THE BEHAVIOR OF VERY LOOSE SAND IN THE TRIAXIAL COMPRESSION TEST

Very loose sand is defined as sand whose state is significantly looser than its critical state. The detailed stress-strain behaviour of very loose sand in triaxial compression is described for the first time within the framework of critical state soil mechanics. It is shown that the undrained behaviour of very loose sand under static loading can be rationalized by normalization with respect to the critical state, an approach that has been successful when applied to clays and to sands dense of critical. Strain contours in normalized stress space are presented for several sands and are shown to be remarkably consistent. The observed normalized behaviour is used to develop a simple constitutive model for the behaviour of very loose sands, based on plasticity theory. It is demonstrated that this model can be used successfully to predict the essential features of the behaviour of very loose sands in undrained and drained triaxial compression including cyclic loading conditions. The model includes the strain so...