Accuracy of Equilibrium Slope Stability Analysis

The accuracy of limit equilibrium slope stability analyses procedures is examined by comparing the results of the Simplified Bishop procedure with results obtained using the finite element procedure of analysis. The distributions of normal stresses along the shear surface were compared and found to be reasonably similar, the agreement between the two procedures being closest for relatively flat slopes with relatively low values of cohesion. The values of the factor of safety, while assumed constant in the Bishop procedure, were shown by the finite element analyses to vary considerably along the shear surface. However, the overall, or average, values of the factor of safety computed by these two procedures were found to agree within 5 percent over the range of conditions investigated. It was concluded from these results that the Simplified Bishop procedure, as well as many other limit equilibrium analysis procedures, do not involve large errors in the computed values for the overall factor of safety of earth slopes.