Toppling failure is a typical type of disaster associated with rock slopes. The deformation behaviors and mechanisms underlying the evolution of rock slope toppling are complex, influenced by adverse geological conditions and external loads. Investigating the deformation characteristics, failure modes, and disaster mechanisms of rock slope toppling, as well as proposing methods for stability evolution, are urgent issues in slope engineering. Approximately 220 cases of toppling slopes in China have been collected, and the regional distribution of these cases is presented. The relationships between toppling failure and several key factors, such as slope height, slope angle, terrain obliquity, and lithology, are thoroughly analyzed. Building on existing classification methods for rock slope toppling, a four-level classification method is proposed based on the tendency relationship between the dominant discontinuity and the slope, the dominant or subordinate status of toppling deformation, the deformation characteristics of the toppling body, and the combination of toppling strata. The deformation behaviors and failure mechanisms of typical toppling types, including block toppling, flexural toppling, and composite toppling, are revealed through a combination of physical model tests and numerical simulations. Systematic presentations of stability analysis approaches, including the G&B method, equivalent continuum method, Liu method, cantilever beam method, and composite analysis method, are provided, along with discussions on their limitations and evolving trends. This research is expected to serve as an important reference for theoretical studies and engineering practices related to rock slope toppling.

Seepage in fractured rock masses is widely encountered in many important engineering fields such as hydropower, civil and transportation infrastructure, energy and mining, and underground disposal repositories. It represents one of the key factors constraining the construction and long-term operation of such projects. As engineering projects advance towards environments characterized by high water heads, great depths, and strong disturbances, conventional models based on linear flow laws have become inadequate for accurately describing seepage behaviors. Nonlinear seepage effects have become increasingly prominent, manifesting as inertial non-Darcian flow at high Reynolds numbers, multiphase nonlinearity in the presence of multiple fluids, coupled nonlinearities arising from interactions among seepage, stress, and chemical processes, as well as boundary- induced nonlinearities under complex boundary conditions. Although significant progress has been made in experimental observation, mechanistic modeling, and numerical methods related to nonlinear seepage, several challenges remain. These include difficulties in conducting in-situ experiments under high-stress and high- pressure conditions, the complexity of quantifying the effects of coupled processes, the empirical nature of model parameter identification, and poor convergence in numerical simulations. Focusing on these theoretical and applied challenges of nonlinear seepage in fractured rock masses, this paper systematically reviews and elaborates on key issues such as the underlying mechanisms, theoretical models, and parameter identification related to non-Darcian flow regimes, multiphase flow effects, coupled processes, and boundary nonlinearities. Furthermore, simulation methods and control techniques for nonlinear seepage in fractured rock masses are introduced. This paper highlights the vital role of nonlinear seepage theory in improving prediction accuracy, enhancing the reliability of safety evaluations, and supporting proactive engineering control. This is demonstrated through engineering applications, including seepage control and assessment in high-pressure water conveyance tunnels, modeling and evaluation of three-dimensional drainage systems in hydropower projects, and long-term performance evolution analysis of seepage control systems. Future research should aim to establish unified theoretical models and highly robust numerical methods, integrate nonlinear seepage analysis throughout the entire engineering design process, and develop intelligent seepage control systems that integrate monitoring, identification, and regulation. By deeply integrating multidisciplinary knowledge with artificial intelligence technologies, a transition from state assessment to proactive control can be achieved.

