Evaluation of the impacts of mining overburden bed separation grouting on the groundwater environment: a case study from Northern China

Mining overburden bed separation grouting is an effective method for controlling coal mining subsidence. However, the slurry that is injected into the overburden bed separation space may impact the groundwater environment during the precipitation and consolidation process. To evaluate the impact of overburden bed separation grouting on the groundwater environment, coupled numerical simulations of groundwater flow and solute transport were carried out with the background of a grouting project in Northern China. In addition, the shallow groundwater quality at the site is monitored and evaluated. The results show that the groundwater level rises as a result of grouting and that the direction of groundwater flow changes in the vicinity of the grouting boreholes. After the end of the grouting project, the groundwater flow field gradually returned to its natural state. The characteristic solute aluminium in the slurry precipitation water slightly contaminates the aquifer above the grouted bed separation space, but the contamination remains within the working face. The contamination gradually disappears after the end of the grouting project. The evaluation results of the shallow groundwater samples collected before and after grouting showed little difference, suggesting that grouting did not significantly affect the quality of the shallow groundwater. The research results provide theoretical support for the protection of groundwater in mining overburden bed separation grouting areas.