Cracking behavior of concrete/rock bi-material specimens containing a parallel flaw pair under compression

Crack propagation and coalescence of pre-existing flaws in concrete/rock bi-material are critical for stability assessments of rock/concrete structures. A hybrid finite-discrete element method (FDEM) was used to simulate the cracking behavior of the concrete/rock bi-material containing a parallel flaw pair under compression. The model was validated by physical tests. The results indicate that the crack evolution does not occur synchronously in the concrete and rock layers. The cracks in the different material layers penetrate the interface and coalesce at lower interface dip angles, whereas an interface crack always forms at higher interface dip angles, preventing crack coalescence in different material layers. A threshold of the strength ratio exists and determines whether the cracks in different material layers coalesce. If the strength ratio is lower than the threshold, the crack propa-gations are limited to one material due to the interface crack. If the strength ratio exceeds the threshold, the cracks in the different materials penetrate the interface and coalesce. Two critical values of the interface reduction coefficient exist for a given interface dip angle. The cracking pattern of the bi-material can be classified into cracking along the interface, local cracking in the different materials, and crack coalescence in different materials.