As the foundation for regional landslide risk assessment, landslide susceptibility prediction (LSP) is a prominent and challenging topic in global landslide disaster prevention and control research. This paper systematically reviews critical issues in LSP, including model selection, identification and integration of conditioning factors, determination and classification of prediction units, methods for selecting non-landslide samples, optimization of the landslide-to-non-landslide sample ratio, assignment of label values to non-landslide samples, and evaluation methodologies for landslide susceptibility results. The literature review indicates that tree-based models, such as Decision Trees and Random Forests, demonstrate superior performance. The selection and integration of conditioning factors should adhere to principles of comprehensive typology and clear physical significance. Prediction units can be defined through multi-scale segmentation of slope units. Non-landslide samples should preferably be randomly selected from areas characterized by very low or low susceptibility. The optimal ratio of landslide to non-landslide samples can be established through experiments under various conditions. Specific small probability values should be assigned to non-landslide samples. Evaluation of LSP results necessitates a comprehensive consideration of multiple metrics, including ROC accuracy, prediction rate accuracy, and the mean and standard deviation of the susceptibility index. Furthermore, to enhance the accuracy of LSP and validate the cross-regional engineering applicability of the semi-supervised imbalanced theory, this study pioneers the application of the Random Forest model based on this theory in Anyuan-Xunwu County, Jiangxi Province. Experiments were conducted under various scenarios, involving different ratios of landslide to non-landslide samples (ranging from 1:1 to 1:260) and varying label assignments for non-landslide samples. Results indicate that as the ratio increases from 1:1 to 1:180, both ROC accuracy and prediction rate accuracy improve gradually from 0.905 and 0.898 to 0.957 and 0.937, respectively. However, no significant improvement is observed in either metric once the ratio exceeds 1:180. Consequently, the optimal ratio of landslide to non-landslide samples is established at 1:180. Additionally, this study collects data from six landslide events that occurred between 2022 and 2024 to validate the results obtained from the 1:180 ratio. The validation reveals that all six landslides are situated in areas of very high or high susceptibility. This not only confirms the effectiveness and engineering applicability of the semi-supervised imbalanced theory in the mountainous and hilly regions of southern Jiangxi but also provides new insights and technical support for the precise prevention and control of landslide risks.

The stability of the compressed air energy storage (CAES) cavern is influenced by ground stresses during the construction phase and by cyclic high internal pressure (≥10 MPa) during the operational phase, resulting in different mechanical responses of the surrounding rock during the unloading and loading phases. This study investigates the stress paths of the CAES cavern from the perspectives of stress evolution and damage modes throughout both construction and operational phases. The findings indicate that during the excavation phase, active support technology significantly reduces deformation by adjusting the principal stress field of the surrounding rock, particularly in low-strength rock formations. Additionally, the load transfer effect decreases the burden on initial supports, such as steel arches. In the operational phase, the high internal pressure causes the sequence of principal rock stresses to shift, with radial stress increasing to the maximum principal stress and circumferential stress transitioning to the minimum principal stress. When exposed to hydrostatic pressure, characterized by low local stress and high rock strength, the surrounding rock at the tunnel wall may experience tensile failure during the high-pressure gas storage stage; otherwise, shear failure will occur at the tunnel wall. When the lateral pressure coefficient ( ) is less than 1, shear failure occurs in the surrounding rock at the side walls. In cases where the lateral pressure coefficient is particularly low, tensile failure may still happen at the arch crown. Conversely, when exceeds 1, shear failure is observed in the surrounding rock at the arch. If the lateral pressure coefficient is notably high, tensile failure may still occur at the side walls. As pressure increases, the area of tensile fractures may subsequently undergo shear failure. Further analysis reveals that conventional grouting and radial bolt systems significantly enhance stability only during the excavation phase. During operation, radial bolts not only lose their reinforcing capabilities but also exacerbate stress concentration in the surrounding rock under compression. In contrast, enhanced circumferential restraint effectively improves the stress state of the surrounding rock. For surrounding rock of good quality and high strength, grouting has limited efficacy in filling fractures. Conversely, grouting measures have been shown to increase the shear strength of formations characterized by low strength. Based on these insights, this study proposes an innovative solution for the stability control of CAES caverns subjected to complex stress paths by forming an anchor network system using crossed diagonal anchors and optimizing the inclination angle of the anchors to achieve a full-cycle tensile state.

