Applied Techniques Of Ground Penetrating Radar (GPR) Numerical Modeling

Ground Penetrating Radar (GPR) is a non-destructive advanced technique of electromagnetic wave probing working at high frequency with very resolution. In this thesis, the finite-difference scheme and equations are derived for 2-dimensional(TM mode) components Ez, Hx and Hy and 3-dimensional components Ex, Ey, Ez, Hx, Hy and Hz based on the Maxwell's Equations. With some special processes for absorbing boundary conditions (ABS), completely marched layer (PML), source position and conductors, 2-D and 3-D Finite-Difference Time Domain (FDTD) numerical modeling program is developed for GPR survey. Detailed numerical studies on models simulating the real application problems for highway pavement inspection, airport runway pavement debonding detection and concrete structure inspection for inner lining of tunnel is conducted with the 2-D and 3-D FDTD modeling program, probing the effectiveness, reliability and detectability of GPR, and building up a direct understanding of GPR applications. In addition, GPR research survey is conducted on some physical models to simulate the real defect conditions, such as air voids, wood blocks, PVC pipe, and etc. in concrete structures. GPR signal reflection characteristics for different type of defects are analyzed and concluded. After detailed numerical study and analysis, physical model experiment, and trial studies were done in real conditions for different applications of GPR for highway pavement thickness inspection, airport runway debonding condition evaluation and defect inspection in concrete lining, "indicative"anormaly patterns in GPR reflected signals for different type of defects were concluded and established. Some results in this thesis from contracts in Hong Kong are shown for highway bitumen pavement structure evaluation (more than 1000 line-km for thickness of coating layer, base layer and sub-base layer, and etc.), airport bitumen runway pavement debonding distribution, and defects in concrete lining of Hongkong Cross-harbor tunnel. All findings by GPR survey were examined by core drilling, and the results were confirmed by core information that the accuracy of GPR survey on thickness and depth of the target layers or defects is up to 95%. It is concluded that numerical study and physical model experiment will provide a theoretical gist, guidance or instructions for practical application of GPR technique, and enhance our understanding of the applicable conditions and capability of the GPR survey, and finally promote the effectiveness of application of GPR technique.