damage by increase the value of the charismatics of debris flow. The indirect damage，which has the characteristics of “multi-pathogenesis and same symptoms”，is controlled by the physical and dynamic characteristics of debris flows. Besides，the charismatics values of discharge and density，the driftwood of debris flow are other important factors to the engineering damage. When encountering a larger hazard than the standard of initial design，the mitigation engineering will cause 7 types of damages such as the impact，the abrasion，the erosion，and the damage due to flow direction change. It is suggested that the effects of discharge amplification and driftwood should be focused on for reconstructing the mitigation engineering of the national park after the earthquake.

The composition and internal structure of rocks play a decisive role in the strength characteristics. Based on the study of material and structure of sandstone at the mesoscopic scale，the correlation between the distribution characteristics of particle pores and the mechanical strength is constructed by using the method of combining fractal dimension theory and numerical calculation，so as to realize the rapid evaluation and estimation of rock strength characteristics. The results show that the pore distribution of particles is skewed. That is，there are a large number of small-sized particle pores inside the specimen while a less number of the large-sized particle pores. When the particle geometric ratio is closer to 1，the roundness of particles is higher. Otherwise，it is mostly densely distributed by needle or columnar particles. The reasonable threshold determined by histogram bimodal method can increase the operability of pore quantitative characterization experiment，which is beneficial to the extraction of 9 indexes such as particle pore area，number and size，etc. The fractal dimension does not change relatively after the representation cell size is determined. The particle pore distribution has fractal characteristics and hence，the dimension can be used to describe the complexity of particle pore distribution. In other words，the more complex the distribution is，the larger the dimension value is. It is also revealed that the fractal dimension has a significant negative correlation with the rock strength and the correlation degree is 0.834，indicating that the strength of the specimen decreases gradually as the fractal dimension increases.

The microstructure and its mechanical properties of grout-rock bonding interfaces fundamentally control the macroscopic deformation and failure behaviors of grouted rock joints. In this paper，a series of macroscopic direct shear tests，microscopic SEM scanning tests and nano-indentation tests were carried out on grouted jointed sandstone specimens. The macroscopic shear mechanical strength parameters，shear failure modes， microstructure characteristics of grout-rock bonding interfaces and micromechanical properties of the interfacial transition zone of the specimens were obtained，and the modification and optimization mechanisms of grout-rock bonding interfaces by using new grouting materials such as ultrafine cement and nano-SiO2 were discussed to overcome the microdefects in grout-rock bonding interfaces resulting from the ordinary Portland cement grout. The results show that the grout-rock interface at the microscale is characterized by high porosity and low strength interfacial transition zone with a certain thickness(about 10–30 μm). The interfacial transition zone is the weakest link in the composite structure of grouted rock joints，and there is a positive linear correlation between the microscopic indentation modulus and microscopic indentation hardness with the macroscopic cohesive force of grouted rock joints. The new grouting materials of ultrafine cement and nano-SiO2 can optimize the microstructure of grout-rock bonding interfaces，reduce the thickness of the interfacial transition zone，thereby improve the micromechanical properties of the interfacial transition zone and the macroscopic cohesive force of the grouted joints，but have little influence on the internal friction angle of the grouted joints.

The surrounding rock mass of underground engineering containing abundant groundwater in fault fracture zones is weak and broken，and is susceptible to severe collapse caused by humidification，thus resulting in many technical problems for engineering maintenance. Taking metamorphic granite of the fault fracture zone at Wuyue Pumped Storage Power Station，Henan province of China，as the object，large-scale tri-axial tests were conducted to investigate the mechanical behavior and wetting-induced deformation of rock masses under the hydraulic environment including moisture content，confining pressure and stress level. The test results reveal that，as the confining pressure increase，the peak strength and peak strain of specimens increase under different water states，and that the peak strength under dry state is respectively 22.90% and 27.33% averagely higher than that under natural and saturated states while the difference between the latter two is only 3.61%. It is worthwhile mentioned that the peak strain is the largest under natural state and the smallest under dry state，indicating that the peak strain is markedly influenced by the moisture content. It is also shown that the wetting-induced strain increment (i.e. axial strain increment －△e1s，volume strain increment －Devs and shear strain increment Dgs) is significantly affected by the stress level and confining pressure，and that effect the stress level on these three indicators is more sensitive compared to the confining pressure. In particular，1 time increment of the stress level will lead to the improvement of the three indicators by an average of 2.59，1.41 and 3.17 times，respectively. Comparison of the strength and deformation of granite samples before and after wetting shows that wetting deformation not only weakens the strength properties of the rock mass but also increases the volumetric deformation. The proposed calculation model upon wetting-induced deformation obtained through the experimental results was recommended as the reference for safety assessment of wetting-induced deformation of surrounding rock masses and the numerical analysis.

