In this paper，the 175m reservoir water level operation process of the Three Gorges Reservoir Project from 2008 to 2020 is analyzed，and a typical curve of the average annual reservoir water level fluctuation is obtained. Taking the Taping landslide in Wushan county as a case study，the relationship between the average reservoir water level fluctuation and the phreatic line in the typical accumulative landslide is established by the modified analytical solution of one-dimensional unsteady seepage equation. Furthermore，the unbalanced thrust method considering time variable is used to calculate the factor of safety of the accumulative landslide under reservoir water level fluctuation. Considering the good connection between reservoir water and groundwater in the reservoir landslide，it is difficult to adopt conventional anti-slide piles in prevention engineering，and hence，the small and medium calibre anti-slide pile group is proposed to be adopted in the prevention design of the reservoir landslide in this paper. It is worth noting that，in August 2020，the Three Gorges Reservoir area encountered the maximum peak discharge since the construction of the dam in 2003，reaching 75 000 m3/s，therefore，the study on the landslide stability in the hydrological year can provide a reference for the stability analysis and prevention design of the reservoir landslides under special working conditions.

As a common rock reinforcement method，grouting technology has been widely used in underground engineering，while the reinforcement performance is largely affected by the external environmental factors such as high temperature and high geo-stresses. Therefore，it is of great practical significance to study the flow and diffusion mechanism of slurry in fractured rock under different external conditions to enhance the grouting reinforcement effects of deep soft rocks and to ensure the construction safety. In this paper，infiltration grouting tests on fractured sandstone samples were carried out using the low-field NMR technology. During the grouting process，the NMR signal characteristics of the slurry were monitored in real time，and the parameters such as the slurry injection volume，the effective grouting time and the slurry-filling rate were analyzed under the conditions of different temperatures，different confining pressures，different slurry flow rates and different numbers of fractures. The results show that the incubation period of the superfine cement slurry decreases with increasing the temperature and that the slurry viscosity performs significant time-dependent and temperature-dependent characteristics. The final slurry injection volume of the fractured rock decreases with increasing the temperature and the confining pressure. The effective grouting time is inversely proportional to the slurry flow rate while positively proportional to the temperature. The slurry filling rate decreases as the confining pressure increases，accompanying with a decreased sensitivity to the confining pressure. Compared to the samples with single fracture，multi-fractured samples show higher slurry injection volume，shorter effective grouting time and larger slurry filling rate. Under a higher slurry flow rate and a higher confining pressure，the percentage of the slurry filling rate in the micro-pores increases significantly，and the slurry preferentially transports into the micro-pores. When the micro-pores reach a certain filling level，the slurry transports into the meso-pores and macro-pores. However，the temperature and the number of fractures have insignificant effects on the diffusion mechanism of the slurry in the rock pores，and the percentage of the slurry filling rate varies a little in each type of pores. The findings in this study can provide necessary guidance for the optimal design and selection of grouting parameters for deep soft rock mass.

