Effects of Cover Depth and Rock Type on Dynamic Response of Road Tunnels Against Internal Explosions

Dynamic response of road tunnels against internal explosions can vary depending on the types and cover depths of surrounding rock mass. However, the influences of cover depth and rock type on dynamic response of road tunnels under internal explosions are very less investigated. Based on the calibrated numerical model of road tunnel, the present study investigates the dynamic response of an arched road tunnel subjected to an internal Boiling Liquid Expansion Vapour Explosion (BLEVE) and its equivalent TNT explosion under varied cover depths and different rock types. The results indicate that the increment of the cover depth can reduce the lining response (e.g., strain energy and damage) against the internal BLEVE. However, beyond a certain cover depth, the TNT explosion-induced lining response (e.g., strain energy) escalates with the increased cover depth due to the enlarged rebound deformations of the lining with the increased in-situ stress. In addition, the rock mass with better mechanical properties is beneficial to reduce the tunnel response under the internal BLEVE but leads to more severe tunnel response under the internal TNT explosion. Using equivalent TNT explosion loads may not give reliable predictions of tunnel responses subjected to BLEVE loads.