Strain localisation in sensitive clays: can rate dependency provide mesh independent results?

Abstract

Finite element modelling involving strain-softening materials becomes mesh dependent if not regularised by a mesh independent length scale. The objective of this paper is to investigate whether the inherent strain rate dependency of a sensitive clay can result in mesh independent results in the post-peak strain-softening regime. It describes first a constitutive model that accurately reproduces the rate-dependent behaviour obtained from laboratory tests on block samples of a natural sensitive clay. Then finite element analyses of soil columns under constant shear displacement rate are conducted. The boundaries are closed but internal flow of pore water is allowed. Strain localisation is triggered using a zone with lower undrained shear strength. The results show an interval of regularised strain-softening behaviour before the solution becomes mesh dependent. Pore water flow is found to delay the onset of mesh dependency. In conclusion, this paper achieves a regularised force displacement response for a strain-softening clay, without the need to introduce an artificial internal length scale.