The accumulation and release of deformation energy within the rock mass of a roadway are primary contributors to the occurrence of rock bursts. This study introduces a calculation model for the kinetic energy generated during roadway excavation, which is based on the fracture and energy states of the rock mass. The relationships among the mining depth, width of the plastic zone, rebound range of the roof and floor, stress concentration factor, and the induced kinetic energy are systematically explored. Furthermore, a rock burst risk evaluation method is proposed. The findings indicate that the energy evolution of the rock mass can be categorized into four stages: energy accumulation due to in-situ stress, energy accumulation resulting from coal compression, energy dissipation through coal plastic deformation, and energy consumption due to coal failure. The energy release from the rock mass is influenced by several factors, including mining depth, stress concentration factor, the width of the plastic zone, and the rebound range of the roof and floor. Within the plastic zone of coal, the energy released per unit volume of coal and the induced kinetic energy exhibit a nonlinear increase with mining depth and stress concentration factor, while they decrease linearly as the width of the plastic zone increases. Similarly, the driving energy per unit volume of the roof and floor shows a nonlinear increase with mining depth and stress concentration factor, a linear increase with the rebound range of the roof and floor, and a linear decrease with the width of the plastic zone. A rock burst risk evaluation method is developed based on the kinetic energy model. Field observations demonstrate that this method aligns with the drilling cuttings rock burst risk assessment method, thereby confirming its validity.

High-salinity wastewater treatment has always been a challenging issue. In this study, coal tar pitch was used as the carbon source and melamine as the nitrogen source to prepare coal tar pitch-based nanosheets (CPN-9) using a salt-template method. The desalination performance of CPN-9 was evaluated using flow-electrode capacitive deionization technology. The results showed that CPN-9 has a high specific surface area (466.34 m²/g), a rich pore structure (micro-/meso-pore volume was 0.28), excellent rheological properties, and hydrophilicity (contact angle of 20.44°), thereby accelerating ion transport. Electrochemical results indicated that CPN-9 exhibits a significant double-layer ion storage mechanism, with a specific capacitance of 176.66 F/g at a current density of 0.5 A/g. CPN-9 has a very low charge transfer resistance. The synergistic effect of aromatic carbon and nitrogen doping (the content of pyrrole and pyridine nitrogen was 36.40% and 35.83%, respectively) in coal tar pitch accelerates electron transfer in CPN-9. The good ion diffusion performance and low impedance of CPN-9 accelerate the ion exchange rate, resulting in outstanding desalination performance. At 1.2 V and 3% mass loading, with a CPN-9 to conductive carbon black ratio of 4:1, the average desalination rate, charge efficiency, and energy consumption reached 0.039 mg/(cm²·min), 48.47%, and 0.012 kWh/mol, respectively. In summary, this study optimized the structure of CPN-9 from the perspective of electronic and ionic transport, enhancing its desalination performance and providing theoretical support for the deionization of high-salinity wastewater.

Rockburst precursors are critical for disaster warning, yet the complexity of rockburst has hindered the identification of a unified precursor. Furthermore, the influence of loading rates (LRs) on acoustic emission (AE) precursors in different rock types remains poorly understood. This study investigates the AE characteristics and early warning times of rockburst in slate and mica-schist under four LRs (0.05, 0.15, 0.25, and 0.5 MPa/s) using true triaxial unloading tests. The micro-crack state of the samples was evaluated using entropy, while critical slowing down (CSD) theory was applied to interpret AE precursors. The results reveal that as the LR increases, the rockburst stress of both rocks initially rises and then declines, with mica-schist exhibiting more severe damage and a higher dominance of tensile cracks. Notably, identifying rockburst precursors in mica-schist proved more challenging compared to slate. Among the methods tested, AE amplitude variance outperformed entropy in precursor identification. Additionally, the rockburst early warning time was found to be negatively correlated with the LR, with mica-schist consistently showing shorter warning times than slate. The CSD-derived precursor, due to its enhanced sensitivity, is recommended for early warning systems. These findings provide new insights into the role of LRs in rockburst dynamics and offer practical guidance for improving precursor identification and disaster mitigation strategies.