In order to study the microscopic pore evolution law and shear mechanical response of grouting fractured rock mass under the action of freeze-thaw cycle，three kinds of grouting reinforcement body samples including ordinary cement(P-type)，superfine cement(C-type) and epoxy resin(H-type) are selected for freezing cycles，nuclear magnetic resonance(NMR) and shear tests. On this basis，the apparent characteristics，microscopic pore structure and shear mechanical properties of the slurry-rock interface layer during the freeze-thaw cycle are analyzed，and the failure mechanisms of macroscopic and microscopic multi-scale grouting consolidation are studied. The results show that：(1) With increasing the number of freeze-thaw cycles，the three types of samples have different degrees of particle spalling，shedding and cracking. The freeze-thaw deterioration of the P-type slurry-rock interface layer is most serious，followed by C-type and H-type. (2) The evolution trends of NMR T2 spectra at the slurry-rock interface layer of the three types of samples are similar and show a right-shift trend with increasing the number of freeze-thaw cycles. The initial pore size is P-type＞C-type＞H-type. In the process of freeze-thaw cycles，the pore size is characterized by the evolution from micropore to mesopore and from mesopore to macropore. (3) The freezing-thawing deterioration of the slurry-rock interface layer is caused by the solid-liquid phase transformation and migration of the internal water under the action of cyclic temperature，and the different grouting materials have a great influence on the freezing-thawing deterioration of the slurry-rock interface layer. (4) The overall shear stress-strain curves of the three types of specimens are similar，and the shear strength(τp) and shear stiffness(KS) of three types of specimens decrease with increasing the number of freeze-thaw cycles. However，τp and KS of H-type specimens are the largest，followed by C-type and P-type. (5) There is a functional relationship between the T2 spectral area and the shear strength of the grouting consolidation body. Based on this，the shear failure mechanism of the slurry-rock interface layer based on the microscopic pore evolution law under different freeze-thaw cycles is obtained. Under the action of the shear stress，the internal pores of the slurry-rock interface layer crack at the tip and connect with the adjacent pores to form a micro-fracture surface. The micro-fracture surface extends along the slurry-rock interface layer to form macroscopic cracks，which eventually leads to the shear failure of the grouting consolidation body along the slurry-rock interface layer. The research results provide a theoretical basis for evaluating the grouting effect of fractured rock mass in seasonal frozen zones and improving the engineering stability of rock mass.

At present，the total footage of roadway excavation exceeds 12 000 km/a，but the roadway support design is basically carried out by using the engineering analogy method. On the basis of summarizing the existing roadway support design theories and methods，the roadway support design principles and design methods are proposed starting with the basic characteristics of roadway support design and the mechanics principles of roadway excavation，as：(1) The influence factors such as the magnitude of in-situ stresses，the geomechanical parameters and indexes of the surrounding rock，the strength of the surrounding rock and the classification of the surrounding rock should be taken into consideration comprehensively，and their values should be determined accurately. (2) The basic features of roadway support design and the mechanical effects of roadway excavation under different surrounding rock geological conditions should be analyzed correctly. (3) The interaction mechanism between the surrounding rock and the support of the roadways with different surrounding rock types should be understood and analyzed correctly. (4) Accurate calculations of the pressure and deformation of the surrounding rock are necessory in accordance with the interaction mechanism between the surrounding rock and the support. In order to accurately understand the principle of interaction between the surrounding rock and the support，this paper briefly gives an analytical method for the whole process of the interaction between the surrounding rock and the support in the elasto-plastic deformation stage. The content，principle，method and process of roadway support design proposed in this paper can provide theoretical basis for the preparation of roadway support design specifications.

Basalt Fiber Reinforced Polymer(BFRP) is gradually used as bolts in underground engineering. In order to study the shear characteristics of jointed rocks reinforced with BFRP bars，laboratory shear tests were carried out to comparatively analyze the shear properties of bolted joint rocks with BFRP bars and steel bars，including shear strength-displacement curve，shear strength，bolt failure characteristics and internal force changes in the bolts，and the influence factors such as roughness，bolt inclination and normal strength were also considered. The results show that，compared with the steel bolts，the BFRP bolted specimens have a lower shear stiffness，a larger peak shear displacement and a higher residual shear strength. The BFRP bolted specimens absorb more energy before the shear peak than the steel bar bolted specimens，although both them absorb the same total energy and exhibit toughness in the shear process. The shear strength of the BFRP bar bolted joint rocks is greatly affected by the inclination angle with a lower shear strength when the inclination angle is equal to 90°. When the inclination angle is reduced to less than 60°，the BFRP bolted specimens have a higher shear strength than the steel bar bolted specimens. The shear failure characteristics of BFRP bolted joint rocks can be categorized as：resin matrix fracture，shearing of both resin matrix and fibers，and fracturing of resin matrix and surrounding rock. When the BFRP bars fail，there is no obvious plastic yield. The resin matrix frequently breaks under a small shear displacement，while the fiber is able to resist a large joint dislocation which improves the contribution of the normal stress to the shear strength. Based on the strain monitoring data，the contribution rates of the axial force and shear force from the BFRP bars and the steel bars to the shear strength were quantitatively analyzed at an inclination angle of 60°. It was found that，compared with the steel bars，the axial force of the BFRP bolts increases faster under the same shear displacement and there was a greater contribution from the axial force to the shear strength.

