Numerical investigation on damage characteristics of surrounding rocks in the deep underground tunnel subjected to full-face smooth blasting

Rocks in deep geological settings are subjected to elevated in-situ stresses, and blasting excavation often induces significant damage to the surrounding rock mass, thereby complicating its stability assessment and support design. This damage may undermine the stability assessment and support design of tunnels. Therefore, it is crucial to characterize the nature of blasting-induced damage in tunnel surrounding rocks under high in-situ stress conditions. In light of this, this study employs the LS-DYNA software coupled with a fluid-structure interaction algorithm to simulate full-face smooth blasting excavation in tunnels, accounting for scenarios both with and without in-situ stress. This study examines the excavation-induced destruction in the three-dimensional profile of tunnels and investigates the influence of in-situ stress on rock damage zoning, aiming to reveal the failure patterns of the surrounding rock in deeply buried tunnels. Furthermore, the Basic Quality Index (BQ) of the rock mass is used as a classification criterion to evaluate the impact of blasting-induced damage on the surrounding rock of the tunnel, and the influence of such damage on rock mass classification is discussed. The results indicate that ground stress substantially limits the depth of blasting-induced damage in the surrounding rock. Additionally, the study classifies the intact surrounding rock into five categories based on the severity of blasting damage, with ground stress playing a pivotal role in the evolution of each class of surrounding rock areas. The findings of this study offer theoretical underpinnings for assessing the safety and stability of deep tunnel surrounding rocks and for developing disaster prevention strategies.