Damage mechanism of jointed granite under high strain rate impact loading

To study the dynamic response characteristics and energy evolution of through-jointed granite under impact load, granite with different dip joints was selected as the research object. Using the theoretical model of damage mechanics for jointed rock masses with varying dip angles, a series of SHPB (split Hopkinson pressure bar) impact tests was conducted on granite samples under high strain rates. The dynamic mechanical properties and energy dissipation characteristics of the rock samples were obtained. The results indicate that: (1) based on the Druck-Prager criterion, the Weibull strength distribution criterion, and the theory of elastic waves, the stress-strain model of jointed rock mass with different dip angles is established. This model can effectively reflect the dynamic mechanical properties of granite as the joint dip angle changes and exhibits a strong dip effect. (2) As the dip angle of the joints increases, the energy reflection coefficient rises linearly, the energy transmission coefficient decreases linearly, and the peak stress of the rock samples gradually decreases. Under the same joint dip angle, as the impact load increases, the energy reflection coefficient first increases and then decreases, the energy transmission coefficient first decreases and then increases, and the energy absorption rate decreases with the increase of the joint dip angle. (3) When the impact load is the same, the fragmentation degree of intact rock samples and those with joint dip angles of 0° and 15° is greater, while the fragmentation degree of rock samples with joint dip angles of 30° and 45° is smaller. When the joint dip angle is the same, as the impact load increases and exceeds the maximum compressive strength of the rock samples, the failure mode gradually transitions from shear and tensile failure to crushing failure, and the degree of fragmentation also increases.