Study on rock breaking characteristics of stress wave and blast-induced gas during CO2 gas blasting

Abstract

To further distinguish the rock breaking mechanism of stress wave and blast-induced gas, and instruct the application of CO2 gas blasting technology in deep coal seam. In this work, the stress distribution on the surface of coal-rock is obtained by introducing the stress intensity factor into the orifice stress concentration equation; moreover, the internal relationship among the stress wave energy, the blast-induced gas energy and the surface stress of coal-rock is described by work-energy principle. The equation set of rock breaking characteristics under CO2 gas blasting is then established. Meanwhile, the stress and ultrasonic characteristics of samples while gas blasting are obtained by utilizing the self-developed CO2 gas blasting experimental platform. Ultimately, the consistency between the experimental results and the theoretical analysis is verified by comparative discussion. The results show that the closer the intensity factor of horizontal stress (Kx) and the intensity factor of vertical stress (Ky) are, the easier the cracking of coal-rock is. When the crack initiation angle is 45° and 225°, Kx is equivalent to Ky and the crack propagation is deepest. Under the synergistic effect of blast-induced gas that is positively correlated with stress, the attenuation coefficient and the stress will reach the maximum in the same period, and the rock breaking effect of stress wave is the strongest in this period. During blasting, the double-peak of ultrasonic is a non-accidental phenomenon, which reflected the accelerated accumulation of coal-rock internal energy under the synergy of blast-induced gas.