Three-Dimensional Stochastic Distribution Characteristics of Void Fraction in Longwall Mining-Disturbed Overburden of Inclined Coal Seam

Fractures in the overburden induced by mining disturbances provide a channel for fluid flow between the surface and the underground. Mining-induced strata movement and fracture distribution are influenced by the gravity and dip angles of rock seams. In this paper, a new three-dimensional theoretical distribution model for void fraction in each partition of overlying rock strata disturbed by inclined coal seam mining was constructed. Based on the theoretical determination model, the three-dimensional random distribution characteristics for void fraction were obtained by combining the random distribution law of void fraction obtained by similar physical simulation experiments and image processing techniques. Theoretical deterministic models, stochastic theoretical models, and similar physical simulations all show that void fraction distribution in the tendency direction of the coal seam shows a bimodal asymmetric distribution with high and low peaks and a symmetric distribution in the strike direction. The void fraction of the overburden in the central part of the mining area is smaller than that of the surrounding area. The results of the theoretically determined model and stochastic model of the void fraction for the strata with different mining lengths and different coal seam inclinations were compared with the results of similar simulation experiments, respectively. The results are in agreement, further verifying the practicality of the model.