Double-arch tunnels,as one of the popular forms of tunnels,might be exposed to boiling liquid expanding vapour explosions(BLEVEs)associated with transported liquified petroleum gas(LPG),which could cause damage to the tunnel and even catastrophic collapse of the tunnel in extreme cases.However,very limited study has investigated the performance of double-arch tunnels when exposed to internal BLEVEs and in most analyses of tunnel responses to accidental explosions.The TNT-equivalence method was used to approximate the explosion load,which may lead to inaccurate tunnel response predictions.This study numerically investigates the response of typical double-arch tunnels to an internal BLEVE resulting from the instantaneous rupture of a 20 m^(3) LPG tank.Effects of various factors,including in-situ stresses,BLEVE locations,and lining configurations on tunnel responses are examined.The results show that the double-arch tunnels at their early-operation ages are more vulnerable to severe damage when exposed to the BLEVE due to the low action of in-situ stress of rock mass on the response of early-age tunnels.It is also found that directing the LPG tank to different driving lanes inside tunnels can affect the BLEVE-induced tunnel response more significantly than varying the configurations of tunnel lining.Moreover,installing section-steel arches in the mid-wall can effectively improve the blast resistance of the double-arch tunnels against the internal BLEVE.In addition,the prediction models based on multi-variate nonlinear regressions and machine learning methods are developed to predict the BLEVE-induced damage levels of the double-arch tunnels without and with section-steel arches.
The Bleve is an explosion involving both the rapid vaporization of liquid and the rapid expansion of vapor in a vessel.The loss of containment results in a large fireball if the stored chemical is flammable.In order to predict the damage generated by a Bleve,several authors propose analytical or semi-empirical correlations,which consist in predicting the diameter and the lifetime of the fireballs according to the quantity of fuel.These models are based on previous experience,which makes their validity arbitrary in relation to the initial conditions and the nature of the product concerned.The article delves into uncertainty analysis associated with analytical and semi-empirical models of the BLEVE fireball.It could explore how uncertainties in input data,and the choice of a more or less inappropriate model,propagate into the model results.Statistical techniques such as global sensitivity analysis or uncertainty analysis are employed to quantify these uncertainties.In this paper,an attempt is made to evaluate and select reasonable models available in the literature for characterizing fireballs and their consequences.Correlations were analyzed using statistical methods and BLEVE data(experimental and estimated data by correlation)to determine the residual sum of squares(RSS)and average absolute deviation(AAD).Analysis revealed that the Center for Chemical Process Safety(CCPS),the TNO(Netherlands Organization for Applied Scientific Research),and the Gayle model revealed a high degree of satisfaction between the experimental and estimated data through correlation.
Accidental boiling liquid expansion vapour explosions(BLEVEs)caused by the bursting of liquified petroleum gas(LPG)tank inside a tunnel can induce vibrations of its surrounding geological media and threaten the stability of adjacent tunnels and structures.Therefore,it is essential to understand the characteristics of vibrations induced by LPG BLEVEs inside the tunnel for the safety design of its adjacent structures.Owing to the difficulty in effectively predicting the LPG BLEVE loads,the current practice usually employs equivalent methods,e.g.,the TNT-equivalency method,in LPG BLEVE load predictions for structural response analysis,which may lead to inaccurate response predictions.This study compares ground vibrations induced by a BLEVE inside an arched road tunnel with those induced by its equivalent TNT explosion via high-fidelity numerical simulations.The results demonstrate that the frequency of BLEVEinduced vibrations is lower than that induced by the TNT explosion at the same scaled distance.The intensity of LPG BLEVE-induced vibrations at relatively small-scaled distances is lower than that of TNT explosion-induced vibrations at the same scaled distance,but becomes higher after a certain scaled distance because of the relatively low attenuation rate.In addition,parametric analysis is conducted to evaluate the effects of various factors on the characteristics of LPG BLEVE-induced ground vibrations.It is found that the surrounding rock type,the rock porosity,and the cover depth of the tunnel have more significant influences than the concrete grade of the tunnel lining.The recommendation for the tunnel design is also given based on the intensity and frequency characteristics of BLEVE-induced vibrations.
