Gradation and Compaction Specifications for Filter Design and Construction

Filters are one of the dam engineer’s best tools to prevent internal erosion and control seepage within embankment dams and their foundations. The dam engineering profession developed the cur-rent guidance on gradation design and specifications for filters in the 1980s. Still today, not all design engineers fully understand all aspects of this guidance. In addition, filters need to be compacted appropriately to serve their intended purpose, but there is no industry consensus on appropriate compaction methods.

This article includes (a) a discussion of filter gradation design and specification, including consideration of flexibility within the current design guidance, and (b) a discussion of filter sand compaction, including recommended practices. This article is a condensed version of a longer paper (France et al., 2020), which includes more information on filter design and construction con-siderations.