New Layer Coefficients for Geogrid-Reinforced Pavement Bases

Abstract

Stabilizing the base layers of flexible pavements is gaining tremendous attention due to the lack of suitable construction materials. A geogrid reinforcement could offer a reduction in granular layer thickness or enhance the service life of the pavement. However, there is no standard direct methodology available for the design of a flexible pavement with a geogrid-reinforced base layer. The current design approaches adopt the base layer coefficient ratio (LCR) derived from the layer coefficient equation proposed by the American Association of State Highway and Transportation Officials (AASHTO 1993), which was initially developed for an unreinforced base layer. Moreover, the accuracy of the existing model for determining the base layer coefficient needs a reassessment since it varies for different subgrade conditions. Hence, an attempt was made to propose a new model which emphasizes on unreinforced and geogrid-reinforced base layer coefficients for weak-to-moderate subgrade conditions. Prior to the analysis, large-scale model pavement experiments were conducted to realize modulus improvement factor (MIF) and range of values of LCR of different geogrids, which are crucial parameters used in the design. In addition, design examples, validation and the MIF and LCR values of geogrid-reinforced base layer were provided for obtaining the base layer coefficients. It was noticed that the MIF and LCR value for the geogrid-reinforced base layers range between 1.6–3.33 and 1.23–1.59, respectively. The newly proposed equation for the base layer coefficients accounted for about a 33% reduction in the base layer thickness compared to the unreinforced case. Hence, a safe and economical pavement section may be obtained from the proposed model.