Research on generation mechanism of"muffled blast"sound phenomenon in surrounding rock of coal seam roadways

LI Gengxin; WANG Kai; ZHANG Xiaoqiang; QIU Pengqi; WANG Wenwei

doi:10.13347/j.cnki.mkaq.20241360

Abstract：Frequent"muffled blast"sounds accompany coal mining in some coal mines in central China,which characterize the sudden release of stored energy and pose a potential threat to the safe production of coal mines.To investigate the generation mech-anism of"muffled blast"sounds in the surrounding rock of coal seam roadways,taking the No.15 coal seam of Yangsheng Coal In-dustry as the engineering background,the sources of"muffled blast"sounds were located via micro-seismic monitoring.After on-site sampling,mechanical tests and acoustic emission monitoring were carried out on coal and rock masses,and a comprehensive analysis was conducted through numerical simulation with the real failure process analysis(RFPA)software combined with field measurements.The results show that the limestone roof stratum has high brittleness,low strength and well-developed fractures.Un-der the action of stress disturbance or periodic stress concentration in high-position strata,fracture propagation occurs in the sur-rounding rock of roadways,generating a large number of acoustic emission signals.The failure of roadway surrounding rock is dom-inated by shear failure,and the acoustic emission signals are mainly concentrated within the range of 15 m in the two ribs and 10 m in the roof of the roadway,with most accumulating near the rib-roof corners.During the deformation and failure process of the road-way,a large amount of elastic energy accumulates in the area where acoustic emission signals concentrate,and the release of this elastic energy gives rise to the"muffled blast"phenomenon.This verifies that the"muffled blast"phenomenon is mainly caused by the instantaneous release of energy during the deformation and failure of surrounding rock,and is not a precursor of rock burst.