Experimental study on the impact disturbance damage of weakly cemented rock based on fractal characteristics and energy dissipation regulation

Abstract

In geotechnical engineering construction, the surrounding rock is often disturbed by dynamic loads such as blasting and earthquakes, resulting in varying degrees of disturbance damage. To study the fracture fractal characteristics and energy dissipation law of different dynamic disturbance-damaged rock masses were subjected to the same failure impact. A series of laboratory tests were carried out by means of a split Hopkinson pressure bar system. Firstly, the disturbance impact test was carried out and the test variables were impact velocity (including high-velocity impact in the velocity range of 1.65 m/s and low-velocity impact in the velocity range of 1.27 m/s) and cycle impact times. Based on the disturbance impact test, the failure impact test with the same velocity (with an average velocity of 3.2 m/s) was carried out to study the relationship between the fractal characteristics of fragmentation and energy dissipation. The results show that the macro damage (crack propagation, edge fracture, and surface particle detachment) increases with the increase of disturbance times. At the same time, after the impact of low-velocity disturbance, the fragments of disturbed specimens have larger fractal dimensions than those of undisturbed and high-velocity disturbed specimens. This indicates that low-velocity impact may produce internal damage that cannot be easily observed directly. The energy dissipation law shows that the high-velocity disturbance impact specimens have higher reflection energy and transmission energy than the low-velocity impact specimens. The regulation and rates of dissipated energy and energy dissipation density are, on the contrary, indicating that the energy utilization rate of the specimen is higher under the impact of low-velocity disturbance. Under the dynamic stress disturbance, the final fracture fractal dimension of the specimen is negatively correlated with the reflected energy during the disturbance impact and positively correlated with the dissipation energy and dissipation energy density. Finally, the meso failure mechanism of weakly cemented red sandstone, subject to disturbance, was analysed based on SEM photos of debris.