Equally-spaced fractures can be commonly found in layered rocks. How to predict the fracture spacing has important significance and practical value for the stability analysis of layered rocks. Considering softening behavior of the shear stress along the rock interface，a tri-linear bond slip model was adopted to calculate the full-range evolution of the shear stress along the rock interface and the tensile stress in fractured layered rocks. A failure criterion for the layered rock considering the influence of the overload was developed and then the analytical expressions for predicting the fracture spacing in fractured layered rocks under different bond conditions were proposed. The feasibility of the proposed calculation formula was verified by finite element simulation and field data. The evolution of the fracture spacing and the influencing factors were analyzed. The results indicate that the proposed analytical solutions can be used to predict the fracture spacing for the rock interface under different conditions，such as bond，part bond，shear stress softening and complete slip.

Aiming to establish the brittleness index for characterizing deep shale gas reservoirs，a new brittleness evaluation method，characterizing the brittleness of rock from three aspects such as rock failure rate()，post-peak instability() and pre-peak plastic yield()，was proposed based on energy balance theory in consideration of the energy conversion rate of the rock system to the outside and the effect of radial expansion on brittleness characteristics，and a series of triaxial compression tests designed according to shale-formation information were conducted to verify the applicability of the index. The test results show that the brittleness characteristics of shale decrease with increasing “formation level”(i.e.，the confining pressure and the temperature)，and compared with the existing brittleness indices，the new brittleness index is superior in describing the brittleness characteristics of shale under different test conditions，especially in the condition of high confining pressure(at 100 MPa) and high temperature(at 190 ℃). Besides，the brittle failure mechanism of shale was analyzed in terms of strength factors，and it is revealed that the strength envelope curve of shale presents bilinear characteristic. Meanwhile，a critical condition for macroscopic fracture patterns of shale was quantified by establishing the correlation of the macroscopic fracture pattern，the brittleness characteristics and the critical principal stress ratio. It is also found that the damage degree of shale can reduce the brittleness characteristics of shale by increasing the pre-peak plastic yield and the contribution rate of the elastic energy.

Based on the fiber Bragg grating sensing test technology，the field pull-out destructive tests of GFRP bars and steel anti-floating anchors were performed. The bonding characteristics of the bar-slurry interface and the slurry-rock interface of GFRP anti-floating anchors were analyzed，and the influences of the anchorage length，the anchor material，the anchor diameter and other factors on the interface bond strength of two kinds of anti-floating anchors were revealed. The results show that the failure modes of GFRP bars and steel anti-floating anchors are mainly pull-off failure and shear-slip failure while the failure loads of GFRP anti-floating anchors with anchoring lengths of 4.5 and 6.5 m are 1.21 and 1.13 times that of the steel anti-floating anchors of the same specification，respectively. The average bond strength of the bar-slurry interface of the GFRP anti-floating anchors，ranging from 0.99 to 1.03 MPa，is higher than that of the steel anchor rods. The anchorage length is the most important factor that affects the bond strength of the bar-slurry interface of the anti-floating anchors. The axial stress of the slurry-rock interface of the GFRP anti-floating bolts decreases with increasing the depth，reaching a largest value at the orifice，while the shear stress of the slurry-rock interface increases first and then decreases with the depth，arriving at a peak at an anchorage depth of about 0.5 m. By comparing different materials and different types of anti-floating anchor rods，it is found that the slurry-rock interface bonding performance of the reinforced anti-floating anchor rods is slightly higher than that of the GFRP anti-floating anchor rods，and increases with the diameter of the anchor rod. The synergistic effect of the GFRP anti-floating anchor bar，the slurry and the surrounding rock and soil is higher than that of the steel anti-floating anchors.

