Mechanics and fracture behavior of rocks with triangular holes: experimental and numerical studies

The mechanical behavior of rock masses is significantly influenced by the presence of internal holes. This study investigates these effects through uniaxial compression tests and two-dimensional Particle Flow Code (PFC2D) numerical simulations on sandstone samples containing triangular holes with varying apex angles. The results reveal a distinct “W” pattern in both peak strength and elastic modulus as the apex angle increases. For holes with angles less than 60°, cracks preferentially initiated at the apex and propagated along the AB side. In contrast, angles of 60° or greater resulted in crack initiation at the base corners, with damage concentrating along the BC side. This behavior underscores the combined influence of hole area and angular geometry on the strength of the specimens. Acoustic emission monitoring during testing enabled the definition of a damage variable, which was subsequently used to develop a constitutive model based on the Duncan model. The proposed model effectively captures the distinct stages in the stress–strain curves, demonstrating both accuracy and practical relevance.