 In response to the engineering challenges posed by unclear disaster-causing mechanisms and inadequate control effectiveness for roadway surrounding rock in steeply dipping and extra-thick coal seams, this study focuses on the +400 mB3 roadway in Wudong Coal Mine. A comprehensive research methodology was employed, integrating on-site monitoring, theoretical analysis, numerical simulation, and industrial testing. The investigation examined the evolution and rotation characteristics of the principal stress path under excavation disturbance in steeply dipping and extra-thick coal seams. Additionally, the study elucidated the driving mechanisms behind mining-induced stress evolution, which leads to fracturing in the coal and rock mass, and revealed the mechanism of roadway surrounding rock disasters induced by the coupling effects of the stress field and fracture field. The results indicate that the surrounding rock in the lower section of the roadway is significantly influenced by mining activities, undergoing a stress evolution process characterized by ?1 loading followed byσ3 unloading. The principal stress axis exhibits spatially differential rotation, deviating from its initial orientation. Notably, the degree of stress rotation is most pronounced in the roadway roof, with rotation angles ranging from 16.7° to 20.8°. Due to the impact of mining activities, the stress level within the coal and rock mass reaches its strength threshold, leading to the formation of mining-induced fractures. The angle of stress rotation determines the predominant propagation direction of these fractures, while the presence of the mining-induced fracture field compromises the mechanical integrity and strength of the surrounding rock in the roadway. After the unloading associated with roadway excavation, mining-induced cracks continue to propagate, primarily characterized by Mode I tensile failure. As the inclination angle of these cracks increases, the anti-unloading failure resistance of the coal and rock mass gradually strengthens, resulting in a transition of the failure mode from crack-dominated to matrix material-dominated. The disaster-causing mechanism of the roadway surrounding rock can be summarized as follows: the orientation of stress rotation governs crack propagation, the formation of a crack network weakens the load-bearing structure, and strength degradation leads to large deformation. Under the coupled effects of the stress field and fracture field, the roadway experiences deformation and failure. To address these challenges, a surrounding rock stability control strategy combining “overall reinforcement with key point strengthening” has been developed for roadways in steeply inclined and extra-thick coal seams. Following the implementation of the reinforcement support, the stability of the roadway?s surrounding rock has been significantly enhanced. The findings of this research provide a solid scientific foundation for the control of surrounding rock in steeply inclined and extra-thick coal seams, as well as in similar roadways.

 Circulating hydraulic fracturing, a flexible transformation method for hot dry rock, is anticipated to reduce reservoir fracture pressure, enhance transformation volume, and ensure efficient and safe storage. This method holds significant promise for the economic and efficient development of hot dry rock geothermal resources. To investigate the evolution and fracture mechanisms affecting the tensile properties of reservoir rock due to cyclic hydraulic fracturing, we conducted cyclic loading-unloading Brazilian splitting tests on granite treated with high-temperature water cooling. Two test conditions were examined: varying heat treatment temperatures (200 ℃, 300 ℃, 400 ℃, 500 ℃ and 600 ℃) and different cyclic load upper limits (peak loads of 65%, 70%, 75%, and 80%). The fracture surfaces were analyzed using scanning electron microscopy. The results indicate that tensile strength initially increases and then decreases with rising heat treatment temperatures but continues to increase with higher load upper limits. The number of cycles leading to fatigue failure decreases as the load upper limit increases, displaying a trend of first decreasing and then increasing with higher heat treatment temperatures. The peak displacement experiences three stages: rapid growth, slow growth, and eventual failure as the number of cycles increases. Notably, when the temperature exceeds 300 ℃, deformation significantly increases, suggesting that granite transitions from brittleness to ductility. Overall, the fracture mode is characterized by failure along the diameter direction. Beyond 300 ℃, the crack mode shifts from a “straight line” tensile crack penetrating the center of the circle to a “curved line” mixed tensile-shear crack deviating from the center. This change is primarily attributed to the substantial softening of mineral crystals and the formation of microcracks due to high temperatures. Furthermore, microstructure analysis reveals that as heat treatment temperature and cycle number increase, the internal crack propagation mode of granite transitions from transgranular to intragranular. Concurrently, micro-damage accumulates, resulting in decreased fatigue strength and increased plastic deformation. Macroscopically, this manifests as a coupling effect of tensile strength attenuation and enhanced fracture ductility. The findings of this research provide theoretical support for the design and construction of cyclic hydraulic fracturing.

