Study on the Cause of Hypoxia in the Corner of Return Air of Shallow Buried Flammable Coal Seam Group Mining Face and the Coordinated Prevention and Control of Coal Spontaneous Combustion

Abstract

Coal is the main energy source in China, and spontaneous combustion of coal is one of the main disasters in coal mines. Fully mechanized caving top coal mining technology is widely used in coal mines. Under the comprehensive action of multiple factors, gas generated by coal oxidation and low oxygen gas in goaf is easy to rush to working face, resulting in lower oxygen concentration in upper corner and exceeding harmful gas concentration. It seriously threatens the health of underground workers and the normal operation of production. If the oxygen concentration in the upper corner is changed, it is bound to cause the change of the oxygen concentration in the goaf and aggravate the threat of spontaneous combustion of coal in the goaf. In order to solve the double threat of low oxygen in upper corner and coal spontaneous combustion in goaf, based on Coulomb model, this paper uses command flow to conduct numerical simulation tests on the failure law of overlying strata, and obtains the influence of mining of the lower 1 coal seam and the lower 5 coal seam on the overlying strata subsidence and surface penetration. Based on the comprehensive consideration of atmospheric pressure, ore pressure activity, external air leakage and other factors, the mixed model of the source and emission of low oxygen gas in goaf was established, and the formation mechanism of low oxygen problem in the corner of return air of working face was defined. The use of pressure air belt to deal with low oxygen in return air corner is proposed creatively. The comprehensive fire prevention measures such as corner plugging, nitrogen injection and grouting are used to inhibit the oxidation of the left coal and the influx of low oxygen gas to the corner in the goaf, so as to achieve the goal of collaborative prevention and control of low oxygen in the corner of return air and coal spontaneous combustion. The research results have important reference significance for the mine with the risk of spontaneous combustion or the problem of low oxygen in the return air corner.