Numerical simulation of the three zones of spontaneous coal combustion in goaf under multi-physical field coupling
Determining the distribution range of the three zones of spontaneous combustion in goaf is crucial for the prevention and control of spontaneous combustion fires.To elucidate the spontaneous combustion behavior of residual coal in goaf and theinfluence range during the mining process of ultra-long working faces,this study focused on the Ji16-17-23260 working face of Pingdingshan No.5 Coal Mine.The distribution patterns and influencing factors of the three zones of spontaneous combustion in the goaf were investigated through experimental research,field measurements,numerical simulations,and theoretical analyses.The oxygen consumption rate,as well as the production rates of CO and CO2,heat release intensity,and other characteristic parameters of coal spontaneous combustion,were obtained through programmed temperature oxidation experiments.The distribution range of the three zones of spontaneous combustion was measured by collecting gas samples using buried bundle tubes in the goaf.A three-dimensional model coupling the temperature field,seepage field,and stress field(Thermal-Hydrological-Mechanical,THM)of the spontaneous combustion zones in goaf was established using COMSOL simulation software.The distribution patterns of the three zones of spontaneous combustion in the goaf of a fully mechanized mining face were established,and the effects of varying wind speeds and different working face inclinations on the distribution of these spontaneous combustion zones were analyzed.The results indicate that the actual heat release intensity of the Ji16-17 coal seam at temperature T is as follows:q(θ)=4.8337e0.0467θ.The THM multi-field coupling simulation results were compared with field measurement data.The maximum widths of the oxidation zone on the intake air lane and the return air lane are 48 m and 31 m,respectively,with relative errors of 0.04 and 0.02.Additionally,the peak temperatures in the oxidation zones are 78.36 ℃ and 68.15 ℃,respectively.The three zones of spontaneous combustion exhibit similar characteristics.In the goaf,the oxidation zone in the x-y section is distributed in an arc shape,while the oxidation zone in the y-z section follows a parabolic distribution.Notably,the width of the three zones near the roof is larger than that near the floor.Consequently,the roof side is a critical area for preventing and controlling the spontaneous combustion of residual coal in the goaf.The range of the three spontaneous combustion zones in the goaf of the working face increases with higher wind speeds and longer working face inclinations,gradually extending deeper into the goaf.
万方数据
维普
