This study was primarily concerned with the geosynthetic reinforcement of an aggregate base of a surfaced, flexible pavement. Separation, filtration and durability were also considered. Specific methods of reinforcement evaluated included (1) reinforcement placed within the base, (2) pretensioning a geosynthetic placed within the base, and (3) prerutting the aggregate base with and without reinforcement. Both large-scale laboratory pavement tests and an analytical sensitivity study were conducted. A linear elastic finite element model having a cross-anisotropic aggregate base gave a slightly better prediction of response than a nonlinear finite element model having an isotropic base. The greatest benefit of reinforcement appears to be due to small changes in radial stress and strain in the base and upper 12 in. of the subgrade. Greatest improvement occurs when the material is near failure. A geogrid performed differently and considerably better than a much stiffer woven geotextile; geogrid stiffness should be at least 1500 lbs/in. compared to about 4000 lbs/in. for a woven geotextile. Reinforcement is effective for reducing rutting in light sections having Structural Numbers less than 2.5 to 3 placed on weak subgrades (CBR less than 3%). As the strength of the section increases, the potential benefits of reinforcement decrease. For somewhat stronger sections, whether reinforcement is effective in reducing rutting where low quality bases and/or weak subgrades are present needs to be established by field trials. Both prerutting and prestressing the aggregate base were found, experimentally, to significantly reduce permanent deformations. Prerutting without reinforcement gave performance equal to that of prestressing and significantly better than just reinforcement. Prerutting is relatively inexpensive to perform and deserves further evaluation. (A)
Abstract