Performance of the constitutive model for soil gUTS

A non-associated plasticity model for soil is described which introduces a number of modifications into an existing critical-state bounding-surface model for clay to extend the range of application to silts and sands, offering a simple unified treatment for soil. This paper discusses these modifications and then presents a number of comparisons illustrating the capability of the model to simulate the behaviour of a range of soil types (as recorded by others) on specimens subjected to essentially uniform states of stress in laboratory test devices. Drained and undrained monotonic and cyclic tests on kaolin clays, silts and silicate sands under a wide range of confinements in both loose and dense states are considered. The significance of including a bi-linear critical-state line (in the conventional semi-logarithmic plot) is discussed and the consequences of allowing the projection centre to move upon stress reversal are illustrated.