Small-strain characterization of Shanghai clays by triaxial compression tests

Abstract

The mechanical properties of the upper Shanghai Layers 2-6 clays at small strain levels have been extensively investigated. Nonetheless, limited data exist on their small-strain characteristics through K 0-consolidated undrained triaxial compression tests, with even less information available for the deeper layers 8 and 10. This study employed a series of K 0-consolidated undrained TC tests on intact samples from both the upper layers 2-6 and the deeper layers 8 and 10 of Shanghai clay. We evaluated the undrained maximum secant stiffness (Eu max) and reference shear strain (γ0.7 ). An increase in over-consolidation ratio (OCR) results in a higher E u max/p’ and a more rapid decay of the G/G max with the increasing shear strain (γ). As the value of γ 0.7 increases with I p and decreases with OCR, a correlation between γ 0.7 and Ip can be established. This study observed significant correlations between the E u max, effective stress (p’), and the maximum deviatoric stress, as well as between E u max and the cone resistance obtained from field cone penetration tests. These correlations offer methods to estimate E u max and γ0.7 values based on parameters that are more readily measurable, which provide critical references for the calculations and design parameters in foundation engineering within the Shanghai region.