In low-temperature environments, the physical and mechanical properties of rocks, as well as their engineering behavior, differ significantly from those at ambient temperature, primarily due to water-ice phase transitions. These differences become more pronounced as the temperature decreases. Considering industry-specific low-temperature classification standards and the environmental conditions of geotechnical engineering, a refined low-temperature zoning framework tailored to geomechanics is proposed, defining the threshold for “deep low temperatures” and further subdividing it into “extreme low temperatures” and “ultra-low temperatures.” Based on findings from laboratory experiments, theoretical analyses, and numerical simulations, this study provides a systematic review of the physical and mechanical properties of rocks under deep low-temperature, with a particular focus on the temperature-dependent evolution of key parameters such as porosity, elastic wave velocity, thermal conductivity, elastic modulus, and mechanical strength. Furthermore, by employing the thermo-hydro-mechanical (THM) coupling models, the mechanisms by which frost heave effects, thermal stress distribution, and water migration contribute to rock damage are analyzed. Numerical simulations reveal the coupled evolution characteristics of the temperature, stress, and seepage fields, as well as their underlying roles in the accumulation and progression of rock damage. Additionally, key scientific and technological challenges associated with deep low-temperature rock mechanics are examined in the context of engineering applications, such as underground energy storage, liquid nitrogen-based waterless fracturing, polar infrastructure, and deep-space resource extraction. Finally, based on current theoretical advancements, technological developments, and engineering demands, several future research directions in rock mechanics under deep low-temperature conditions are proposed. These include investigations into the micro-scale phase transition dynamics and multi-scale damage mechanisms of rocks in deep low temperatures, the development of non-equilibrium multi-field coupling theoretical frameworks, and the spatiotemporal prediction of long-term rock performance under deep low-temperature conditions.

Rockburst is a dynamic disaster characterized by the sudden instability and violent fracturing of chambers under high-stress conditions, with the critical stress serving as the most pivotal indicator. In this study, the maximum load criterion and the maximum potential energy criterion for the occurrence of rockbursts in chambers were proposed, and the theoretical critical stress formulas for rockbursts in circular chambers under hydrostatic pressure were derived. The discrepancy in critical stress derived from the two discrimination criteria is less than 2%. This study indicated that the critical stress was mainly influenced by uniaxial compressive strength, rockburst energy index, internal friction angle, and support stress. The biaxial isobaric loading experiments were conducted on circular chamber specimens of granite gneiss and basalt with dimensions of 150 mm× 150 mm× 50 mm. The average error between the experimental and theoretical values of the critical stress was 2.53%. Comparative analysis with field cases revealed an average ratio of 0.55 between actual stress and critical stress, prompting subsequent refinement of the formula. The application of the critical stress formula was discussed from the aspects of hazard assessment, prevention design, and safety evaluation of chamber rockbursts.

As cold region engineering expands to higher altitudes and latitudes，the application of fractured rock masses(FRM) in cold region engineering has increased significantly. However，existing  theories in frozen soil mechanics are insufficient to address the engineering challenges in these areas. This study investigates the mechanisms of freeze heave(FH) in FRM under low temperatures and freeze-thaw cycles. Through theoretical analysis，laboratory and field experiments，and numerical simulations，the research explores the formation mechanism and failure patterns of FH pressure in FRM. The study finds that FRM exhibit various FH mechanisms，including volumetric expansion，segregated ice，and mixed FH. The semi-elliptical open fissure mixed FH model provides a better description of these mechanisms. FH in FRM is a complex coupling of thermo-hydro-mechanical processes that involve moisture migration，multiphase heat conduction，and crack propagation. Factors such as fissure structure，saturation，sealing properties，freeze mode，ice-rock interactions and phase transitions significantly influence FH pressure and damage. The primary mechanism of damage in FRM is driven by FH pressure promoting the crack propagation，which is significantly influenced by the characteristics of the fissure and rock mass. Moreover，laboratory and field tests show differences in FH behavior，especially concerning freeze-thaw cycles，crack initiation temperature，and water absorption conditions. Future research should focus on micro- and meso-mechanisms，supported by laboratory and field experiments，to investigate moisture migration and ice-rock interactions. The objective is to solve FH pressure，explore the evolution of fracture networks using numerical methods，and develop an adaptive monitoring and decision-support system for predicting FH failure，integrating artificial intelligence and big data.