To explore a new method for coal and rock dynamic disaster prediction based on weak current technique，field tests of weak current of coal mass in front of the mining face of a mine with rock burst risk were carried out using a self-developed weak current measuring device. The spatial distribution laws of weak current of the surrounding coal of the roadway and the response laws of weak current of the coal mass in front of the working face in the mining process were obtained. Combined with the information of microseismic events monitored，the precursory characteristics of coal instability or failure based on weak current responses were determined，and the feasibility for using the weak current method to predict coal and rock dynamic disasters was verified. The results show that the distribution of weak current in surrounding coal mass is almost consistent with the stress distribution，showing a trend of “increase-decrease-stable” from the roadway side to the deep of coal mass. Weak current responses well to the advancing process of the working face，showing a stepped increasing trend. Specifically，weak current increases gradually in the mining period while fluctuates stably in the stopping period. In addition，weak current could response to mining tremors in advance，and the acceleration of the current can be used as the precursor of mining tremors or coal failures. The weak current method has a wide application prospect in underground engineering due to its advantages of strong anti-interference ability，sensitive response and advanced disaster warning. However，the weak current method is still in the experimental stage，and the technique still needs to be further verified and improved through more field tests so as to provide technical support for accurate prediction of coal and rock dynamic disasters.

In order to study the effect of the early load on the later mechanical properties of cemented gangue backfill(CGB)，the specimens cured for 7 days were loaded at 4 stress levels，and after 28 days of continuously loading，unloaded and used for carrying out uniaxial compression test. The ultrasonic wave velocity changes in the CGB during the continuous loading process and the acoustic emission response characteristics during the uniaxial compression process were monitored，and the microscopic morphology of the specimens was observed using a scanning electron microscope. The results show that the early load has a great influence on the mechanical properties of the CGB. When the early stress level is less than 80%，the load has a significant strengthening effect on the compressive strength and the elastic modulus of the CGB. With increasing the early stress level，the transverse strain and the Poisson¢s ratio increase exponentially，and the specimen failure form gradually changes from shear failure to split failure. The ultrasonic wave velocity shows obvious multistage characteristics during the continuous load process，and the acoustic emission activity of the CGB subjected to high stress levels decreases. Early load promotes cement hydration reaction and contributes to the improvement of the strength. According to the test results，a damage evolution model of the early loaded CGB was established under uniaxial compression，which can provide a basis for the design of the backfill in the structural filling.

Figuring out the vibration characteristics induced by different kinds of boreholes in tunnel drilling and blasting and the inherent differences is an important issue. Taking the full-faced tunnel blasting excavation as an example，the blasting boundaries of different kinds of boreholes were analyzed in terms of the inner and outer acting effects in rock blasting. Based on the onsite single-hole and production blasting experiments，the peak particle velocity(PPV) and the dominant frequency(DF) induced by three kinds of typical boreholes，including cutting borehole，breaking borehole and smooth borehole，were compared and analyzed. Moreover，the differences of the inner and outer boundary conditions of different boreholes and their dynamic responses were further investigated by the numerical simulation. Finally，the inherent causes of the differences of vibration characteristics induced by different kinds of boreholes were outlined and discussed from the view of blasting energy distribution and plastic zone development. The results indicate that，for the cutting boreholes which are always detonated under single free-surface condition，the blasting clamping force is much stronger and the outer blasting effect is relative weaker，resulting that more explosion energy is converted into blast vibration and the PPV is relative larger. Compared with the breaking boreholes and the smoothing boreholes，the row spacing and the decouple-charging coefficient of the cutting boreholes are much smaller，and hence，the inner blasting effect as well as the area of the blast-induced plastic zone is increased while the DF is relative lower. Due to that both the breaking boreholes and the smooth boreholes initiate under two free surfaces including one natural surface and one blasting created surface，their outer and inner blasting effects as well as the PPV and DF distributions are similar although the later have a larger decouple-charging coefficient and a smaller spacing. In practice，the safety control of blast vibration could be realized in a way of adjusting the inner and outer blasting effects by changing the inner and outer boundary conditions.

