There are thermal infrared and acoustic emission signal changes in the rock fracture process. Therefore，it is of great significance to study the thermo-acoustic signal in the fracture process of fractured rock. In order to study the thermal-acoustic sensitivity of the failure process of different lithological fractures，uniaxial compression tests on samples of granite，basalt，red sandstone，limestone and marble were carried out，and the temperature of the free surface and the internal acoustic signal of the samples during loading process were monitored. A joint analysis index of thermal-acoustic sensitivity is proposed. The results indicate that the time series sensitivity of the combined thermal-acoustic index is as follows：red sandstone，limestone，marble，granite and basalt，but the peak sensitivity of the combined thermal-acoustic index is as follows：basalt，granite，marble，limestone and red sandstone. Thermal infrared temperature signal is earlier than acoustic emission signal. The joint index can avoid the lag of acoustic emission signal and the spatial limitation of thermal infrared. The thermo-acoustic signal and the stress have a good corresponding relationship in the fracture process of each lithological rock. The research can provide a useful reference for the analysis and prevention of sudden rock failure.

High position and long runout landslides have a large height of fall，potential energy and kinetic energy conversion space，and obvious dynamic disintegration effect，which is one of the difficulties and hot issues in the research field of geological disasters. Based on the discrete element numerical model test，the influences of structure plane density，structure plane strength and disintegration degree of landslide rock mass on dynamic disintegration during movement are deeply analyzed. Also，the dynamic mechanism of high position and long runout landslide-debris flow is revealed. The results show that (1) high position and long runout rock landslide dynamic disintegration mode is mainly divided into two types：the active disintegration of differential motion and the passive disintegration of impact collision. (2) Structural plane density，structural plane strength and disintegration degree are the fundamental causes affecting the high rock landslide dynamic disintegration effect；(3) Dynamic disintegration reflects energy conversion and consumption. Friction，inelastic deformation and disintegration are the main energy consumption modes，and the friction energy consumption is the leading energy consumption，accounting for more than 50%；(4) The front sliding body has significant speed transmission，and the velocity transmission phenomenon of the sliding body with high disintegration degree is more obvious than that of the sliding body with low disintegration degree. The research results show that in the process of geological disaster investigation，monitoring and prediction，the structural feature investigation and evaluation of the rock mass should be fully conducted. Also，the impact of the dynamic disintegration effect should be fully considered in the risk assessment of high position and long runout landslides.

To investigate the uplift patterns of underground lined rock caverns for compressed air energy storage (CAES) under the action of high gas internal pressure，based on upper bound theorem of limit analysis，uplift failure function f(x) and limit internal pressure pu are derived under the assumption that the rock mass obeys the associated Hoek-Brown criterion. Considering the thermodynamic response laws of CAES caverns，an anti-uplift failure criterion is established. A sensitive analysis on the parameters affecting the failure function f(x) is performed. Research results indicate that the uplift failure function f(x) of CAES caverns is a typical power function，which is mainly related to the rock uniaxial compressive strength ，Hoek-Brown empirical parameters A and B，and the buried depth H. The slope of f(x) gradually decreases as and A increase，while gradually increases as parameter B increases. The limit internal pressure pu is closely related to the failure mechanism function f(x). The limit internal pressure pu increases as the parameters ，A and H increase. However，as parameter B increases，the limit internal pressure pu decreases gradually. Compared with existing anti-uplift criterion of CAES caverns，the calculation method proposed in this paper fully considers the influence of rock mass strength parameters and failure patterns. Therefore，the use of this new criterion will greatly reduce the buried depth of the cavern to resist uplift failure under the premise of safety. As a result，the construction cost for CAES caverns will decrease greatly，which is conducive to promotion and application of CAES technology.

