Acoustic Emission Characteristics Stucty of Typical Coal Rock Failure under Uniaxial Compression

The occurrence of mine dynamic disaster is often accompanied by coal rock failure. Study on the evolution characteristics of coal rock fracturing can provide a theoretical basis for the monitoring and early warning of mine dynamic disaster. Four typical coal rock samples, including coal, mudstone, sandstone and shale, which are common in coal measure strata of a mine, are selected for uniaxial compression tests to study the acoustic emission characteristics of their failure process. The results show that: The ringing counts can precisely reflect the failure law of coal and shale samples in each stage, and the increasing inflection point of cumulative ringing count curve appears at the beginning of plastic stage. In the failure process of mudstone and sandstone, the ringing count is less, and the inflection point of the cumulative ringing count curve appears in the late plastic stage. The failure modes of the four coal rock samples are mainly tensile failure and the average proportions of tensile failure of coal, mudstone, sandstone and shale samples are 64.97%, 73.12%, 84.45% and 92.21%, respectively. The number of peak frequencies of each frequency band shows a sudden increase before the failure. The main fracture frequency of coal and sandstone is Ⅲ (150~200 kHz), mudstone is Ⅰ (50~100 kHz) and Ⅴ (280~330 kHz), and shale is mainly concentrated in Ⅱ (100~150 kHz) and Ⅴ (280~330 kHz). The acoustic emission b-value of the four types of coal rock generally show the characteristics of "uptrend-fluctuation-decline stage". The b-value can effectively reflect the fracture process of the four kinds of coal rock, and the decreasing trend before the failure can be used as an important precursor information of the failure and instability of coal rock.