2020 Volume 76 Issue 4 Pages 363-373
River levees suffer occasionally from damage during flooding in the form of backward erosion piping within or below the levees. It is invisible to current methods of inspection until it manifests itself at the exterior surface. Therefore, there is strong needs to develop techniques that can identify internal damage.
This report describes detailed investigation on the left bank levee of Hiji River where significant sand boiling and subsidence of the levee slope were observed during a flooding event in July 2018, with a focus on the mechanism of sand boiling and progress of piping. Dynamic cone penetration tests were conducted at small intervals, both in vertically and horizontally, and a large pit was excavated to expose soil sections to identify the fundamental mechanism of the damage to the levee. A digital elevation map with a good resolution and accuracy confirms the area where backward erosion piping affected.