In order to explore the size effect of rock dynamic fracture toughness，the dynamic split loading test was carried out using the split Hopkinson pressure bar(SHPB) system on the cracked straight-through Brazilian disc(CSTBD) specimens with diameters of 50，100，150 and 205 mm，respectively. The variation of the dynamic fracture toughness with the size of the specimens was analyzed. The length of fracture process zone，the incubation time and the fracture energy of the specimens with different sizes were determined by virtual crack model，theoretical analysis and dynamic finite element method. A method for determining rock dynamic fracture toughness considering space(length of fracture process zone)-time(incubation time of fracture process zone) domain was proposed. At the same time，the digital image correlation method(DICM) was used to monitor the surface of the specimens，and the failure process of the specimens was explored. The results show that the test values of the fracture toughness increase with the size，showing an obvious size effect. The length of fracture process zone and the incubation time increase with the size，indicating that the contribution of the stored energy increases with the size，which is consistent with the size effect of the fracture energy and indirectly explains the reason of the size effect of the fracture toughness. Considering the space-time domain，the size effect of the fracture toughness of larger size specimens(D = 150 mm，D = 205 mm) is reduced. The method to eliminate the size effect from the overall size needs to be further explored. The crack propagation direction of the specimens is from the crack tip to the loading end，and a wedge-shaped failure zone is formed at the loading end.

The characterization of the roughness of rock fractures and their seepage has been a difficult and hot issue in the field of rock mechanics and engineering geology. Based on the basic principles of fractal theory and hydrodynamics，the irregular roughness elements on the fracture surface were first quantified，and the quantitative relationship between the relative roughness and the fractal dimension as well as the fracture microstructure parameters was established. Then，the effect of the roughness on seepage was transformed into the effect of the equivalent opening of fractures on flow characteristics. Combining the power-law relationship between the fracture opening and the fracture length，a fractal model for calculating the permeability of rough fractures was established. Finally，the effects of fractal dimension and geometric characteristics of fractures on seepage properties were studied，and the rationality of the model was verified using relevant experimental data. The results show that the influence of the fracture roughness on seepage cannot be ignored. There is a square relationship between the permeability and the maximum fracture opening，and the fracture opening and geometric characteristics of rough elements are the key factors affecting seepage performance. The proposed permeability model does not contain any empirical constants，which avoids the tedious process of data processing and has better applicability.

To study the mechanism of silica sol imbibition grouting for mud-bearing low-permeability rock，imbibition tests were carried out on two low-permeability artificial cores. The microscopic seepage characteristics during the imbibition grouting process of the low-permeability cores were tested based on the low-field nuclear magnetic resonance(NMR) system，which revealed the pore filling and closure patterns from the microscopic scale. The injectability of silica sol to low-permeability rock was analyzed in combination with core pore size distribution and silica sol-gel growth law，and the mechanism of silica sol imbibition grouting and engineering application prospects were discussed. The results show that silica sol has an outstanding ability to absorb and infiltrate low permeability cores，with an affinity of 92.2% of that of deionized water. The absorption curve of silica sol is characterized by exponential three-stage distribution，in which the absorption process of 0.1 mD core is mainly controlled by micropores while the absorption of 20 mD core is successively controlled by mesopores and micropores. The characteristics of nano-pores and the growth of silica-sol gel have significant effects on the injectability of silica-sol imbibition，and the injectability and capillary force jointly affect the results of absorption. Silica sol imbibition grouting can meet the engineering requirements of nano-scale pore-fracture sealing in the low-permeability rock mass.

To study the steering mechanisms of directional water pressure fracturing in the hard roofs of coal mines，the equations for evaluating the stress intensity factor，the fracturing initiation angle and the critical water pressure of the mechanical model of directional hydraulic fracturing involving wellbores and pre-slits were deduced under water pressure and geo-stresses based on the theory of linear elastic fracture mechanics. On this basis，the parameters affecting the stress intensity factor the fracturing initiation angle and the critical water pressure were analyzed and the fracture characteristics of directional water pressure fractures were discussed. The results show that during the critical initiation state of directional hydraulic fracturing，tension fractures or tension-shear composite fractures occur at varied pre-slit angles. The fracturing initiation angle decreases with increasing the stress intensity factor ratio / . At smaller / ，the hydraulic fracture initiation deviates from the pre-slit direction under the action of shear dislocation. To control the directionality of hydraulic fractures，the influence factors of and should be considered comprehensively. Specifically， is much larger than when the pre-slit angle is low and the water pressure is high. is also larger in wellbores with a large radius and a low pre-slit angle. With a low angle and a high pre-slit length， arrives at a larger value，while with a 45° pre-slit angle and a high pre-slit length， can reach a larger value. Both and are sensitive to the coupling effect of the lateral pressure coefficient and the pre-slit angle. When the lateral pressure coefficient is small， is larger than . When the lateral pressure coefficient is large， is greater than at a low pre-slit angle，while is greater than at a high pre-slit angle.

