Gas drainage in seam with large auto variable diameter bore holes

Base in the mechanism in the plasticity zone of the borehole, the application of the conventional drilling rig and auto variable diameter boreholes drilling tools to the large diameter borehole drilling in seam with coal and gas outburst in potential has solved the coal and gas outburst occurred in the large diameter borehole drilling in seam with coal and gas outburst in potential. In the comparison with the gas drainage results, the test results showed that the effective gas drainage radius of the large diameter borehole was 1.84 times higher than the conventional borehole and the gas drainage value was improved by 1.58 times.