Influence of unloading-induced brittle damage on laboratory properties and behavior of hard rocks: Insights from the hybrid Finite-Discrete Element Method (FDEM)

• Published in: Computers and geotechnics 2024-12, Vol.176, p.106766, Article 106766
• Main Authors: Amiri, Fatemeh, Bahrani, Navid, Lisjak, Andrea, Mahabadi, Omid, Ha, Johnson, Li, Yalin
• Format: Article
• Language: English
• Subjects: Core damage; Heterogeneity; Micro-cracks; Stress path; Voronoi blocks, Finite-Discrete Element Method (FDEM)
• ISSN: 0266-352X
• DOI: 10.1016/j.compgeo.2024.106766

It is known that rock cores drilled from high-stress environments experience a complex stress path. The induced tensile stresses within the cores may result in the formation of micro-cracks, potentially leading to incorrect estimation of their laboratory properties. In this research, the influence of coring stress path on damage formation and the consequent changes in the laboratory properties of intact rocks were investigated using a 2D numerical program based on the hybrid Finite-Discrete Element Method. For this purpose, two models with distinct grain geometries (triangular and Voronoi) were generated. They were initially calibrated against the laboratory properties of the undamaged Lac de Bonnet granite. The calibrated models were then subjected to a coring stress path to generate damage in the form of micro-cracks. The calibration process also involved the laboratory properties of damaged granite, focusing on capturing the nonlinearity in the stress–strain response due to crack closure during uniaxial loading. It was concluded that both models can effectively capture the formation and opening of micro-cracks during unloading, their closure during compressive loading, and the nonlinearity in the stress–strain response. However, the model with Voronoi grains more accurately represented the reduction in peak strength and Young’s modulus resulting from unloading-induced damage.