Mechanical Mechanism Analysis of Roof Fracture Evolution in Stope with Variable Length Based on Elastic-Plastic Structure Theory

Stope with variable length is formed by change of mining face due to the irregular distribution geological rock pillars, which a typical representative complex coal seam mining. According geometric characteristics and mechanical boundaries each stage stope length, roof structure models four boundary conditions were established solved successively using small deflection thin plate bending theory. Combined simulated images MATLAB FLAC3D, fracture laws corresponding engineering phenomena analyzed. pressure zoning, overburden model “three stopes, three areas, structures” constructed. The research shows that traditional “O-X” occurs in stope. For cracks generated prolonged drift mutative are similar crack development large stope, so they integrated into full-scale broken “X-O” shape, continues develop produce extended fracture, forming theory “two stopes two laws.” conclusion strongly reveals failure law from tension instability plastic abnormal ground during length. It provides basis for exploring essence migration strengthening prevention control under occurrence deep seams.