Determination of critical value of an outburst risk prediction index of working face in a coal roadway based on initial gas emission from a borehole and its application: A case study

This study developed a platform for determination of the predictive index for outbursts by simulating the field working face of coal roadway and a system for determining briquetting pressures of coal briquettes. Taking a predictive index called the 'initial gas emission from a borehole' (IGEB) as an example, this research carried out the test for measuring this index in the laboratory and determined its critical value for outburst risk in the 31,011 working face in Xinyuan Coal Mine, Shanxi Province, China. Moreover, outburst risk at the 31,011 working face was predicted in the field. The research results on this premise of ignoring the influences of human factors on the outburst risk in the working face showed that the established platform for simulating the determination of the predictive index for outburst risk in the working face in the coal roadway can realise 100% accuracy in predicting the condition with no outburst risk by using critical value of the predictive index. Briquetting pressure of coal briquettes shows a relationship of exponential function with apparent density of the coal samples. When the briquetting pressure is greater than 30 MPa, the rate of increase thereafter in apparent density decreases, so that coal briquettes undergo work-hardening. The IGEB is a comprehensive predictive index for outburst risk reflecting in situ stress, gas pressure, and mechanical properties of coal mass. The index value can, both sensitively and continuously, reflect changes in the conditions for occurrence of coal mass in front of the working face.