Deformation and damage mechanisms of Y-intersecting jointed rocks under uniaxial compression

This study systematically analyzes the influence of different combined joint dip angles on rock mass failure modes and damage mechanisms through uniaxial compression tests on granite specimens with prefabricated Y-shaped discontinuities, combined with digital speckle and acoustic emission (AE) monitoring. The results show that as the dip angle of the primary joint increases, the failure mode transitions from overall failure to wedge block ejection and shear failure. A failure mode identification model was established based on main crack dip angle thresholds (40°, 45°), uniaxial compressive strength thresholds (40, 90 MPa), and energy core zone proportion thresholds (20%, 10%), achieving an accuracy of 93.3%. In the overall failure and wedge block ejection modes, a sharp increase in shear crack ratio and a sudden drop in the acoustic emission b-value occur in the high-stress phase (>0.6σ_c), while in the shear failure mode, significant fluctuations are observed due to the shear-tension alternation, making it difficult to identify a single critical point. Additionally, joint slip in the overall failure and wedge block ejection modes primarily occurs during the failure instability phase (>0.8σ_c). These findings provide theoretical support for stability evaluation of complex fractured rock masses and practical guidance for engineering safety construction.