Prevention And Control Technology Of Coal Spontaneous Combustion In Goaf Of Full Mechanized Caving Face In Shallow Extremely Thick Coal Seam

Due to shallow burial,large thickness of mining and weakly cemented overburden,the overburden instability movement in fully mechanized caving mining in shallow and thick seams is large,the surface movement and destruction are severe,and a large number of mining cracks are generated.Some of the mining cracks are connected to the surface and the goaf.Under the negative pressure ventilation conditions of the mine,the wind leakage flows through the surface cracks into the goaf and then flows to the working surface,causing the working surface to be ventilated,resulting in carbon monoxide(CO)concentration in the goaf.Abnormal increase and over-limit of CO concentration in the working face,even caused spontaneous combustion of coal in the goaf,seriously threatening the safe production of the mine.Based on the geological occurrence conditions and production technical conditions of coal-rock layers in the ChuanCao-Gedan coal mine,this paper adopts comprehensive research methods such as theoretical analysis,numerical simulation and on-site measurement.Under the condition of surface air leakage,the mining of fully mechanized caving face in shallow and thick seam is adopted.The research on self-ignition prevention technology of residual coal in the area has been studied.The research results have important theoretical and practical significance for the prevention and control of spontaneous combustion of residual coal in the goaf of fully mechanized caving mining in shallow mining area and thick coal seam in western mining area.Based on the engineering geological conditions of fully mechanized caving mining in the extra-thick coal seam of Chuancao’s coal mine,the combination of on-site measurement and numerical calculation is used to study the location and distribution of surface mining cracks in shallow and thick seams,and the dynamic changes of mining cracks.The relationship between the dynamic change of mining cracks and the propulsion distance of the working face,and the distribution of the fractures of the overlying strata in the horizontal directionBased on the combination of on-site measurement and theoretical analysis,the study shows the characteristics of the induced wind leakage in the goaf of the fully mechanized top coal caving mining face,the distribution law of overburden fractures in goaf the gas concentration distribution in the goaf,and The source of CO and its influencing factors under the influence of surface air leakage The influence of surface air leakage on the safe production of fully mechanized caving mining face in shallow and extra-thick coal seams is summarized.Based on the combination of FLUENT numerical simulation and on-site measurement,the distribution law of the airflow field in the goaf of the fully mechanized extra-thick coal caving face and the gas distribution in the goaf are studied under the influence of surface air leakage,and the distribution range of the“three belts”of spontaneous combustion in goafs.Based on the above research results,the prevention and control technology of spontaneous combustion of residual coal in the goaf of fully mechanized caving face in shallow and thick seam is proposed.According to the"three belts"distribution of spontaneous combustion in the shallow-buried and extra-thick coal seams,the filling and sealing technology of surface mining cracks is proposed,and the reasonable filling medium and flat plugging cycle,working face pressurized ventilation technology are determined to determine the reasonable underground.Ventilation pressure range,nitrogen injection and fire prevention technology in the goaf,determine the reasonable nitrogen injection range and nitrogen injection amount;determine the reasonable advancement speed of the working face.According to the actual situation,it is determined that the fully mechanized caving face of the ChuanCao’s coal mine mainly adopts the filling and sealing technology of surface mining cracks.The best viscous drag coefficient of filling is 1×10~7(1/m~2),the best filling seal The blocking distance is 40m after the lag working face;the pressure difference between the upper and lower wells is maintained between-200pa-200pa by using pressurized ventilation;the advancement speed of the mining face is determined to be not less than 4.35m/d.