Depth-dependent mechanical-seepage behavior and safety mining distance of the steeply inclined coal mine underground reservoir
Ersheng Zha, Hongfei Duan, Mingbo Chi, Jiulin Fan, Jianjun Hu, Baoyang Wu, Yu Cong, Jiancheng Tong
Abstract
Coal mine underground reservoir (CMUR) technology mitigates water scarcity in China’s coal-rich western regions but lacks tailored solutions for steeply inclined coal seams. This study develops a novel framework of steeply inclined coal mine underground reservoirs (SICMUR), which is a paradigm shift from conventional CMUR that the coal seam itself serves as the reservoir floor, challenging conventional designs due to depth-dependent permeability and mechanical constraints. Triaxial mechanical-seepage tests on Xinjiang Wudong coal samples (100, 200, 300 m depths) revealed a 3.5 MPa triaxial strength increase per 100 m depth and a 58-fold post-peak permeability surge at 300 versus 100 m. Similar model simulations revealed mining-induced stress redistribution and significant deformation effects, particularly subsidence and water-conducting fractures during lower coal seam mining. Results indicate a minimum 40 m safety distance between reservoirs and lower coal seams. Critical construction parameters were investigated for Wudong mine SICMUR as collapse zone heights (9.9–12.31 m) and water-conducting fracture zone heights (31.96–37.40 m). This work systematically bridges SICMUR concepts to field implementation, offering a framework for water preservation in steeply inclined mining while addressing safety concerns, providing a new approach for water reservation in steeply inclined coal mining.