In order to study the effect of block form on the shear mechanical behaviors of the soil-rock mixture(S-RM)，a novel 3D block geometry modelling approach is proposed on the basis of CT technology and spherical harmonic series，for generating blocks with different forms(spheroidal，prolate，oblate and blade) but same convexity and angularity. Based on the improved non-overlapping cluster generation method，the 3D DEM block models，characterized by a higher computational efficiency，are established. The numerical direct shear tests were performed on S-RM models with different block shapes and breakable characteristics. The maro- and meso- mechanical properties of S-RM were deeply analyzed and the effect mechanism of block form was revealed. The results show that the occlusion，sliding friction degree and rotation magnitude of the spheroidal and prolate blocks are larger than those of the oblate and blade ones. The breakage of block increases the degree of block occlusion and rotation，but reduces its sliding friction degree. Under the combined effect of sliding friction and rotation of blocks，the breakage degrees of spheroidal blocks are the largest while the blade ones are the smallest，and the shear strength and dilation of S-RM with spheroidal and prolate blocks are larger than those with oblate and blade ones. Due to the breakage degrees of the spheroidal and oblate blocks are larger，the S-RM nonlinear characteristics of strength are more obvious than those of the S-RM with prolate and blade blocks. Due to the occlusion degrees of the spheroidal and prolate blocks are larger，the peak frictional angles of S-RM are larger than those of the S-RM with oblate and blade blocks.

As a heterogeneous composite material，the macro properties of rock largely depend on the micro-nano scale structural characteristics of the material. With the popularization and development of nanoindentation technology，the nano-mechanical information of rock materials has been widely reported. In order to understand the research status of nanoindentation technology in rocks，the relevant literature at home and abroad is reviewed. First，the basic principles of applying nanoindentation technology to test the elastic modulus，fracture toughness and creep of rock materials are explained. Then，the sample preparation method and test parameter selection for nanoindentation test are summarized. On this basis，the nanoscale characteristics of common rock materials such as shale，coal，sandstone and mudstone are summarized and classified，and the key factors affecting their nanomechanical parameters are analyzed. The results show that due to its high precision in both force and displacement，nanoindentation can be utilized to extract the localized mechanical properties of individual grains，thereby avoiding the requirement of conventional mechanical testing for the size of the specimen. However，the nanoindentation test has specific requirements for the surface roughness of the sample and the loading and unloading regime，and special rock samples need matching sample preparation methods. In addition，the mineral composition and external environmental have an important influence on the nanomechanical properties of the rock material. Although nanoindentation technology has been widely used，its research in rock materials started relatively late，and it still faces many difficulties in data analysis，multi-scale model building and multi-scale mechanical property transfer.

It is necessary to test the mechanical properties of crack initiation，crack propagation and slip process of fracture surface for multi-size rock under compression shear composite stress. A multi-dimensional rock compression shear fracture test device has been developed，which can apply compression load and shear load synchronously or successively on biaxial. In comparison，some deficiencies exist in existing related equipment，such as the sample size that can be tested is small and single specification，the maximum test force is not high，etc. The developed device is mainly composed of frame，loading and force measuring mechanism，sample box，sample positioning mechanism，electro-hydraulic servo control system，operation software，etc. Cube sample，cuboid sample with the same width or equal ratio can be tested in the size range of 50–300 mm. The maximum normal load is 1 500 kN and the maximum tangential load is 3 000 kN. The stiffness of the test loading system composed of frame and loading mechanism was analyzed. The transition condition from the load control before rock fracture to the displacement control during the slip process of the fracture surface was discussed. The load accuracy calibration of the test device has been carried out. The results show that the indication accuracy reaches 0.5% in the load test range of 2%–100%. A preliminary experimental study on the multi-size cuboid granites，with an aspect ratio of 2∶1，have been carried out. The results are as follows：Firstly，the minimum and large normal load were applied separately to granite samples. Test accuracy and stable loading have been showed by obtained relationship curves of shear load with time or displacement. Then，the test values of two tangential load cell，located at the loading end and support end of the sample box，were obtained. During the initiation and propagation of rock cracks，it is found that the measured values were not synchronized through comparative study. Then，the peak shear load increased with the increase of normal load when different normal loads were applied to the same size samples. Finally，when the normal stress of 10 MPa and 20 MPa was applied to three continuous size samples respectively，the peak shear stress was a nonlinear relationship with the increase of samples size.

