Experimental Study on the Effect of Hydraulic Fracturing on the Stress of Coal Seam

In order to study the variation law of water injection pressure and surrounding coal seam stress during hydraulic fracturing, the experiments simulation with similar materials were carried out in the laboratory. The results showed that the increase of the injection pressure and the rupture velocity of coal body are affected by crustal stress.The greater the crustal stress, the greater the water injection pressure, the slower the rupture velocity of coal body.Pressure relief range of drilling hydraulic fracturing test is within a circular area with a radius of 75 mm which taking the water injection hole as the center, the stress of coal body is transferred to the deep direction after water injection; the fracture is divided into three grades that centered on hydraulic fracturing hole and extended along the radius.The fracture is the largest within the circular area with a radius of 40 mm, followed by that of the circular area with a radius from 40 mm to 65 mm, and it is the smallest when the area with a radius from 65 mm to 80 mm.According to the experimental results, the field application was carried out within 200 m area of cutting hole in the 40201 working face of Xiaozhuang Coal Mine, the concentrations of gas extraction increase by 20% compared to conventional extraction, the gas flow rate of borehole extraction is 40% higher than that of conventional extraction.