Failure behavior and dynamic monitoring of floor crack structures under high confined water pressure in deep coal mining: A case study of Hebei, China

Abstract

The coal mining process may make cracks in the floor to connect the confined aquifers, causing water inrush from the coal seam floor. Through the inclusion theory and compression failure criterion, the failure model of floor crack structures in deep mining is built by adding the additional water pressure. Under the compressive stresses, the additional water pressure in the cracks increases linearly as the mining-induced stress and the mining depth increase. As the confined water pressure rises, the failure strength of the floor crack structures decreases linearly, while the growth length increases nonlinearly. Yet, the failure strength first decreases and then increases as the angle of crack structures increases, and the dominant failure angles of crack structures in the floor range from 30 to 70°. Thus, the various dynamic monitoring technologies of crack structures, such as water-rich area detection, hydrological and micro-seismic monitoring, and failure depth exploration in the floor, are improved on the mining site. And these technologies are combined to establish a reliable early warning system for floor water inrush, and provide a safe guarantee for deep mining under high confined water pressure.