Addressing the technical challenges of severe deformation and maintenance difficulties in gob-side roadways with retained pillars under hard roof and thin coal seam conditions during mining-excavation interaction at Binhu Coal Mine, this study employs integrated theoretical analysis, numerical simulation, and field experiments to investigate the movement characteristics of the adjacent goaf-side overlying strata, the morphology of the caving structure, and the induced roadway instability mechanism. Key parameters for roof-cutting pressure relief and roadway protection were optimized and applied in engineering practice. The research indicates that two dominant key strata exist within the overburden of the No. 16 coal seam. Their structural characteristics and mechanical behavior govern the movement patterns and caving structure morphology of the adjacent strata. The dynamic evolution (formation, movement, and caving) of the lateral suspended roof in this zone subjects the roadway surrounding rock to significant multiple dynamic load impacts and high static stress, substantially increasing the risk of roadway instability and failure. Using the maximum principal stress deviatoric as the evaluation indicator, the optimal roof-cutting height and angle were theoretically determined as 16 m and 10°, respectively. Field tests further optimized the blasting parameters, establishing a spacing of 2 m for deep boreholes and 1 m for shallow boreholes. Additionally, a comprehensive support system comprising a primary "bolt-mesh-cable-belt" support combined with temporary reinforcement using "unit hydraulic props" was proposed to enhance the load-bearing capacity of the surrounding rock. Ground pressure monitoring confirmed that roadway deformation was effectively controlled, achieving a self-stabilized state approximately 140 m behind the working face. This validates the effectiveness of the roof-cutting pressure relief technology in resolving the maintenance challenges of gob-side roadways under thin coal seam and hard roof conditions.

Large-scale development of surface fractures exacerbates ecosystem degradation, damages engineering infrastructure, and poses constraints on regional ecological security and socio-economic development. To characterize the scale characteristics of fractures under high-intensity mining and establish an effective prevention and control system, this study took the 615 working face of Guanbanwusu Coal Mine as the research background. The overlying strata structure was divided under the guidance of the combined rock strata theory, and a fracture-rate-based quantitative characterization method was proposed for the fracture development process. Furthermore, quantitative relationships between the depth-thickness ratio and surface fracture scale parameters (maximum width, average penetration, and average advance distance) were revealed, and the corresponding collaborative control technology was proposed. The following beneficial findings were yielded. The overlying strata damage is divided vertically into four zones (according to the distribution of thick-hard strata and collapsed blocks) and horizontally into five zones (according to the extent of mining influence). Four combined rock strata structures of the overlying strata are determined, and stepwise breakage in overlying strata ultimately drives fractures to the surface. The intensified dilatancy of rock blocks near the goaf enhances the skewness and irregularity of the subsidence curve. The depth-thickness ratio shows a negative linear correlation with the maximum fracture width, and a negative exponential correlation with both the average penetration and advance distance. A decreasing depth-thickness ratio induces a transition in fracture type, from tensile and step-type dominance to collapse and step-type dominance. Based on these findings, the collaborative control technology of surface fractures was proposed. Key measures include optimization of mining sequences to mitigate surface subsidence, geophysical positioning combined with targeted remediation to enhance the stability of the overlying strata structural arch, and zone-specific treatment based on fracture classification and zoning. These measures conduce to facilitating the restoration of the regional ecological environment. This research provides significant insights for safeguarding regional ecological security and human settlements.

The complex environment of mining working faces—including dust, high humidity, and smoke—causes severe feature degradation in monitoring images under varying fog concentrations. Moreover, existing dehazing models trained mainly on synthetic data exhibit domain gaps with real mining fog, limiting intelligent monitoring effectiveness and posing safety risks. This study proposes a dehazing method for working face images based on fog grading and domain differences. First, fog evaluation metrics guide image grading, enabling adaptive network selection for light and dense fog scenarios. Second, a contrastive learning strategy refines negative samples based on fog concentration, improving feature discrimination and cross-domain generalization. Finally, an unsupervised fine-tuning strategy with cyclic consistency mitigates domain bias between synthetic and real fog images without requiring annotations. Experiments show that the proposed method outperforms existing approaches on both synthetic and real datasets, supporting safe and intelligent monitoring in coal mines.

