Use of Index Gradients and Default Tailwater Depth as Aids to Hydraulic Modeling of Flow-Through Rockfill Dams

Abstract

To assess the potential for unraveling failure of flow-through rockfill dams, a systematic study of three aspects of the hydraulic design of these structures was conducted. First, the gradient that is most useful in independently computing the height of the point of first flow emergence was established. The proposed method is based on the idea of the angle of the emergent flow field within the toe of the structure. Secondly, as a result, this study presents a method for independently computing the variation in hydraulic head within the vertical that allows the toe of the structure (i.e., downstream from the vertical associated with first flow emergence) to be isolated. This is based in part on a separate parametric study of 24 numerically simulated flow-through rockfill dams. Thirdly, the gradient that allows for the independent estimation of the default tailwater depth is presented and verified, with the help of laboratory results. The hope is that these three computational tools will facilitate the design and assessment of flow-through rockfill structures, as a particular class of pseudohydraulic structure.