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

Geotextiles in Embankment DamsPublished design standards, such as those by the Bureau of Reclamation and U.S.Army Corps of Engineers, which prohibit geotextile use in critical applications,reflect the current main stream opinion regarding geotextile use. For non-criticalapplications, these design standards are useful, but do not reflect current filtrationdesign practice and may not always yield optimal filtration design results.Further, new products are being developed to address multiple design issues. Anexample is the bonding of different types of geotextiles into a single sheet to obtain acomposite material with superior filtration and strength properties. Other materialsemerging on the market are “smart geotextiles” which combine sensing elementssuch as fiber optics to monitor stress and moisture change in a buried geotextile.Dam engineers have recognized the need for and insist upon a strict quality controlprogram for granular filter construction including specifying handling procedures toavoid segregation and contamination, limiting maximum fines content to avoidclogging, and sampling and testing installed materials to verify material breakdownhas not been excessive. A similar intensive effort must be applied to geotextiledesign and construction for a successful installation.It is the policy of the National Dam Safety Review Board thatgeotextiles should not be used in locations that are critical to thesafety of the dam.7.7 RecommendationsA comprehensive document on the design, installation and monitoring of geotextilesin dams is needed. A rewrite of the 1992 Bureau of Reclamation Design Standards,Chapter 19 - Geotextiles, is a potential candidate. Such a document would benefitfrom the incorporation of a failure mode assessment of the dam’s response toforeseeable problems with the geotextile. This assessment should be melded withthe Design Classification scheme into a matrix to aid the designer in the appropriateuse of geotextiles in dams. Appropriate use here refers to the combination of thesteps taken to minimize the likelihood of the geotextile suffering a problem and thecomplementary measures provided to mitigate the consequences should thegeotextile experience that problem.138• Multi-layered geotextiles are an advancement that may provide a “graded filter”with superior filtration and strength performance. Such new products areworthy of research efforts regarding dam embankment filtration applications.• The anticipated loads and strength requirements for geotextile service inembankment dams should be developed.