Dynamic Distribution of Voidage in Longwall Coal Mining-Disturbed Strata

Two-dimensional dynamic distribution models of voidage in each longwall mining-disturbed stratum were proposed to investigate the heterogeneous distribution and periodical responses of voids with the extraction of coal. It indicated that the developed zone of voids periodically extends forward with the advance of the longwall mining face. Along coalbed strike and dip, the voidage in the caved zone has a "basin-type" distribution, and the transverse and longitudinal voidage distribution in the fractured zone are "saddle-type" and from "arch-type" to "saddle-type", respectively. Additionally, the voidage gradually decreases from the deep to the shallow around the perimeters of mining-disturbed stratum, but the change is inverse near the center. Further research illustrated that the distribution shape of transverse voidage along the strike alters from the "∩-type" to the "M-type" as time goes on. However, the distribution shape of longitudinal voidage keeps in the "M-type". The distribution models of voidage can be hopefully applied to guide coalbed methane extraction, water influx prevention, coal fire prevention and control, and so on.