IntroductionTo address the lack of a reliable basis for optimizing blasting parameters in deep high-stress tunnels, this study aims to investigate the evolution mechanism of blasting damage and parameter optimization under a confining pressure of 20 MPa.MethodsA numerical model of double-hole blasting coupling ground stress and charge configuration is established using ANSYS/LS-DYNA software, with the RHT constitutive model for rock and the JWL equation of state for explosives.ResultsThe results indicate that confining pressure suppresses stress wave propagation. Damage is mainly concentrated at the bottom and on both sides of the boreholes. The fragmentation zone is distributed around and between the boreholes, while the fracture zone expands along the direction of the smooth blasting layer, reflecting a synergistic fragmentation effect of “stress wave superposition and blast gas wedging”. The fracture zone volume decreases with increasing smooth blasting layer thickness and borehole spacing, whereas the peak effective stress near the blast source is inversely proportional to the borehole spacing.DiscussionThrough multi‑parameter coupled analysis, the optimal parameters are determined as a borehole spacing of 350 mm and a smooth blasting layer thickness of 400 mm. This scheme can improve energy utilization efficiency while controlling the damage range, thus providing a theoretical basis and parametric reference for smooth blasting design in deep high-stress roadways.