Factors that trigger the development of mining-induced ground fissures, and standards to treat them in shallow coal mining areas

Abstract

The exploitation of shallow coal seams causes severe surface subsidence and triggers the development of numerous ground fissures, which threaten the safety of underground mining and damage the surface eco-environment. We studied the law of surface movement and the development of ground fissures at three panels in the Daliuta coal mine, Shendong mining district of western China. The results showed that mining-induced ground fissures developed in a cycle of ‘crack-expand-close’, and formed permanent cracks that were arranged in an elliptical shape on the edge of the goaf. There was a positive linear relationship between the fissure width and the surface horizontal deformation, as one would expect, and a positive logarithmic relationship between the fissure angle and the mining rate during coal face advancing. We propose a basis and standard for treating dynamic fissures which recommends that, to ensure the safety of underground mining, the fissures should be treated when the surface cracks extend as far as the fractured zone of rock strata. The results will support predictions of the development of mining-induced ground fissures so that disasters can be prevented in shallow coal seam mining areas.