Investigation of the critical state behavior of unsaturated silty sand with different fine contents in terms of net and effective stresses

Abstract

This paper investigates the effect of fine content and matric suction on the behavior of silty sand soil through both net and effective stress variables in the critical state soil mechanics framework. For this purpose, a set of CD triaxial tests in saturated and unsaturated states were performed on the samples of sand with different fine contents. The results showed that in term of net stress variables the position of the critical state line (CSL) in stress space for a given non-plastic fine depend on suction. However, these lines approach each other by choosing a proper effective stress relationship. The CSLs in the coordinates of the void ratio in the term of effective stress changed as a function of the non-plastic fine content and matric suction. However, using the concept of the equivalent intergranular void ratio and considering a special mean effective stress variable depending on suction, the CSLs were converged so that a single line can be defined to describe the behavior of the silty sand at the critical state. Finally, the stress-dilatancy relationship of two constitutive models was examined and it was shown that the use of the equivalent state parameter could facilitate the use of these relationships.