Application Of Ground Penetrating Radar In Coastal Embankment Engineering

In recent years, ground penetrating radar is commonly used in geotechnical engineering as a non-destructive detection and effective method. Riprap embankment is one of general coastal projects, and explosive compaction is used in foundation treatment of soft soils. Because of uncontrollability of explosive results, residual mud zone in embankment bottom would have negative impacts to stability of riprap embankment. Therefore, investigation of riprap bottom boundary detection with GPR in coastal riprap embankment is an important issue, which is just the object of this thesis.Based on the summary of related work, the parameters and detection methods are discussed. TDR is used in measurement of electrical properties of clay, seawater, gravel. GPR is chosen to measure the permittivity of gravel with saltwater immersion, and permittivity formulas are gotten in different saltwater depths. Furthermore, model experiments are conducted to investigate the influence of seawater on the signal and image of GPR, especially to figure out the image variation of riprap bottom boundary. Then, the measured results are compared with that obtained by numerical FDTD analysis for verification. The back-analysis emphasizes the shape image of riprap bottom boundary under the effects of seawater intrusion. Riprap bottom boundary is calculated respectively through average permittivity method and layered calculation. After comparing the results of both, cause of accuracy error and applicable condition are investigated.The experiment results indicate that seawater has great influence on dialectical properties of materials. GPR is effective to identify the riprap bottom boundary of coastal embankment without seawater. When it is submerged by seawater, the electrical properties of mediums changed significantly, moreover, measurement error is a little bit bigger and the interface image appears fuzzy.