Fault stick slip instability can easily induce fault slip rockburst. In order to further explore the stick-slip evolution characteristics of faults with different dip angles and AE and charge induction multi-source precursors，bidirectional friction tests were carried out on syenitegranite with faults with different prefabricated dip angles. The accumulated energy and spectral characteristics of acoustic emission and charge induction signals during fault stick-slip were analyzed，the AE sources were located，and the nonlinear characteristics of AE and charge induction time series were studied based on multifractal theory. Three quantitative indexes(maximum multi-fractal dimension Dqmax，spectral width Δα and multi-fractal parameter Δf(?)) with good correlation with stick slip instability were constructed，and the following conclusions were drawn：(1) With the increase of fault dip angle，the fault failure mode changes from sliding failure along the plane to sliding failure through the plane，which increases the intensity and energy of AE and charge induction signals. (2) The maximum multi-fractal dimension Dqmax and spectral width Δα of the AE and charge induction signals gradually increase with the increase of fault dip angle. The maximum multifractal dimension and spectral width of the AE and charge induction signals can reflect the difference of energy released when the fault stick slip instability or severely damaged. The multi-fractal parameters Δf(?) of AE and charge induction signals are all less than 0 when the fault is instability or severely damaged.，and the critical value of Δf(?) can be used as the prediction index of fault stick slip instability and severe failure. (3) Compared with the AE and charge induction signals generated by shear slip failure along the plane of 34°and 45°faults，the AE and charge induction signals generated by 56°faults through the plane slide failure has lower dominant frequencies. It can be considered that the dominant frequencies of the AE and charge induction signals are related to fracture scale.

The fractures make the thermal-hydro-mechanical(THM) characteristics of rock mass and soil mass obviously different，and the existing frozen soil theory is difficult to solve the freeze-thaw disaster problem of low temperature rock mass. The migration mechanism of fracture water，the heat transfer mechanism of fracture，the dynamic evolution of fracture characteristics and the multi-field coupling of thermal-hydro-mechanical in heterogeneous rock mass are the key to study the freeze-thaw disaster of low-temperature rock mass. In this paper，the research progress of low-temperature rock mass with phase change is analyzed from four aspects： water migration mechanism，heat and mass transport characteristics，physical and mechanical characteristics and THM coupling characteristics. The research results on low-temperature rock mass at home and abroad are abundant，but the heterogeneity caused by fractures and the special characteristics of the THM properties of fractures under the condition of phase change are not fully considered. The mechanism of hydrothermal migration in fracture of low-temperature rock mass has not been proved，and there is lack of large-scale test equipment for studying the THM characteristics of low-temperature fractured rock mass. Although the fracture propagation caused by frost heave has been studied，the dynamic fracture evolution equation considering the whole process of freeze-thaw and the freeze-thaw cycle has not been established. The freeze-thaw disaster of low-temperature rock mass involves hydrothermal migration at the micro-level，fracture evolution at the meso-level and deformation and failure at the macro-level. So far，no THM coupling model has been established which integrates the results of micro-meso- macro. In order to explore the THM characteristics of low-temperature rock mass，the ice-water phase should be taken as the breakthrough point，the discontinuous characteristics caused by fractures should be closely linked，large-scale laboratory equipment should be developed，the mechanism of hydrothermal migration in fractures should be verified，the fracture evolution equation should be derived，the THM coupling model should be constructed，and numerical simulation programs should be developed，to finally realize the simulation of freeze-thaw disasters in low-temperature rock mass.

Prestressed anchor rods exhibited effects on the mechanical properties of intact rock mass and fractured rock mass. Uniaxial compression tests of intact rock mass and direct shear tests of fractured rock mass were conducted under different pretension anchor rod support conditions. Additionally，the crack-changing characteristics inside the rock mass were revealed by acoustic emission. The results of uniaxial compression tests show that compared with unsupported rock mass，the changes in compressive strengths of intact rock mass exhibited unobvious under ultra-low and low pretension supporting conditions，while the compressive strengths were significantly improved by medium and high pretension supporting. The rock mass showed obvious single-inclined plane shear failure under no support and ultra-low to low pretension bolt support conditions. Specifically，as the pretension force of the anchor bolt increased，the failure mode of the anchor rock masses changed from shear failure to tension splitting failure. These failure characteristics aligned with the crack type characterized by the RA-AF value. The results of direct shear tests show that the pretension bolt could enhance the bearing performance of fractured rock mass. The shear strength of fractured rock mass increased with the increase in the pretension force of anchor bolts. The crack evolution mode of anchor fractured rock mass during shear loading was revealed through acoustic emission signal analysis. At the initial loading stage，the proportion of tensile cracks was close to that of shear cracks. As the progress of loading continued，the shear crack became dominant. This work could provide theoretical basis for studying the mechanism of active support and the design of anchor support.

