The slope stability of embankments is analysed using the traditional slope stability and the partial factors of safety according to the case C from Eurocode 7 (EC7). These analyses are performed by means of rigid-plastic methods (Fellenius and Bishop) and the elastoplastic finite element method (FEM). In the analysed cases there is a good agreement between the rigid-plastic methods and the elasto-plastic finite element method.
The traditional methods of slices with circular (Fellenius, 1927; Bishop, 1955) and non-circular (Morgenstern and Price, 1965; Sarma, 1973, Matos et al, 1986) surfaces of sliding has been broadly used to analyse the stability of slopes. All these methods are of the type "rigid-plastic methods". Another way of analysing the stability of slopes is through the finite element method. Duncan (1996) summarised seventeen finite element analysis of slopes and embankments performed using elasto-plastic and elasto-visco-plastic stress-strain relationships. Comparisons between the slices and finite element methods were also done before by most of the authors of this paper (Martins et al, 1997, Martins et al, 1998). The purpose of this paper is to continue the comparisons between the factors of safety using the traditional methods of slices of Fellenius and Bishop and the elasto-plastic finite element method. These comparisons are done for the traditional case of slope stability analysis and the new partial safety factors analysis according to Eurocode 7 (ENV 1997 – 1: 1994). Only the case C of the EC7 is analysed because according to the EC7 the "case C is generally critical in cases such as slope stability problems, where there is no strength of structural elements involved". This was confirmed in other publications (Martins et al, 1997, Martins et al, 1998). The finite element analysis is performed with the professional version 7 of the PLAXIS program (1998).