Computational Analysis Of The Propagation Law Of Shallow Explosion Stress Wave In Layered Medium

Layered media is widely existed in nature,it is of great significance to study the underground explosion damage effect of layered media for the development of underground space,the protection of underground structures and the inversion of earthquakes.The roadbed of the airport is mostly layered medium.As a military key target,the traditional airport runway protection is mainly for the study of the near-explosion area.In this paper,the shallow-buried explosion stress wave propagates in the layered medium,and the research is shallow.The volatility effect of the buried explosion in the far field.This research has important value for the protection of important targets of the airport.Taking the airport runway as the research background,this paper uses the airport runway layered medium as the layered elastic medium.Based on the theory of elastic dynamics and the theory of pressure acoustics,the theoretical analysis and numerical simulation method are used to study the shallow buried explosion.The wave effect in the far field.The main contents are as follows:(1)Using the principle of one-dimensional stress wave reflection-transmission at the interface of two layers,the law of reflection transmission at the multi-layer interface is analyzed,which shows that the wave impedance of the medium determines the relationship between the amplitude of the reflection transmission and the energy.Taking the airport runway as the object,calculate and analyze the distribution relationship of stress and energy in each layer of medium when the one-dimensional stress wave is normally incident,and compared with the single interface,it indicates that the wave impedance is increasing(decreasing)layered medium,which will not Reduce the intensity of its transmission.(2)The soil layer-gravel layer-concrete layer-air layer frequency domain analysis model was constructed by Comsol Multiphysics numerical simulation software.The transmission coefficient and absorption coefficient were customized,and the stress wave was decomposed into independent longitudinal and shear waves.The transmission and absorption coefficients and the changes of stress and energy at different angles and frequencies are solved respectively.The results show that at low frequencies,the transmission coefficient and absorption coefficient change gently,and the transmission of stress waves is strong.At high frequencies,stress The wave passes through the layered medium,the transmission coefficient and the absorption coefficient change significantly,and the stress amplitude and energy attenuation are severe.Due to the existence of the natural frequency of the structure,the transmission coefficient and the absorption coefficient change periodically,and the two exhibit opposite relations.As the incident angle increases,the transmission capacity of the stress wave decreases significantly,especially at high frequencies.At the same frequency,as the incident angle increases,the shear wave stress and energy decay are significantly more pronounced than the longitudinal wave because the shear wave velocity is small,the wavelength is short,and it is easy to scatter and absorb in the layered medium.(3)The soil layer-gravel layer-concrete layer-air layer time domain analysis model was established by Comsol Multiphysics numerical simulation software.The propagation characteristics of the explosion stress wave in the layered medium were analyzed from the transient point of view.At the moment of explosion,the blast wave spreads around and rapidly decays.When encountering the interface without the medium,the phenomenon of reflection and transmission will occur;in the forward direction,the amplitude of the stress and the energy attenuation are slow,and the attenuation is in different directions from the blast.Significantly,this is consistent with the frequency domain analysis;although excited by the microsecondlevel explosion pulse,the stress wave maintains the inherent wavelength propagation in each layer of medium;over time,a stable failure zone is formed.The spatial size of the damaged area is symmetrically distributed.