In-Situ Behavior of Geosynthetically Stabilized Flexible Pavement
Appea, Alexander Kwasi
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The purpose of a geotextile separator beneath a granular base, or subbase in a flexible pavement system is to prevent the road aggregate and the underlying subgrade from intermixing. It has been hypothesized that in the absence of a geotextile, intermixing between base course aggregate and soft subgrade occurs. Nine heavily instrumented flexible pavement test sections were built in Bedford County Virginia to investigate the benefits of geosynthetic stabilization in flexible pavements. Three groups of different base course thicknesses (100, 150 and 200mm) test sections were constructed with either geotextile or geogrid stabilization or no stabilization. Woven geotextile was used in sections 2, 5 and 8. Geogrids were used in sections 3, 6 and 9, and sections 1, 4 and 7 were controls. Six Falling weight deflectometer (FWD) tests were performed on all the nine sections over 30 months. The nine sections were subjected to at least 5 load drops with wide loading range each time. The measured deflections were analyzed using the MODULUS back-calculation program to determine layer moduli. The measured deflections were used together with elastic, viscoelastic and the MODULUS program to determine the extent of intermixing at base-subgrade interface. The study concluded that a transition layer would develop when a separator is absent, especially in the weak sections (designed to fail in three years). Other measurements such as in-situ stresses, rut depth, and subsurface profiling (using ground penetrating radar) support the conclusion of the development of a transition layer.
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