Innovative groundwater disaster prevention and control systems for ultrawide working face mining in deeply buried confined aquifers

Abstract

Coal mining in confined aquifers is generally threatened by water inrush disasters originating from the floor. As mining depth increases, the complexity of hydrogeological conditions, coupled with limited exploration accuracy, and ineffective prevention measures pose significant challenges to accurately managing mine water disasters. Especially, ultrawide working face mining in confined aquifers, the prevention methods of floor water disaster have not been systematically studied. Based on the mining of the working face (width more than 400 m) above the Ordovician limestone confined aquifer, this paper carried out joint exploration of hydrogeological conditions, numerical simulation of ultrawide working face mining, evaluation of water inrush potential of mining floor and dynamic monitoring of water coupling in working face. The results show that the hydrogeological and structural geological conditions of the working face and its surroundings are accurately identified by the multi-method joint exploration. The stress evolution rule of ultrawide working face before and after roof cutting is revealed. The failure depth, maximum shear stress, maximum principal stress, vertical stress and pore water pressure of the floor after roof cutting are reduced by 28.6 %, 30.9 %, 12.1 %, 15.5 % and 14.3 %, and the stress concentration factor is also reduced by 19.5 %. The prediction model of mining floor failure depth and the evaluation model of floor water inrush potential are constructed, with the accuracy of 94.0 % and 88.2 %, respectively. This study put forward a water prevention scheme of pre-mining treatment and dynamic monitoring in mining, establishes a dynamic multilevel geological guarantee system for ultrawide working face mining in confined aquifers, integrating “joint exploration, precise prevention and control, and water resources.” Finally, the system was successfully applied to the 21,609 working face of Binhu Coal Mine, liberating 359,000 tons of coal resources. Compared to traditional method, the failure depth of mining floor is reduced by 44.3 %, significantly decreasing the possibility of floor water inrush. The research results provide a typical demonstration for the secure, efficient and environmentally friendly coal mining operations in confined aquifers, enrich the theory of mining under pressure and the methods of water prevention.