Study on fracture characteristics of high key stratum and development law of water and gas transport channels in Datong mining area

Abstract

AbstractThe study aimed to examine the problem of the abandoned mine water and harmful gas downflow from the overlying Jurassic of Tongxin coal mine in the Datong mine area, China. A theoretical analysis, physically similar simulation, and field measurement were used. A fracture aperture mechanical model based on key stratum fracture was used to analyze the main influencing factors of high key stratum fracture and rotation. We also compared the fracture characteristics, displacement changes, and fracture development of the high‐key stratum. The results showed that: (1) the main influencing factors affecting the fracture characteristics of high key stratum are the thickness of coal seam mining, the thickness of high key stratum, and the distance between high key stratum and 3–5# coal seam. (2) When both 8309 and 8207 working faces reached critical mining, the high key stratum was fractured and the mining‐induced fracture was developed to the 14# coal seam goaf, which coincided with the field tracer gas measurement results of the 8309 working face, indicating that when the distance between 3 and 5# coal seam and the overlying 14# coal seam goaf is less than 220.9 m, 8309 and 8207 working faces will form the channel for water and gas inrush. (3) The fracture length of the high key stratum above the working face of 8207 is smaller than that of 8309, and the pipeline of water and gas transport channel formed after the critical mining of its working face is larger and wider, which makes it more prone to the disaster of water and gas inrush. Before mining the extra‐thick coal seam, it is necessary to detect and pump the water and gas in the 14# coal seam goaf, so as to avoid the water and gas inrush hazard during the coal seam mining.