Research on pressure relief control technology of thick and hard roof of main roadway group in kilometer-deep mine

The mining depth of the No.8 coal seam in the Hetaoyu Coal Mine has reached the level of kilometers. The main roadway group has the characteristics of high buried depth, dense distribution with other roadways, and a thick hard roof above, so the surrounding rock of the main roadway has the hidden danger of rockburst accidents. Taking the pressure relief control of the hard roof of the main roadway group in the kilometer-deep mine as the research background, through field investigation, in-situ stress test, and roof structure analysis, it is obtained that the main roadway section near the end coal pillar side of the mining face is the impact hidden danger section, and the maximum horizontal principal stress is measured to be 30.34 MPa, which belongs to the ultra-high stress area. It is necessary to fracture the thick and hard roof in the 40 m area above the main roadway group. A hydraulic fracturing technology is designed to implement multiple ultra-long horizontal holes on the roof of the main roadway group in the connecting alley. The backward segmented fracturing method is adopted, and the roof pre-splitting blasting in the stop mining line area is also adopted. At the same time, a hydraulic fracturing model of thick and hard roof based on discrete elements is established. It is verified that the fracture of the thick and hard roof will reduce the degree of stress concentration of the surrounding rock of the roadway group, the fracture connectivity of three horizontal holes is good, and the continuous fracture zone is successfully generated above the roadway group, which provides a reference for field related projects.