An analytical model for quantification of geosynthetic benefits in roadway base stabilization
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Stabilization of base aggregate using geosynthetics may provide improved performance in flexible pavements. Through the aggregate-geosynthetic interaction, the induced shear stress in the base aggregates is transferred to the geosynthetic resulting in the development of tensile stresses. The tensioned geosynthetic applies in turn additional lateral confinement to the aggregates to restrain their movement under repeated traffic loading. The use of geosynthetics in base stabilization has been reported to result in reduced rutting depths in roadways. Design guidelines, either empirical or mechanistic-empirical, have been established for the design of non-stabilized roadways. These guidelines, however, do not take the geosynthetic effect into account. Accordingly, the geosynthetic benefits in base stabilization need to be quantified in a way that can easily be incorporated into the existing design procedures. This study proposed an analytical model to achieve this goal. In this study, the additional lateral confinement provided by the geosynthetic was modeled as a uniform additional confining stress within the geosynthetic influence zone. The pavement section was considered as an infinitely long elastic solid under plane strain conditions, which allowed the model framework to be established using the theory of elasticity. The aggregate-geosynthetic interaction, on the other hand, was modeled using the soil-geosynthetic composite (SGC) model. As a result, an additional confining stress could be defined from the stress-displacement relationships in the elastic model framework. An increased elastic modulus could then be predicted from the additional confining stress with a specific criterion for equivalency of the original base course with additional confinement and an alternative base course with enhanced elastic modulus but without additional confinement. The increased modulus can be used as an updated property for the geosynthetic-stabilized base aggregate in mechanistic-empirical pavement design procedures. The predicted equivalent increased moduli were validated using the results from repeated loading triaxial tests of two published studies. Overall, reasonably good agreement was found between model predictions and the test results. Predictions from this model were also compared against those of another analytical model, and close results were observed. A sensitivity analysis conducted using the proposed model indicated that model predictions are particularly sensitive to the original base modulus, geosynthetic properties (including confined geosynthetic stiffness and the stiffness of the soil-geosynthetic composite) and the thickness of the geosynthetic influence zone.