Estimation and Comparison of Suction Compression Index for Oklahoma Subgrade Soils

Pavements constructed on expansive soils suffer from distress in response to climatic and environmental conditions. Drying and wetting cycles result in volumetric changes in expansive subgrade soils. Suction compression index (γ_h) is an important parameter in characterizing expansive soils and predicting their volume change (shrinkage and swelling) behaviors. The γ_h defines the changes in volumetric strain with respect to the changes in suction. Several methods are available for estimating the γ_h values. This paper presents a comparison study for estimating the suction compression index using the results obtained from the coefficient of linear extensibility (COLE) tests and soil index properties such as liquid limit, plasticity index, and clay content. Shelby tube soil specimens were obtained from different locations across Oklahoma for laboratory testing. In addition, the soil property values were extracted from the USDA-NRCS database for utilizing in the comparison study. All the data is also used to classify the Oklahoma soils according to expansion potential based on the COLE and index properties of the soils. Finally, contour maps of the γ_h parameter for the Oklahoma soils are prepared based on the COLE and soil index properties. The outcome is a set of reliable evaluation of γ_h and prepare contour maps of γ_h for shrinkage and swelling soils in Oklahoma for practicing engineers to use.