A unified 3-d critical state bounding surface plasticity model (gUTS) has been developed which is able to provide realistic simulations of the behavior of clays, silts and sands both in drained and undrained conditions over a wide range of monotonic and complex cyclic paths. A strong feature of this model is its ability to treat loose and dense states of the same material with a single set of material constants. The link between the two states is made by introducing an apparent normal consolidation line for sands and adopting a volumetric plastic strain hardening/softening model (similar to the critical state models for clays). This and other features enable the model to degenerate to simpler forms including the classic modified Cam-Clay formulation. To date, simulations have concentrated on the medium to high strain range (10-3 to 10-1). To address a wider strain range, this paper reports on a new series of simulations for sand in the range 10-6 to 10-
