Shear band analysis of silt-clay transition soils under three-dimensional stress-strain conditions

This paper investigates shear banding as a possible failure mode for silt–clay transition soils under general three-dimensional stress conditions. Drained and undrained true triaxial tests with constant b values were performed on tall prismatic specimens of such soils with systematically varying silt contents. Based on the values of critical plastic hardening modulus, shear banding does not govern the strength characteristics of the soils for b values less than 0.2. For larger b values, shear band formation is essentially critical as it takes place in the hardening regime of the stress–strain curves prior to the smooth peak failure points. An increase in silt content appears to move the onset of shear banding to lower levels of shear in the stress–strain relations of the silt–clay transition soils. It is also demonstrated that a non-associated constitutive model with a single hardening law is capable of accurately predicting the onset of shear banding in normally consolidated silt–clay transition soils based on bifurcation theory.