Deep mining of coal resources is commonly accompanied by high in-situ stress and progressive energy accumulation, which can readily trigger dynamic disasters such as rock bursts. From the perspective of material toughening, elucidating the impact-mitigation mechanisms of coal-based cemented fill materials and establishing an quantitative characterization and evaluation index system for toughening based on the energy dissipation theory are emerging as promising approaches for achieving impact-mitigation control and optimizing material-oriented design. To clarify the impact-mitigation mechanisms, this study employed coal-based solid wastes as the primary constituents and systematically investigated the coupled effects of aggregate gradation, binder-to-aggregate ratio, curing age, and fiber toughening through uniaxial compression tests, energy evolution analysis, rock burst propensity assessment, and scanning electron microscopy (SEM). The results indicate that aggregate gradation, binder-to-aggregate ratio, and curing age exert significant influences on the mechanical performance of the cemented fill. The uniaxial compressive strength grows with the increase in curing age, and rises first and falls subsequently with the increases in Talbot index n and binder-to-aggregate ratio, reaching an optimum at a curing age of 28 d with n=0.6 and a binder-to-aggregate ratio of 2.5∶1. The incorporation of polypropylene fibers markedly enhances the compressive strength and improves post-peak ductility, broadens the energy-dissipation pathways, and enables sustained absorption and dissipation of externally imposed impact energy during the post-peak failure stage. Based on the energy dissipation theory, a FIMI-Lite impact-mitigation evaluation framework comprising five indices (energy dissipation ratio, dynamic toughness index, residual load-bearing ratio, brittleness index, and equivalent vibration isolation coefficient) was proposed to quantitatively characterize the impact-mitigation performance of cemented fill materials. Comparative analyses show that fiber-toughened fills outperform the conventional counterparts across all indices, with the fiber-toughened fill at n=0.4 achieving the highest comprehensive FIMI-Lite score. SEM observations reveal that an appropriate gradation promotes the formation of a dense load-bearing skeleton, whereas the incorporation of fibers conduces to constructing a three-dimensional "particle-cementitious matrix-fiber" network. The synergy of these two factors refines the pore structure, retards crack propagation, and enables stepwise energy absorption and progressive release. The above microstructural findings establish a mechanistic linkage to the macroscopic impact-mitigation performance. The proposed approach provides a scientific basis for optimizing the design of coal-based cemented fill materials and for preventing and controlling coal burst hazards in deep coal mining.

As the mining of mineral resources extends to depths, the importance of cemented backfill in maintaining stope stability and achieving green mining has become increasingly prominent. The cemented backfill is a multi-phase heterogeneous material. After the filling slurry is filled into the stope, the mechanical properties of the cemented backfill are affected by the coupling of multiple factors such as material composition, maintenance conditions, external loads, and seepage fields. It shows significant spatiotemporal evolution and nonlinear characteristics. Solving the quality problems of the cemented backfill induced by seepage has far-reaching theoretical value and engineering practical significance for ensuring safe, efficient, and green mining of mines. In recent years, fruitful results have been achieved in the mechanical evolution characteristics, failure characteristics and fluid-solid coupling response of cemented backfill at macro-fine-micro scales. First, the influencing factors and evolution rules of the strength of the cemented backfill are summarized from the aspects of cementitious material type, proportioning parameters, maintenance conditions, etc., and the spatiotemporal evolution characteristics of the cemented backfill are clarified. Second, the failure mode and crack propagation behavior of the cemented backfill under static and dynamic loads are summarized, and a comparative analysis is conducted with the failure theory of rock-like materials. Furthermore, the application results of multi-scale observation methods based on SEM, XRD, CT scanning, acoustic emission and other methods in revealing the intrinsic relationship between the microstructure evolution and macroscopic mechanical behavior of the cemented backfill are summarized; the mechanical response and damage evolution mechanism of the cemented backfill under the action of seepage-stress coupling are focused on, and the characteristics, limitations of indoor tests and numerical simulation methods are reviewed. Finally, in view of the problems in current research such as insufficient universality of constitutive models, unclear multi-scale mechanisms, and disconnected field applications, future development directions such as constructing a time-varying damage-seepage coupling model, developing a multi-scale collaborative observation and simulation platform, and promoting a closed-loop research system of "indoor experiments-numerical simulation-field monitoring" are proposed, in order to provide theoretical support and technical reference for performance improvement, stability evaluation, and engineering applications of the cemented backfill in deep complex environments.

