Numerical Simulation Of Ground Penetrating Radar Electromagnetic Wave Propagation In Rigid Pavement With Voids Based On FDTD

Void is a common disease in rigid pavement. Identifying the locations and sizes of voids, and taking effective repair measures are of great importance to enhance the serviceability, elongate the life span of rigid pavements. The Ground Penetrating Radar(GPR) has been widely used, due to its speed, nondestructive, successive in the field of road detecting. However, because the automated degree of the GPR image interpretation is very low, and there are many man-made factors when evaluation of road, so the results bring about much subjectivity. And it is hard to achieve quantitative identifying, so there are limitations in application of GPR in the field of rigid pavement detection.FDTD method is a kind of high-frequency electromagnetic field simulation method, based on the principles of physical optics, and developed in recent years, which has many advantages, such as small storage capacity, fast operation, general procedures, parallel computing, and so on. The method is now widely used in the field of electromagnetic simulation. In this dissertation, research is conducted focusing on 2D numerical simulation of GPR electromagnetic waves propagation in rigid pavements with voids based on FDTD. The main researches and conclusions are summarized below:1. Based on the basic principles of electromagnetic wave theories, the differential form of Maxwell curl equations is differenced, we arrive at 2D-FDTD update equations. The GPR electromagnetic wave forward simulation program is compiled based on FDTD, through implementing PML boundary conditions with the method of CPML, and the program is operated in MATLAB environment;2. The propagation model of GPR electromagnetic wave which transmits in rigid pavement structure with air-filling voids and water-filling voids is established. The different horizontal and vertical dimensions of voids parameters is setted and inputted, a series of 2D radar reflected images are obtained, influences on reflected signal propagation in pavement with voids are analyzed by comparing the obtained images; 3. The propagation models of GPR electromagnetic waves which transmit in rigid pavement structures with round shape andâ…¤-shape voids are established. The features of radar reflected images corresponding to round andâ…¤-shape voids are analyzed, and related conclusions are obtained;4. Related experiments are designed according to the established forward model, the detected GPR images and corresponding simulated images are compared and analyzed, and related conclusions are obtained.The results show:images which are obtained through the way of numerical simulation of GPR electromagnetic wave propagation in rigid pavement with voids based on FDTD, are close to the detected GPR images, and in this way we can identify void diseases in different conditions; at the same time, the achievement of this paper provide an important basis for GPR images interpretation, and make a theoretical foundation for further backcalculation research on detecting voids in rigid pavements with GPR.