Insights into fracture modes of 3D sand-printed rock-like models with T-shaped crossed fissures

Crossed fissures or faults in rock masses markedly affect fracture and failure modes, directly impacting rock engineering safety. However, research on their effects remains limited. This study employed 3D sand printing technology to fabricate rock-like samples with T-shaped crossed fissures at varying intersection angles (α) and orthogonal T-shaped crossed fissures at different inclination angles (β). Uniaxial compression fracture tests, employing Digital Image Correlation (DIC) technology, were conducted alongside numerical simulations using an improved Smoothed Particle Hydrodynamics (SPH) method to investigate the effects of fissure properties on rock masses fracture modes and mechanical behavior. The numerical approach was validated through comparison with experimental results. Findings revealed that for larger α values (α = 90° and α = 75°), tensile cracks initially formed near the primary fissure midpoint or secondary fissure lower end, followed by shear or mixed cracks at both ends of the primary fissure. As α decreased (α = 60°, 45°, 30°), the primary fissure’s tensile crack initiation point gradually shifted to the right end, while the shear crack at the primary fissure’s right end disappeared, and a shear crack formed at the secondary fissure lower end. Additionally, with increasing β (0°–15°, 30°, 45°, 60°), the tensile or mixed crack initiation point at the primary fissure shifted rightward, the crack initiation priority between the primary and secondary fissures changed, and shear or mixed cracks at the primary fissure right end became progressively “shielded”, while new shear cracks formed at the secondary fissure lower end. Furthermore, as α decreased from 90° to 30° and β increased from 0° to 60°, the peak strength of T-shaped crossed fissure samples declined. Finally, the study provided a detailed discussion on the influence of T-shaped crossed fissure properties (α and β) on crack initiation, emphasizing their role in stress concentration redistribution. These findings enhance the understanding of how crossed fissures govern rock mass failure modes and demonstrate the applicability of SPH in revealing potential failure mechanisms in rock structures.