Experimental study on the prevention and control of mine earthquake by high pressure water fracturing of huge thick strata in vertical shaft

It is difficult to prevent and control mine earthquakes and rock burst disasters caused by the movement of huge and hard rock formations，which has become a major obstacle to safe production in mines with many huge and hard rock formations in China.Taking the work face with huge thick hard rock strata in the sixth mining area of Dongtan Coal Mine as an engineering background， according to the law of occurrence of earthquakes during mining，the characteristics of the strata structure and the mining conditions of the coal seam，the ground vertical shaft segmented hydraulic fracturing has been proposed to prevent thick and hard rock motion⁃type mine seismic. Through the ground vertical well fracturing，the integrity of the thick hard rock is reduced，and the elastic energy re⁃ leased by the movement of the thick hard rock is reduced. The self⁃developed high⁃precision continuous acquisi⁃ tion micro⁃seismic monitoring system during the fracturing period is used to monitor the fracture morphology formed during the fracturing process. The pipeline pressure curve during the fracturing process，the micro⁃seismic e⁃ vents，and the law of micro⁃seismic events occurred during the recovery process at the 63 up 06 face after fracturing are analyzed. The following conclusions are obtained:1 Based on the analysis of the fracturing curve and the tempo⁃ ral distribution of the effective micro⁃seismic events received during the fracturing process，the entire process of the for⁃ mation and development of hydraulic fracturing fractures in the huge thick rock formations in vertical ground wells is divided into five stages including initiation，rock fracture expansion，main crack formation，main crack extension and crack closure backflow.2 According to the micro⁃seismic monitoring results，the direction of the main fractures formed by high⁃pressure water fracturing in vertical ground wells is between 143° and 150°，the length is between 220 m and 300 m，and the vertical height is between 300 m and 344 m. Full thickness fracturing of thick hard rock is achieved.3 According to the micro⁃seismic monitoring results of the 63 up 06 working face during the mining opera⁃ tion in the ground vertical well fracturing area， compared with the three adjacent working faces during the 0 -500 m mining period，the average reduction of 1.5 magnitude or more mine earthquake events is about 54%，and the expected ground surface is basically realized. The fracturing damping target provides a guarantee for the safe mining of the huge thick hard rock face in the sixth mining area of Dongtan Coal Mine.