Mechanism of Roof Cutting and Stress Relief in Coal Seams with Hard Sandstone Coverage

Blasting roof cutting when the working face is directly covered with a hard roof can change the roof structure, which is an important factor for preventing dynamic disasters induced by hard roofs. This article used theoretical analysis to establish an expression for the distribution of the side abutment stress near the end of the working face before and after roof cutting. The stress reduction showed a power function growth trend with increasing crack zone height and a linear growth trend with increasing cantilever length of the hard roof. The results of the theoretical analysis provide a new approach for evaluating the effect of roof cutting and stress relief. The numerical simulation method was used to analyze the stress and plastic zone of the stope and the deformation characteristics of the roadway after roof cutting. The results showed that the advance and side abutment stresses of the working face decreased after roof cutting, and the range of the roof plastic zone increased. In addition, the displacements of the sides and floor of the roadway were reduced after roof cutting, which is beneficial for roadway stability control. Based on the research results, the roadway support scheme was optimized, and the advance support of the roadway was removed. This greatly reduced the work intensity and support cost and ensured the stability of the roadway.