Study On The Characteristics And Prevention Of Spontaneous Combustion Of Coal Seam In The Fault Zone

The macroscopic effect of coal spontaneous combustion on faults is unclear.The differences in spontaneous combustion characteristics between coal bodies in the fault zone and the coals in the normal area are unknown.The three-band and air leakage conditions of the coal in the fault zone are unknown,and the coal spontaneous combustion classification warning and emergency response are not perfect.Using the combination of laboratory testing,physical similarity simulation,fluent numerical simulation,on-site comprehensive testing and theoretical analysis,the differences in overburden collapse around the fault-free and fault-working face,the most likely differences in the distribution of spontaneous combustion zones,The multi-scale pore characteristics of coal and the spontaneous combustion characteristics of coal,the distribution characteristics of coal spontaneous combustion three-band distribution in the working place of the fault zone and the coal spontaneous combustion early warning classification prevention and control system are systematically studied.There have important practical and scientific value for the prevention and control of spontaneous combustion in coal seam mining at fault areas,and provide theoretical support and technical support for the safe and efficient production of mines.Through the physical similarity simulation of coal mining without fault and fault place,it is found that fault activation affects the roof collapse period,the height of the caving zone and the development of the fracture zone.The top-span periodic fault working face is two times more than the non-fault working face,and the height-fault working face of the caving zone is 3.6 m higher than the non-faulted face.The average fracture rate of the fracture zone of the fault working face(19.36%)is higher than that of the faultless working face(14.56%).It is proposed that the most likely spontaneous combustion zone of the fault directly across the working face is “the two-dimensional two-line + fault-through formation of triangular coal and broken coal rock accumulation area”.The most likely spontaneous combustion zone for moving in the fault face is“two roads and two lines” + “fault activation zone” + “two roads and two lines”.Through the comprehensive test of multi-scale pore characteristics and thermogravimetric and differential scanning calorimetry of tectonic coal and raw coal,the paper obtained that the firmness coefficient,volatile matter content and carbon content of tectonic coal are smaller than that of raw coal,and the ash content is slightly higher than that of raw coal.The cumulative pore volume of the structured coal(pore size >100nm,pore size between 2-100 nm and pore size <2nm)is larger than that of raw coal;except for the range of 2-10 nm,the pore volume of the structural coal stage is also larger than that of raw coal.It is found that the structured coal has more open pores and ink bottle-type pores than the raw coal and has high connectivity,so that the specific surface area of the open pores of the constructed coal is higher than that of the raw coal.Both the constructed coal and the raw coal undergoing heat and spontaneous combustion have experienced three stages: loss of weight reaction,weight gain of oxidation reaction and weight loss of combustion reaction,and two stages of endothermic and exothermic.There is a significant difference in the activation energy of the oxidation reaction in the weight gain stage.The activation energy of the raw coal is1.486 times that of the structural coal.The heat absorption of the coal in the endothermic stage is much smaller than that of the raw coal.The exothermic heat of the raw coal in the exothermic stage is much larger than that of the structural coal.The gas-thermal parameter simulation model of coal spontaneous combustion danger zone in fault working face was established.The oxygen concentration field of the lower goaf before and after the different atmospheric pressures,different ventilation air volumes,different initial geothermal temperatures,different nitrogen injection steps and the setting of resistance plugging were simulated.The distribution characteristics of the temperature field.The results show that the pressure drop in the inlet duct will reduce the influence range of air leakage and air leakage in the goaf,and the oxidation speed of the coal seam will be slowed down.When the ground temperature rises,the influence range of the air leakage in the goaf is enlarged and the goaf is easy to oxidize and heat up.Increased resistance to plugging and nitrogen injection can narrow the oxidative spontaneous combustion zone in the goaf and delay the appearance of high temperature zones.Through the program temperature experiment and grey correlation analysis of structural coal and raw coal,the composite grading prediction index of structural coal was determined.According to laboratory experiments,on-site air leakage test and comprehensive theoretical analysis,the risk of spontaneous combustion of coalin fault area is divided into four levels: safety,basic safety,spontaneous combustion threat and spontaneous combustion danger.The four-level response parameters of the fire protection of the working face were determined,and four emergency response technical measures were given.