Embankments: some design and construction considerations

Embankments are raised on natural ground in order to achieve a design formation level. Compared to the design of cuttings, the design and construction of embankments requires consideration not only of the embankments themselves (the fill), but of the engineering performance of the ground forming the foundation on which they are built. Embankments are usually constructed from remoulded materials whose engineering properties may be more difficult to predict than those of the undisturbed natural ground. Design of embankment slopes cannot be seen in isolation from the strength and settlement characteristics of the foundation: a granular fill that would perform safely at say 1 (vertical) in 1.5 (horizontal) on a hard foundation could not be placed at this slope on soft clay without the risk of excessive settlement and/or bearing capacity failure. Therefore, for this particular type of fill, it may be necessary to slacken the embankment side slopes to prevent failure of the embankment toe and/or to strengthen the founding strata to prevent overall failure or excessive settlement over the design life of the earthwork.