Ground fracturing pre-control technology for potential mine seismic risk of thick and hard roof

Mines with thick and hard roof face high risks of mine seismic activities and mine pressure during mining, which easily leads to dynamic disasters in mines. To pre-control and prevent such risks, it is necessary to pre-control the thick and hard roof of the mine. By field investigation, engineering analogy, theoretical analysis, laboratory test and numerical simulation, the occurrence characteristics of mine strata, potential mine seismic risk, fracturing of thick and hard roof and the mechanism of ground fracturing pre-control mine seismic risk are studied. The theoretical analysis shows that the mine with thick and hard roof not only has the mine seismic risk induced by the first breakage of the low and high thick and hard roof of a single panel, but also has the risk of aggravating the mine seismic event induced by the high thick and hard roof with the increase of the mining void of the mine. The analogy of engineering cases with similar conditions in Inner Mongolia and Shaanxi shows that mines with thick and hard roof occurrence conditions and mining conditions have the possibility of high mine seismic risk since the second panel is mined. Through the fracturing test of thick and hard roof, the rock brittleness coefficient is 59%~143%, and the average brittle mineral content is about 68%. The comprehensive results show that the fracturing characteristics of the thick and hard roof of the mine are better. The simulation comparison analysis shows that after the pre-splitting of the thick and hard roof, the concentration degree of the front abutment pressure and the front influence distance of the working face are obviously reduced. Based on various research results of thick and hard roof, the mine seismic risk pre-control technology using local ground fracturing pressure relief method is put forward, that is, fracturing is carried out by ‘L’ type drilling on the ground to thick and hard roof to reduce the integrity and compactness of thick and hard roof. The engineering application shows that in the fractured section, the highest frequency of microseismic events in the underground section is reduced by 52.2%, and the maximum energy release of microseismic events in the section is reduced by 56%. This shows that the ground fracturing pre-control technology of thick and hard roof successfully reduces the mine seismic risk and ensures the safe and smooth extraction of panels.