ABSTRACT
Robertson & Bolton, 2001; Cheng, et al. 2003; Cheng, 2004).
1.2 Previous definitions of critical states
Critical States were originally defined macroscopically as ultimate states of continuous shear flow at constant volume, at which the voids ratio, e, uniquely determines both the deviator stress, q, and the mean effective (intergranular) stress, p′ (Roscoe et al. 1958). Later, a different way of defining critical states was used by Schofield (1980). He considered a set of specimens all at the same voids ratio at the moment of failure during drained triaxial tests. He observed that brittle, dilatant shear ruptures occur at low pressure but that the rate of dilation decreases as p′
increases up to a critical pressure p′crit beyond which the behavior changes to plastic work hardening with volumetric compression at yield.Variation of p′crit with e defines what Schofield took to be a line of critical states.
