Performance and damage assessment of fault-crossing road tunnel subjected to internal boiling liquid expanding vapor explosion (BLEVE)

Road tunnels constructed in complex rock strata may encounter unfavourable geological formations such as rock faults. Grouting into rock faults around road tunnels or installing flexible joints for tunnel structures have been widely used in engineering practice to improve the performance of fault-crossing road tunnels against static and seismic loads. However, flexible joints with low stiffness and likely low strength may be subjected to direct explosion loads and their performance in resisting blast loads has not been investigated. In this study, the resistance of a typical fault-crossing road tunnel to an internal Boiling Liquid Expansion Vapour Explosion (BLEVE) caused by the rupture of a 20 m³ Liquified Petroleum Gas (LPG) tank is numerically investigated. The response and residual load-bearing capacity of the fault-crossing road tunnel with and without the grouting and rubber joints under the internal BLEVE are calculated and compared. It is found that the combined measures greatly enhance the BLEVE resistance of the fault-crossing road tunnel due to the fact that grouting greatly improves the mechanical properties of the fault-affected rock mass, and the rubber joints significantly attenuate the BLEVE-induced stress wave propagation inside the tunnel lining. In addition, parametric analyses are conducted to investigate the effects of the grouting and rubber joint configurations on the BLEVE resistance of the fault-crossing road tunnel. Damage criteria considering the tunnel’s residual load-bearing capacity (RLBC) are also established to evaluate the collapse risk and potential collapse zone of the fault-crossing road tunnel after being exposed to internal BLEVE. The results show that the potential collapse zones of the fault-crossing road tunnel along the longitudinal direction of the tunnel can be effectively reduced by increasing grouting thicknesses and installing narrower rubber joints.