Abstract The paper discusses alternative ap- proaches to stability analyses including the tradi- tional deterministic principle, the so-called partial factor principle and the probabilistic approach which assesses the probability of failure rather than the factor of safety. To illustrate the different prin- ciples and approaches, stability analyses of road cuts near Trondheim, central Norway, are used as examples. It is concluded that although the tradi- tional deterministic approach has the advantage of being well established and easy to understand, to conform with new standards and guidelines it is likely to be replaced by the partial factor principle. To obtain the best possible basis for evaluation it is useful to include a probabilistic analysis. Résumé L’article présente de nouvelles approches pour les analyses de stabilité comprenant l’analyse déterministe traditionelle, la méthode dite des coef- ficients partiels et l’approche probabiliste qui évalue une probabilité de rupture plutôt qu’un facteur de sécurité. Afin d’illustrer les différentes méthodes et approches, des analyses de stabilité relatives à des déblais routiers près de Trondheim, au centre de la Norvège, sont présentées à titre d’exemples. Bien que l’analyse déterministe tradi- tionnelle ait l’avantage d’être bien admise et facile à comprendre, on conclut qu’elle sera probablement remplacée par la méthode des coefficients partiels afin de suivre les nouvelles règles et recommanda- tions. Pour obtenir la meilleure base possible de diagnostic il est utile de considérer également une approche probabiliste. Key words Rock slope stability 7 Deterministic analysis 7 Partial factors 7 Probabilistic analysis 7 Factor of safety 7 Input parameters Bull Eng Geol Env (2000) 58 : 173–178 7 Q Springer-Verlag 173 New trends in rock slope stability analyses B. Nilsen Received: 5 August 1999 7 28 August 1999 B. Nilsen (Y) Norwegian University of Science and Technology, Department of Geology and Mineral Resources Engineering, Alfred Getz vei 2, 7491 Trondheim, Norway e-mail: bjorn.nilsen6geo.ntnu.no Fax: c47-73-590898 Mots clés Stabilité de pente rocheuse 7 Analyse déterministe 7 Facteurs partiels 7 Analyse probabiliste 7 Facteur de sécurité 7 Paramètres de calcul Introduction Traditionally, in the fields of geological engineering and rock mechanics, the deterministic principle of calculating the stabilizing and driving forces to arrive at a factor of safety has been the predominant method of rock slope stability analysis. In the last few years, however, alternative methods have become more widespread. To a great extent, this is due to the introduction of new standards and recommendations, such as Eurocode 7 (Comité Européen de Normalisation 1994) and NS 3480 “Geotechnical Plan- ning” (Norwegian Council for Building Standardization 1988) which require all stability analyses to be carried out according to the so-called partial factor method, with partial factors for action and strength. In soil mechanics this principle was commonly adopted many years ago, while in geological engineering/rock mechanics the calcu- lation principles have been changed only to a minor extent. In addition, the probabilistic approach, with the calcula- tion of the probability of failure instead of a factor of safety against failure, has become more common practice, as reflected by the many international conferences over the last few years focusing on this issue (Li and Lo 1993; Shackelford et al. 1996; Lee and Lee 1998). The steps of the analysis that precede calculation, i.e. defi- nition of potential stability problem and quantification of input parameters, are crucial for the final result. The main focus of this paper, however, is the advantages and disad- vantages of the alternative methods, in particular the inter- pretation of calculation results. Calculation example To illustrate the different approaches and principles, a case representative of a common stability problem with road cuts around Trondheim, central Norway, has been used.