Coupling Treatment of Gas Drainage and Nitrogen Injection for Fire Prevention in the First Stratified Mining goaf：Theoretical Calculation and Field Experiment

ABSTRACT

In order to solve gas and spontaneous combustion in high gassy and combustible coal seam, in this work, the hazard control of gas and spontaneous combustion was studied by numerical simulation and on-site experiments, combining data from the first stratified mining working-face in Gushan Mine, China. Fracture variation in roof and floor of the coal were simulated by the UDEC software with the influence of mining operations. The on-site experiments and COMSOL Multiphysics numerical simulation method were carried out to study the width variation of oxidation zone in goaf with buried pipe extraction and nitrogen injection. The results showed that the combined use of high position borehole drilling, buried pipe in goaf and downward floor hole could reduce the amount of gas extraction, but the stereoscopic gas extraction would enlarge the width of oxidation zone. However, the nitrogen injection measures in goaf could reduce the amount of gas extraction and width of the oxidation zone at the same time, while it also increased the pumping capacity of downwards hole. Besides, the goaf nitrogen injection had a good inhibitory effect on both residual coal seam spontaneous combustion and bottom stratification gas emission.

KEYWORDS:

• First stratified mining
• floor fracture development
• stereo gas drainage
• fireproof by nitrogen injection
• coupling prevention

Acknowledgments

This work was supported by the National Natural Science Foundation of China (grant numbers 51574279 and 51804107), Science and Technology Research Project of Chongqing Education Commission (grant numbers KJQN202003405，KJQN201803401 and KJQN201803405), and Research Project of Chongqing Vocational Institute Engineering (grant numbers 2020KJB2020001).