Strength and failure characteristics of hard rock containing a single structural plane under varied loading angles: A true triaxial investigation

• Peak strength of hard rock with a structural plane decreases with loading angle β up to 45°, then stabilizes; intermediate principal stress angle ω has a strengthening effect. • Deformation is predominantly post-peak, with strains ε1 and ε3 2–3 times higher than intact rock, highlighting brittle-ductile transition under true triaxial stress. • Failure mode is strongly controlled by the structural plane when ω=0°, while at ω=90° failure localizes near the σ3 surface, indicating distinct anisotropic failure mechanisms. • Provides critical experimental data for deep rock engineering, aiding design of excavation and support systems in structurally controlled high-stress environments.