Alteration of soil structure following seepage-induced internal erosion in model infrastructure embankments

The flooding of infrastructure embankments has the potential to cause lasting destabilisation through seepage-driven internal erosion development. To understand the effects of such erosion on slope behaviour it is imperative to identify where in slopes material alteration most commonly occurs. Laboratory testing on scale models of transportation embankments was undertaken to identify the locations within slopes where material movement, and likely property alteration occurs, caused by seepage through slopes. Changes in material properties were most commonly found to occur along the base of slopes and in regions of slopes adjacent to water inflow. Slope toes were found to have a greater proportion of fine material than elsewhere, with the mean grain size of the slope toe region 4.5% smaller and the coefficient of curvature 9% higher than in the main slope body, suggesting the development of a low permeability region towards the slope toe. The source zone for material deposited at the toe of slopes was the section of slopes adjacent to water inflow and the base of slopes away from the toe, shown by a coarsening of sediment in these zones. Material alteration following flooding was best identified using a combination of coefficient of curvature and mean grain size data. These results have implications for the stability of earthworks during and after flood events, and for the design of earthwork inspection and maintenance regimes.