Performance of road tunnel subjected to BLEVE occurring inside adjacent tunnel

Abstract

Twin tunnel is a common and popular type of road tunnel. The safety of twin tunnel (i.e. with left and right branches) subjected to Boiling Liquid Expansion Vapour Explosions (BLEVEs) is important but less investigated in open literature. The present study numerically investigates the dynamic response of right branch of a twin-arched-tunnel subjected to a BLEVE with a 20 m3 Liquified Petroleum Gas tanker occurring inside the left branch by using LS-DYNA. The BLEVE loads and the model of tunnel lining and rock mass subjected to blast loading have been calibrated by the authors in earlier studies. Based on the calibrated numerical model, the response of right branch of the twin-tunnel due to stress waves caused by the BLEVE occurring inside the left branch is first compared with that of the equivalent TNT explosion. It is found that the lining damage of the right branch under BLEVE-induced stress waves can be underestimated by using the TNT equivalence method. In addition, the influences of tunnel cover depths, twin-tunnel separation distances, rock types around tunnels, and concrete strengths of tunnel lining on the dynamic response of the right branch of twin-tunnel against BLEVE-induced stress waves are investigated. Compared to enhancing the concrete strength, increasing the twin-tunnel separation distance is more effective to reduce the damage of the tunnel surrounded by the rock mass with weak mechanical properties under BLEVE-induced stress waves. In addition, empirical formulae for prediction of the PPV and tensile stress on adjacent tunnel surface induced by BLEVE are proposed, which can be used for the determination of the safe separation distance between the twin tunnels against accidental BLEVE loads.