Georadar detection assisted with TDR and Numerical Simulation

• Main Authors: Jian-Hua Liao, 廖建華
• Other Authors: none
• Format: Others
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/70589852940407722283

碩士 === 國立雲林科技大學 === 營建工程系碩士班 === 92 === The electrical parameters for the same kind of soil can be different because the water content, the density and the fine soils are not at the same level. This affects the electromagnetic wave propagation on the two main electrical parameters, leading to the dielectric constant and conductivity. This article is divided into two major parts. This first is a lab model test. This research obtains the electrical parameter of soil under different water content using the Time Domain Reflectometry (TDR), and studies the dielectric constant and conductivity to be influenced by the amount of fine soils. The test results indicate that for the Cho-Shui sand and the sand with the different amount of the low-plastic clay, when the water content is low, the difference of electrical parameters is not big, but the dielectric constant and the conductivity increase along with increasing amount of the low-plastic clay. When the soil is saturated, the dielectric constant and the conductivity slightly decrease with increasing amount of the low-plastic clay. The second part is the numerical simulation aspect. Generally speaking, one had better carry on the lab model test of georadar, to measure the characteristics of signals for different underground objects before field test. The quite complex shape of underground objects and some difficulties in the lab test, such as manpower requirements, the physical resources, the funds, the scale, and the required space, can be overcome using the numerical simulation although it can not take place of georadar field test completely. The numerical simulations use the Finite Difference Method and the Finite Element Method, to study the characteristics of electromagnetic wave signals of underground objects in the different medium. The results indicate that the signal of rupture-plane seems to weaken with the inclination angle and the water content increased; The rebar signal seems to reduce along with the vertical burial depth of rebar increased and the diameter decreased. The signal of rupture-plane filled with water compare the signal of rupture-plane filled with air, creating a more obvious tendency. It has been found that the results of numerical simulation and the results of georadar lab tests have the same tendency.