Research on hydraulic fracturing roof cutting and roadway protection technology with wide sublevel coal pillar

In view of the difficult problems of high stress and large creep deformation of the surrounding rock in the gob side entry during the mining process of the working face, the mechanical analysis of the surrounding rock structure along the remaining roadway was carried out using the theoretical calculation method with the No.1309 working face of Zhaozhuang mine as the research background and put forward the two-way hydraulic fracturing technology and effect detection method for the roof of the mine.The research results show that the deformation degree of the No.13092 roadway is determined by the uniaxial compressive strength of the coal body, the burial depth of coal seam and the strength of roof rock beam.Under the superimposition of the above factors, the lateral roof of the gob squeeze the coal pillar, resulting in the expansion of the plastic area within the coal pillar and the transfer of the side stress to the deep part of the coal pillar.Before the roof fracture, the vertical stress of the elastic-plastic interface area in the coal pillar reaches the maximum value, and the strong creep deformation of the roadway No.13092 is affected by the peak of the lateral stress,which makes the maintenance of the roadway section difficult; By arranging two-way hydraulic fracturing holes in No.13091 roadway, the integrity of roof are weakened in advance, and the conditions of stress transmission and energy accumulation are destroyed.It effectively prefabricates the artificial fracture line, improves the tendency of the fault line above the coal pillar, and slows down the degree of coal pillar extrusion; In addition, the hydraulic fracturing hole constructed above the roadway can effectively promote the rotation and subsidence of key rock block B, reducing the length of lateral overhang of the No.1309 working face, and the collapse of key rock block B can better form the supporting effect on the high-level rock stratum; After the construction of hydraulic fracturing hole, the tunnel deformation in the corresponding area is reduced by 40%, and the number of microseismic events and microseismic energy values in the boundary area of coal pillar are greatly reduced, ensuring the stability of surrounding rock during the mining of the roadway.The research results explored the feasibility of roof hydraulic fracturing roadway in Shanxi coal mine area, and provided engineering guidance for fracturing technology under similar mine conditions.