This paper investigates the efficacy of an alternative construction methodology proposed by the authors in the form of a ‘C’-shaped lime stabilized capping. It is used for confining expansive clay subgrade soil under embankments carrying flexible pavement at their top, to enhance their performance. The role of capping in controlling moisture ingress responsible for swelling is assessed by studying vertical displacements and suctions in expansive subgrade soils. The load-displacement behavior and the variations in suctions of expansive subgrade soil are studied by using Mohr-Coulomb material model and Van Genuchten Hydraulic Model respectively in FEM based Software PLAXIS 3D. It is observed from the results that; the swelling displacements are considerably reduced and suctions under embankment toe are observed to increase. It can therefore be concluded that, the lime stabilized capping consisting of horizontal buffer layer and vertical cut-offs is effective in controlling swelling displacements in expansive subgrades.
The performance of flexible pavements constructed on embankments founded on expansive clay subgrade is greatly affected by the distress caused in these embankments as they are subjected to swelling displacements. These are caused by the volume changes in expansive subgrade soil due to moisture variation. The authors have suggested the technique of ‘C’-shaped lime stabilized capping in their earlier studies which is useful for controlling swelling displacements within the expansive subgrade. In the present study, the authors have attempted to assess the efficacy of the capping material itself for controlling swelling displacements at the top and bottom of embankment which is directly responsible for improving the performance of pavements on these embankments. This assessment is carried out with respect to stiffness and reduction in permeability of capping material. Stiffness of the buffer layer controls swelling displacements within the embankment under flexible pavement and the reduced permeability of the capping will control moisture variations and the corresponding pavement distress. The stiffness assessment is carried out through laboratory Unconfined Compression Strength (UCS) tests for modulus estimation by curing the samples for short-term and long-term strength gain. Assessment of permeability reduction is carried through the study of permeability of expansive soils after lime stabilization. Swelling displacements are estimated using Finite Element Analysis (FEA) of the numerical model. The experimental and numerical analysis results indicate that with the increased modulus and reduced permeability of the buffer layer material the swelling displacements at the top and bottom of pavement embankment have reduced. This will help in improving the performance of pavement constructed on the embankment founded on the expansive subgrade.
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