Mechanical Behavior and Failure of Pre-Existing Crack Rock Under Compression and Creep: Experimental and Numerical Insights

Understanding the mechanical behavior of pre-cracked rock masses is essential for assessing geohazards in deep mining. This study combines laboratory experiments and numerical modeling to investigate the effects of double-crack inclination angles on the strength, crack evolution, and creep behavior of sandstone. Uniaxial compression and multi-stage creep tests were conducted on red sandstone specimens with a fixed crack 1 (60°) and a crack 2 varying from 0° to 150°. A UDEC-Voronoi grain-based model was calibrated against experimental results. The results show that uniaxial compressive strength varies non-linearly with crack angle, reaching a minimum at 30° and a maximum at 90°. Tensile microcracks dominate the failure process (>90%), while shear cracks play a minor role. Under creep loading (70–95% of peak strength), creep lifetime decreases sharply with increasing stress, and microcrack accumulation follows three distinct phases: decelerating, steady-state, and accelerating creep. The numerical model successfully reproduces the observed strength anisotropy, crack patterns, and time-dependent deformation. These findings highlight the critical role of crack inclination in controlling rock mass instability and provide a validated modeling approach for long-term geohazard assessment in fractured rock environments.