Pressure- preserved coring technologies are critical for deep-earth resource exploration but are constrained by the inability to achieve multidirectional coring, restricting exploration range while escalating costs and environmental impacts. We developed a multidirectional pressure-preserved coring system based on magnetic control for deep-earth environments up to 5000 m. The system integrates a magnetically controlled method and key pressure-preserved components to ensure precise self-triggering and self-sealing. It is supported by geometric control equations for optimizing structural stability. Their structure was verified and optimized through theoretical and numerical calculations to meet design objectives. To clarify the self-triggering mechanism in complex environments, a dynamic interference model was established, verifying stability during multidirectional coring. The prototype was fabricated, and functional tests confirmed that it met its design objectives. In a 300-meter-deep test inclined well, 10 coring operations were completed with a 100% pressure-preserved success rate, confirming the accuracy of the dynamic interference model analysis. Field trials in a 1970-meter-deep inclined petroleum well, representative of complex environments, demonstrated an in-situ pressure preservation efficiency of 92.18% at 22 MPa. This system innovatively expands the application scope of pressure-preserved coring, providing technical support for efficient and sustainable deep resources exploration and mining.

The fatigue characteristics of rock materials significantly impact the economy and safety of underground structures during construction. Hence, it is essential to conduct further investigation into the progressive damage processes of rocks under cyclic loading conditions. This research utilised both laboratory experiments and discrete element simulations to investigate how confining pressure and fatigue upper limit stress influence the mechanical behaviour and crack development of marble under low-cycle fatigue conditions. By introducing synthetic displacement and reasonable assumptions, the classical damage evolution law was updated, resulting in a fatigue life prediction formula applicable to various rock materials and loading conditions. The results indicate that lower fatigue upper limit stress can delay the accumulation of damage and extend the fatigue life of the rock, but it results in more severe ultimate failure. The damage variable’s correlation with the relative number of loading cycles for different fatigue load upper limits under the same confining pressure can be approximated by the same functional relationship. The modified damage evolution model provides an effective characterisation of this trend. The proposed fatigue life prediction method comprehensively accounts for different rock materials, confining pressures, loading frequencies, and initial damage, showing a close match with actual results.

In the process of deep engineering excavation, the mechanical properties of rock are significantly influenced by the coupled effects of water and high stress, which greatly increase construction difficulty. To more accurately investigate the impact of water disturbance on the failure process of dry rock under high stress and the failure mechanisms of saturated rock in underwater environments, a water environment test chamber and a prefabricated borehole specimen through-water device were designed. A series of experiments were conducted, including uniaxial tests, water-disturbed granite cylinder tests, and through-water disturbance tests on prefabricated hole square specimens. The results showed that the acoustic emission (AE) hits and accumulated energy after the through-water disturbance at the same time were 8.77 and 12.08 times higher than before the disturbance, respectively. And water disturbance increased the proportion of tensile failure and reduced the proportion of shear failure. A key observation was that AE events were mainly generated in the permeation areas near the borehole. The main reason was that under high stress, the weakening effect of water led to the failure of the local mineral structure of the rock, promoting crack extension and triggering overall instability. Notably, failure of the saturated specimens underwater was only observed when the applied load approached the saturation strength of the prefabricated hole square specimens. The study results provide an important theoretical basis for understanding the damage mechanism of water-disturbed rocks in deep engineering, and have significant implications for the design and construction of engineering.

The energy-focusing blast is an innovative and ingenious method to achieve directional fracturing. Understanding its energy regulation mechanism is critical to enhancing its practical effectiveness. This study investigates the energy regulation mechanism and explores the medium-filling effects within the energy-focusing blast by employing theoretical analysis, numerical simulations, and model tests. The findings by theoretical and numerical analysis first reveal that two stages of the fracturing and tensile stage govern the directionally crack propagation, in which the explosion energy in the non-energy-focusing direction is suppressed, compressing the borehole wall, while redirected energy produces tensile stress in the energy-focusing direction, driving the formation of directional cracks. The choice of filling medium significantly affects directional cracking due to its impact on energy distribution and regulation, and key properties such as wave impedance and compressibility of the filling medium are critical. Experimental comparisons using air, sand, and water as filling media further disclose the distinct effects of the medium on energy regulation and directional crack growth of the energy-focusing blast. The maximum shaped-energy coefficients for air, sand, and water are 1.30, 4.41, and 6.12 in the energy-focusing direction, respectively. Meanwhile, the stress attenuation rate of air, sand, and water increases in that order. The higher wave impedance and lower compressibility of water support efficient and uniform energy propagation, which subtly enhances the tensile actions in the focusing direction and intensifies the overall stress impact of the energy-focusing blast. In addition, the stresses in the non-energy-focusing directions decrease as the angle from the energy-focusing direction increases, while the stresses are relatively uniform for both air and water but noticeably uneven for sand; meanwhile, the fractal dimensions of blasting cracks in the case of air, water, and sand are 1.076, 1.068, and 1.112, respectively. Sand as a filling medium leads to increased crack irregularities due to its granularity and heterogeneity. The water medium strikes an optimal balance by promoting the blasting energy transition and optimizing the energy distribution, maintaining the least flatness of the directional crack during energy-focusing blasts.

