Dangerous Region Judgment Of Spontaneous Combustion In Overlying Goaf Of Excavation In Shallow Depth Contiguous Seams Group

Represented by Shen Dong mining area of western China,the coal seams are of shallow, near distance and easy spontaneous combustion characteristics.Influenced by the secondry mining of underlying seam, the already closed fracture of overlying goaf activated and secondary developed, causes the goaf air leakage more complicated; meanwhile,when mining underlying seam,fissures of upper and lower goaf connected with each other and even with the surface crack.These fissures intensify the air leakage of overlying goaf and make the coal spontaneous combustion very frequently.In order to prevent and control coal spontaneous combustion of overlying goaf effectively, it is necessary to study fracture evolution and air leakage under influence of excavation disturbance in shallow depth contiguous seams and judge the spontaneous combustion dangerous area of overlying goaf.Based on the shallow depth contiguous seams of Shen Dong mining area, the article studied the law of overburden fracture through simulation experiment; put forward the mechanism of action of fracture of overlying strata; mastered distribution characteristics of air leakage passage in goaf when excavation in shallow depth contiguous seams;and classified cracks in the surface through the overlying goaf by field tests, revealed that the surface cracks in a certain range to obey normal distribution.The article analyzed the reasons, the features and the laws of spontaneous combustion in overlying goaf when excavation in shallow depth contiguous seams. Based on Bulianta 22305 working face and 12306 overlying goaf, simulated stress distribution characteristics of overlying goaf under excavation in shallow depth contiguous seams, calculated the height of caving zone and fissure zone of overlying strata when excavation in shallow depth contiguous seams, obtained porosity and permeability distribution of overlying goaf, established mathematical model of coal spontaneous combustion in overlying goaf.Combined with case of coal spontaneous combustion in overlying goaf of Bulianta 22305 working face in June 2012 and mathematical model of coal spontaneous combustion, simulated distribution characteristics of wind flow field, oxygen concentration field and temperature field of overlying goaf, preliminary delineated dangerous area of coal spontaneous combustion in overlying goaf and verified the reliability and validity of the results of simulation by field drilling measurement method.