ASDSO Dam Safety Toolbox

Composite Dams

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Folsom Dam, located just outside the city of Folsom, California, northeast of Sacramento, is comprised of a central concrete spillway flanked on either side by earthen wing dams.

(Image Source: Wikipedia)

Composite dams are designed and constructed using both earth embankment and concrete sections. The most common type of composite dam is a combination of concrete and embankment structures. It is common in composite dams to construct the outlet works, necessary hydropower structures, spillway (either gated or uncontrolled), and stilling basin as either part of or connected to, the concrete portion of the dam.

The earth embankment portion(s) of the dam, including any necessary saddle dams, are typically greater in volume than the concrete section(s), reducing the overall cost of the structure and preventing internal erosion along conduits and other concrete structures that would typically be built in and underneath a dam constructed entirely of an embankment. Additionally, issues with internal erosion and piping that often occur as a result of constructing conduits and other concrete structures through and underneath earthen embankment dams are minimized, since these structures are contained within the concrete section(s) of the dam. Special care is taken during design and construction to prevent seepage and internal erosion between earthen embankment section and concrete section interface(s). The interface between two sections of a composite dam is critical as this presents a discontinuity in the structure that may contribute to potential failure modes.

Revision ID: 7309
Revision Date: 07/18/2023