The research on early warning of gradual-change landslides has made great progress，and early warning and prediction have been realized in many cases. But the early warning and prediction of sudden-onset landslides are still impotent. Focusing on the internal and external response relationship between the stress release from the rupture of the internal rock and soil body and the coordinated deformation of the rock body on the slope surface in the evolution of landslides，we study the characteristics of the dynamic change of the stress-sliding force-deformation in order to obtain the precursor information of sudden-onset landslide destabilization. In the process of landslide from static deformation to dynamic slip，the potential slip surface is initially deteriorated by local rupture，and then accelerated by the rate effect after the overall penetration. Thus a parameter deterioration model considering the local rupture and accelerated deterioration of the slip surface is constructed. Based on the vector sum method，the landslide resistance and decline force are calculated，and a time-dependent degradation mechanical model considering the deterioration of the mechanical parameters of the slip zone is established. The model is used to calculate the force and deformation characteristics of the whole process of landslide formation and evolution，revealing the stage characteristics of stress-slip force-deformation in the process of landslide formation. The results show that landslide stress，slip force and deformation indicators show obvious stage characteristics，which can be divided into initial，isokinetic，accelerated and near-slip stages. When the landslide enters the near-slip stage，the sudden drop in slip resistance and stress is earlier than the rapid increase in landslide deformation，which is helpful for early warning and prediction of sudden-onset landslides.

In order to study the dependence of the mechanical properties of fractured hard rocks，including their strength，deformability，failure mode，characteristic of energy dissipation and bursting liability，on fracture distribution and volumetric or areal damage variable，uniaxial compression tests were carried out on limestone specimens with a single fracture，three coplanar and non-coplanar fractures at different inclination angles. The results show that：(1) the elastic deformation is mainly affected by the volumetric damage variable，while the strength is mainly affected by the areal damage variable. For the specimens with a single fracture，the unified Young?s modulus and peak strength increase monotonically with the fracture inclination angle，and the relation between the unified Young?s modulus or peak strength and the component of Oda?s second-order volumetric damage tensor or areal damage vector along the loading direction，can be well fitted with an inverse proportional power function. For the specimens with three coplanar or non-coplanar fractures，both the curves of the unified Young?s modulus and peak strength with the fracture inclination angle are W and V shapes respectively，and prediction for their upper limit and average can be given by the above relations with the component of volumetric and areal damage tensors obtained from the specimens with a single fracture respectively. (2) In general，the fractured limestone specimen may undergone three damage evolution stages，i.e.，initiation and propagation of cracks，formation of macroscopic failure surface(zone) and residual deformation. There are three basic failure modes：split，stepped and blocky failure. (3) Some of the limestone specimens show certain degree ductile characteristics due to the existence of the fractures，namely，their stress-strain curves change from single peak to multi-peaks. For the specimens with single peak stress-strain curve(type I)，the elastic energy accumulated before the peak stress is rapidly transformed into dissipated energy. For the specimens with multi-peaks stress-strain curves(type II and III，multi-peaks during softening and hardening stages，respectively)，the elastic energy accumulated before each peak stress is released and transformed into dissipated energy step by step. Both the unified total strain energy and energy storage limit of the specimen may increase linearly with the unified peak strength，and therefore is inversely proportional to the component of the two damage tensors. and (4) Both the intact and fractured limestone specimens at failure appeared different degrees of bursting phenomena such as particle ejection and making sound. Compared with the elastic strain energy index and bursting energy index，the comprehensive index of elastic strain and bursting energy(the ratio of the elastic strain energy before the peak strength to the total strain energy)，can more reasonably represent the bursting liability of the fractured specimens with multi-peaks stress-strain curve，and coincide very well with the degrees of bursting intensity observed in the test.

Compressed air energy storage(CAES) is a kind of large-scale energy storage technology that is expected to be commercialized. As an underground gas storage engineering structure，the newly-excavated hard rock cavern has attracted much attentions due to its wide adaptability and practicability. Compared with traditional underground engineering，underground rock caverns for compressed air storage face many new challenges due to the periodic high internal pressure and temperature during the course of operation. Recently，great advances about the construction and operation of compressed air energy storage in hard rock caverns have been made by researchers around the world. It is thus imperative to systematically review the progress in this direction，which can help engineers to better understand the development of such emerging energy storage technology in practice. Firstly，the basic principles and scientific problems of compressed air energy storage are described. Secondly，the research progress related to construction and operation is summarized，including airtight performance of sealing structure，thermal transition process of surrounding rock-lining-sealing layer-air during the process of inflation and deflation，uplift failure of the rock mass，and plug stability. Besides，several key scientific and technological issues which need to be further studied are discussed.

