Estimation of Layered Structures Using Backscattering Responses and Particle Swarm Optimization

In recent years, road collapse caused by the occurrence of underground cavities have been frequently reported in Japan. Maintenance of social infrastructure in the process of aging and redevelopment has become a priority issue, and it is important to inspect the occurrence of cavities under the road without excavation to prevent sudden accidents by the collapse. This paper describes an estimation method of underground structure using the backscattering response of radio waves transmitted from the ground surface. The underground is approximated by a multi-layered model, and the structural parameters of the model are optimized so that the scattering response of the model matches that from the underground. Swarm intelligence optimization is used for the parameter optimization. It is shown that the cavity information can be estimated via the numerical experiments using electromagnetic field analyses for the structure instead of the measurement.