Modelling the stress-strain behaviour of Bothkennar clay

A programme of triaxial stress path tests on samples of Bothkennar clay from Scotland was undertaken to investigate the validity of the elasto-plastic constitutive model S-CLAY I for natural anisotropic soft clays. The experimental results showed that the rotation of the yield curve during plastic straining was reasonably consistent with the model. The shape of the yield curve for Bothkennar clay following isotropic loading (and possibly other forms of loading) was not however well matched by the S-CLAY1 yield curve, in contrast to several Finnish clays. There is therefore a need for a more flexible yield curve expression, capable of representing the various yield curve shapes of different natural soft clays within a single anisotropic elasto-plastic model.