Three-dimensional stability assessment of slopes with spatially varying undrained shear strength

The variation of the undrained shear strength (cu) is an important consideration for assessing slope stability in engineering practice. Previous studies focused on the three-dimensional (3D) stability of slopes in normally consolidated clays generally assume the undrained shear strength increases linearly with depth but does not vary in the horizontal direction. To assess the 3D stability of slopes with spatially varying undrained shear strength, the kinematic approach of limit analysis was adopted to obtain the upper bound solution to the stability number based on a modified failure mechanism. Three types failure mechanism: the toe failure, face failure and below-toe failure were considered. A serious of charts was then presented to illustrate the effect of key parameters on the slope stability and failure geometry. It was found that the stability and failure geometry of slopes are significantly influenced by the gradient of cu in the depth direction. The influence of cu profile inclination on the slope stability was found to be pronounced when the increasing gradient of cu in the depth direction is large. Slopes with larger width-to-height ratio B/Hare more sensitive to the variation of cu profile inclination.