Particle-Based Investigation of Damage Evolution and Mechanical Response of Inclined Rock Pillars under Uniaxial Compression

: This study investigates the damage mechanisms and mechanical behavior of inclined rock pillars relevant to the assessment of structural stability through integrated experimental and computational approaches. Gypsum specimens with varying dimensions and inclination angles were fabricated on concrete bases and subjected to uniaxial compressive loading. Following the calibration of particle-based numerical models for both gypsum and concrete, three-dimensional pillar models with identical geometries were developed and subjected to axial loading at a controlled rate. Three distinct damage evolution mechanisms were identified. The first mechanism involves wedge-shaped damage along the pillar walls, resulting in an hourglass-shaped intact core, in which tensile and shear cracks initiate at the pillar boundaries, propagate obliquely, and coalesce to form wedge-shaped damage zones. The second mechanism involves splitting tensile cracks that initiate near the pillar walls and propagate parallel to the pillar axis. The third mechanism comprises mixed tensile–shear damage that develops obliquely at approximately 60° to the longitudinal axis. Parametric computational analysis reveals that increasing pillar height at a constant width promotes inclined shear failure, whereas increasing pillar width at a constant height favors wedge-shaped damage. Decreasing pillar width or increasing pillar height results in reductions in both elastic modulus and compressive strength. Notably, increasing the inclination angle of pillars with identical dimensions enhances both stiffness and strength. These findings provide mechanics-based computational insights into damage evolution and failure progression in inclined pillars, with practical implications for the structural design and stability assessment of underground excavations.