Mechanism and effect of rock burst prevention using overlength horizontal hole staged fracturing technology

Aiming at the problem that it is difficult to achieve a large⁃scale treatment of high⁃level thick and hard roof in rockburst coal seams，a super⁃long horizontal hole segmented fracturing anti⁃scouring technology is proposed. The CDEM numerical simulation method is used to analyze the rock burst prevention and pressure relief effect of over⁃ length horizontal hole staged fracturing for weakening thick and hard roof. The simulation shows that the roof collapse is more sufficient，the weighting step is shorter，the weighting strength is lower，and the advance abutment pressure of working face and lateral abutment pressure of roadway are also significantly reduced after fracturing，so the pressure relief effect is obvious. The principle of roof regional fracturing to reduce rock burst is put forward，that is，by greatly re⁃ ducing the overall strength of the strata， the stress of the strata above the coal seam is transformed from “ hard transfer” to “soft transfer”，so as to reduce the overall static load level of the mining coal seam. At the same time，the weakened thick and hard roof can collapse and fill the goaf in time during the mining process，so as to reduce the dy⁃ namic load of the roof. By simultaneously reducing the dynamic and static loads causing the rock burst initiation，the peak stress area of the roadway is always below the critical stress value of the rock burst，which can significantly re⁃ duce or even eliminate the hidden danger caused by the rock burst of thick and hard roof. The field engineering prac⁃ tice shows that the pressure curve fluctuates zigzag in a stable range，indicating that the fracture development is contin⁃ uous and sufficient during fracturing. In the fracturing area，the frequency of high⁃energy microseismic events is signifi⁃ cantly reduced，the low⁃energy events are increased，the clustering effect is weakened，and the mining disturbance range and intensity are also significantly reduced. Finally，the safe mining of working face is realized，and the effect of pressure relief to prevent rock burst is remarkable.