A tale of two dams : A comparative study of performance and internal erosion

Internal erosion occurs when fine-grained particles are allowed to erode in a material by the action of seepage, and it is one of the major causes for the failure of embankment dams. Embankment dams are normally composed of zones, each with a purpose: the imperviousness of the core, the erosion-control and structure-stability provided by the filter and the support fill, respectively. A poorly functioning zone will adversely affect the performance of a dam, and the filter, if inadequate, is thus unable to protect against internal erosion of the core. Two existing embankment dams are studied herein, both are located in Sweden and with cores composed of glacial till against granular filter, but with different performance records; one has suffered a sinkhole-event due to internal erosion, the other has operated without signs of distress. A comparative assessment is performed by using available internal erosion criteria in the literature, and although relatively similar in design and composition the assessment reveals a possible explanation as to why there are differences in performance of these dams in terms of internal erosion.