Compressive response, fragmentation characteristics and energy dissipation of red bed soft rock subjected to impact loading

In engineering, soft rock is often damaged by dynamic loads such as dynamic compaction, vibrating compaction and blasting, resulting in varying degrees of damage. To understand the compressive response, fracture characteristics and energy dissipation characteristics of red bed soft rock under different dynamics, we carried out a series of dynamic impact tests by the separated Hopkins pressure bar system. The experimental results show that the dynamic peak stress, critical strain and toughness of red bed soft rock increase with the increase in strain rate with the increase in strain rate, which ranges from 37 to 102 s⁻¹. Specifically, the dynamic compressive strength of red bed soft rock at 98 s⁻¹ is 4.63 times that of the quasi-static average. As the strain rate increases, the fracture characteristics: integrity, slightly split and pulverized, and the size of fragments decrease and the number of fragments increases. When the strain rate exceeds the critical value 72 s⁻¹, the fracture characteristics are pulverized. The energy dissipation density increases with the strain rate and increases faster when the strain rate exceeds the critical value. The energy utilization first increases and then decreases, when the strain rate is 88 s⁻¹, the maximum utilization rate is 38%.