In order to explore the evolution of permeability of coal with different water contents under the combined effect of effective stress and dynamic slippage，a gas-containing coal thermal-fluid-solid triaxial servo seepage device was used to measure the permeability of coal in the effective stress rise process under different water contents. A coal permeability model was established considering the effective stress，the water content and the dynamic slippage effect. The seepage characteristics and dynamic slippage effects of coal were further analyzed under different effective stresses and water contents. The research results show that，when the water content is a constant，the coal permeability decreases exponentially with increasing the effective stress，and that，when the effective stress is a constant，the greater the water content，the lower the coal permeability. A dynamic slippage factor model considering the changes of the effective stress and the water content is established. Under the conditions of various water contents，the coal fissure channels are gradually closed with increasing the effective stress and, at the same time，the slippage factor shows an increasing trend. In addition，under the same effective stress，the slippage factor increases with the water content，specifically，a slow increase while the water content less than 1.80% and then a sharp rise. A permeability model of water-bearing coal was constructed and its reliability was verified. The contribution of the slippage effect to the permeability was further quantified. A permeability model of coal considering the difference of fracture shapes in actual reservoirs was proposed. The permeability characteristics of coal under dry conditions were studied. The permeability of coal with circular fractures is the smallest，followed by square fractures and equilateral triangle fractures. The research on the migration law of coalbed methane in reservoir under the comprehensive action of multiple factors is helpful for improving the recovery of coalbed methane.

In order to study the distributions of shear stress and axial force along the length direction of soil nailing  of slopes in cold regions considering frost heaving effect，in this paper，the movement law of the freezing front is discussed based on the heat transfer theory and the differential equation of solid-liquid two-phase coexistence，and the calculation formula of free frost heaving deformation of a slope in cold regions is further derived according to the formula of frost heaving rate. On this basis，regarding the supporting effect of soil nailing on slopes as shear distributed force along the length direction of soil nailing and considering the stiffness difference between the frozen layer and the unfrozen soil layer of a slope，the displacement analytical solution of any point on the interface of nail and soil interaction is derived by combining the stiffness layer method with Mindlin solution after coordinate transformation. Finally，Based on the displacement compatibility condition of soil and nailing interaction，the Riemann integral equation of the shear distribution force along the length direction of soil nail is established. The axial force distribution of soil nailing is obtained by using the compound trapezoidal integral formula of closed Newton-Cotes method and MATLAB software programming，and verified by comparing the numerical solutions and the measured values. In addition，the influence of the frost heaving rate and the initial water content on the shear stress and axial force distributions along the length direction of soil nailing is analyzed. The results show that the distribution of the axial force of soil nailing obtained by the developed coupling calculation method is basically consistent with the numerical simulation results and the measured values，indicating that the coupling calculation method is reasonable and feasible. It is also revealed that the distributions of the shear stress and the axial force along the length direction of soil nail conform to the neutral point theory，the axial force curve presents a parabola shape with small ends and large middle，and the maximum axial force appears at the position where the shear stress is zero. The influence of the frost heaving rate，the initial water content and the nailing length on the shear stress and the axial force along the length direction of soil nailing can not be ignored. The research results can provide a useful scientific reference for the design of soil nailing support structure of slopes in cold region under frost heaving condition.

Comparative model tests on the bearing capacity and the multi-interface performance of jet grouting soil-cement-pile strengthened piles(JPP) with four different combinations(upper，lower，segment-Ι and segment-II) under compressive and uplift loads were carried out based on large-scale pile foundation load test equipment system. Model piles were buried by sand pour method. Model test results show that：(1) The bearing capacity of JPP piles is affected greatly by combination forms. Particularly，the segment-II combination can achieve the maximum bearing capacity in compressive load test while the lower combination can achieve the maximum value in uplift load test，indicating that JPPs should be segmented and the soil-cement segment should be placed in the lower of JPP piles in the engineering design. (2) The uplift bearing capacity is about 10%–15% of the compressive bearing capacity，and the average side resistance under uplifting load is approximately 13%–20% that under compressive load. (3) The side resistance of JPPs under both compressive and uplift loads increases with increasing the relative displacement between pile and soil in a hyperbolic form. The relative displacements necessary for the side resistance of JPPs reaching the limit value are around 2 and 7 mm under compressive and uplift loads，respectively. (4) At the initial stage of loading，the interface friction increases rapidly with a small relative displacement between core pile and soil-cement，and the interface shear stiffness tends to infinity. With increasing the load，the interface shear stiffness decreases while the relative displacement increases，showing a flexible work stage. As the load increases further，the interface friction increases faster and soon reaches the shear failure. (5) The interface shear stiffness between core pile and soil-cement under compressive and uplift loads is about 400 and 200 times that between cement-soil and soil around JPP，respectively，which ensures that core pile and cement-soil can work together to enlarge the diameter and to increase the bearing capacity.

