Shear behavior of loess: The role of drainage condition

This technical note investigates the shear behavior of loess using a specifically designed triaxial test scheme, in which five different drainage conditions of loess were controlled by a strain increment ratio (dεv/dεa) in the shear stage. It was established that with an increase in the strain increment ratio, the behavior of the loess samples changed from strain-softening to strain-hardening behaviors in the triaxial test. When dεv/dεa was less than zero, a strong contractive strain-softening behavior was revealed with a large collapsibility index. In the shear stage of a partially drained condition, the loess sample yielded a ‘limited flow’ behavior, which was marked by an occurrence of phase transformation from contractive to dilative response in the q-p’ diagram. More importantly, a unique relationship between the strain increment ratio and stress ratio (q/p’) was established for the test materials. The experimental results suggest a pressing need to thoroughly consider the drainage conditions of loess and the associated impacts on shear.