Research For GPR Numerical Modeling And Imaging Methods

Ground Penetrating Radar (GPR) is an important shallow layer geophysical exploration method which detects the underground structure and the distribution law, as an advanced technique of electromagnetic wave probing working at high frequency, it possesses a lot of virtue, such as rapid and continuous surveying, simple and convenient operation, high resolution, nondestructive detection etc. It is applied to engineering, environment, archaeology and other aspects widely. However, it has many aspects needed to be improved, such as radar image recognition which still relies on manual operation. Forward modeling of common detection objects is helpful for us to understand the law of propagation of electromagnetic waves, According to GPR image analysis, we can accumulate the experience of how to determine the underground structure; Forward modeling technology can also be used to verify a large number of experiments, greatly improve the accuracy of ground-penetrating radar detection results, the detection efficiency and image interpretation accuracy.In this thesis, the finite-difference scheme and equations are derived for2-dimensional(TM mode) components Ez, Hx and Hy. With some special processes for Mur absorbing boundary conditions and Ricker sub-wave excitation,2-D Finite-Difference Time Domain (FDTD) numerical modeling program is developed for GPR survey. We study the numerical simulation about some common models, such as: point-like objects Model, dipping interface model, ladder-like model, complex model and so on. Researching characteristics and laws of ground-penetrating radar response about these goals provides an intuitive perceptual awareness for Ground-penetrating radar technology about the feasibility and application of non-destructive quality testing. According to the forward modeling results, we know:forward section of GPR about point-like objects shows a hyperbolic form of events; forward section of GPR about dipping interface model is also a dipping interface events. But the tilt angle was significantly slowed; forward section of GPR about Ladder-like structure is ambiguous due to the interference of diffracted wave.Because the original GPR sections commonly show the distorted underground geology body structure, the original GPR sections are needed to be migrated in order to make the reflection points of GPR trace records return to their real positions, Diffraction scan stack migration is an effective and relatively economical method; GPR sectional images after migration are obtained through the Diffraction scan stack migration process, it have showed the real underground geology body structure.