Failure of a highway embankment on soft clay foundation - A case study with remedial measures

The paper presents a case history of a highway embankment which failed while being constructed over soft to very soft marine clays improved with band drains and preloading. The failure occurred at a height greater than the height determined from the bearing capacity considerations. The paper examines the reasons and nature of failure and briefly describes the remedial measures that were proposed for implementation during reconstruction of the embankment. The measures suggested included provision of basal reinforcement, construction of wide berms and providing band drains at closer spacing to achieve early strength grains. In addition, staged construction was recommended besides checking out performance of the embankment through a comprehensive instrumentation programme. Critical considerations involved in the design of prefabricated vertical band drains are presented and discussed in relation to the project site conditions.