Study on stability and control of pre-excavated withdrawal channel under mining influence

Pre-excavated withdrawal channel (PWC) is an effective means to shorten the withdrawal time of fully mechanized working face and improve the efficiency, safety, and reliability during the withdrawal. However, the key to the success of the withdrawal method is the influence of mining on the stability of PWC, taking the III32upper1 working face of Zhuzhuang coal mine as the engineering background. By theoretical analysis and numerical simulation, the deformation of the PWC is analyzed and the mechanical model of the influence of the instability of the main roof fracture on the PWC is established. And the effect of the fracture and rotation of the main roof on the PWC is analyzed. The result shows that the instability of the coal pillar leads to the fracture and rotary deformation of the main roof as the width of the coal pillar gradually decreases, which further aggravates the deformation of the PWC and the degree of ground pressure behavior. Based on the influence of mining on the PWC, a control method is proposed. This method uses hydraulic fracturing technology to weaken the mining stress and prevent the fracture of the main roof above the PWC. The control effect of hydraulic fracturing on PWC is analyzed through the establishment of numerical calculation model. The result of engineering practice demonstrates that the mining stress is significantly reduced, and the deformation of surrounding rock in the PWC is effectively controlled after hydraulic fracturing.