Relying on the construction project of a test bridge pile adjacent to a subway tunnel in Hangzhou，a simplified mechanical model of the steel casing construction of bridge piles is established，and a revised calculation formula for the additional force resulted from the construction of the full-pipe cast-in-place piles considering the construction characteristics of casing sections and the effect of soil squeezing is proposed. At the same time，based on the Mindlin stress solution and two-stage analysis method，the additional stress and longitudinal vertical deformation of the existing tunnel caused by the construction of the bridge piles are calculated，and the dynamic influence law of the whole process of construction of the bridge piles is further analyzed. The following conclusions are drawn：(1) The application of the reduction factor of the soil plug height and the section correction to respectively calculate the pile tip pressure，the pile side radial pressure and the pile side vertical friction is more in line with the distribution law of the additional force due to bridge pile steel casing construction. (2) The theoretical calculation results of the longitudinal deformation of the subway tunnel caused by the construction of the bridge pile steel casing are more consistent with the actual measurement data. (3) With continuously increasing the construction depth of the bridge pile steel casing，the existing tunnels first uplift slightly，then subside and finally tend to be stable，accompanied by the longitudinal settlement area further expanding. When the construction reaches near the buried depth of the tunnel，the tunnel reaches the maximum uplift，and the junction of uplift and settlement is located at the depth of 1.5D at the bottom of the tunnel. (4) The pile side vertical friction is a key factor that causes the deformation of the existing tunnel，and the influence will expand with the construction depth. The influence of the pile tip pressure will weaken after the construction is far away from the tunnel buried depth for a certain range, and the pile side radial pressure has little effect on the vertical deformation of the tunnel. (5) During the whole process of construction of bridge piles，attention should be paid not only to the development of the maximum vertical deformation of the tunnel，but also to the longitudinal heave change of the tunnel and the longitudinal dislocated deformation of the segments due to changes in the construction depth.

After unloading，the K0 overconsolidated clay has both initial anisotropy and overconsolidation characteristics. Specifically，the characteristic of the K0 overconsolidated clay has the following three aspects：(1) When the major principal stress is loaded along the direction normal to the K0 consolidation deposition surface，the shear modulus is higher than that of the isotropic consolidation. (2) Due to the initial deviatoric consolidation，the critical state stress ratio of the K0 consolidated clay under triaxial compression is larger than that of the isotropic consolidation. (3) Cyclic loading leads to more significant overconsolidation characteristics and stress-induced anisotropy. Based on the UH model of the overconsolidated clay，a rotational axis parameter ζ，reflecting the initial anisotropy of the boundary surface，is introduced to increase the plastic modulus of the overconsolidated clay by inclining the boundary surface. By analyzing the dilatancy characteristics of the stress ratio，the state stress ratio is proposed to replace the normal stress ratio in the unified hardening parameter for reflecting the phenomenon of strain hardening and softening. The introduction of the rotational hardening rule is used to reflect the stress-induced anisotropy under complex loading paths. The unified hardening parameter is modified to reflect the plastic volume strain accumulation characteristics under cyclic loading，hysteresis and ratchet characteristics of plastic deviatoric strain and plastic deformation characteristics of unloading path. Based on the stress transformation method of t criterion，the new model is converted into a three dimensional constitutive model. By comparing the test and prediction results for a series of K0 overconsolidated clays in the undrained loading and cyclic loading paths，it is revealed that the new model can be conveniently applied to model the stress-strain relationship for K0 overconsolidated clay under complex loading paths.