FRACTURE RELIEVING METHOD FOR STRESS CONCENTRATION OF PILLAR LEFT IN OVERLYING GOAF

摘要

A fracture relieving method for stress concentration of a pillar left in an overlying goaf. The method comprises: first, fracturing a top plate directionally to optimize the stress of the top plate to reduce the source of a force; second, fracturing a coal pillar with pulse to generate a gap network so as to weaken the rigidity of the coal pillar (14) and reduce the bearing capacity of the coal pillar; and finally, fracturing a rock stratum of a bottom plate of the coal pillar with pulse to weaken the ability of transferring stress concentration. Fracture drill holes are separately constructed in spaced fashion in the direction in which a lane (1) is oblique to the coal pillar of the upper goaf to set depths by means of a drilling machine. An oblique fracturing hole can fracture the top plate, the coal pillar, and the bottom plate using retrograde multistage fracturing; and the directional fracturing position of the top plate is about 1 m above the middle of an upper roof (5) above the coal pillar. The method reduces the width of a coal pillar of a lower coal layer, improves the extraction rate of coal, reduces the deformation of a lane in the lower coal layer, effectively resolves the rock pressure problem and pressure bumps of the coal pillar of the working face of the lower coal layer, and coal and gas outburst problem during lower coal layer mining, and features a high safety coefficient, simple implementation, convenient construction, and low costs.