The influence of circular cavity on the characteristics of dynamic crack propagation in rocks using a single notch triangle approach

Abstract

We used a novel single-notch triangle (SNT) sample to conduct dynamic fracture tests and investigate the effect of a circular cavity on the dynamic fracture mechanisms that occur in fractured rock masses subjected to a single crack under dynamic loads. Dynamical loads were applied with a drop hammer weight device. A modified finite difference method code was developed to simulate the dynamic cracking behavior of SNT samples under the action of impact loading. Next, we calculated the maximum principal stress and circumferential stress around the circular cavity and investigated dynamic crack initiation toughness (DCIT) by applying both experimental and numerical approaches. We also investigated the mechanisms that occur in the circular cavity with regards to the initiation of dynamic cracking and the cracking behavior by applying numerical models. Analysis demonstrated that the circular cavity promotes cracking initiation behavior and that the most significant impact was detected at a horizontal offset distance of 15 mm. Furthermore, the crack initiation time and DCIT were used effectively to evaluate the dynamic stability of cracks. However, the DCIT is accurate parameter for investigating how a mass of fractured rock changes according to different dynamic loads. We found that the roughness of the fractured surface around the crack tip was more significant than that of the fractured surface behind the circular cavity; this demonstrated that the circular cavity enhanced the energy consumed during crack propagation.