<p>Although rock mass structure exerts a critical influence on blasting outcomes, current research efforts remain predominantly focused on blasting within homogeneous rock masses of uniform properties. Much less attention has been paid to the inherent influence of complex geological formations, such as interbedded rock masses. This study employs the Particle Expansion Method to investigate how interbedding affects blasting through multiple aspects: reflected stress evolution, crack propagation patterns, and contact force dynamics. The results indicate that both the blasting environment and layer thickness exert considerable influence on blasting effectiveness, whereas the interlayer angle has minimal impact. This finding is consistent with experimental blasting results. Specifically, in hard rock environments, reflected stress initially increases and then attenuates with greater layer thickness, and the average contact force converges under larger thicknesses. In soft rock environments, reflected stress shows little variation with thickness, but crack propagation changes significantly even at small layer thicknesses, with contact forces stabilizing early under thin-layer conditions.</p>