Application of mechanical cavitation enhancement technology in gas extraction of coal seam drilling

In or der to effectively solve the problem of low gas extraction efficiency when drilling coal seam in coal roa dway construction, the coal rock mass aroun d the coal roa dway is divi de d into "three zones" un der the effect of stress. Consi dering the characteristics of poor gas permeability an d low permeability of coal bo dy deep in the drilling, the mechanical reaming an d cavitation metho d in the hole is a dopte d to carry out the test.The average gas extraction ra dius of the borehole was increase d by 2.4 times, an d the extraction ra dius can reach 3.7m at 300 days.The gas extraction concentration in the 30 d cycle decays from 97.62% at the peak to 60.55%, an d from 51.77% to 23.69% compare d with the normal drilling, which was still in the state of high concentration extraction.In terms of gas extraction purity in dex, the former was 80.04～31.59 m³/d, the latter is 45.7～11.28 m³/d, an d the extraction effect has obvious technical a dvantages.