GEOPHYSICAL APPLICATIONS FOR EFFICIENT MANAGEMENT OF SEA DIKE

In general, it is difficult to manage the entire section of the sea dike periodically. In addition, reinforcement is required to improve the safety of the embankment because the weakened part of the embankment may gradually increase dut to sinking or subsidence. In particular, information indicating the physical properties of the embankment is important for choosing a reinforcement range.

Geophysical methods can be usefully applied to the safety diagnosis of sea dike. In this study, we assessed vulnerable areas of the Saemangeum sea dike using ground penetration radar (GPR) and electrical resistivity (ER) and multichannel analysis surface wave (MASW) methods. Effectively applying these three methods, facility managers can safely manage the entire area of the sea dike at low cost and can prepare for subsidence at the crest. As a result of GPR exploration, some anomalous responses and some weak regions along the entire dike was identified and analyzed. In addition, as a result of electric resistivity and MASW explorations, some anomalous zone with lower than 10 ohm·m resistivity were extracted and S wave was observed response of lower than 175 m/s in velocity at some vulnerable zones. This low electrical resistivity indicates a medium affected by seawater, and a low velocity shear wave means a medium with a relatively low density. Considering these two factors at the same time, it is possible to analyze the safety of each section of the sea dike.

Finally, we proposed a method to select the reinforcement range based on the quantitative analysis of geophysical results in the dike maintenance process. These results can be used as annual monitoring data for maritime safety management and basis data for repairing vulnerable areas that represent anomalous and leaking areas through the Saemangeum sea dike.