Use of geosynthetics to mitigate problems associated with expansive clay subgrades

Geosynthetics have recently been used for base course stabilization of roadways subjected to environmental loads associated with the presence of expansive clay subgrades. Repeated cycles of wet and dry seasons have often led to significant, non-uniform moisture changes within clay subgrades, resulting in differential settlements between the roadway edges and its centerline and, ultimately, in environmental longitudinal cracks. This paper quantifies the field performance of different sites in order to assess the effectiveness of using geosynthetics to stabilize the base course of roadways constructed on expansive clay subgrades. This includes evaluation of five full-scale field projects that had been subjected to actual traffic and environmental loads. The long-term performance of geosynthetic-stabilized and control sections was evaluated by quantifying the development and extent of longitudinal cracks and the degradation of the base course stiffness. Collectively, the performance evaluation of the multiple geosynthetic-stabilized and control sections in the five case studies demonstrates that geosynthetics can effectively mitigate roadway problems associated with expansive clay subgrades. In addition, field performance data also indicates that unconfined stiffness and tensile strength may not be sufficient for proper geosynthetic selection, pointing to the need for selecting them using properties that also quantify the soil-geosynthetic interaction.