Study on characteristics of pressure relief by roof cutting under nonpillar-mining approach

Study on characteristics of pressure relief by roof cutting provides useful underground stope stability information under the nonpillar-mining approach—noncoal pillar mining with automatically formed gob-side entry (NMAFGE). This paper analyzes the pressure relief characteristics in three aspects: directional roof-cutting blasting (DRCB), stress path cut off (SPCF), and bearing function of the gangue (BFG). In DRCB analysis, dynamic (explosive stress wave) and quasi-static actions (explosive gas pressure) are considered to study the crack evolution process in roof slot holes after cumulative tube blasting. Combined with field internal crack detection results, the roof hole crack rate reaches 73%. In SPCF analysis, the rock burst experiment single unloading method is adopted to simulate the SPCF effect on roof rock. The experimental results indicate that under SPCF, the rock rapidly releases energy, rupture occurs, and the broken state is mainly fragmented. As the fracture surface rock collapses, a new fracture surface is formed, and the SPCF front moves to the working face interior with increasing rock collapse. In BFG effect analysis, the elastic foundation coefficient and experimental gangue compaction apparatus are introduced. The results demonstrate that the gangue bearing stress increases with increasing compaction degree in the compaction process. Cluster analysis is performed to study hydraulic support pressure monitoring results in the NMAFGE experimental working face. The pressure relief phenomenon caused by single-side roof cutting in the NMAFGE experiment not only determines the pressure distribution around the gob-side entry but also alters approximately 46.9% of the pressure distribution in the underground stope.