In order to explore the mechanical properties and energy evolution law of unloading coal under cyclic loading，the MTS816 rock mechanics test system was used to carry out triaxial cyclic loading tests with variable lower limit and constant lower limit of coal samples. The relationship between mechanical parameters of coal samples was analyzed by obtaining the whole process stress-strain curve，and the energy evolution law of coal samples during cycle loading process was studied based on the energy principle. The results show that：(1) Compared with the CG group，the peak stress increment extreme value of the coal samples under cyclic loading is 3.540 MPa，and the overall change is not large. The axial strain and lateral strain of the XH1 and XH2 groups are positively correlated and negatively correlated with the confining pressure，respectively. The volumetric strain of the XH1 group increases first and then stabilized and then increased，while that of the XH2 group increased first and then decreased and then increased. (2) The loading modulus of coal samples under cyclic loading is positively correlated with the number of cycles and negatively correlated with the stress level. Both the strain hardening modulus and the drop modulus are negatively correlated with the confining pressure. The high confining pressure condition weakens the ability to resist the inelastic model，and this weakening trend is independent of the stress path. The cyclic stress path has a significant effect on the deformation characteristics of coal samples. (3) The energy density of coal samples is higher under the action of constant lower limit path or high confining pressure. The dissipation energy density of coal samples in each cycle level is basically consistent with the input energy density，showing a trend of decreasing first and then stabilizing，and the elastic energy density is generally stable. (4) Under cyclic loading，the elastic energy density of coal samples accounts for more than 89.11% of the total input energy density，and the mean value of the two is linear. The total energy is mainly stored in the form of elastic energy，and this storage capacity is independent of confining pressure. The average value of dissipated energy density and elastic energy density changes in a power function type，and the energy competition ability of dissipated energy gradually increases with the increase of cyclic stress level.

In order to solve the control problem of dynamic impact phenomena in roadways with high stresses，and to clarify its occurrence law and the control mechanism of the surrounding rock，a physical simulation test system for dynamic impact phenomena in deep roadways of coal mines is developed. It includes balanced loading device，boundary energy storage device and multi-source monitoring platform，which can achieve high stress equilibrium loading of the model body and instantaneous compensation of boundary stress. Therefore，the stress environment before and after the occurrence of dynamic impact phenomena in deep roadways is effectively simulated by this system. On the basis，a series of physical simulation comparative tests on dynamic impact phenomena in deep roadways are carried out with a typical deep high stress mines as simulation object combined with the developed high-strength energy absorbing support material. It reproduces the entire occurring process of dynamic impact phenomena in models with different types of support parameters. The dynamic failure mode，stress-displacement evolution law of surrounding rock in different parts of the roadway are analyzed. Meanwhile，the interaction and impact response characteristics between different support materials and surrounding rock are clarified. The control advantages of energy absorption in the dynamic impact phenomenon of deep roadways by the new energy absorption support material are revealed. The average deformation of the surrounding rock decreases by 36.9% though the application of this support material as the dynamic impact phenomenon occurs. According to the test results，further research is conducted on the field application of energy absorption support，which effectively reduces the risk of dynamic impact phenomena in deep roadways and ensures the safety of surrounding rock throughout the roadway operation cycle.

