Visual Exploration of the Spatiotemporal Evolution Law of Overburden Failure and Mining-Induced Fractures: A Case Study of the Wangjialing Coal Mine in China

The borehole television approach is an effective way of detecting mining-induced fractures in overburden strata as it can visualize fractures to facilitate a quantitative analysis of size, quantity, length, and other features. In this article, the borehole television approach is applied on panel 20105 of the Wangjialing Coal Mine in China to investigate the overburden movement and spatiotemporal evolution law of mining-induced fractures from the coal seam to ground surface. The results revealed that the overburden strata experienced the phases of roof caving, generation of fracture, bed separation, dislocations, fracture propagation, surface subsidence, and closing of fractures. The process can be divided into the initiation stage, the active stage, and the degradation stage along the mining direction. For exploited working faces, the caved zone height is 2.9-4.11 times the mining height, and the height of the fractured zone is 19.35-22.19 times the mining height. The height range of the three parts in the fractured zone is 24-26, 40-45, and 30-35 m. Significant fractures were observed in the bending zone. Step subsidence and cracks, which indicate severe damages, were observed on the ground surface above the goaf.