ABSTRACT
Suffusion, which is classified as one of internal erosion, causes change in physical and hydraulic properties of soils during permeation, while the mechanism of permeability change for sands due to suffusion is not sufficiently clear. In the present study, permeability tests of gap-graded sand are performed by increasing levels of hydraulic gradient. During the tests, X-ray micro CT is applied to observed internal structure of sand specimens, and then the progressive formation of concentrated seepage path caused by suffusion is visualized by image analysis. It is found that permeability of gap-graded sand increases until a concentrated seepage path completely goes through the sand along a direction of seepage due to suffusion.
