Update on GSI's Geotextile Highway Separation Study

This short paper presents updated information on GSI's highway geotextile separation study. In the transportation industry one of the major uses of geotextiles is a separator between fine grained subgrade soils and the overlying drainable base course materials in a pavement system. The purpose being to prevent the intrusion of the fine grained soils into the drainable base materials and vice versa, the gravel base course from protruding into the soil subgrade. This current study, under the auspices of the Geosynthetic Institute, is to evaluate the performance of geotextiles as separators under various roadway and environmental conditions. There are currently 13 sites, widely distributed in the U.S., under investigation. Geotextiles as separators in pavement cross sections are significantly under-utilized. One of the impediments is the unknown cost-to-benefit ratio of geotextile systems as compared to conventional, nongeotextile, ones. While geotextiles have been used as separators between soil subgrade and stone aggregate for over 25 years, their life-cycle improvement of pavement systems has only been qualitatively assessed. Thus, a nationwide study is underway to quantify geotextile performance in this application. The focus is to access the benefits of a geotextile separator used in paved roads underlain by stiff and firm subgrades. This study is not focused on stabilization or reinforcement of highways on soft subgrades, an area in which the benefits of geotextiles have long ago been demonstrated. It is felt that a large database is needed to assess the performance with and without geotextile separators at the same location, and then a quantitative assessment of the performance of the respective sections over the lifetime of the roadway is necessary. Even further, this assessment should be national in scope. In this way, all types of traffic, subgrade, climatic and environmental conditions can be included in the assessment.