Comparison of large deformation failure control method in a deep gob-side roadway: A theoretical analysis and field investigation.

Under the dual influence of the mining disturbance of the previous working face and the advanced mining of the working face, the roadway is prone to large deformation, failure, and rockburst. Roadway stabilization has always significantly influenced deep mining safety. In this article we used the research background of the large deformation failure roadway of Fa-er Coal Mine in Guizhou Province of China to propose two control methods: bolt-cable-mesh + concrete blocks + directional energy-gathering blasting (BCM-CBDE method) and 1^st Generation − Negative Poisson's Ratio (1G NPR) cable + directional energy-gathering blasting + dynamic pressure stage support (π girder + single hydraulic prop + retractable U steel) (NPR-DEDP method). Meantime, we compared the validity of the large deformation failure control method in a deep gob-side roadway based on theoretical analysis, numerical simulations, and field experiments. The results show that directional energy-gathering blasting can weaken the pressure acting on the concrete blocks. However, the vertical stress of the surrounding rock of the roadway is still concentrated in the entity coal side and the concrete blocks, showing a 'bimodal' distribution. BCM-CBDE method cannot effectively control the stability of the roadway. NPR-DEDP method removed the concrete blocks. It shows using the 1G NPR cable with periodic slipping-sticking characteristics can adapt to repeated mining disturbances. The peak value of the vertical stress of the roadway is reduced and transferred to the deep part of the surrounding rock mass, which promotes the collapse of the gangue in the goaf and fills the goaf. The pressure of the roadway roof is reduced, and the gob-side roadway is fundamentally protected. Meantime, the dynamic pressure stage support method with π girder + single hydraulic prop + retractable U steel as the core effectively protects the roadway from dynamic pressure impact when the main roof is periodically broken. After the on-site implementation of NPR-DEDP method, the deformation of the roadway is reduced by more than 45%, and the deformation rate is reduced by more than 50%. [ABSTRACT FROM AUTHOR]