A kinematic hardening model based on endochronic theory for complex stress histories

While the field of soil constitutive modeling is rich, the availability of models that capture the behavior of different soil types under complex loading is limited. This study presents the development and validation of the Multi-Mechanical Model (MMM). The MMM is an elasto-plastic kinematic hardening model, which extends an earlier endochronic model by introducing the third stress invariant, accounts for shear-volumetric coupling in granular materials, and displays ratcheting behavior during stress reversals. A series of triaxial and isotropic consolidation tests are used to calibrate the MMM to materials found in conventional unbound granular materials and subgrades, such as crushed limestone, Leighton Buzzard sand, and Vicksburg Buckshot clay. The MMM is tested against resilient modulus test data that present complex stress histories. The study shows the MMM is straightforward in its calibration, while also displaying a robust capability in capturing the complex behaviors of the different soil types under various loading conditions. While positioned for applications in other areas, the MMM’s capabilities in capturing the short-term pore pressure response of fine-grained materials, the shear-induced volume change and stress-hardening effects of granular materials, and ratcheting behavior during repeated loading conditions make it well-suited for addressing pavement problems.