Elastoplastic Modeling of Sandy Clays Based on Equivalent Void Ratio Concept

Naturally sedimentary soils, such as marine clays, weathered residual soils, and glacial deposits, usually possess a certain amount of sand particles. These types of soils could be classified as sandy clay, because the coarse fraction is usually under the transitional content. Their mechanical properties (e.g., compressibility and shear strength) are dominated by the clay matrix and significantly affected by the evolving interparticle structure. Previous research into sandy clay is experimental or numerical, and theoretical investigations that considered the reinforcing effect of coarse inclusions have seldom been reported. Therefore, the effect of sand content was incorporated based on the equivalent void ratio (e*) and equivalent compression curve (ECC) of sandy clays. A unified structure parameter (χ) was introduced, which could capture the reinforcing effect of sand particles on the stiffness and shear strength of sandy clays well. The constitutive relationship was formulated by incorporating the equivalent void ratio concept into an elastoplastic framework. Validation of the proposed model was achieved by comparing the predicted results with experimental data that were compiled from the literature. This revealed a satisfactory prediction for the mechanical response of sandy clays and other gap-graded soils (i.e., gravel-clay mixtures) with a broad spectrum of coarse fractions.