Ordered Solidification Technique Under Low Pressures in the Loading of Molten Explosives

In order to improve the quality of loading and make the ammuni- tion safe in use,a new loading technique of ordered solidification has been studied.The study shows that the adoption of this new technique makes the charge more compact and brings about a satisfactory supplement of liquid ex- plosives,thus increasing the charge density,which is most advantageous to the crimination of pores,cavities,gaps at the bottom and in loose struc- tures.The physical mechanical properties of the charge are hence greatly im- proved,and the sensitivity of the charge to environmental stimulations is much lowered.

Numerical Simulation of Underwater Explosion Loads

Numerical simulation of TNT underwater explosion was carried out with AUTODYN soft-ware. Influences of artificial viscosity and mesh density on simulation results were discussed. Deto-nation waves in explosive and shock wave in water during early time of explosion are high frequency waves. Fine meshes (less than 1 mm) in explosive and water nearby, and small linear viscosity co-efficients and quadratic viscosity coefficients (0.02 and 0.1 respectively, 1/10 of default values) are needed in numerical simulation model. According to these rules, numerical computing pressure profiles can match well with those calculated by Zamyshlyayev empirical formula. Otherwise peak pressure would be smeared off and upstream relative errors would be cumulated downstream to make downstream peak pressure lower.

Numerical prediction of ground vibrations induced by LPG boiling liquid expansion vapour explosion(BLEVE)inside a road tunnel

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.