Influence of uncertainties in internal erosion assessments of existing embankment dams

The evaluation of a dam’s susceptibility to internal erosion is fraught with difficulties related to uncertainties in relation to the in-situ geotechnical properties of materials. These uncertainties include imperfect knowledge of actual soil conditions, imperfect representation of reality by models and variability of soil properties. Experience has shown that our current capability for mathematical analysis and modelling of potential seepage patterns far exceeds our capability to make judgments of comparable accuracy concerning the geology of a dam site or, for example, how the soil properties may be affected during construction of a dam. The uncertainties about the actual performance of embankment dams are discussed in this paper and illustrated by three case histories. These examples show the influence of various types of uncertainties in internal erosion assessments as well as efficient means to reduce them.