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In Fucun Coal Mine, the average spacing between the 3upper coal seam (UCS) and 3lower coal seam (LCS) is only 6 m. In the process of mining upper coal, the lower roadway (LR), which is 60 m away from upper pillar, becomes unstable. In order to control the surrounding rock of lower roadway, a physical model experiment and a 3D numerical calculation were performed in this study. The results of physical similarity simulation experiment show that mining of longwall face in UCS will lead to fracturing of key layers at a high elevation (KLHE) far away from the coal seam. The expanded goaf area caused large‐scale fracturing and rotation of the KLHE, which resulted in significant strata pressure behavior in LR. The numerical calculation results show that the LR should be within 19 m of the coal pillar. Finally, a plan which includes a proper location and a supporting system was proposed. The feasibility of the proposed plan is verified by an industrial application.

Coal mine goafs can be used to store and purify mine water; therefore, they are important for mitigating the environmental impact of mining on ecologically fragile areas in Western China. Coal gangue in goafs can reduce turbidity, suspended matter, total hardness, and chemical oxygen demand (COD) in mine wastewater. Because gangue in goaf areas is rich in clay minerals, they serve as ion exchange sites. We investigated the adsorption of heavy metal ions by silty mudstones in the Ulan Mulun mine. The adsorption kinetics and isothermal adsorption characteristics of four heavy metal ions, i.e., Pb(II), Cd(II), Cr(III), and Mn(II), were investigated using batch experiments. Under a pH of 6.75 and temperature of 20°C, the adsorption capacity of silty mudstone particles (<74 μm) was 6.3012 g, 1.5701, 1.2571, and 1.3729 mg/g for Pb(II), Cd(II), Cr(III), and Mn(II), respectively. Based on the experimental results, quantitative relationships between the adsorption quantity per unit of rock surface and the equilibrium concentration of heavy metals in solution were developed using Langmuir, Freundlich, and D–R equations. The relationships were used to obtain the equilibrium concentration of the solution. Finally, the ratio of the f value of the water-rock contact area in the goaf to the water volume was calculated and analyzed. The f value was inversely proportional to the average vertical opening of gaps between gangues in the goaf. The adsorption rate functions for Pb(II), Cd(II), Cr(III), and Mn(II) in the goaf were obtained, and the corresponding adsorption capacities were calculated. The adsorption capacities were controlled by the f value and adsorption properties of the gangue. These results can be used in future studies on mine wastewater treatment.