A new conditional algorithm for generating granular packing is proposed，by which the granular has the same complex geometries with the realistic granular and follows the target particle size，orientation angle and aspect ratio distributions. Firstly，amounts of morphology information of realistic granular is obtained through original particle image and a database is established. Secondly，by using the Minkowski difference for collision detection，the particle overlap check and the new particle packing could be carried out efficiently. Finally，in combination with the optimized advance front method，a particle packing model is generated，particle-by-particle. Compared with the existing methods，the granular generated by the developed method has the same complex geometries as the realistic particles and can consider arbitrary particle size，orientation angle and aspect ratio distributions. In addition，the granular packing model generated has a higher packing rate and packing volume ratio，for instance，respectively more than 800/s and 75% for rectangle particles in the MATLAB environment. A generation of complex granular material demonstrates the particle packing generated by the method can represent the same geometries and microstructure of realistic granular. Three direct shear test simulations carried out by the discrete element software of UDEC reveal that the developed method can be widely used in the analysis of mechanical properties of granular materials.

It is of significant importance to evaluate the stability of landslide dams accurately and rapidly for emergency rescue. At present，however，all the rapid evaluation methods cannot evaluate quantitatively the influence of the grain composition of landslide dam deposits on the dam stability. In this study，a database of landslide dams is established based on 1434 unstable and stable cases around the world，and then a set of new rapid evaluation method is proposed by using the logistic regression methodology. The method can consider the morphological characteristics and grain composition of the landslide dam，as well as the hydrodynamic conditions of the dammed lake. Further，based on the available information of material composition of the landslide dam deposits，a detailed evaluation method is developed by 27 unstable and stable cases with the grain-size distribution curve，and the simplified evaluation method is proposed by 115 unstable and stable cases with the description of material composition. Subsequently，15 cases with the grain-size distribution curve and 67 cases with the description of material composition are reselected to verify the new evaluation method and to compare it with the similar evaluation methods domestic and overseas. The calculated results show that the absolute accuracy rate，conservation rate and false rate of the detailed evaluation method are 86.67%，93.33% and 6.67%，respectively，and the absolute accuracy rate，conservation rate and false rate of the simplified evaluation method are 88.06%，94.03%，and 5.97%，respectively. In addition，the comparisons with other evaluation methods prove the reliability and superiority of the new evaluation method.

There are numerous data available to reflect the geological conditions during the operation period of full-section tunnel boring machine(TBM). The aims of this paper are to measure information of rockmasses in time and to intelligently optimize the tunneling parameters based on TBM operating data and CART-based ensemble learning algorithms，i.e. random forest and AdaCost. In order to establish models for rapidly and accurately predicting TBM tunneling parameters and surrounding rockmass conditions，a new pattern recognition method is proposed to divide a TBM tunneling cycle into empty pushing section，ascending section and stable section. Random forest model and the first 30 seconds data of ascending section are used to predict the values of the thrust and cutterhead torque during stable section，with the accuracy of 0.90 and 0.87 respectively. Moreover，a cost-sensitive AdaCost algorithm is used to predict the surrounding rockmass conditions with 16% and 50% precision improvements of grades IV and V compared to the random forest model，which solves the problem that the traditional machine learning algorithms are not applicable to imbalanced database. TBM operating parameters such as thrust，cutterhead power，cutterhead torque and advance rate are proved to be closely related to TBM tunneling，while cutterhead rotational speed，boot pressure，boot angle of pitch，advance rate and boot roll position and so on are shown to better reflect the surrounding rockmass conditions. These results are of great significance to TBM tunneling parameters optimizing and risk warning and will provide a reference to establish a data-based TBM intelligent decision and control platform in the future.

