Phyllite, characterized by well-developed foliation, is a low-grade metamorphic rock. This study offers a comprehensive investigation into its failure patterns and micro-fracture classifications when subjected to Brazilian splitting tests, combining experimental observations and numerical simulations. The analysis includes interpreting AE signals in various contexts, highlighting two distinct failure modes based on the foliation-loading angles, and revealing the emergence of an M-shaped brittleness tendency as \(\theta\) increases. Micro-crack classification is achieved through frequency band and spectrum analysis, culminating in deriving the formula \(AF = 116.565 \times RA + 80.146\) , which furnishes a detailed understanding of crack development. Utilizing the PFC3D software, sensitivity analyses are conducted to investigate the influence of joint parameters on failure strengths, damage patterns, and micro-crack progression within this transverse isotropy rock. Key findings include the observation that shear strength enhancement tends to shift the rock from a layer-activated fracture pattern to mixed and central damage patterns and amplifies the impact of \(\theta\) at larger angular intervals on failure strength. Stiffness strengthening is found to significantly inhibit rock matrix cracking, particularly at smaller foliation-loading angles, while the influence of friction coefficients is deemed negligible. These insights into Phyllite damage mechanisms and behaviors contribute to the design and assessment of structures in stratified strata, offering valuable guidance for enhancing stability and safety.