Deep rock mass engineering is in high water pressure and high stress environment，its response characteristics are significantly influenced by the environmental conditions，which is an important basis for deep rock mass engineering blasting design and construction. In order to investigate the dynamic response characteristics of the rock under deep high water pressure environment，impact tests were carried out on red sandstone based on a self-developed high water pressure and high stress rock dynamic testing system，and 4 axial static stresses and 9 water pressure levels were set to simulate the occurrence environment of engineering rock mass. The effects of water pressure and axial static stress on the dynamic stress-strain curve and dynamic peak stress of rock were investigated by calculating dynamic stress and strain data of rock based on incident，reflected and transmitted waves. The pre-peak and post-peak energy conversion characteristics of stress-strain curves were considered comprehensively，and the water-inrush tendency index of rocks was defined by energy evolution parameters. The relationships between rock dynamic residual stress，residual strain，water inrush tendency index and wave impedance with water pressure were analyzed，the empirical models of dynamic peak stress strengthening coefficient，residual stress，residual strain，water inrush tendency index，wave impedance and water pressure，as well as dynamic peak stress and axial static stress were constructed. The influence mechanisms of high water pressure and high stress on the dynamic strength and deformation characteristics of rock were explored. The results show that the dynamic stress-strain curves of rock gradually change from type I to type II with the rise of water pressure. Under the same axial static stress，the dynamic peak stress strengthening coefficient，residual stress and wave impedance of the rock increase rapidly at first and then slowly with increasing water pressure，and the water inrush tendency index and residual strain decrease with the increase of water pressure. Under the same water pressure，the peak dynamic stress of the rock decreases as the axial static stress increases. High-pressure water has dual effects on rock dynamic strength，that is，the water wedge effect promotes crack propagation and reduces rock strength，while the Stefan effect and other viscous effects and external confining water hinder the destruction of pore structure and enhance the dynamic strength. The two effects play a game with each other and jointly affect the dynamic response characteristics of rock under deep high water pressure environment. The results of the study are favorable for blasting and excavation of engineering rock mass and stability analysis of surrounding rock under deep high water pressure environment.

In order to prevent premature breakage of anchor cables under shear loads in support engineering，a structure named Anchor Cable with C-shaped tube(ACC) was proposed，which combines a C-shaped steel tube with anchor cables. Shear strengthening mechanism of this structure has not yet been fully revealed. A nonlinear finite element refined model of the ACC was established using ABAQUS software. The actual model of the seven-strand structure was adopted for the anchor cable，and shear resistance mechanism of ACC was studied considering the contact，failure，and other interactions of each component. The results show that in the initial stage of shearing，ACC forms an “S” shape of bending and symmetrical plastic hinge under the action of shear force at the shear plane and symmetrically distributed bending moment. Afterwards，the deformation is mainly caused by extension of the plastic hinge away from the shear plane and the stretching of the middle part of the anchor cable. Finally，the failure reason of ACC is the tensile-shear composite failure of the anchor cable，which is mainly tensile fracture. With the increase of the shear load，the C-shaped tube gradually closes within the bending range of the anchor cable，and works together with the anchor cable to enhance the overall bending stiffness of the structure. The slit opening and overall torsion of both ends of C-shaped tube are coordinated with the closure deformation of its middle part. C-shaped tube can make the distribution of the contact pressure more uniform between the structure and the concrete blocks，improving stress conditions. Partial concrete located at the interface of blocks is in a triaxial compression state. With the increase of the shear load，the bearing area gradually expands inside the concrete blocks，and the progressive failure of concrete occurs synchronously with the expansion of plastic hinge of ACC.

With the continuous expansion of the scale of rock mass engineering and the increasing complexity of the occurrence environment，the phenomenon of rock joint shear slip causing rock bolt breakage is becoming more and more prominent. It is very important to recognize the shear characteristics and shear mechanism of bolted joints for the stability control design of rock mass engineering. In this paper，the effects of full anchor and end anchor modes on the macro and micro shear properties of rock joints and their mechanisms are systematically studied through shear tests and numerical simulation of anchored joints. The results show that the presence of anchoring agent can make the bolt play its“pin role”quickly in the full-anchor mode，while the bolt does not play its role until the shear displacement exceeds the gap between the borehole and the bolt in the end-anchor mode. Before the anchor rod fractures，the peak shear stress and breaking shear stress in the full-anchor mode are greater compared to the end-anchor mode. Under the same shear displacement，the number of cracks in the anchored joint is more in the full-anchor condition compared to the end-anchor condition. Under full anchoring method，the cracks are concentrated near the anchor rod，especially at the intersection of the anchor rod and the joint，while under end anchoring method，the cracks are distributed in the end bolted，the intersection of the anchor rod and the joint and the gasket. Under the same shear displacement condition，the shear stress of full-anchored bolt is much greater than that of end-anchored bolt，but its axial stress is mainly concentrated near the joint surface due to the restriction of anchoring agent. The axial stress of end-anchored bolt is fully mobilized and can effectively increase the normal stress of the joint after being transferred to the gasket. After the peak shear displacement，the deformation range of end-anchored bolt and full-anchored bolt increases continuously，but the deformation range of end-anchored bolt is significantly larger than that of full-anchored bolt.