Seepage-thermal dynamical coupling model for spontaneous combustion of coalfield outcrop and its application

The characters of gas seepage in coalfield outcrop and the thermal dynamical system of outcrop spontaneous combustion were analyzed. A model coupling seepage with thermal dynamics for spontaneous combustion of coalfield outcrop was set up. The calculation equation of volatile output during coal spontaneous combustion was deduced. One coal fire in Xinjiang Uygur Autonomous Region of China was selected as the simulated object by the seepage-thermal dynamic model. It is shown that when spontaneous combustion of coal outcrop results from the mining, the combustion center centralizes near the roof and spreads to the outcrop direction quickly. The high-temperature region locates below the roof and the temperature gradient out of the combustion area is not obvious. Gases produced by coal spontaneous combustion mainly flow in the downstream of the spontaneous combustion area and the combusted gases only exists a small region on the upstream of the combustion area. The higher temperature distribution accords with the seepage scope of spontaneous combustion gases. Whereas, coal spontaneous combustion accelerates gas seepage in the coal and rock medium and is helpful to development of spontaneous combustion. At last, based on the simulated results, some measures on the coalfield fire location, fire control and fire monitor were analyzed.