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

Chapter 7—Conclusions and Recommendationsgeotextiles can be provided with anti-oxidation formulations that are expected toattain service lives of up to 200 years for buried applications.There is no evidence that biological organisms attack the geotextile polymersthemselves. Oxidation, ultraviolet light, and other factors can degrade geotextiles;however; burial of the material significantly reduces the rate of degradation.Excessive clogging remains as a concern for geotextile applications. Knowledge ofthe effects of geotextile compression upon filtration properties, better filtration andpermeability design criteria, and development of construction practices (use of finegravel) to provide for intimate contact of the geotextile with the base soil, haveprovided more reasonable designs than past practices. Filtration testing can beconducted to evaluate filter performance for a proposed geotextile filter and soilcombination.The issue of installation damage from construction activities and post installationservice remains as the most significant objection to the use of geotextiles inembankment dams. The issue includes:• Installation damage that can occur during construction and may not be detected• Plant intrusion after construction that clogs void space and reduces itspermeability;• Burrowing animal damage (holes or cuts) which compromises filterperformance; and• Tearing of the fabric due to settlement and cracking of the embankment.• To avoid internal erosion, the geotextile filter must be constructed withoutholes, tears, or defects. This is difficult to achieve in typical constructionoperations.7.4 Design and constructionDesign criteria for geotextiles has advanced and in the area of filtration, existinggovernment design guides are out of date and need to be revised. Current designcriteria recognize soil conditions where geotextiles should not be used for filtrationbecause of the difficulty in establishing a stable filter cake. Those instancesprincipally involve dealing with two extremes: dispersive, narrowly graded, fine soilsand broadly graded soils with very high uniformity coefficients (>50). These two135