Study on effect of wind speed to air leakage and spontaneous combustion in goaf of contiguous seams

This paper studies the distributions of air leakage and coal spontaneous combustion in gob of contiguous seams under different intake air velocities.Based on the theory of “three horizontal zones” and “three vertical zones”,a three dimensional model of a U type ventilation contiguous seams gob was established to simulate a real mine working face.Numerical simulation was conducted in Fluent to study the airflow in gob under different intake air velocities.The three zones of spontaneous combustion in gob were determined according to the simulation results.Using area calculation software and Origin numerical analysis,the area changes of gob oxidized zone under different intake air velocities were illustrated and a mathematical model was developed to calculate the area of coal spontaneous combustion zone.The results show that the air leakage in gob was concentrated in the area which has a horizontal distance between 0 and 23 m from the inlet of working face.Due to air leaking into gob,the risk of coal spontaneous combustion in overlying gob was greater than that of mined out area.The results also show that the area of oxidized zone in gob was proportional to the height of gob when the air velocity is constant and the area of oxidized zone reaches the maximum value when the velocity is 3 m/s and the height of gob is constant.Moreover,the area of oxidation zone in gob is proportional to the height of gob under different air velocities.The results suggest that,to improve mine safety,the determination of air velocity should take into consideration of gob conditions,the real-time gas monitoring in gob should be implemented,and coal spontaneous combustion prediction technology should be improved