Durability of nonwoven geotextiles for the mechanical protection of PVC geomembranes in dams and reservoirs

Nonwoven geotextiles have proven to be an essential element in the installation of waterproofing systems in dams and reservoirs, especially in the case of use with PVC geomembranes. The paper first illustrates the properties to be taken into account for a correct design and an appropriate technical specification. The protection function is the main item to consider in this application, so a proper dimensioning of the mechanical performances is necessary, with a special focus on energy absorption and puncture resistance. The mechanical performance of such geotextiles has to be evaluated both in the medium term, in order to guarantee the installation to the installation stage, and also in the long term, in order to guarantee the behaviour of the system over the years. Depending on the site’s chemical and environmental conditions affecting the service life of the geotextiles, such as pH values, orientation and inclination of the slope and latitude, the different polymers and grade of polymers of the geotextiles can offer customized and appropriate performances. Also the interaction with the geomembrane layer must be considered to make the choice of the appropriate geotextile. This applies to the case of geotextiles that are heat-coupled to the geomembrane in the factory, as well as in the case of geotextiles installed separately from the geomembrane. The European Harmonized Standard EN 13254:2014 Geotextile and geotextile-related products – Characteristics required for the use in the construction of reservoirs and dams – among other properties also addresses the durability of geosynthetics. The paper will correlate the standard with field experience on specific projects. The variables to be considered to ascertain the durability of geotextiles will be examined in the paper, which will report the results of durability test in the field, carried out during more than ten years. A method is suggested for determining the influence of resistance problems on the installation procedures, and also for maximizing the safety of the overall project.