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

Geotextiles in Embankment Damsdam. Designers are cautioned to evaluate the consequences of failure during thedesign process and decide if the risks are worth taking.There are numerous factors that can lead to performance problems with geotextileinstallations. The performance problems are related to one of the following generalmechanisms:• Excessive clogging or piping• Stress induced distortion• Environmental degradation• Slope instability• RuptureThe performance problems can be caused by improper design, poor installation, postinstallation damage, or degradation.4.1 Excessive clogging or pipingClogging occurs when particles fill the void space of a geotextile and reduce itshydraulic conductivity. A reduction in permeability and permittivity occurs inproportion to the amount of void space that becomes clogged with foreign material.The clogging can be caused by filling the voids with soil, with biologicalmicroorganisms and their byproducts, or with inorganic chemical precipitates. Somedegree of clogging always occurs with a geotextile. If a large amount of the poreswithin the geotextile become clogged, the geotextile is likely to fail to adequatelyperform its intended filtration and drainage functions. Such a material which can nolonger effectively perform its intended filtration and drainage function is described asbeing excessively clogged. Excessive clogging can not be allowed to occur.A related problem, referred to as “blinding” occurs when fine-sized particlesaccumulate on the surface of the geotextile. The problem of blinding oftenoriginates where a geotextile is not placed in direct contact with the soil to befiltered. The void spaces between the soil and the geotextile become filled with fineparticles having a lower permeability than the base soil or the geotextile. Blindingcan be considered a form of clogging where the blockage is at the surface of thegeotextile rather than within it. Many authors in the field of geotextiles make nodistinction between clogging and blinding and use the term clogging to imply eithermechanism.72