Evaluation of Geosynthetics Used as Separators

Abstract

Geosynthetics have been used in pavement systems for several purposes, including reinforcement, layer separation, drainage, and moisture barriers. For the layer-separation application, the geosynthetic material is used to prevent soil fines from migrating into the base-course layer as well as stones from this layer from penetrating into the subgrade. This material migration would affect the drainage capability as well as the structural capacity of the pavement. However, such an effect is very hard to detect since soil pumping will occur under the pavement surface, and therefore a comparison of the performance of different types of geosynthetic separators is almost impossible. A 3-year project to study the in situ behavior of geosynthetically stabilized flexible pavements in Bedford County, Virginia, ended recently. Results from ground-penetrating radar surveys and materials excavation are presented. Ground-penetrating radar surveys, falling-weight deflectometer results, rutting measurements, and ground-truth excavation indicated that the separation provided by geotextiles was important in reducing base-course contamination by subgrade soil. Such a reduction will significantly reduce the resilient modulus of the base-course layer. In addition, service-life predictions of evaluated sections were conducted based on the traffic applied and rutting distress. Geosynthetics improved secondary-road pavement performance; geotextiles increased service life more than geogrids, due to their separation function.