Failure Evolution and Instability Mechanism of Surrounding Rock for Close-Distance Parallel Chambers with Super-Large Section in Deep Coal Mines

Abstract

The stability of surrounding rock for large or super-large section chambers is extremely hard to control in deep coal mines, as well as in close-distance chambers. Based on the on-site geological conditions of the super-large-section chamber group of a coal gangues separation system in Longgu Coal Mine, Heze City, Shandong, China, this paper will establish a FLAC3D numerical simulation model to research the failure evolution of the surrounding rock under different chamber spacings and thicknesses of the loosening circle. The results show that the interaction between chambers increased with the decrease of chamber spacing and the increase in the loosening circle thickness, the critical spacing (L2) range was 15–10 m, and the critical thickness of the loosening circle was 4–5 m. Based on this, the instability mechanical models of the surrounding rock that is controlled by chamber spacing and loosening circle will be established, respectively. Then, L2 and loosening circle radius without chain instability (R*a) will be obtained theoretically. Finally, the theoretical verification will be realized by on-site calculations. This research revealed the chain instability mechanism of the chamber surrounding rock and provided theoretical guidance and reference for the close-distance parallel chamber with a super-large section design under deep mining conditions.