| In the information war of nuclear deterrence,it is not only required that the defense underground tunnel project can withstand the shock wave,thermal radiation,nuclear radiation and other effects caused by the nuclear weapon explosion,but also must ensure that the electronic and electrical systems can operate safely in the high-power electromagnetic environment such as nuclear electromagnetic pulse.In other words,the defense underground tunnel project is the primary target of high-precision fire strike in modern war.Its information technology system and other electronic and electrical systems are important military facilities,which play an important role in supporting operations,and are also the key targets of strong electromagnetic weapons.In order to ensure the viability and operation ability of electronic information equipment or support system in the predetermined electromagnetic environment,necessary electromagnetic protection measures are essential from the perspective of electromagnetic compatibility(EMC)and electromagnetic protection.How to quickly evaluate its electromagnetic coupling effect is also very significant.However,considering the multiple practical uncertainties such as the uncontrollability of the actual electromagnetic environment,the relative complexity of the engineering protective structure,the randomness of the electromagnetic parameters of the special medium and the diversity of the electromagnetic coupling modes,the engineering practice is more based on the actual measurement to carry out the coupling effect mechanism analysis and the effect law exploration.The undeniable fact is that the actual measurement brings huge human and material consumption.It is of great significance to take effective and fast electromagnetic coupling calculation methods to evaluate typical engineering protective structures,which can increase the evaluation efficiency of engineering protective structures,expand the application range of wider frequency band and guide the construction of engineering electromagnetic protection.In this dissertation,the electromagnetic coupling calculation of the strong electromagnetic environment on the complex ground,the fast electromagnetic coupling calculation method of engineering structures and the coupling effect mechanism involved in the electromagnetic coupling calculation of typical engineering protective structures are studied.The main research objects are the actual non-uniform engineering protective structures such as the metal mesh,reinforced concrete and advanced composite protective materials.The main research contents and conclusions are as follows:(1)Aiming at the analysis of the electromagnetic environment of the early high-altitude nuclear explosion in the case of the ground laying the metal mesh and taking the parallel metal array as an example,a calculation scheme for calculating the electromagnetic environment of the early high-altitude nuclear explosion above and below the ground near the parallel metal array is proposed,and the influence of the parallel metal array structure on the electromagnetic environment of the high-altitude nuclear explosion is obtained.First of all,the coupling of electromagnetic wave to parallel metal array is discussed based on the coupling of electromagnetic wave to uniform ground,and then the electromagnetic pulse environment on the ground of metal mesh is evaluated.The calculation results show that the reflection and transmission effects of electromagnetic waves on the ground are significantly enhanced when the parallel metal wire array is laid on the ground,compared with the uniform half-space ground.The analytical calculation scheme can be extended to the situations near the ground of different metal mesh structures and different incident electromagnetic pulse situations in engineering,providing effective calculation scheme and strong electromagnetic environment guidance for the typical electromagnetic environment description in engineering practice.(2)Aiming at the calculation and analysis of the shielding effectiveness of multi-layer metal meshes,a new model for the analysis method of the shielding effectiveness of multi-layer metal mesh is proposed,which can be used for the broadband fast analysis of the shielding effectiveness of multi-layer metal mesh.Based on the Hyun impedance model of singlelayer planar metal mesh and combined with the shielding theory of multi-layer conductor,the multi-level metal mesh impedance cascade model is developed.Compared with the calculation results of commercial software HFSS,it shows that the new multi-layer metal mesh shielding analytical model can be accurately calculated in a wide frequency band,which brings a new solution for the shielding analysis of metal mesh in engineering practice.At the same time,considering the reflection characteristics of different layers of metal mesh and combined with the equivalent impedance transmission line method of uniform medium,an improved scheme for calculating the reflection coefficient of double-layer sparse square hole metal mesh in broadband is proposed based on the Hyun equivalent impedance model of single-layer metal mesh,which can also effectively ensure the accuracy of the reflection coefficient in high-frequency resonance region.(3)According to the structural characteristics of symmetrical and uniform layered protective structure,an analytical algorithm of equivalent four-terminal network for fast calculation of structured electromagnetic coupling is presented.Compared with the propagation matrix method,it reduces the number of matrices,avoids a large number of matrix multiplication in the propagation matrix method,and can quickly calculate the reflection coefficient and transmission coefficient of the lossy symmetric dielectric layer when calculating multiple frequency points or broadband bands,thus realizing the accurate calculation of the broadband electromagnetic coupling characteristics of the structure.In addition,the broadband equivalent electromagnetic parameter model of the inhomogeneous symmetric layered structure embedded with lossy cross fibers is studied combined with the homogenization equivalent parameter theory.Combined with the structured analytical algorithm of the equivalent four-terminal network for fast calculation of electromagnetic coupling,the effectiveness and efficiency of the electromagnetic coupling calculation of this advanced composite protective structure can be guaranteed.(4)In view of the few reports on the research results of electromagnetic coupling characteristics of three-dimensional reinforced concrete engineering protective structures in the existing literature,the three-dimensional single-layer reinforced concrete cavity protective structure is taken as the research object to simulate the simple three-dimensional space structure.The shielding effectiveness of it is evaluated,and the shielding effectiveness of multi-layer reinforced concrete structures is also further investigated.The influence of the structural parameters of the steel bar and the electromagnetic parameters of the concrete on their shielding effectiveness is analyzed in detail.The influence of it on the shielding effectiveness of reinforced concrete is analyzed as well and how to eliminate the resonance characteristics are discussed.The specific research results have certain reference value for the analysis of shielding effectiveness of reinforced concrete cavity in different actual situations and the design of reinforced concrete cavity with good shielding effectiveness in the wide frequency band.In addition,based on the actual electromagnetic pulse transient behavior,the time-domain coupling shielding effect of typical layered uniform structure,non-uniform metal mesh,reinforced concrete structure,and three-dimensional steel cage as the representative of three-dimensional protective structure is discussed from the perspective of time-domain shielding effectiveness.The specific research results provide effective guidance for the electromagnetic protection of the actual electromagnetic transient pulse behavior. |
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