The Steady State of Sandy Soils

Abstract

An alternative procedure to evaluate the void ratio of triaxial test samples is introduced. This method is recommended particularly when very loose samples are tested and an important volume change occurring during the saturation process is expected. In addition, using Toyoura sand a comprehensive set of triaxial tests carried out under both undrained and drained conditions of monotonic loading is presented. For the undrained contractive responses, the results showed two stages associated with the steady state. After the peak strength, the deviator stress drops to a minimum value which can be seen as a quasi steady state, thereafter, the strength increases to an ultimate value corresponding to the actual steady state. Undrained dilative responses clearly indicated the existence of an ultimate state developed at large deformations which represents the steady state of deformation. The results indicate that the quasi steady state is slightly affected by the initial mean stress, whereas, the steady state is unaffected by the initial mean stress. Furthermore, the locus of the ultimate states achieved through drained conditions of loading was shown to be coincident with the steady state line evaluated by means of undrained tests. Finally, according to the relative position of the steady state line with respect to the isotropic consolidation curves for the loosest and densest states of a given soil, the index, Relative Contractiveness, R c , is proposed. It is postulated that R c is related to the inherent liquefaction vulnerability of a soil.