Design, Performance and Economics of Separation Geotextiles in Pavements

Fully drainable pavements are more commonly utilized as a solution to premature pavement distress. With these pavements, drainage is achieved by a coarse graded aggregate layer with little or no fines. The gradation of various soil and aggregate layers comprising a pavement must be such that intermixing of materials, and the resulting loss in performance, is minimized. A second solution is to utilize a geotextile separation layer at critical interfaces to prevent contamination from intermixing of adjoining materials. This solution permits a broader range of materials meeting strength and drainage requirements that can be used in a pavement. A review of the literature suggests that geotextiles are effective in performing the separation function in pavements. The primary design considerations for such geotextiles are construction survivability and soil retention. Geotextile construction damage decreases exponentially with an increase in mass per unit area. Geotextile apparent opening size is related by a factor of 1/2 to 1 with d₈₅ size of the soil being retained. The benefit of use of geotextile for any specific project depends on the availability and cost of soils and aggregates meeting filter and separation specifications.