Study on the fracture regularity of extra thick and hard roof in “short-face” mining and its blasting weakening technology

Based on the 211113 “short face” of Xinji No. 2 Mine of China Coal Group, this study investigated the weakening regularity of blasting vibration and rock bursting of roof through FLAC3D numerical simulation on the basis of the hard roof fracture regularity through theoretical analysis. The results show that the vibration frequency of the hard roof increases linearly with the increase of the distance from the source, and the vibration amplitude decreases exponentially with the increase of the distance from the source within 20 m from the blasting relief hole. Based on the above results, from the three indexes of controlling the amplitude, frequency and duration of pressure relief blasting vibration, it is proposed that the roof on the 211113 “short face” needs to be controlled by the advanced overlying strata weakening technology, and the parameters of advanced deep hole pre-splitting blasting are optimized. After the roof was weakened by the advanced deep-hole pre-splitting blasting, it can basically fall with mining. The blasting method can effectively avoid the phenomenon of large-area “hanging arch” and effectively prevent the occurrence of rock burst.