Characteristics of microseismic signals and its frequency-spectrum evolvement rule during the static cracking of coal

The coal cylinder models were static cracking destroyed at different rates by soundless cracking agent. The microseismic signals in the rupture process were monitored by ZDKT-1 type coal or rock dynamic disasters experimen-tal simulation system. The authors tried to analyze the amplitude,energy and frequency-spectrum characteristics of mi-croseismic signals during the static cracking of coal. It was found that the longitudinal cracks were more than transverse cracks after the static cracking of coal,the radial tensile stress was more obvious than the axial tensile stress. The static cracking process of coal could be divided into three stages:micro crack stage,expansion stress transfer stage and cleav-age stage. With the static explosion process,the greater of the average amplitude of microseismic signals,coda wave de-velopment,and the frequency domain of signals were wider too (but dominant frequency decrease). The frequency do-main of main shock and coda wave are different. It is possible to evaluate the process of the static cracking of coal seams by the amplitude of microseismic,the development of coda wave and the spectral characteristics. The micro-seisms signals are paroxysmal,the amplitudes and energies of microseismic signals in the static cracking process do not change monotonically,but show volatility changes. The numbers of microseismic events are related to the macro crack areas. It is possible to evaluate the permeability improvement effect in the process of the static cracking of coal seams by microseismic count.