Cosserat FE modeling of the bearing capacity and instability of strip footing on marine-sensitive soils considering heterogeneity and nonlinear softening

Marine-sensitive soils exhibit significant strength heterogeneity and nonlinear strain softening, which are vital characteristics in geotechnical engineering. This study introduces a novel soil strength formulation that effectively captures both of these key characteristics. This formulation is incorporated into the Mohr-Coulomb matched Drucker-Prager yield criterion. To address the mesh-dependence challenges typically encountered in classical finite element (FE) analysis for strain localization, this paper establishes a robust constitutive integration algorithm within the framework of Cosserat continuum theory. The numerical implementation is accomplished through the UEL function in the ABAQUS FE software. Following validation, the methodology is applied to conduct thorough FE analyses on the bearing capacity and progressive failure process of strip footings. Additionally, through parametric investigations, we explore the influence of nonlinear strain softening parameters and the heterogeneity parameter on the bearing capacity coefficient (Nc) and the underlying foundation failure mechanisms. By simulating the complete progressive failure process of the foundation, this numerical method exhibits its remarkable capability to accurately replicate the entire progressive instability process. Derived from parametric analyses, a remarkably accurate formula (Nc(λ = 0)) is obtained, accounting solely for nonlinear strain softening. Furthermore, a comprehensive formula (Nc) is introduced, capturing both strength heterogeneity and nonlinear strain softening. •Introduction of a soil strength formulation capturing both strength heterogeneity and nonlinear strain softening.•Implementation of a Cosserat continuum model through FEM, incorporating soil heterogeneity and nonlinear strain softening.•Model validation via plane strain tests and an experimental method for parameter acquisition.•Analysis of heterogeneity and nonlinear strain softening impact on strip footing capacity and soil progressive failure.•Presentation of Nc expression for strip footing considering coupled strength heterogeneity and nonlinear strain softening.