Study on the influence of periodic weighting on the spontaneous combustion "three-zone" in a gob

The spontaneous combustion "three-zone" of a gob is one of the key fields in the study of the self-heating of residual coal and it is a coupled result of several factors. This paper studies the impact of periodical weighting by introducing weighting intervals into the coupled model of coal self-heating in gobs. The simulated result under field conditions matches well with the measured oxygen concentration distribution in situ. Further simulations of the validated model have been carried on under different weighting intervals, which reveals that the "three-zone" appears to be an asymmetric structure: it moves deeper on the air-intake side but closer to the working face on the air-return side, and the "three-zone" is wider in the middle and tapers when extending to the walls of the gob. The greater weighting interval makes the "three-zone" move deeper into the gob, and the spontaneous combustion zone declines in width. In addition, the highest temperature point proceeds into the depth of the gob at a decreasing speed as the weighting interval rises. This study may be a guide for the problem related to the spontaneous combustion of residual coal in gobs and for the optimization of the ventilation mode in the working face.