In deep coal mines, the prominent conflict between the high in-situ stress and the low strength of soft surrounding rock frequently induces large-scale deformation disasters that pose a severe threat to safe production. Borehole pressure relief technology, which improves the strength-to-stress ratio of surrounding rock through stress release and space compensation mechanisms, has achieved remarkable advancements in both theoretical development and engineering practice in recent years. This paper systematically reviewed the research dynamics of borehole pressure relief technology both domestically and internationally, focusing on four aspects, i.e., operational mechanisms, parameter design, model testing, and effect evaluation. The following key conclusions were drawn: ① Pressure relief boreholes facilitate the coordinated regulation of triaxial stresses and compensate for shear dilation by inducing fracture propagation, resulting in a stress distribution pattern characterized by “shallow-pressure relief and deep-bearing capacity” and forming a “pressure relief-support” synergic system when combined with high-strength support. ② Key parameters such as borehole diameter, spacing, and depth significantly influence the pressure relief effectiveness. Although multi-factor coupled design criteria have been preliminarily established, their applicability under complex geological conditions requires further validation. ③ Current technical bottlenecks include an incomplete quantitative evaluation framework for pressure relief effectiveness, unclear energy evolution mechanisms, and underdeveloped theories for dynamic pressure relief-support coupling. Looking forward, research should focus on constructing a “multi-field coupling and static/dynamic synergy” analytical framework and developing dynamic constitutive theories integrating thermal-hydraulic-mechanical-damage (THMD) effects. Innovations in precise pressure relief equipment enabled by while-drilling sensing and intelligent decision-making are also needed. Furthermore, optimizing differentiated support and grouting reinforcement and building an integrated “pressure relief-support-reinforcement” control system will drive borehole pressure relief technology toward intelligent, precise, and large-scale applications.

With the escalating global demand for carbon emission reduction, CO₂ sequestration and enhanced coal-bed methane (CO₂-ECBM) has attracted widespread international attention due to its distinctive advantages in promoting the synergistic development of energy development and carbon emission reduction. This paper systematically reviewed recent advances in CO₂-ECBM research across scientific, engineering, and policy-economic dimensions. Besides, it elucidated the sequestration mechanisms governed by a synergistic suite of processes, including adsorption trapping, capillary trapping, structural trapping, solubility trapping, and mineral trapping, and further evaluated the technological maturity and economic feasibility of the technology. The results demonstrate that CO₂-ECBM technology not only effectively promotes coalbed methane recovery but also offers substantial sequestration potential and favorable geological stability. Through a comparative analysis on typical demonstration projects conducted worldwide, it is pointed out that practical applications of this technology still face challenges such as poor injectability of coal seams, permeability decline induced by CO₂ injection, insufficient assessment of long-term sequestration safety, and economic feasibility hampered by technical costs and carbon price volatility. Drawing on bibliometric analysis and hotspot evolution mapping, this study outlines the current research landscape and development trajectory, highlighting critical future priorities such as geological suitability evaluation systems for sequestration sites, high-efficiency technologies for coal seam permeability enhancement, multi-field coupled multi-scale CO₂ migration mechanisms, and intelligent monitoring and early warning systems for sequestration stability. Concurrently, it is imperative to strengthen technology integration and policy support to accelerate the commercialization and scaling of CO₂-ECBM technology. These initiatives are critical for underpinning global efforts toward achieving carbon neutrality goals.

As the mining depth of steeply inclined and extremely thick coal seams continuously increases, the rock burst disasters associated with them are becoming increasingly severe. The rock burst-inducing factors exhibit diversity and keep evolving, which poses difficulties to precise prevention of rock bursts. To address these issues, this paper explored the evolutionary patterns of inducing factors in a typical steeply inclined and extremely thick coal seams mine in Xinjiang by means of case analysis, field monitoring, and theoretical analysis. By analyzing five typical rock burst events in the mine, the main inducing factors were found to be steeply inclined roofs, intermediate rock pillars, remaining coal pillars, mining depth, mining intensity, and horizontal tectonic stress. Moreover, an improved analytic hierarchy process incorporating triangular fuzzy numbers was proposed to quantitatively evaluate the weights of these inducing factors and characterize their evolutionary patterns. The results disclose that steeply inclined roofs and intermediate rock pillars possess the highest weights and constitute the most significant inducing factors, and their weights keep growing with the continuous mining of coal seams. The weights of mining depth and horizontal tectonic stress generally rise with the continuous mining of coal seams, which reflects their enhanced inducing effects. In contrast, the weight of remaining coal pillars generally shows a decreasing trend, suggesting their gradually diminishing influence within the gob on rock bursts. The weight of mining intensity also decreases overall. Fianlly, the evolutionary patterns of inducing factors in steeply inclined and extremely thick coal seams were well verified through mining data analysis, microseismic monitoring, ground stress testing, numerical simulation, and theoretical research. The research results can provide support for precise control of rock bursts in steeply inclined and extremely thick coal seams.

