Features of microseismic events and precursors of rock burst in underground coal mining with hard roof

Abstract：The characteristics of rock burst were analyzed based on the microseismic data from No.8935 working face in Xinzhouyao Coal Mine,Datong Mining Group.The geology of this working face was characterized by the thick sandstone roof and coal seam,both with relative higher stiffness and strength.In order to investigate the mechanism and precursors of rock burst occurred in No.8935 working face,the locations of microseismic,the relationship of microseismic energy and frequency and the spectrum of microseismic signals were analyzed.The results show that the rock burst in No.8935 working face are mainly induced by the seismic caused by roof failure.The coal pillar near the goaf is more easily to bump.The statistics results indicate that the rock burst are mainly occurred in the gate road near the pillar,less than 50 m ahead of working face and located in the hard roof adjacent with coal seam.Moreover,the frequency,energy,b-value and frequency spectrogram of microseismic events are found to decrease before rock burst.It was found that the frequencies of the microseismic events before rock burst mainly concentrates upon 5-60 Hz.The sudden decreasing of frequency and increasing of amplitude of microseismic events can be regarded as a precursor of rock burst.