Study On The Shallow Sealing Method Of Mine Fire And Surface Fire Coexisting Areas

Surface fire and mine fire coexisting area is characterized by deep,intense combustion and complicated air leakage channels.Long term fire extinguishing experience shows that surface fire and mine fire coexisting area is prone to re-ignition under traditional fire extinguishing process.This paper analyzes the structure characteristics and development model of surface fire and mine fire coexisting areas,studies the feasibility and applicable conditions of surface fire and mine fire coexisting areas.It is helpful to deepen the understanding of the coal fire development law and provides theoretical support for the improvement of coal field fire-fighting technology.According to the statistics of fire area data,it is known that many fire areas in Xinjiang are hilly areas.Most of the fire areas are characterized by multi coal seam layers,large thickness and large dip angle,result to a large number of surface fire and mine fire coexisting areas.The ground surface temperature field and underground fragmentation in the fire area of Daquan Lake in Urumqi are studied and the structure characteristics and development model of surface fire and mine fire coexisting areas are analyzed.Several fire area structure models are classified from real cases.The problems of traditional fire extinguishing process in surface fire and mine fire coexisting area are discussed and the basic ideal and main effect factors of shallow sealing method are summarized.Based on the Heat-Flow-Chemical multi-field coupling mathematical model and typical surface fire and mine fire coexisting areas physical model,the numerical simulation is carried out to study the evolution law of different opening degree fire areas and the effect of the shallow plugging conditions on the deep fire source.The result shows that the smaller the opening degree is,the smaller the temperature range of the coal and rock mass is between the surface fire and the underground fire.Permeability of shallow sealing layer should be small enough to effectively restrain the deep fire source.Concealed air leakage roadway has a great adverse effect on shallow sealing,but under proper conditions,the sealing degree of plugging layer can be significantly reduced.The variation of the blocking thickness in the engineering area has little effect on the oxygen isolation effect.But considering that the plugging material is liable to fail at high temperature baking,the plugging layer is severely heated in the high opening degree fire area,and the thickness of the plugging layer will greatly increase the failure risk of the plugging layer,while there is less heat in the fire zone with low opening degree,and proper reduction of the thickness of the plugging layer will not cause serious effects.A three-dimensional model is built to further explore the main factors that affect the cooling time after shallow plugging in fire area.The result shows that air circulation in the underground goaf after shallow plugging increases the residual oxygen to participate in the high temperature zone reaction,which is not conducive to the cooling down of the fire area.The increase of temperature and the increase of average temperature significantly prolonged the cooling time.High permeability goaf is beneficial to cooling,with the decrease of permeability in goaf,the cooling time in fire zone presents a rule of first large increase and a slight decrease.The fire-fight engineering processes of Kueraken 8# fire area were studied and the parameters such as temperature and oxygen concentration after fire management were collected.The reasons for the re-ignition after the firs fire-fighting process and the success after the second remedy process are analyzed.The experience of on-site management of shallow plugging method is summarized,and some of the conclusions obtained from simulation are verified.