Influence of dynamic disturbance on coal-rock damage under local static load constraints

Abstract:

To obtain the influence characteristics of cyclic impact loading on coal-rock damage under local static load constraints, we studied the damage factors and crack evolution of coal-rock samples during constant impulse cyclic impact and incremental impulse cyclic impact under local static load constraints by using the self-developed constrained pendulum-impact dynamic loading device. Experimental results show that when the constrained zone was in an elastic state, the partition with larger static load restraint area had stronger impact resistance; when the constrained zone was in a plastic state, the partition with larger static load restraint area had weaker impact resistance. The incremental impulse cyclic impact had higher damage efficiency to coal-rock than the constant impulse cyclic impact. The difference in rock breaking efficiency between the two cyclic impact methods was mainly reflected in the static load constrained zone, and the greater the static load value was, the higher the sensitivity of the damage factor to the impact method was. The crack propagation on the coal-rock surface was consistent with the zoning characteristics of the damage factor. When the static load constrained zone was in an elastic state, the static load had an inhibitory effect on the crack growth, and the cracks mainly expanded and derived along the partitions that were less constrained. When the static load constrained zone was in a plastic state, the cracks mainly propagated in the partitions that were more constrained, and tensile cracks in vertical direction were dominant in the constrained zone, while the cracks in the non-constrained zone mostly grew in an oblique direction. As the static load value increased, the fractal dimension of the surface cracks on the sample decreased first and then increased. The local static load constraints improved the impact resistance of coal-rock, and the damage factor of coal-rock showed obvious zoning characteristics.