The materials modelled by critical state models appeared to be mostly limited to saturated clays and silts, and stiff overconsolidated clays did not appear to be generally modelled with critical state formulations. This fact was probably related to the poor performance of critical state models for soils on the 'dry side'.

(2) Granular materials were rarely modelled by critical state models. In spite of the fact that a number of 'double hardening' sand models (e.g. Nova and Wood, 1979; Vermeer, 1978; Lade, 1977) had been available for many years they did not appear to have been widely used in numerical analyses. This was partially due to the fact that two separate yield surfaces are used in these models for mod- elling hardening and softening, which may cause significant numerical difficul- ties. Another reason may be that a large number of constants (some of these constants have no clear physical meaning) need to be determined before these sand models can be applied

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