A quantitative comprehensive structural parameter is defined using ratio of principal stress difference of intact loess to that of disturbed saturated loess under triaxial stress condition

which can not only reflect arrangement but also coherent structure of soil particles. The relationship between variation quantity of the structural parameter - and axial strain can be fitted with hyperbola ( is initial structural parameter)

equation of the structural parameter obtained with which can reveal the influence of confining pressure

water content

density

stress and strain on structure of intact loess. The structural parameter can make stress- strain curves of intact loess under different water content normalize to structural stress-strain curves which can be described using that of disturbed saturated loess at the same confining pressure simulated with the model proposed by Duncan and Chang. A constitutive relation describing stress-strain behaviour of intact loess is presented by introducing the structural parameter to that of disturbed saturated loess

which can consider structural effect and describe both hardening and softening stress-strain behaviour. Its rationality is confirmed by the agreement of results calculated by using this relation with that tested.