Stability of Embankment on Clay

The paper describes the failure of an embankment on clay and the investigation carried out to determine the mechanism of the failure. The slip surface passed through a thin layer of soft silty clay. Measured deformations and pore-water pressures are summarized. The shear strength of the silty clay was measured by unconfined compression tests, triaxial tests, and simple shear tests. Stability analyses using the undrained shear strength measured by the unconfined compression test and the simple shear test give safety factors between 1.1 and 1.4. The consolidated-undrained triaxial test was found to overestimate the undrained shear strength by a considerable amount. Stability analysis using effective stress and measured by triaxial and simple shear tests also overestimate the safety factor. Probability analysis was used to evaluate the effect of the various uncertainties on the computed safety factors.