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

Geotextiles in Embankment Dams2.1.5 Liquid barrier function (IGS symbol B)A geosynthetic of very low permeability will provide an effective barrier to fluidmigration from one area to another as in an upstream lining on the face of a dam. Itshould be noted that geomembranes are the only geosynthetic that can perform thisfunction. GCL’s, although exhibiting low permeability once hydrated, allow fluidmigration.2.1.6 Protection function (IGS symbol P)A geosynthetic of usually heavy mass per unit area provides mechanical protection toa geomembrane. This function, although relatively simple is a very large applicationarea and one that is underrated due to the importance of protecting the vital fluidbarrier (geomembrane). Nonwoven, needlepunched geotextiles with mass per unitarea greater than 10 oz/yd 2 (350 g/m 2 )are commonly used. It is interesting to notethat this geotextile may also perform the transmission or planar drainage function aswell (i.e. downstream layer of a geomembrane on a dam face). Geocomposites oflayered geotextiles that are over 30 oz/yd 2 (1000 g/m 2 )or geonet composites are alsoused as protection.2.1.7 Surface stabilization function (IGS symbol E)One of the fastest growing segments of the geosynthetics industry is erosion control.The myriad products (many are geocomposites of some type) all provide stabilizationof the immediate surface soil to prevent soil particle migration and mass movementdue to water flow. These products are increasingly being used in dams, especially inspillways and downstream slope protection and overtopping protection of smallerembankments and levees. This function can in fact combine filtration, separation,reinforcement and sometimes barrier during performance in erosive environments.Geocell’s and geomats are examples of materials used in this important function.16