Undrained Behavior of Sand-Fines Mixtures and Their State Parameter

Abstract

The influence of fines on the undrained behavior of sand was investigated experimentally over a range of fines content and effective mean stress. The role of fines on compressibility and formation of meta-stable soil fabric was analyzed. For a fines content in the range of 5–30%, most of the specimens manifested reverse behavior opposed to the normal behavior of clean sand. The addition of fines led to shifting of both the isotropic consolidation line and the steady-state line, increased compressibility, and occurrence of reverse behavior. All these behavior attributes are linked when the test results are interpreted in the context of the critical-state soil mechanics framework. In particular, reverse behavior is associated with an isotropic consolidation line that locates above the steady-state line. Several quantitative measures for characterizing the undrained deviator stress-strain responses were proposed, and these measures manifested correlation with the state parameter at the start of undrained shearing. These correlations were also tested with two published datasets.