Study on the distribution of plastic zone of borehole under the combined action of slitting and fracturing

In order to accurately obtain the distribution law of plastic zone of borehole under the combined action of ultra-high pressure hydraulic slit and hydraulic fracturing, based on the unified strength theory, considering the plastic softening of coal mass and the intermediate main stress, the mechanical model of borehole under the combined action of slitting and fracturing was established, the expression of plastic zone of borehole was deduced, and through the example analysis, the influence laws of relevant parameters on the plastic zone of borehole were concluded.The results show that:after using the combined action of slitting and fracturing technology, the radius of plastic zone of borehole almost remains unchanged with the increase of the intermediate principal stress coefficient, decreases with the increase of the softening coefficient, and increases with the increase of fracturing pressure; compared with the normal drilling construction and the ultra-high pressure hydraulic cutting, the radius of the plastic zone of borehole increases significantly. The research results can provide a theoretical basis for better solving the technical problem of gas drainage and control in low permeability coal seam.The research results can provide a theoretical basis for the mine to better solve the technical problems of gas drainage and control in low permeability coal seam.