Study on regularity of three- dimensional spontaneous combustion zone in gob of narrow face with thick coal seam

In view of the complex changes in the distribution of the three-dimensional spontaneous combustion zone in the gob caused by the narrow working face,t hick coal seam,and fast advancing speed of No.6304 working face in Yunhe Coal Mine ,the traditional beam tube monitoring results only reflect the static three-zone dist ribution of spontaneous combustion at the bottom of the gob. In order to understand the distribution law of the three-dimensional spontaneous combustion zone in this t ype of gob,through on-site beam tube monitoring,combined with the measurement of working face pressure and the characteristics of the caving void structure in the go b,the three-dimensional spontaneous combustion zone range under the air leakage intensity of the gob is inverted. The working face is used as a prototype to construct a three-dimensional model of the gob,write a custom UDF function,and use Fluent software to numerically simulate the gas pressure, air leakage wind speed and 02 CO ncentration in the gob,and establish a three-dimensional spontaneous combustion zone prediction model for the gob. The simulation results show that the three-zone sp ontaneous combustion range retrieved by pressure measurement is in consistent with the three-zone spontaneous combustion zone monitored by the traditional beam t ube; the intake side of the heat dissipation zone is larger than the return air side,and the three-zone spontaneous combustion range is larger than the return air side; Aff ected by caving compaction in the middle part,the spontaneous combustion zone in the middle part is convex. The simulation shows that the range from the spontaneou s combustion zone of the working face is: heat dissipation zone 80 m; The two sides of the roadwa y are significantly affected by the falling void structure,and the spontaneous combustion zone will move back by 10 ~ 15 m in the vertical direction; the simulation resul ts of the spontaneous combustion zone under different inlet wind speeds show that the range of the heat dissipation zone moves back with the increase of wind speed,a nd the range of spontaneous combustion zone widens. The accuracy of the three-dimensional spontaneous combustion zone range established by the three methods of 02 concentration,air leakage wind speed and simulation prediction in thick coal seams and narrow face gobs was proved. Air leakage in gob should be controlled,and k ey spontaneous combustion areas should be strictly prevented,and specific measures should be formulated for thick coal seam mines in combination with the characteri stics of gob gap structure and the idea of establishing three-dimensional spontaneous combustion zones to improve the safety of coal mining.