Technical methods and practical investigation of gangue backfilling reclamation for construction land

Driven by China's vigorous promotion of the "Integrated Protection and Restoration Project of Mountains, Rivers, Forests, Farmlands, Lakes, Grasslands, and Deserts" (hereinafter referred to as the "Shan-Shui Initiative"), the systematic and ecological management of mining solid wastes has emerged as a crucial issue for achieving regional sustainable development. Gangue, as the primary solid waste generated during coal mining and washing and selection processes, not only occupies extensive land resources upon long-term accumulation but also poses risks of severe environmental pollution due to spontaneous combustion and leaching. Utilizing gangue for backfilling and reclaiming construction land in mining subsiding areas actively embodies the "shan-shui initiative" concept, driving the systematic ecological restoration practice of "mitigating hazards with waste and converting waste into resources." Drawing upon engineering case studies, this study comprehensively analyzes foundation stability and constructability in subsidence areas. It further evaluates the suitability of gangue-backfilled foundations and systematically investigates the technical key points and overall workflow of backfilling and reclaiming construction land with gangue. The results indicate that utilizing gangue as a foundation backfill material in stabilized subsidence areas, combined with layered vibration pressure, can effectively meet the construction requirements of low- to medium-rise buildings. During the preliminary design phase, the potential "water-soil-gas" environmental impacts of coal gangue must be thoroughly evaluated to prevent secondary pollution. Throughout the backfilling process, an appropriate ratio of "gangue-soil" mixture should be applied to ensure the bearing capacity and stability of foundation. Study emphasizes that testing the bearing capacity of the backfilled foundation is an indispensable step requiring prioritized attention. Furthermore, the impacts of gangue weathering, deliquescence, hydrolysis, and salt precipitation on the foundation must be accounted for to accomplish the dual objectives of ecological restoration and land utilization.