A study on critical failure surface in slope stability analysis

Abstract

      When an earthern slope was unstable the failure surface can be of any shape. In slope stability analysis due to the difficulties in determining the shape of critical failure surface, usually circile sliding surface was selected. In most cases choosing circle failure surface are appropriate and lead to reasonable results. How ever in several cases the shape of actual failure surfaces are very far from circular shape, as a result safety factor canculation using circular failure surface will cause large errors. In this paper the authors evaluated the safety factors and shape of critical failure surfaces of several dam cross sections. In each case both safety factor of circular failure surface and safety factor of critical failure surface determined by optimization technique are analyzed and compaired. The results show that in case of embankment dam with counter berm the different between two analysys can be as large as 20-30%. Threrefore in these cases slope sstability analysys with failure surface determined using optimization technique should be used to attain safety margin.