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

Chapter 4Potential Performance Issues Associated withGeotextilesThe significant economic and technical advantages of geotextiles cannot be realizedif performance is compromised. Performance issues with geotextile products fallinto three common categories: (1) Limitations that can be accommodated by design,conservative assumption of material properties, use of safety factors; (2) Harshenvironments that may be recognized and avoided; and (3) Inherently high-riskapplications which should be avoided or undertaken with caution and fullunderstanding of the risks.Under the first category, design assumptions can be conservatively made forgeotextile properties and for loading conditions. Material properties of geotextilesare generally well established since they are manufactured materials. Uncertaintiesmay include ultraviolet degradation, installation damage, and design methods forusing geotextile products. These concerns are normally addressed in designconservatism and construction quality control. These common performance issuesare relevant to all applications of geotextiles in civil engineering and construction.These issues require attention to detail, but do not preclude use of geotextiles forclasses of applications, such as in dams.Harsh environments have contributed to documented failures of geotextiles.However, these conditions can usually be recognized through site investigation andexperience gained from past performance problems. Environmental degradationincludes the effects of ultraviolet light, high temperatures, hydrolysis, chemicals,radioactive materials, and biological organisms. Degradation of the polymers used ingeotextiles has been shown to be inconsequential for typical soils. Difficultapplications may also contribute to geotextile failures. Filtration in dispersive soilsand filtration in flow reversal are applications that can cause clogging. These issuesrequire increased attention to detail, and in some cases high-risk environments canbe avoided by early recognition. But these concerns do not generally preclude theuse of geotextiles in embankment dams.The last category involves inherently high-risk applications. Perhaps the highestconcern is use of geotextile filters for drainage in portions of a dam that are notreadily accessible for removal and replacement. Failure of an internal feature of alarge dam is not only very expensive to repair; it could jeopardize the safety of the71