Discrepancy Between Safety Factors of Slope Stability on the Two Layers Problems Taken by Fellenius and Bishop Methods

摘要

The Fellenius method and the simplified Bishop method are currentlyapplied when analyzing the slope stability of a project design. However,it is well known that large discrepancies exist between the safetyfactors calculated by both methods, especially in the case of two layerproblems where a sandy layer is filled over a clay layer. Theresearchers investigated those problems and presented the results ofcomparative study. Although this problem is frequently encountered onoffshore project of reclamation, there seems to be no clear rule todecide which method to apply when designing. In this paper, therefore,we show that this discrepancy between safety factors increases whenthe inclination angle defined at the end of a failure circle exceeds acertain size. This is excised by dividing the slope stability equationsinto two components related to internal friction angle and cohesion,respectively. In addition, an important zone for slope stability, a part ofthe assumed failure zone, is discussed, which should be inspected whendesigning a project.