The specific frequency interference and background noise are the problems that seriously affect the microseismic monitoring and early warning of rockburst disasters in deep rock engineering. In order to solve these problems，firstly，the advantages of the classical FIR bandstop filter which is good at processing the fixed-frequency noise signal are made use of to denoise the interference. Then，in view of the problem of wavelet threshold denoising method，an unbiased estimation wavelet denoising method is proposed，which solves the problem that the threshold is difficult to be accurately determined when using the wavelet threshold denoising method to filter noise. Next，through organically combining the FIR bandstop filter and unbiased estimate wavelet threshold denoising methods，a FIR-wavelet joint filtering algorithm for microseismic signals is put forward and the FIR-wavelet joint filtering module is developed. The proposed algorithm is verified by the synthesized sinusoidal signal and microseismic signal. The results show that the proposed algorithm has better filtering effect and good robustness under different SNR conditions. The application to the TBM construction of the diversion tunnel of NJ hydropower station in Pakistan under strong environmental noise interference shows that the proposed algorithm improves the accuracy of P-wave picking and the location accuracy of rock fracture signals，provides powerful support for the early warning and prevention of rockburst，and hence has important theoretical and practical significance.

Implementing an experimental research on the evolution of gypsum mechanical characteristics at different loading rates has great theoretical research significance for the study of instability and failure of goaf as well as refinement treatment in gypsum mines. At a confining pressure of 10 MPa，triaxial compression tests of gypsum at different loading rates are implemented to study the effects of the loading rate on the physical and mechanical characteristics of dihydrate gypsum as well as energy accumulation，and to deeply analyze the law of energy evolution. The results show that the failure mode of gypsum samples is shear failure. Both the peak strength and the elastic modulus of the gypsum sample increase with increasing the loading rate，and the sample maintains a constant stress value without an obvious stress drop in the late stage of loading. When the loading rate is greater than 0.04 mm/min，the stress yield occurs at the peak value and the stress shows an increasing- decreasing-stabilizing trend，which shows that，at a high loading rate，the gypsum sample adjusts the internal structure to release strain energy and exacerbates the internal damage of the sample. The dissipated energy of the gypsum sample exceeds the elastic energy gradually in the plastic stage. After the peak stress，the dissipated energy increases rapidly，and the total energy is mainly transformed into the dissipated energy which becomes the main distribution mode. The total energy generated by the press machine after the peak value is mainly absorbed by the friction between the shear planes of the sample. When the axial strain is 0.01，the total energy and the dissipated energy tend to increase with increasing the loading rate while the elastic energy decreases. the higher the loading rate is，the larger the shear angle of the sliding surface of the gypsum sample is，and the higher the degree of failure is，which has a positive relation with the corresponding dissipated energy. The dissipation energy after the peak is the essential factor that determines the degree of shear failure of the gypsum sample.

In order to solve the problems of blockage of drainage plate and large energy consumption in vacuum preloading combined with electroosmosis(VPEO)，a combination method of stepped vacuum preloading and intermittent electroosmosis(SVPIEO) was proposed. Four sets of indoor model tests were carried out，and the water discharge and the surface settlement of soil were monitored. The reinforcement effect was evaluated，and the improvement effect of SVPIEO on VPEO in soil reinforcement and silting was investigated. In addition，the soil microstructure images were obtained by means of scanning electron microscopy，and the changes of soil pore characteristics after VPEO and SVPIEO were analyzed by image processing software. The experimental results show that，for SVPIEO，applying stepped vacuum pressure can alleviate the drainage board blockage，and intermittent energization can reduce anodic corrosion and increase soil current to promote soil drainage. Compared with VPEO，the water discharge and the vane shear strength of soil by SVPIEO increase by 13.2% and 19.2% respectively，and the soil moisture content decreases by 13.7%，showing significant improvement effect. After treatment by SVPIEO，the apparent porosity，number of pores and average pore area of the soil are larger. The smooth drainage channel of the soil helps drainage，and the soil pores are arranged more orderly and the pore shape is more complicated.

