Mechanical Behaviour and Failure Characteristics of Heterogeneous Conglomerate: Insights from Numerical Analysis

As a heterogeneous rock cemented by gravel and matrix, understanding the mechanical behaviour and failure mechanism of conglomerate is of great significance for engineering projects. A three-dimensional grain-based model (3D-GBM) incorporating both microstructural and material heterogeneity of conglomerate is developed based on particle flow code (PFC3D). With the model’s rationality and microscopic parameters validated, the failure process and fracture mechanism of conglomerate under uniaxial and triaxial compression are numerically investigated. The numerical results reveal that the established 3D-GBM can simulate the mechanical behaviour and fracture characteristics of conglomerate. As the confining pressure increases, the failure mode of the specimen transitions from matrix tensile cracking to matrix shear cracking. During the loading process, the microcrack evolution and contact force distribution in the gravel, matrix, and cementation area exhibit pronounced heterogeneity. Confining pressure promotes the fragmentation of gravel and the initiation of shear microcracks. In addition, the effect of gravel size and content on the mechanical behaviour and microcracking characteristics of conglomerate is quantitatively investigated. Variations in gravel size and content influence the distribution of inter-particle contact forces, thereby altering the failure characteristics and mechanical properties of the specimen.