The analysis of the stability of dams and other slopes is usually carried out using Limit Equilibrium Analysis (LEA). In most situations more detailed analysis using numerical methods, e.g. finite element analysis, is not necessary. However if it is necessary to model the deformations and stresses of the dam or the effects of strain weakening, as in progressive failure, numerical methods must be used. Comprehensive reviews of slope stability analysis have been written by Fredlund and Krahn (1977), Whitman and Bailey (1967), Fredlund (1984), Graham (1984), Mostyn and Small (1987), Duncan (1992, 1996a and b), Morgenstern (1992), and Hungr (1997).