Calculation of BLEVE energy and overpressures inside a tunnel using analytical and CFD methods

Abstract

Nowadays, more and more road tunnels have been constructed to cope with the transportation demands due to population growth and rapid economic development. Meanwhile, increasingly more Boiling Liquid Expanding Vapour Explosions (BLEVE) accidents have been reported, some of which occurred inside tunnels. The effect of BLEVE on tunnel structures, which may lead to catastrophic tunnel structural failure, has been rarely investigated and is not explicitly considered in the design and construction of road tunnels. In the tunnel engineering industry, the equivalent-TNT method is commonly used to predict accidental explosion loads. However, such an empirical method may not give good predictions of explosion loads due to the lack of consideration of the BLEVE mechanism, which may lead to unsafe or uneconomic designs of tunnel structures against BLEVE load. In this study, the energy-based analytical method and Computational Fluid Dynamics (CFD) simulation are used for more accurate BLEVE pressure prediction, which makes the more reliable assessment of BLEVE effects on tunnel structures become possible. The detailed procedure of BLEVE pressure prediction is provided, which compensates for the incapacity of the ANN method proposed in a previous study for large-scale BLEVE pressure calculation inside a tunnel. The analytically determined tank rupture pressures are utilized as input data in CFD simulations. The explosion wave propagation and reflection inside tunnels are also modelled in explosion load calculation. Twelve BLEVE and tunnel conditions are considered in numerical simulations. Data consisting of 360 peak incident pressures, 360 reflected pressures, and 360 reflected pressure wave velocities are extracted from CFD simulations. Two correlations representing the best-fitted results are derived for the reflected pressure calculation on tunnel walls. The incorporated analytical and CFD methods suggested in this study provide tunnel engineers meaningful guidelines to calculate the initial BLEVE energies, tank rupture pressures, peak incident and reflected pressures on tunnel walls.