When λ= 0, the factor of safety is obtained for JSM and BSM. The intersection point shows the factor of safety for M-PM or SM. The Janbu’s generalized method is close to the intersection point. The generalized limit equilibrium processes have the advantage to make comparisons of a factor of safety in the same diagram. The stability analysis for composite and circular SS can be used in the procedure. The variable interslice force function describes the inclination of interslice forces after the subsequent iterations.
The generalized limit equilibrium considers both shear and interslice forces, satisfies both force and moment equilibriums, allows selection for the interslice force function and depicts the comparison of most advanced and common limit equilibrium methods.The OM is calculated by hand. JSM sand BS have used widely for the stability analysis. The methods are common because in most cases, a factor of safety can be estimated with the adequate accuracy. The methods have some limitations in the satisfying moment and force equilibrium. The BSM is used for the analysis of circular shear surface.
The JSM is flexible in examining the factor of safety for the non-circular surfaces. The advantage of JGM can be handled effectively at both failure surfaces and irregular slopes. The moment equilibrium for the slices shows the solution for the force equilibrium which is close to the factor of safety.The BSM shows a higher factor of safety than JSM and declines within 5% of the factor of safety obtained from rigorous methods. The factor of safety can differ by 15% in comparison to the results calculated by Morgenstern-Price and Spencer methods.
The factor of safety from force equilibrium can be seen more sensitive to the f(x) from moment equilibrium. The factor of safety is sensitive to the section of f(x).In the case of the anchors or point loads, the moment equilibrium factor of safety has considerable shifting towards the lower factor of safety. The factor of safety from the moment equilibrium is considered as more sensitive in the application of the external forces. The interslice shear forces increase due to the anchor forces or point loads. It can decrease the normal base force, and the shear strength is decreased.