Deformation and Failure Mechanism of the Lower Roadway in a Close-Range Residual Coal Pillar Area

The Tashan coal mine is selected as a case study to determine the deformation and damage mechanisms of lower roadway in close-range residual pillar area. Roof drilling peephole technology applied detect roof surrounding rock. A boundary invisibility equation derived for plastic zone circular hole based on theory butterfly non-uniform stress field which principal occurs at an arbitrary angle vertical. Maple mathematical drawing software combined with FLAC 3D numerical simulations investigate influence ratio direction zone. results indicate that rock assumes shape when bidirectional large, butterfly-shaped failure related direction. Field test images are show asymmetric pattern area influenced by presence main deflected.