Geometric Concerns in Slope Stability Analyses

Abstract

Geometric approximations necessary in the Simplified Bishop Method of Slices for slope stability analysis can lead to inadvertent errors. Depending on the method of computation of the slice area and base inclination angle, significant extraneous error may be introduced. Use of the exact slice area and straight line base angle results in consistently accurate estimates of the overturning and resisting moments and factor of safety. Convergence to an exact solution as a number of slices is increased is also demonstrated. Unconservative estimates of the factor of safety may be obtained using a trapezoidal area approximation together with a straight line slice base inclination angle, particularly for deep circles in cohesive soils using a limited number of slices.