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 K₀-consolidated undrained triaxial compression tests, with even less information available for the deeper layers 8 and 10. This study employed a series of K₀-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 (E^u_max) and reference shear strain (γ_0.7). 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 I_p 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 γ_0.7 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.