Study on the Dynamic Mechanical Properties of Metamorphic Limestone under Impact Loading

To study the dynamic damage and fracture of metamorphic limestone under explosive load and the stability of the surrounding rock, the stress-strain curve, fracture morphology, and energy dissipation characteristics of metamorphic limestone in the Dahongshan mining area under different strain rates were studied by the Hopkinson pressure bar (SHPB), stress wave analysis, and fractal theory. The experimental results show that the crushing form and degree are significantly affected by the loading strain rate. There are several typical failure modes. When the strain rate is 17.56 s(-1), there is no obvious failure except corner cracks. When the strain rate is between 26.92 s(-1) and 56.18 s(-1), the failure mode of the specimen is axial splitting failure, and when the strain rate is 67.34 s(-1), splitting and shearing failure occur. With the increase of the strain rate, the growth rate of the dynamic compressive strength slows down. Compared with static compressive strength, the strength factor increases from 1.15 to 4.19. Also, the fractal dimension shows a gentle increase. When D-f is in the range of 1.82 similar to 2.24, there is a sudden change in fragmentation when the strain rate is in the range of 34.70 s(-1) similar to 56.18 s(-1). Energy dissipation density increases logarithmically with the strain rate. The results reveal the dynamic breaking and energy consumption laws of metamorphic limestone under impact loads with different strain rates and could provide some reference value for the safe and efficient construction in the Dahongshan mining area and similar engineering projects.