The paper describes a general approach to the development of a constit
utive model for predicting the generalized small-strain behaviour of s
oils. The model incorporates non-linear stress-strain behaviour, stres
s-path dependence and a consistent definition of the small-strain regi
on (SSR), Based on this general approach, a simple model is proposed w
hich incorporates cross-anisotropic elasticity within the linear elast
ic region (LER) and elliptical boundaries for the LER and SSR, The mod
el leads to unique normalized stress-strain behaviour of undisturbed B
othkennar clay for the complete range of stress probe directions in tr
iaxial stress space, The comparison confirms the uniqueness of the nor
malized volumetric and deviatoric stress-strain behaviour, The model c
an easily be incorporated into numerical procedures for solving two- a
nd three-dimensional boundary value problems.