Abstract: During the process of fully mechanized caving for extremely thick coal seam,there are some issues to be solved,such as slow advance in working face,great amount of left-over coal in mined-out area,serious leakage,and easy to be spontaneous combustion,so the seepage flow and diffusion mathematical model for the fully mechanized caving of the extremely thick seam was built.With the use of features of 22# goaf at -380 m front of Fuli Mine,corresponding assumptions on the mined-out area in extremely thick coal seam were made,and the spontaneous combustion “three zones” in mined-out area were divided,ultimately determining that the oxidation zone away from the working face was within the range of from 25 m to 60 m.According to the numerical simulation,fire prevention measures of nitrogen injection and grouting were adopted,with good effects obtained.Meanwhile,data fitting with the field data in working face was made to verify the effect of fire prevention measures.It can be better to achieve the purpose of fire prevention.

Key words: Extremely thick coal seam, Spontaneous combustion “three zones&rdquo, Numerical simulation, Data fitting