Multi-frequency Synthesis Method For The Simulation Of GPR Electromagnetic Wave Propagation In Inhomogeneous Pavement Media

Ground Penetrating Radar(GPR)is a non-destructive detection equipment which using ultra-wideband electromagnetic pulse to target detection underground. It has some features such as effective, speedy, continuous and non-destructive, high precision and low detection cost and so on. The road materials are usually regarded as homogeneous materials when the GPR is used for road detection. The GPR data interpretation is mainly due to the uniform medium theory and homogeneous assumptions. In fact, the composition and structure of the road materials are inhomogeneous, which are made up of three-phase constituents, such as aggregate, liquid, gas. The properties of dielectric properties in different locations are different as a result of the materials'composition and structure inhomogeneous. It will not be truthfully accurately reflects the inherent characteristics of actual materials if do not care the inhomogeneous of material adopting homogeneous medium theory to interpret the waveform data.The simulation of GPR electromagnetic waves propagation in inhomogeneous media is studied in this paper in order to solve the above problems of GPR applied technology. The main research achievement and conclusions are as follows:(1) The dielectric constant of road materials (asphalt concrete, cement concrete) are tested based on the test trial, the test data analysis shows that the road engineering materials inhomogeneous are an objective reality.(2) Electromagnetic wave propagation properties and the reflection wave and transmission wave amplitude and propagation velocity in one-dimensional inhomogeneous media are analyzed base on electromagnetic wave theory.(3) Through the discrete division on each layer of pavement structure, the equivalent model of one-dimensional inhomogeneous medium are established combined with pavement structure system and the characteristics of road materials. The electromagnetic wave propagation in inhomogeneous media of pavement layer are simulated by the multi-frequency synthesis method, and the corresponding program is also developed aim to achieve the simulation of electromagnetic wave propagation.(4) Analysis the results of electromagnetic wave propagation simulation in homogeneous media and heterogeneous media, and the results show that the simulated waveforms which consider the inhomogeneous media of pavement media are more consistent with the measured waveforms.Wealth of material information which contained in radar simulation wave signal will be sufficiently ascertainment when the research carried out on the simulation of GPR electromagnetic wave propagation in inhomogeneous pavement media, the simulation of GPR electromagnetic waves propagation in inhomogeneous media are more consistent with the characteristics of engineering materials. The research results will provide theoretical support for the GPR data interpretation,...