Aiming to solve the challenges of low detection accuracy，poor anti-interference ability and slow detection speed in the traditional tunnel leakage detection methods，a depth semantic segmentation algorithm for tunnel leakage is proposed on the basis of the DeepLabv3+ semantic segmentation algorithm. Firstly，the lightweight classification network EfficientNetv2 is used as the backbone network，which enhances the recognition accuracy while reduces network parameters. Secondly，Convolutional Block Attention Module(CBAM) is integrated to increase the weight of the effective channels in the image，thereby improving the ability of extraction of leakage feature information. Traditional semantic segmentation algorithms，including DeepLabv3+，PSPnet and Unet，are used for comparative experiments from three aspects：image recognition accuracy，model size，and detection speed. The results show that the mean pixel accuracy(mPA)，mean intersection over union(mIoU)，model size and image processing speed(FPS) of the proposed algorithm are 93.99%，89.87%，33.4 MB and 39.87 f/s，respectively. Compared with the three comparison algorithms，the detection accuracy and efficiency of the proposed algorithm have been significantly improved. Furthermore，the proposed algorithm has better edge segmentation effect and anti-interference ability，which is suitable for tunnel leakage detection tasks in complex environments，so as to better meet the needs of engineering detection.

In order to characterize the natural three-dimensional(3D) spatial variability of frozen soil layer and to clarify the evolution process of temperature eigenvalue of freezing curtain，the thermal parameters of frozen soil layer are modeled as 3D random fields，and a new tetrahedral discretization methodology of 3D random field is proposed. An analytical formula and a numerical formula of the covariance for any two tetrahedral random field elements are developed by the volumetric coordinate transformation and gauss integral transformation. A stochastic analysis model for the thermal characteristics of freezing curtain considering the 3D spatial variability of frozen soil layer is established. The dynamic evolution process and statistical law of temperature eigenvalue are obtained，and the influence of the correlation structure of 3D random field on the temperature eigenvalue of the freezing curtain is discussed. The results show that the tetrahedral discretization methodology can be perfectly combined with the tetrahedral finite element method. Also，the corresponding relation is clearer and the computer codes are simpler. The spatial variability of thermal parameters of frozen soil has significant influence on the temperature eigenvalue of freezing curtain，and the spatial variability of thermal conductivity has the greatest influence. The effects of different correlation structure of 3D random field on temperature eigenvalue of freezing curtain are different. The triangle model has the greatest influence，the Gaussian model has the median value，and the exponential model has the least influence.

As a retaining structure suitable for seismic areas，cantilever retaining walls(CRWs) are widely used，at the back of which backfills show a certain slope angle. Many problems(such as how to determine the level and point of action of the seismic earth pressure，displacement and deformation and failure mode) still occur during seismic design of retaining walls. Moreover，micropiles with favourable seismic behaviours have been extensively used in the fields of controlling shallow landslides and reinforcing slopes. Research on mechanical characteristics，load and deformation accumulation of micropiles under the lateral dynamic load remains sparse. To this end，the seismic response characteristics of a micropile-reinforced cut slope behind a CRW under multistage continuous earthquake loadings were studied by means of a centrifuge shaking-table model test. At the same time，the typical shaking event is numerically simulated. The seismic response characteristics of the slope system supported by micropiles and CRWs were analyzed and discussed from three aspects of seismic acceleration response of the slope and the settlement and deformation of the slope crest，seismic response of the micropiles and distribution of bending moment on the piles，and the level and point of action of the dynamic earth pressure，the bending moment and the influence of the bending moment of inertia generated by the self-weight of CRWs，displacement and deformation mode during an earthquake and cumulative development of the residual bending moment. A transfer-function analysis of the input and output accelerations shows that the slope soil has a significant acceleration amplification effect on the frequency components of the input seismic waves approaching their natural frequency. It is necessary to set the rigid connected beams on the upper part of the micropile structure，which is able to improve the mechanical performance of micropiles. Due to the flexibility and ductility of micropiles，more energy can be dissipated under the effect of seismic load. The bending moment of inertia on the CRWs cannot be ignored because it exceeds 22% of the dynamic bending moment. When there is a large slope angle of backfill，and loads are applied to the upper part of the slope crest，the dynamic earth pressure coefficient ΔKae is much larger than that when the backfill is flat and no additional loads are applied. In addition，the significant residual bending moment is accumulated on CRWs and micropiles after earthquakes，which needs to be considered during the seismic design of retaining structures.

