Strength reduction technique with finite element method for slopes without stabilisation measures

Although limit equilibrium analyses currently dominate in practical geotechnical engineering to obtain factors of safety of natural and cut slopes, the finite element method is increasingly being used to calculate ultimate limit states and consequently factors of safety, usually by means of the so-called “strength reduction” technique. In many cases results obtained from the strength reduction approach are comparable to the those obtained with limit equilibrium methods, but in some cases significant differences are observed. By comparison with rigorous limit analyses, it is at first demonstrated that the strength reduction method is a reliable method for analysing failure of slopes. Secondly, it is shown that finite element analyses are superior to limit equilibrium analyses in assessing ultimate limit state conditions. Finally some guidelines for performing strength reduction analyses are given and the scope of application is defined. Possible numerical difficulties are also briefly addressed.