Abstract: A physical study of slope stability has been done by means of geotechnical centrifugal model test to investigate the influence of presence of soft stratum immediately over inclined bedrock on slope stability and failure mode. And the limit equilibrium method based on the failure mode of translational slide is used to predict the factor of safety against sliding simulated in the model tests. It is found from the centrifugal model tests that, in the case of a thin layer of soft soil with lower shear strength over the inclined bedrock, the slip plane is close to the bedrock, and that lateral displacement at failure is of equal value almost throughout the entire slope mass, exhibiting a typical failure mode of translational slide. It is also seen that, in the case of absence of soft soil layer over the inclined bedrock, the slip plane is away from the inclined bedrock at a distance, and that the slope mass above the slip plane is of translational slide whereas the slope mass under the slip plane is of forward tilt slide. It is shown that the stability of slope is not solely determined by the average shear strength of slope soil mass when soft stratum is present over bedrock. It is confirmed that the suggested limit equilibrium analysis is able to predict the factor of safety of a slope on inclined slope by comparison of the factor of safety measured by physical centrifugal model test and the calculated one.

Key words: slope stability, soft stratum, failure mode, centrifugal model test, limit equilibrium analysis