Design and Characterization of Solidified-Soil–Coal-Gangue Composites: Pore Structure Control and Enhanced Thermal Stability for Reclamation Applications

Abstract

To address the high spontaneous combustion risk associated with the direct backfilling of coal gangue in mine reclamation, this study investigated the thermal stabilization effects of varying dosages of a solidified-soil (SS) material on coal gangue with different particle-size distributions. The thermal control behavior of SS in coal gangue reclamation was investigated using X-ray CT, thermogravimetry–differential scanning calorimetry, and in-situ Fourier-transform infrared spectroscopy, and a large-scale ecological backfilling method for coal gangue disposal has been proposed. At a gangue-to-SS mass ratio of 7:3, the composite exhibited a favorable balance between thermal stabilization performance and engineering cost. The SS effectively fills and seals the interstitial voids within the stacked gangue, modifying the apparent activation-energy profile during the endothermic heating stage, leading to reduced low-temperature mass-loss and thermal response intensity in the SS–gangue samples, thereby reducing the self-heating tendency of the coal gangue. One year after reclamation, the average temperature of the reconstructed SS–gangue layer at depths below 10 m was 10℃ lower than that of the directly backfilled gangue layer. These results provide a materials-based foundation for the application of SS–gangue composites in coal gangue reclamation. By regulating the pore structure and potentially limiting oxygen accessibility, these composites may help to mitigate self-heating risks.