Application of the Kenney–Lau stability index to quantify the post-erosion gradation of internally unstable soil

The well-established Kenney and Lau method is applied to estimate the post-erosion gradation of internally unstable broadly-graded soils after the finer particles are washed out. A novel semi-empirical relationship between the erosion fraction loss ( E F ) and the stability index ( H/ F) min of the original soil gradation is developed to estimate the upper bound of erosion. This relationship is validated using data from 44 internal stability tests across seven independent studies. It is found that the erosion fraction loss ( E F ) increases approximately linearly as ( H/ F) min decreases . The proposed framework offers a practical approach for quantifying post-erosion gradation of internally unstable soils at the stable state and can serve as a screening tool to evaluate the continuation of erosion through embankment dams and their foundations.