Four long-term failures of embankments founded on areas of landslip

Summary Four case records are presented of road or railway embankment failures where the bank has been constructed over previously landslipped areas. These records draw attention to the possibility of long-term failure resulting from the existence of the landslip shear surfaces beneath the embankment, even when the bank has been successfully constructed without the development of short-term failures. Evidence is presented which shows that the delayed failure at least in part results from the swelling and consequent reduction of strength of the embankment fill following the development of a perched water table in the crest of the bank. However the final ‘trigger’ causing failure may be the result of exceptional groundwater conditions following heavy rain.