The triaxial consolidation undrained(CU) shear tests and magnetic resonance imaging(MRI) scans were conducted on undisturbed samples of granite residual soils under multiple dry-wet cycles，and the stress-strain curves，shear strength parameters and pore volume content were obtained to evaluate the damage effect of hot and rainy weather on the soil. The experimental results show that，after 0–2 dry-wet cycles，the stress-strain curves of the samples present strain softening and weak strain hardening behaviors under low and high confining pressures，respectively. However，the stress-strain curves of the samples after 3–8 cycles all present weak strain hardening behavior. With increasing the dry-wet cycle number，the effective cohesion and effective internal friction angle gradually decrease，while the attenuation amplitude of the effective cohesion is more obvious. Based on the surface relaxation coefficient of granite residual soils，the pore-volume distribution curves were acquired from the T2 distribution curves，and subsequently，the pores were divided into micropores and cracks according to the pore diameter. It is also revealed that，with increasing the dry-wet cycle number，the content of the micropores declines slightly while the content of the cracks increases significantly. The pore volume content and the effective strength index show a negatively correlated linear relationship，indicating that the decaying patterns in mechanical properties are synchronized with the evolution laws of the pore structure. The damaged effects of dry-wet cycles on granite residual soils are caused by the increase of the matrix suction during dehumidification，the expansive force and the loss of cements during moisture absorption.

Collapsible loess is sensitive to water，and floating collapsible foundation of loess tunnels is easy to cause lining cracking and other diseases. In order to guide the design of tunnel foundation treatment in loess areas，in this paper，a ground immersion model test device was developed relying on a loess metro tunnel project，the model test of surface triaxial mixing piles treating tunnel foundations was systematically carried out，and the effects of two main factors including the pile spacing and the treatment depth on treatment results were evaluated through monitoring the mechanical deformation characteristics of the tunnel structure. The results show that，the smaller the pile spacing is，the smaller the change values of the lining bending moment，axial force and earth pressure caused by foundation soaking are，while that，as the pile spacing is reduced to a certain value，the further reduction of the pile spacing will not increase the foundation treatment effect obviously. The larger the foundation treatment depth is，the more obvious the stress control of the lining structure caused by foundation soaking is. When the treatment depth reaches a certain value，however，the stress change of each point of the tunnel lining caused by soaking is not obvious，so the treatment depth only needs to reach the threshold value with a allowed amount of residual collapse. It is also indicated that the sensitivity of the stress of the tunnel structure to the treatment depth is greater than the pile spacing. When the treatment depth of the foundation reaches the threshold value，further reducing the pile spacing has no obvious effect on the treatment effect. Therefore，when dealing with the collapsible foundation of tunnels，it is suggested to first consider ensuring sufficient treatment depth of the foundation，following the principle of “long better than dense”.

The excavated foundations have been widely used in transmission line construction. The bearing capacity characteristics of excavated foundations in stiff clay under different loading conditions are investigated in this study by a series of centrifugal model tests. The results show that the failure mode of foundation soil under solo uplift loading is affected by the embedment ratio of foundations and the critical embedment ratio is between 2 and 3. For high outcropping foundations，the horizontal bearing capacity will reduce significantly with increasing the dimensionless outcropping height. The ultimate uplift capacity of no outcropping foundations with an embedment ratio of 2 will increase to some extent when the horizontal load is applied first. The greater the horizontal load，the stronger the uplift capacity. Under the same horizontal load at the foundation top and the same moment at the ground point before pullout，the ultimate uplift resistance of outcrop foundations with an embedment ratio of 2 has a difference no more than 10% with that of no outcrop foundations，which indicates that the moment of outcrop foundations at the ground point has no obvious influence on the uplift resistance under combined uplift and horizontal loading. The research work can provide a reference for the design of excavated foundations of transmission lines in various loading cases.

Conventional repeated load triaxial(RLT) tests can only simulate the cyclic load pulsed vertically. In order to study long-term deformation and failure mechanisms due to moving wheel loads more realistically，a series of RLT tests with both constant and variable confining pressure levels were conducted on typical base and subbase unbound granular materials. Different realistic in-situ stress paths defined by stress path slope，stress path length and minimum mean principal stress were applied. The coupling effect of cyclic deviatoric and confining stress components on the accumulation of the axial plastic strain was explored. Considering that the existing shakedown criteria for permanent deformation behavior cannot accurately distinguish different stages of permanent deformation behavior and are established from traditional RLT tests with constant confining pressure，a new criterion was proposed to address such insufficiencies. The improved accuracy and applicability of the modified shakedown analysis method and its criteria were confirmed by the realistic stress path test results obtained in this study.