Study On Impact Resistance Of Layered Protection Structure For Civil Air Defense Engineering With Buffer Layer

The layered protective structure is the engineering protective form adopted by the air defense engineering against the attack of weapons.Because of its good performance against conventional weapons and nuclear weapons,it has been widely used in civil air defense engineering.Based on the concept of protection effectiveness design of civil air defense engineering,it is believed that all kinds of protection measures play an independent role in function.Layered protective structure is an important defense line of civil air defense project.If the efficiency of the project is improved in this respect,it will play a positive role in improving the viability of the project.Weapon damage to civil air defense engineering is mainly caused by explosion impact.The load produced by explosion of weapon charge is the main design load of underground civil air defense engineering.The purpose of adding buffer layer in layered protective structure is to reduce the ultimate load acting on the project and play the role of energy dissipation and load reduction.The buffer layer in is divided into air buffer layer and polyethylene buffer layer.Taking air as buffer layer is mainly considered from two aspects.The first is the attenuation of shock wave by air,and the second is the utilization of underground space formed by air buffer layer.Taking polyethylene as buffer layer is mainly considered for its low density,light weight,good deformation recovery ability,and effective isolation of heat transfer and water vapor permeation.It is suitable for use in underground environment,and can reduce the infrared exposure symptoms of the project,which is conducive to the camouflage of the project.Based on the existing research on civil air defense engineering and layered protective structure,the effect of explosive shock on civil air defense engineering is expounded.Also compares the change rate of pressure when shock wave propagates in air medium and geotechnical medium,and analyses the layered distribution of buffer layer structure with the theory of stress wave propagation.Through the field explosive model test,the thickness of air layer and shelter layer is changed,and the shock wave pressure on the model is measured.Using numerical simulation as a supplementary means,the propagation and distribution of pressure are observed,and the curve fitting of data is carried out to obtain the calculation formula of shock wave incident overpressure.The impact test of polyethylene buffer layer was carried out by using drop impact test device.The optimum location of buffer layer was obtained by model test at different locations of the layer.In addition,according to the test results,combined with the relevant practical engineering background,the application effect of buffer layer is analyzed,and the application method of buffer layer in civil air defense engineering and urban underground space is put forward,which can provide reference for engineering construction and transformation.