Analysis and Practice of High-Temperature Control Schemes for Coal Mine Spoil Dumps

The coal gangue waste dumps formed by open-pit coal mining are prone to low-temperature oxidation and heat storage, creating deep hidden high-temperature abnormal areas, continuously releasing toxic gases, and causing complex disasters such as slope instability and water and soil pollution. At present, self-ignition prevention and control technology is only applicable to the shallow treatment of small and flat gangue mountains. For large, deep, high-temperature waste dumps with significant height differences, multiple steps, and large areas, there is a lack of an integrated, complete set of technologies. The multi-field coupling mechanism of grouting fire extinguishing lacks engineering verification, and there is no quantitative evaluation system combining long and short periods. This paper takes the deep spontaneous-combustion high-temperature area of the No. 5 spoil dump of Lutian Coal Mine of Wuhai Energy as the research object. With the core goals of precisely delineating the fire zone space, revealing the multi-field coupling fire extinguishing mechanism of grouting, and establishing a long-term quantitative evaluation system, this study proposes a multi-process joint governance technology, along with a standardized hole filling and zoned differentiated grouting parameter system. The research systematically demonstrated technical feasibility through on-site drilling, large-scale grouting construction, and full-process quality control and error analysis. The results show that the 50 m interval geothermal gradient boreholes can accurately identify high-temperature distributions in the deep part of the dump from 0 to 34 m. The maximum combustion depth of the fourth-level and fifth-level platforms is 34 m and 20 m, respectively. A total of 1578 grouting boreholes have been constructed, with a total grouting volume of 139,289.3 cubic meters. After the treatment, the concentrations of toxic gases were all below the detection limits of the equipment, and the single cooling range reached 43% to 87%. This research refined relevant theories on the spontaneous combustion control of large-scale multi-step waste dumps, established standardized engineering processes, and provided theoretical and engineering references for the prevention and control of spontaneous combustion of solid waste in similar mines. It holds significant value for the ecological safety of mines and regional pollution control.