Through-Flow Analysis for Rockfill Dam Stability Evaluationsby Nicholas J. Markevich, PG&E, San Francisco, United States,
Catalino B. Cecilio, PG&E, San Francisco, United States,
Abstract: Existing rockfill dams may have spillways that are not adequate to pass the current probable maximum flood (PMF), having been designed prior to the publication of the latest Hydrometeorological Report (HMR). In some cases the amount of theoretical overtopping of the dam crest or parapet wall during the PMF is quite small and lasts for only a few hours. Because modification of the dam or its spillway may be quite expensive, it is worthwhile to analyze the effects of the flow as it passes through the rockfill structure. The experimental basis and theoretical background for the analysis of flow through rockfill are briefly summarized in the first part of this paper. Following that is a more detailed discussion of the analysis procedure and hydraulic calculations used to determine the throughflow profile and velocities in a rockfill dam. Finally, the results from two actual studies are presented. As in at least one of the examples, modifications may be avoided or reduced in scope if the dam can accommodate the resulting throughflow velocities and forces.
Subject Headings: Earthfill dams | Rockfill dams | Rock fills | Spillways | Floods | Hydraulic design
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