Effective gas extraction radius of different burial depths under creep-seepage coupling

In order to study the effective gas extraction radius of different burial depths,the visco-elastic-plastic model of the surrounding coal was established,the aperture variation and effective extraction time of different burial depths were researched,the gas migration model under creep-seepage coupling was established,and the effective gas extrac-tion radius of different burial depths were determined. The results show that the effective gas extraction radius of deep coal seam is affected by the creep deformation of coal body,the decrease of permeability and the increase of gas pres-sure. The coal deformation of 400 m and 600 m depth is more gentle,and the boreholes shrinkage range is relatively smaller,still maintain a good extraction channel,all extraction time are effective extraction time,but the coal creep de-formation of 800 m depth is more intense,boreholes shrinkage rate increases rapidly,only 30 d will plug extraction channel,the effective extraction time is only 30 d. The effective gas extraction radius of 400 m,600 m and 800 m are respectively 2. 88 m,1. 62 m and 0. 82 m,the numerical results are in agreement with the field observations. The re-search results can provide the reference for the optimal layout of boreholes.