Research on the Effective Influence Radius of Hydraulic Reaming in Mining Seam

According to the present situations that the construction amount of the gas drainage boreholes in mining seam is large and the gas drainage effect in low permeability coal seams doesn’t yield perfect, the hydraulic reaming technology in mining seam is proposed to increase the gas drainage efficiency. Through the gas flow method, the effective influence radius of hydraulic reaming is determined. And the fluid-solid coupling model of gas drainage along boreholes after hydraulic reaming is established theoretically. Then the change laws of gas content around the boreholes in the coal seam are simulated and analyzed. The results indicate that hydraulic reaming can effectively promote the stress-relief and permeability-increase of the coal mass around the boreholes, and the coal mass around the reaming boreholes can be divided into gas flow increase zone, gas flow delay attenuation zone and fast decay zone. The effective influence radius of hydraulic reaming is 5.5~6 m. The simulation results are basically in accordance with the field investigation.