To address the inadequate understanding of the fracturing behavior of thick-hard strata and the collapse-movement mechanism of overlying strata in 10 m ultra-large mining height faces of extra-thick coal seams, this study took the 122104 working face of Caojiatan Coal Mine as the engineering background. A combined approach involving physical similarity simulation, image processing with statistical analysis, and field monitoring was adopted to investigate the dominant role of thick-hard strata breakage in the overburden collapse and movement process. The engineering applicability and consistency of the model results were verified with field measurements. (1) An automatic fracture extraction and multi-index quantification method based on multi-temporal overburden images was proposed, enabling efficient quantification of parameters such as fracture development height, coverage area, and total length. The results show that the fracture parameters exhibit a pronounced "step-like" jump evolution with face advance, where each abrupt change strictly corresponds to the breakage sequence of specific thick-hard strata (I, II, and III). This quantitatively reveals, from the perspective of fracture evolution, the controlling effect of thick-hard strata breakage on overburden movement. (2) The breakage mechanism of thick-hard strata is characterized as a "cantilever beam-coordinated collapse" process. Before breakage, thick-hard strata form a large-span cantilever beam structure that constrains overburden collapse; when the cantilever reaches its limit, sudden breakage occurs, triggering large-scale coordinated collapse of the overburden, demonstrating typical structural failure characteristics. (3) Field monitoring data, including layered subsidence, mine pressure, and microseismicity, provide effective mutual validation with the model experiments. The coordinated movement mode of strata revealed by the layered subsidence curves aligns well with the "step-like" propagation pattern of fractures observed in the model; mine pressure monitoring indicates that the breakage of thick-hard strata II and III directly induces intense periodic weighting; microseismic monitoring further confirms that the periodic breakage of thick-hard strata constitutes the main source of concentrated energy release in the overburden. These results jointly verify, in terms of spatial evolution and energy release, the field applicability of the mechanism by which thick-hard strata breakage dominates overburden movement. From the perspective of fracture evolution, this study systematically elucidates the mechanism of thick-hard strata breakage-dominated overburden collapse and movement under ultra-large mining height conditions, providing a quantitative theoretical basis for improving overburden movement theory and preventing roof disasters in 10 m ultra-large mining height faces.

The surrounding rock of roadways often contains complex joint fractures, holes of different sizes, and other internal structural characteristics, which seriously affect their stability. Indoor physical model tests are one of the main ways to study the stability of engineering rock masses. However, traditional methods struggle to produce physical models with exactly the same structures and properties, and the mechanical properties and internal structures of physical models differ considerably from those of in-situ rock masses, which greatly limits the scientific nature of physical model tests in reflecting the actual engineering roadway. In recent years, the rapid development of 3D printing technology has effectively made up for the shortcomings of traditional methods. At the level of material research and development, sand-powder 3D printing coal-rock-like materials with high similarity to natural coal-rock in mechanical behavior are successfully prepared by systematically regulating printing matrix, particle gradation, binder saturation, and glass fiber content. This progress lays a material foundation for the production of physical models. At the level of mechanism research, based on mechanical tests on anchorage bodies using such coal-rock materials, the anchorage mechanisms of supporting elements such as bolts have been systematically revealed. These tests verify the feasibility of using these materials to simulate the anchorage in natural rock masses and provide a theoretical basis for the design of supporting structure. Finally, at the level of physical model tests, researches have employed the sand-powder 3D printing technology with the layered printing process to construct physical models of anchored roadways under the conditions of both intact surrounding rock and fractured surrounding rock. The influence of cracks on the deformation and failure law of roadway is quantitatively analyzed with the aid of the biaxial loading system and the digital speckle technique (DIC). The failure modes revealed by the tests are highly consistent with the field observation results. Collectively, these studies confirm that the sand-powder 3D printing technology can achieve high-precision reconstruction with respect to material properties, internal structure, and mechanical response, effectively overcoming the shortcomings of traditional model tests and showing good application prospects and scientificity in physical simulation research of rock mass engineering.