Interpretation of constant suction direct shear test

Constant suction direct shear test enables the understanding of failure mechanism in rainfallinduced landslides. It can be conducted using a conventional apparatus with some modifications. The constant is carried out two stages. In first stage, unsaturated soil specimen consolidated to target net normal stress and matric then sheared second stage. Matric usually controlled axis-translation principle. commonly observed that an shows strain-hardening behaviour at large displacements making determination difficult. Hence, objective this study critically examine tests analysis results obtain strength parameters for soils. data were collated from literature. was found interpretation has inconsistencies: (1) taking arbitrary displacement strain or limit, dependent on size apparatus, (2) correcting only contact area. effect these consequences range negligible significant. resolved by plotting stresspath plot. effects area correction are shown almost small horizontal less than 2 mm both square circular boxes. A more consistent demonstrated where inconsistencies considered.