Abstract：In order to study on the influence on the aperture of bedding borehole for gas pre drainage under the mining stress,viscoelastic-plastic softening model was established around the coal borehole,and the expression formula of the borehole aperture was obtained,using the method of drilling cuttings to study on the distribution laws of the stress in the solid coal. Taking the 3103 north working face of the eight coal mine in Hebi as an example,the space-time evolution laws of the aperture of bedding borehole is analyzed in the soft and hard coal under the same mining stress. Research shows that( 1) being implemented the bedding borehole in the soft coal seam,the borehole is easy collapse at the stress concentration area in the initial,as time goes on,the borehole of the stress concentration area is gradually compacted,even in the original stress area also appeared borehole collapse,the gas drainage channels is fast destroyed which is difficult to maintain long-term and high concentration gas drainage;( 2) being implemented the bedding borehole in the hard coal seam,the aperture narrows with time,but the borehole is stable and not collapse,the gas drainage channels is smooth which can guarantee the long-term and high concentration gas drainage. So it fully considers the influence on the aperture in the specific coal seam under the mining stress,providing the basis for the stability protection of the borehole and which is very important to improve the gas drainage effect.

Keyword：mining stress;drilling cuttings;gas drainage borehole;borehole aperture;space-time evolution;