Application of modified solidified soil in in-situ backfilling of coal gangue: evaluation of arsenic stabilization effect and mechanism study.

As a typical ecologically fragile area, the Wudong Coal Mine region in Xinjiang generates large accumulations of coal gangue each year, which, in the alkaline soil environment, can easily lead to significant leaching and accumulation of As. This study developed a stabilizer (CFD) using cement, fly ash, and desulfurized gypsum to modify in-situ soil in the Xinjiang mining area, resulting in a modified solidified soil with excellent geotechnical performance and As stabilization capability. The study results showed that when CFD content exceeded 14.5% (H8), the unconfined compressive strength was above 350 kPa. The adsorption capacity of the solidified soil for As could exceed 90%. Leaching experiments revealed that the As leaching amount from solidified soil-coal gangue was below 0.01 mg/L, meeting China's Class III groundwater standard, thereby effectively reducing ecological and environmental risks. The modified solidified soil prepared in this study expanded the application scenarios for cement, providing a technical basis for the large-scale in-situ disposal of coal gangue in Xinjiang mining areas. It reduced the disposal costs of coal gangue and offered insights into its resource utilization and harmless use.