Geotextiles in Embankment Dams - Association of State Dam Safety ...

Geotextiles in Embankment DamsFailure mode (FEMA, 2004): A physically plausible process for an embankmentdam failure, resulting from an existing inadequacy or defect related to a naturalfoundation condition, the dam or appurtenant structure’s design, the construction,the materials incorporated the operation and maintenance, or aging process, whichcan lead to an uncontrolled release of the reservoir.Fibers (Frobel, 1987): Basic element of fabrics and other textile structures,characterized by having a length at least 100 times its diameter or width which can bespun into a yarn or otherwise made into a fabric. (See Yarn.)Filament (Frobel, 1987): A fiber of extreme length.Filament Yarn (Frobel, 1987): Yarn made from continuous filament fibers. (SeeYarn, Woven Geotextiles.)Filling (Frobel, 1987): Yarn running form selvage to selvage at right angles to thewarp in a woven fabric.Film (Frobel, 1987):not greater than 0.010in.An optional term for sheeting having nominal thicknessFilter: A zone of material designed and installed to provide drainage, yet preventthe movement of soil particles due to flowing water.Chimney: A chimney filter is a vertical or near vertical element in an embankmentdam that is placed immediately downstream of the dam’s core. In the case of ahomogenous embankment dam, the chimney filter is typically placed in the centralportion of the dam.Collar: A limited placement of filter material that completely surrounds a conduitfor specified length within the embankment dam. The filter collar is located nearthe conduit’s downstream end. The filter collar is usually included in embankmentdam rehabilitation only when a filter diaphragm, in that a filter diaphragm is usuallylocated within the interior of the embankment dam.Diaphragm: A filter diaphragm is a zone of filter material constructed as adiaphragm surrounding a conduit through an embankment. The filter diaphragmprotects the embankment near the conduit from internal erosion by interceptingpotential cracks in the earthfill near and surrounding the conduit. A filterdiaphragm is intermediate in size between a chimney filter and a filter collar. Thefilter diaphragm is placed on all sides of the conduit and extends a specifieddistance into the embankment.162