A hypoplastic model for sand-fines mixtures

The presence of fines can significantly influence the mechanical behavior of soils. In this study, a hypoplastic model is extended to simulate the stress-strain relationship of sand-fines mixtures. Firstly, three modifications are incorporated into the model to accurately simulate the effective stress path, hardening rate, and limited flow type response of sand during undrained loading. Additionally, a novel formulation is proposed to capture the critical state line of soil mixtures across a wide range of fines content. This formulation is then integrated into the characteristic void ratios of the hypoplastic model, enabling it to effectively consider the combined influence of void ratio, confining pressure, and fines content on the density state of the sand-fines mixtures. The predictive capability of the model is demonstrated through a comparison of simulation results and experimental data for undrained triaxial tests conducted under various conditions.