U.S. Army Corps of Engineers design procedure was reviewed to validate the existing criteria for geotextile-reinforced unpaved roads and to modify the criteria for the addition of stiff biaxial geogrids. Geogrid stiffness here refers to products demonstrating good torsional rigidity and aperture stability. The theoretical basis for the existing design procedure was reviewed to ensure that appropriate assumptions were used to derive the current design method. Historical test section results were used to validate the empirical bearing-capacity factors, Nc, used for unreinforced and geotextile-reinforced base materials. In addition, an empirical bearing-capacity factor for geogrid reinforcement was derived to modify the existing design procedure for both geotextile and geogrid use. The relevant theory used in the development of the existing design method to establish the basis for the analyses is described. Previously unpublished test section results are presented and used to calculate experimental bearing-capacity factors, and the calculated factors are compared with the theoretical values used in the existing procedure. The results of the analyses support the use of the existing design procedure's bearing-capacity factor for unreinforced sections; the existing bearing-capacity factor for geotextile-reinforced unpaved roads appears to be unconservative for the conditions of the full-scale test section presented. Finally, a bearing-capacity factor for the use of a geogrid and geotextile combination is recommended for modification of the existing Corps of Engineers design procedure.
Abstract