In cold regions, slope rocks are inevitably impacted by freeze-thaw, dry-wet cycles and their alternating actions, leading to strength weakening and pore degradation. In this study, the mechanical and microstructural properties of schist subjected to four conditions were investigated: freeze-thaw cycles in air (FTA), freeze-thaw cycles in water (FTW), dry-wet cycles (DW), and dry-wet-freeze-thaw cycles (DWFT). Uniaxial compressive strength (UCS), water absorption, ultrasonication, low-field nuclear magnetic resonance, and scanning electron microscopy analyses were conducted. The integrity attenuation characteristics of the longitudinal wave velocity, UCS, and elastic modulus were analyzed. The results showed that liquid water emerged as a critical factor in reducing the brittleness of schist. The attenuation function model accurately described the peak stress and static elastic modulus of schist in various media (R²>0.97). Different media affected the schist deterioration and half-life, with the FTW-immersed samples having a half-life of 28 cycles. Furthermore, the longitudinal wave velocity decreased as the number of cycles increased, with the FTW showing the most significant reduction and having the shortest half-life of 208 cycles. Moreover, the damage variables of compressive strength and elastic modulus increased with the number of cycles. After 40 cycles, the schist exposed to FTW exhibited the highest damage variables and saturated water content.

Dynamic stress adjustment in deep-buried high geostress hard rock tunnels frequently triggers catastrophic failures such as rockbursts and collapses. While a comprehensive understanding of this process is critical for evaluating surrounding rock stability, its dynamic evolution are often overlooked in engineering practice. This study systematically summarizes a novel classification framework for stress adjustment types—stabilizing (two-zoned), shallow failure (three-zoned), and deep failure (four-zoned)—characterized by distinct stress adjustment stages. A dynamic interpretation technology system is developed based on microseismic monitoring, integrating key microseismic parameters (energy index EI, apparent stress σa, microseismic activity S), seismic source parameter space clustering, and microseismic paths. This approach enables precise identification of evolutionary stages, stress adjustment types, and failure precursors, thereby elucidating the intrinsic linkage between geomechanical processes (stress redistribution) and failure risks. The study establishes criteria and procedures for identifying stress adjustment types and their associated failure risks, which were successfully applied in the Grand Canyon Tunnel of the E-han Highway to detect 50 instances of disaster risks. The findings offer invaluable insights into understanding the evolution process of stress adjustment and pinpointing the disaster risks linked to hard rock in comparable high geostress tunnels.

This study systematically analyzes the influence of different combined joint dip angles on rock mass failure modes and damage mechanisms through uniaxial compression tests on granite specimens with prefabricated Y-shaped discontinuities, combined with digital speckle and acoustic emission (AE) monitoring. The results show that as the dip angle of the primary joint increases, the failure mode transitions from overall failure to wedge block ejection and shear failure. A failure mode identification model was established based on main crack dip angle thresholds (40°, 45°), uniaxial compressive strength thresholds (40, 90 MPa), and energy core zone proportion thresholds (20%, 10%), achieving an accuracy of 93.3%. In the overall failure and wedge block ejection modes, a sharp increase in shear crack ratio and a sudden drop in the acoustic emission b-value occur in the high-stress phase (>0.6σ_c), while in the shear failure mode, significant fluctuations are observed due to the shear-tension alternation, making it difficult to identify a single critical point. Additionally, joint slip in the overall failure and wedge block ejection modes primarily occurs during the failure instability phase (>0.8σ_c). These findings provide theoretical support for stability evaluation of complex fractured rock masses and practical guidance for engineering safety construction.