This paper describes an anisotropic elastoplastic based constitutive model for describing the
behaviour of lignosulfonate stabilized soils. The proposed model is an extension of the earlier model
developed by Dafalias (1987). The theoretical formulations of the current model were based on
the frame work of critical state concept. The novel feature of this model is the incorporation of a
material constant b, which takes into account of the degree of cementation. It is demonstrated
that the model can capture the behaviour of lignosulfonate treated soil.