Dynamic characteristics and fracture process of marble under repeated impact loading

Understanding dynamic behaviours of rock materials under repeated blast loading is of great significance to evaluate stability of the surrounding rock in rock tunnel engineering. In this study, repetitive impact loading tests were conducted on marble specimens to investigate dynamic characteristics of the rock. Besides, numerical model of the SHPB test was established based on the finite element software LS-DYNA to simulate repeated impact loading for the first time, and repeated impact tests with constant and variable velocities were carried out on the rock numerically. The results show that, stress-strain relationships of the marble are sensitive to both impact velocity and impact number. As the impact velocity increases, dynamic compressive strength of the specimens increases, and the impact numbers that the specimens need to be destroyed decrease. Strain rate increases with increasing impact number under the same impact velocity. When the peak stress is below 120 % of the static strength of the rock, it will not cause severe damage in the marble specimen with fewer impact number. Fracture process of the rock could be separated into four stages: local failure on the end faces, failure in the core, rapid development of failure and slow development of failure.