عنوان مقاله [English]
One of the fundamental aspects of sandy soils mechanical behavior is the failure state. Diverse experimental works existing in the literature show that the failure state in sands depends on confining pressure, density and stress path, however the most of these works were performed at the medium or high confining pressures (more than 100 kPa generally), and also the majority of
constitutive models have been based on these type of results. The dependence of the failure state on confining pressure for low levels of this pressure is little studied and needs more investment. In this study, after a brief literature review, a set of drained triaxial tests with different confining pressures (10-200kPa) were performed. Finally, based on obtained experimental results, some of advanced constitutive models, such as Wang, Nova and CJS models were validated. The obtained results show a nonlinear relation between the failure state parameter ($\sigma_1/\sigma_3$) and confining stress. This nonlinearity is more important for the low levels of confining stress and must be properly introduced in the failure surfaces of constitutive models.