Deformation laws and hydraulic fracturing pressure relief control technology for mining roadway surrounding rock in isolated island working face

The mining roadway of the isolated island working face experiences the secondary mining action of the adjacent working face and the working face, and the deformation and damage are serious and the support is difficult. Especially under the condition of hard roof, the influence of mining is more intense. In view of the above problems, taking the 1505 isolated island working face of a mine in Weinan, Shaanxi as the engineering background, the stress concentration effect, deformation and failure characteristics and dynamic pressure behavior mechanism of the mining roadway in the isolated island working face are analyzed, and the pressure relief mechanism of hydraulic fracturing is revealed. The directional long-hole hydraulic fracturing technology is proposed to soften the overburden structure and block the stress transfer path. The optimization criterion of fracturing horizon （preferred key layer or thick and hard roof） is established. The specific implementation scheme of hydraulic fracturing in directional long-hole area is determined, and industrial tests are carried out. The results show that the floor heave deformation of the non-fracturing section of the mining roadway is serious and the stress concentration of the coal pillar is high, while the floor heave and the stress of the coal pillar in the fracturing section are greatly reduced. The average floor heave is 32 cm, and the average peak stress of the coal pillar is 11.5 MPa, which is 60.5% and 49.6% lower than that of the non-fracturing section of the mining roadway. The number of microseismic events, the total energy of the event, the maximum energy, the average energy, the number of events of three or more times, and the number of on-site dynamic pressure appearances in the fractured section of the mining roadway are significantly lower than those in the non-fractured section. The directional long-hole hydraulic fracturing pressure relief technology effectively solves the large deformation problem of the surrounding rock of the mining roadway in the 1505 isolated island working face. The research results provide a guarantee for safe and efficient mining of isolated island working face.