A novel experimental study on impact tendency of real time borehole coal samples under lateral constrained compression

The impact tendency of coal is a necessary condition for the occurrence of pressure bumping and a measure of the degree of damage. Through the combination of self-made lateral restraint device and high-speed camera, the variation law and failure mode of burst tendency index of coal samples under real-time drilling and pressure relief of lateral restraint under different loads were studied. The results show that: (1) With the increase of real-time drilling load under lateral constraints, the burst tendency index of coal samples changes. (2) The failure order of coal samples is as follows: the corner coal flakes peel off and pulverized coal is sprayed out, cracks and deformations are generated around the borehole, and finally the coal flakes peel off and the cracks penetrate to cause large-area damage of the coal samples. At the same time, the internal energy of the coal samples is released through borehole, which significantly reduces the damage of the coal samples. (3) The lateral restraint device makes the coal samples always in a stable state before and after drilling, resulting in the weakening effect of the burst tendency of the coal sample is not significant, and the pressure relief effect is not obvious. The research results can provide new ideas and methods for drilling and pressure relief test, and also provide basis and guidance for the prevention of pressure bumping in coal mines.