Undrained capacity analyses of sensitive clays using the non-local strain approach

Normally consolidated to slightly over-consolidated clays with moderate to high sensitivity tend to display post-peak strain softening response in undrained loading. A total stress based elasto-plastic constitutive model (NGI-ADPsoft) is used to model this behavior. To reduce the effect of mesh dependent results a simple non-local strain approach is adopted in the model. This paper gives a short description of the constitutive model, the implementation of the non-local strain approach into the softening formulation of the model and the calculation procedure for the non-local strain in the FE-program used in this study. The performance of the material model is studied by analyses of a simple shear problem and an undrained bearing capacity problem. It is shown that the model works well as long as the shear band thickness is larger than the element size. However, this requires a very fine mesh in order to model a realistic shear band thickness of clays.