Microseismic fuzzy comprehensive evaluation method of coal burst - A case study in Zhaolou Coal Mine

Based on a coal burst in LW 1305 and combined with the curve of stress vs. strain, six multi-parameters are proposed to forewarn coal burst induced by static high-stress concentration and impact loading, containing microseismic (MS) activity S value, fault total area A(t) value, lacking of shock b value, statistical Z value, MS entropy value and the dominant frequency. The precursors mainly characterize the enhancement trend of S value, the suddenly and sharply rise of A(t) value, the continuous and abnormal lower b value, the increasing absolute value of Z sharply and large than 2, the continuous and abnormal decline of Q t value, and the dominant frequency moving to low-frequency band, respectively. The coal burst in LW 1305 was induced by the intrinsic static high-stress concentration and the external strong impact loading generated by fracturing of the key stratum. Essentially, a lot of micro-fissures inside the key stratum had initiated, converged and connected to form the macro-fracture above LW 1305, which was verified by the attenuation rate of K value. Considering the time-varying effect of the overlying stratum movement, the curves of the six multi-parameters have a good agreement with that of stress vs. strain, which indicates it is reasonable to take the observed zone as a whole system to investigate variation of the multi-parameters and fracturing of the key stratum. It is noteworthy that the MS multi-parameters should be combined with reasonable mining arrangement and corresponding prevention measures to monitor, forecast and control coal bursts in the field.