Cross-anisotropic stiffness characteristics of a compacted lateritic clay from very small to large strains

Abstract

Lateritic clay is widely distributed in tropical and subtropic regions, with distinct engineering properties from other clays. Its stiffness properties, which are often anisotropic and crucial for analysing the serviceability limit state of earthen structures, have not been well understood. This study investigated the cross-anisotropic stiffness of compacted lateritic clay through comprehensive isotropic compression and consolidated drained and undrained shear tests. Both vertically and horizontally cut specimens were tested using triaxial apparatus equipped with bender elements and local strain measurements. The results show that compared with other clays, the lateritic clay shows a weaker dependency of shear modulus to confining pressure, a higher shear modulus at the same confining pressure, and a higher degradation rate of stiffness with strain. The lateritic clay behaves like granular material due to its large-size aggregated microstructure and 42% sand content. The widely used correlations between stiffness parameters and plasticity index seem unsuitable for it. Furthermore, the elastic shear modulus in the vertical direction is slightly higher than that in the horizontal direction, and the anisotropy evolves during shearing. A complete set of cross-anisotropic stiffness parameters for both effective and total stress analysis were determined. They are useful for developing constitutive models and analysing earth structures' serviceability involving lateritic soils.