Investigation of the Dynamic Pure-Mode-II Fracture Initiation and Propagation of Rock during Four-Point Bending Test Using Hybrid Finite–Discrete Element Method

Abstract

A hybrid finite–discrete element method (FDEM) is proposed to investigate dynamic pure-mode-II fracture behaviors. The transition of continuum to discontinuum was applied to the FDEM through the use of three fracture modes, so that the whole fracture process could be modeled naturally. The FDEM was then employed to model the dynamic pure-mode-II fracture behavior of rock during a four-point bending test with a prefabricated notch. The results showed that the fracture initiated from the tip of the prefabricated notch under a relatively lower loading rate, i.e., 1 m/s and 5 m/s. However, when the loading rate reached higher levels, i.e., 10 m/s and 50 m/s, the prefabricated notch played a small role in the fracture patterns. Under these conditions, the fracture initiated from the center of the beam bottom or the stress concentration vicinity, instead of the tip of the prefabricated notch. Regardless of the loading rate, the obtained force-loading displacement curves showed a typical brittle material failure process. Additionally, by incorporating the empirical correlation between the static and dynamic strengths obtained from the dynamic rock fracture tests, the hybrid finite–discrete element method could effectively reflect the impact of the loading rate on the strength of the rock. To conclude, the hybrid finite–discrete element method is an effective instrument to investigate the fracture initiation and propagation of rock, since it can both naturally simulate the process of rock fracture and capture the effect of the loading rate on the rock behaviors.

FDEM numerical study of the influence law of geostress on state and pressure of tunnel surrounding rock

“…The correctness and effectiveness of FDEM have been confirmed through laboratory and engineering scale simulations. FDEM has been widely applied in various fields including tunnel excavation (Lisjak et al, 2014;Lisjak et al, 2015a) and support (Lisjak et al, 2015b), surrounding rock reinforcement (Liu et al, 2019), slope stability analysis (Zhong et al, 2022), hydraulic fracturing (Yan and Zheng, 2017a;Yan and Zheng, 2017b), rock fracture acoustic emission (Lisjak et al, 2013;Zhao et al, 2015), complex rock block modeling (Yan et al, 2015), uniaxial compression (An et al, 2022), triaxial compression (Song et al, 2022), Brazilian splitting (Zhang et al, 2021), direct shear test (Min et al, 2020), rock thermal failure (Yan and Zheng, 2017c) and blasting failure (Trivino and Mohanty, 2015). However, the application of FDEM in studying surrounding rock pressure is still limited.…”