Evolution Law of Stress Field and Pressure Relief Effect of Coal Seam After Drilling

As an effective means of coal burst prevention, large-diameter drilling pressure relief technology have been widely used in coal burst mines in China. Engineering practice shows that drilling pressure relief has obvious time-effect. Through the establishment of drilling pressure relief numerical model, the evolution law of stress field and plastic zone in different periods after drilling was studied. The evolution of the pressure relief effect of large-diameter borehole is closely related to the development degree of cracks around the borehole. The stress transfer process after drilling can be divided into the pressure relief beginning stage, rapid pressure relief stage, and pressure stable stage. The pressure relief time effect is affected by borehole parameters. When the diameter increases from 100 to 250 mm, the time required for the stress transfer process is reduced by 50%. When the borehole spacing is reduced from 2 to 0.5 m, the time required for the stress transfer process is reduced by 33.3%. Changing the borehole depth has no significant effect on the stress transfer rate. Therefore, in the coal burst risk roadway, pre-relief should be carried out to leave sufficient time for large-diameter boreholes to make pressure relief work.