Influence of effective normal stress in the measurement of fully softened strength in different origin landslide soils

• At low ENS, a lower fully softened strength for loess is found in ring-shear testing.
• A lower fully softened strength for mudstone is found in ring-shear testing.
• Fully softened strength is related to consolidated structure and shear direction.

In the present study, triaxial compression and ring-shear tests were performed on mudstone and loess soil samples to investigate the effect of effective normal stress on fully softened strength parameters. The study revealed that at lower effective normal stresses, a lower fully softened strength angle, ϕfs, was found in the loess sample in ring shear testing in comparison to triaxial testing. In contrast, a lower ϕfs was found in the mudstone sample in ring shear testing in comparison to triaxial testing at all effective normal stresses.