Controlled blasting technology for high in-situ stress and biased pressure tunnels: research and application

High deviatoric stress severely challenges safe and efficient excavation. Following the principle of 'disaster mitigation by blasting', this study optimizes blasting parameters for deep buried bias-pressure roadways through integrated theoretical analysis, numerical simulation, and field tests, the blasting parameters for deep buried bias pressure roadways were optimized. An analytical solution for the second invariant of deviatoric stress (J₂) was derived to reveal stress distribution patterns for lateral pressure coefficients k ranging from 0.6 to 3.0. This study proposes a combined initiation strategy-simultaneous blasting on the non-deviatoric side and hole-by-hole delayed blasting on the deviatoric side-to mitigate asymmetric collapse in deep roadways under high deviatoric stress. Through theoretical derivation, numerical simulation, and field tests, the optimal blasthole spacing is determined to be 600 mm, and a 5 ms inter-hole delay is adopted. The results show that the optimized scheme increases the half-hole ratio by 54.5% and reduces vibration velocity by 78.3%.The study indicates that the proposed optimization scheme provides a theoretical basis and practical guidance for optimizing blasting parameters, enhancing surrounding rock stability, and improving construction safety in deep-buried, high-geostress, deviatoric stress tunnels.