A coupled experimental and discrete numerical study of mixed-mode fracture in rock-like materials

Abstract

In rock-like materials, fractures often occur under complex stresses involving both shear (mode II) and tensile (mode I) stresses. Traditional mixed-mode fracture models typically incorporate elements related to shear components. However, recent research has indicated that a model omitting the shear component might effectively describe mixed-mode fractures, although further in-depth investigations are necessary. This study employs a discrete numerical approach to investigate mixed-mode fracture mechanisms in rock-like materials, with a specific focus on tension–compression interactions at the mesoscale, not involving shear-related terms. This approach is enhanced by integrating a reinforced or weakening compression response within a cohesive zone-like model, which allows for a more accurate representation of complex stress responses in these materials. The comparative study shows that the model can achieve high agreement with the experimental results in mixed-mode fracture tests, including load–displacement behavior, crack opening displacement (COD) determined by discrete digital image correlation (DDIC), and fracture pattern. Later, the fracture mechanism and cracking behavior are analyzed numerically, and the correctness and feasibility are verified through several complex fracture scenarios, involving tension-shear and compression-shear. The numerical model, which correlates macro-level fiber stress tensors with traditional strength criteria for bond fracturing, offers a promising numerical tool for addressing various fracture issues, particularly in complex three-dimensional scenarios.