Disaster mechanism and control technology of large roadway group with repeated impact in extra-thick coal seam

In view of the increasingly severe rock burst problem of coal mine roadway groups, taking the central roadway composite structural area of a mine as the engineering background, the repeated rock burst mechanism and prevention methods of roadway groups are studied by using the methods of theoretical analysis, numerical simulation, on-site monitoring and engineering practice. The conclusions are as follows: (1) The rock burst in the composite structural area of the central roadway is a self-generated rock burst absolutely dominated by static load under the superposition of specific geological environment and engineering structure; (2) After rock burst, the decline of the overall rock burst resistance of roadway surrounding rock and the continuous recovery of coal stress are the fundamental reasons for the repeated occurrence of rockburst, while the thick bottom coal without support bears high concentrated stress and becomes the breakthrough of energy release, which is manifested as bottom coal rock burst; (3) A super-long horizontal hole segmented fracturing technology in the roof is used to relieve the pressure in composite structure area of the central roadway. Through fracturing, a large number of network cracks with different directions and lengths are formed in the originally complete and hard target rock layer, which greatly reduces the overall strength of the rock layer, and the broken rock layer can be regarded as a plastic cushion, It can absorb part of the energy and weaken the stress transmission of the overlying roof, transform the stress from “hard transmission” to “soft transmission”, and then reduce the overall static load level of the coal seam below the fracturing area, so that it can not recover to the critical load required for the occurrence of rock burst, so as to achieve the purpose of reducing the risk of disaster caused by rock burst. © 2022 Academia Sinica. All rights reserved.