Visualization of Seepage Behavior in a Model Ground Around Sheet Pile Using μ-Focused X-Ray CT System

River levees are used for not only flood control, but also for flood inundation. In recent years, river floods caused by short duration torrential rains and large typhoons have occurred in Japan. The principle that river dikes must be constructed using only soil is still followed. This is due to the availability of materials, the fact that the structure does not deteriorate, and the ease of restoration if the structure fails. Meanwhile, the entire function of a continuous dike can be lost when a localized weak point causes a breakout. In this study, an experimental apparatus was developed to investigate the formation of "localized" water channels at the boundary between unsaturated soil and steel sheet piles in a river dike, which is caused by the fluctuation of water level in the river due to rainfall. A seepage test was performed using the experimental apparatus, and the results confirmed that the permeability increased with the penetration of the steel sheet piles. In addition, an analysis of CT images showed an increase or decrease in the pore space in the model ground. Changes in the modeled unsaturated ground was successfully visualized using a X-CT scanner.