The coal seams in the Zhaogu mining area are characterized by great burial depth, hard coal quality, and difficulty in fracturing the top coal. To address the challenges of top-coal drawing in the working face, this study focuses on the external coal pillar working face in the Second Panel. Through laboratory experiments, field tests, and PFC numerical simulations, the coal drawing parameters and top-coal caving techniques were systematically investigated to provide technical support for on-site production. Key findings include: (1) Borehole observations revealed that adjacent goaf mining activities induced stress redistribution toward deeper zones, promoting full fragmentation of top coal. (2) Numerical simulations demonstrated the significant influence of mining-to-drawing ratio (MDR) on top-coal failure characteristics, with optimal recovery rate (TCRR) achieved at 1:1 MDR. (3) Parameter analysis showed the lowest gangue content occurred at 0.8 m drawing step distance, while single-round multi-opening interval drawing strategy delivered superior economic benefits and higher recovery compared to traditional multi-round approaches. (4) Similarity simulation tests uncovered funnel interaction patterns between adjacent drawing openings, with peak efficiency during initial drawing phases and an overall simulated recovery rate of 86.23%. Field applications confirmed the method’s effectiveness, showing no significant fluctuations in support pressure during operation. The research results provide critical parameter optimization schemes and technical implementation pathways for efficient extraction of deep-buried hard coal seams under complex geological conditions.

The geomechanical and seepage evolution characteristics of coal masses during mining are the key factors that affect the drainage of coalbed methane and the safety of coal mining. Nevertheless, the influence of mining paths on coal seam permeability is rarely investigated given the complexity of mining-induced stress experiments. To study the effect of mining-induced stress on coal mining, the mechanical properties, acoustic emission characteristics and energy evolution of coal masses were experimentally evaluated through mining-induced stress experiments. Experimental results indicated that at peak intensity, the deviatoric stress and axial strain of coal samples under the stress path of protective coal-seam mining are lower than those of coal samples under the non-pillar stress path. The unloading ratio of confining pressure is large under a stress path of non-pillar mining, and the elastic energy, the absorbed energy, and the dissipated energy of coal mass are low during destruction. The effect of high confining pressure on AE events is pronounced under the non-pillar mining path. The overall b value under high confining pressure is smaller than that under low confining pressure, and AE events generally have high energy. The fracture structure of coal mass is complex, and the fractal size of coal is large under high unloading rates of confining pressure, which induce the increase of permeability after coal destruction.

To study the seepage law and sectional morphological characteristics in splitting sandstones of different grain sizes, three‐dimensional morphological scanning tests and seepage characteristics tests are conducted on the splitting rock samples of siltstone, fine‐, medium‐ and coarse‐grained sandstone, and the differences in morphological characteristics and seepage law in different grain size sandstones are compared and analyzed. The test results show that the sections of siltstone and fine‐grained sandstone have the overall morphological characteristics of “one high and one low” with large undulation, while the sections of medium‐ and coarse‐grained sandstone have a more uniform distribution and less undulation. In the relationship between pressure gradient and flow velocity, siltstone and fine‐grained sandstone are precisely characterized by the Forchheimer formula, and medium‐ and coarse‐grained sandstone are well characterized by the Izbash formula, and the fitting effect is good. The results of the study are of great reference significance for improving the cross‐sectional morphological characteristics and seepage law of the splitting rock samples.

With the deep extension of coal mining in China, fault water inrush has become one of the major disasters threatening the safety production of coal mine. Based on the control equations of steady state and non-Darcy seepage in fractured rock mass, the multi-parameter nonlinear dynamic seepage equations of fractured rock mass are established in this paper. Based on the nonlinear dynamics theory, the function of the state variable in the system is derived, and the influence of the gradual change of non-Darcy flow factors on the structural stability of seepage system is studied. The research achievements show that there are three branches in the equilibrium state of the seepage system. Specifically, the stability of the equilibrium state changes abruptly near the limit parameter. The seepage dynamic system of fractured rock mass has the delayed bifurcation, and the coal mine disaster such as fault water inrush occurs easily at the bifurcation point. The research results are of great significance to enrich the theory of fault water inrush in coal mine, and to reveal the disastrous mechanism of fault water inrush and guide its prevention and control technology in coal mine, which can provide the theoretical reference for predicting the water seepage stability in fractured rock mass.

In the mining process of the II1 coal seam at Zhaogu No. 2 coal mine, a method of stratified mining is employed, leaving relatively wide coal pillars in sections. To enhance the resource recovery rate, the mine carries out the cooperative mining of the sectional coal pillars and the lower layer coal seam. The 14,022 cooperative working face of fully-mechanized and fully-mechanized top-coal caving at Zhaogu No. 2 coal mine is taken as the research object. Through numerical simulation, theoretical calculations, and on-site industrial trials, a comprehensive analysis of the overburden structural characteristics and the support adaptability at the working face is conducted. It is clarified that a stress arch bearing structure can be formed above the sectional coal pillars during cooperative mining, and this structure is controlled by key strata. The formation of a stress arch bearing structure in the overburden above the sectional coal pillars provides protection for the underlying mining area. A formula for calculating the working resistance of hydraulic supports under the stress arch in sectional coal pillar is derived. Based on these results, the working resistance of hydraulic supports in the coal pillar area is calculated and selected. Field application shows that the working resistance of the support is 10,000 kN in the fully-mechanized top-coal caving working face, and is 9000 kN in fully-mechanized working face, meeting the support requirements and ensuring safe mining at the working face. This study provides a valuable engineering reference for achieving cooperative mining of abandoned sectional coal pillars and lower layer coal seam in stratified mining method.