Due to structural and initial stress anisotropy，the mechanical and deformation characteristics of undisturbed loess are particularly complex. It is of great significance to study the constitutive relation of undisturbed loess in theory and practical engineering application. Based on the modified Cam-clay model，the structural evolution law of undisturbed loess under water and force conditions was analyzed in this paper. Furthermore，the volumetric change equation of structural loess considering the effects of water and force was proposed，which can reasonably describe the initial anisotropy of undisturbed loess by introducing the concepts of relative stress ratio and relative critical stress ratio. A constitutive model reflecting both structural and initial stress anisotropy of undisturbed loess was derived further by using the correlation flow rule. When the structural and initial stress anisotropy are not considered，the model can be reduced to the modified Cam-clay model. Compared with the triaxial test results and model prediction results of undisturbed loess，the model in this paper can reasonably describe the deformation behavior of undisturbed loess under water and force conditions.

In order to investigate the penetration characteristics of jacked piles in layered clay，in-situ full-scale tests of hydrostatic piles were carried out based on a pile foundation project in Dongying，Shandong Province. The variation law of the jacking force of open and closed jacked piles is analyzed，and the distribution form of the end resistance and the shift resistance of open and closed jacked piles during jacking is discussed. The distribution characteristics of the radial soil pressure and the pore water pressure at the pile-soil interface are revealed. The influence mechanism of the effective radial earth pressure on unit shaft resistances is also revealed. The test results show that the change of the jacking force basically reflects the change of soil properties，and the soft and hard degree of soil restricts the change of the jacking force. The jacking force of open piles is obviously less than that of closed piles，and the open pile accounts for 33.9%–79.7% of the closed pile at the end of jacking. The soft and hard degree of soil layers has a great influence on the pile end resistance，and the sensitivity of closed piles to the soft and hard degree of soil layer is higher than that of open piles. The development of the shaft resistances is closely related to the properties of soil layer. The shaft resistance caused by soil layer change is not obvious near the depth，and the unit shaft resistance appears obvious degradation. The increase of the soil pressure at the pile-soil interface is closely related to soil properties. The distribution forms of the pore water pressure and the excess pore water pressure are related to the permeability of soil layer. The calculation formula of the excess pore water pressure based on hydraulic fracturing theory and cylindrical pore expansion theory can better reflect the distribution characteristics of the excess pore water pressure. The ratio of the effective radial earth pressure to the unit shaft resistance is about 0.28 in silty soil layer，and 0.3 in silty clay layer. The degradation shaft resistance actually reflects the degradation of the effective radial earth pressure.

New energy power engineering construction is promoting the application of metal grillage foundations in aeolian sand areas. The design of the slab spacing involves the calculation of uplift bearing capacity and cost control. Therefore，full-scale uplift tests and trapdoor experiments for grillage foundations were carried out in aeolian sand. The variation in bearing capacity，stress and surrounding soil pressure of foundations as well as the development of the soil arch between the slabs，were investigated in the cases of the ratios of the slab spacing to the slab width of 1.0，1.5 and 2.0. The results show that：(1) the uplift bearing capacity of metal grillage foundations decreases linearly with the slab spacing；(2) the stress in the support decreases with the slab spacing，while increases with the height from the bottom slab. The change of the stress in the bottom slabs is opposite to that in the support，and the maximum stress mostly appears in the cantilever parts of the slabs；(3) the slab spacing has little effect on the location of the sliding plane，and the back-calculated angle of the slip plane to the horizontal is 20°；(4) the results of trapdoor experiment indicate that the larger the slab spacing is，the higher the soil arch is and the larger the lost volume of soil between the slabs is resulting in increasing loss of the foundation resistance；(5) considering the soil arching effect between the slabs，the soil weight method is modified，and the calculated results are closer to the tested uplift bearing capacity. The research can provide references for optimal slab spacing in grillage foundation design.