Protection Effects Of Sandwich Structures With Air Interlayer Subjected To Underwater Explosion

In recent years,underwater blasting method is widely used with a large number of underwater projects which were built.The methods have been widely adopted in the underwater explosion projects.The shock wave produced by underwater explosion will inevitably have some effects to the hydraulic structures?aquatic organisms as well as staff in the vicinity.Meanwhile,with the rapid development of precision guided weapon and the increasing frequency of terror attack,firing explosives may take great threats into safety performance of underwater structures.At present,the existing protective measures are mainly aimed at air explosions,researches of protection measures of underwater explosion are rare.So study on analysis on preventive measure of underwater structures underwater explosion load have great value and importance in engineering practice and analytical theory.Due to differences in physical properties of water and air as well as different interface effect of explosive products,there are great differences in the propagation characteristics of blast wave in water and air.The ability of underwater explosion to destroy the structure is much better than that of air explosion.More and more attention has been paid to the protection of underwater structures.Utilizing wave impedance difference between air and water medium,the protective effect of air interlayer on underwater explosion is studied,viewed from influence of air interlayer on propagation characteristics of underwater explosion shock wave and its buffer effect,protective effects of sandwich structures with air interlayer on concrete slab subjected to underwater explosion.the basis for the protection design of underwater structures is provided.The main research contents and conclusions are as follows:(1)Based on the theory of one-dimensional stress wave transmitting and reflecting at the interface between two medium,the influences of low impedance medium,such as,air on underwater explosion shock wave propagation were analyzed.The fully coupled model for underwater explosion containing air interlayer was established.Considering the dynamic interaction among underwater explosion shock wave,air interlayer and detonation products,the mitigation effects of air interlayer on underwater explosion shock wave were investigated.The development process of air interlayer was revealed.At the same time,the influences of thickness and location of air interlayer on its mitigation effects on underwater explosion shock wave were analyzed.The results showed that the air interlayer can effectively buffer the propagation of underwater explosion shock wave.the closer the distance between airlayer and the projected object,the better the protection effects.(2)In order to play the buffering effect of air medium,withstand direct action of underwater explosion shock wave,an air sandwich structure was proposed which was applied to underwater concrete slab.The fully coupled model for underwater explosion containing sandwich structure was established.Comparison different response and destructive development process between existence and inexistence of sandwich structure,protective effects of sandwich structure on concrete slab was confirmed.At the same time,the influences of design parameters of sandwich structure(steel Span?plate thickness?whether the steel plate is provided with supporting structure)on protective effects on concrete slab was investigated.The resulted showed that the air sandwich structure can effectively buffer the propagation of underwater explosion shock wave,the damage range of concrete slab is greatly attenuated,supporting of plate go against structure protection,span of air sandwich structure is not as small as possible,thickness is not as thick as possible.