Two methodologies for the three-dimensional simulation of the run out of rock avalanches are presented: one based on a granular approach and the other based on a continuum equivalent approach. An evaluation of the possible run out area of the Oselitzenbach landslide (Carnic Alps, Austria) has been carried out applying the two methodologies. The combined use of these two approaches makes it possible a comprehensive assessment of the run out area.
Deux methodologies pour la simulation tridimensionnelle de la propagation des avalanches rocheuses sont presentees: la première est basee sur un modèle de type granulaire et la deuxième sur un modèle du continu equivalent. Une evaluation de la propagation eventuelle de l'avalanche de Oselitzenbach (Alpes Carniche, Autriche) a ete realisee en utilisant les deux methodologies. Les resultats obtenus montrent que la combinaison des deux approches rend possible une analyse plus complète de la phase de propagation.
Fuer die dreidimensionale Modellierung eines Felsmassensturzes (sturzstrom) werden zwei Methoden, eine granulare und eine kontinuumsmechanische Methode, vorgestellt. Beide Methoden wurden zur Abschatzung der Ausbreitung (runout) der Massenbewegung Oselitzenbach (Karnische Alpen, Österreich) herangezogen. Die kombinierte Anwendung beider Methoden ermöglichte eine umfassende Beurteilung des möglichen Ausbreitungsbereichs.
'Rock avalanche is an extremely rapid, massive, flow-like motion of fragmented rock from a large rock slide or rock fall' (Hungr, 2001).
The movement of the debris involved is usually very rapid and tends to exhibit a higher degree of mobility than can be reasonably expected. Mobility seems to increase with volume but, up to now, none of the numerous explanations proposed by different authors have gained universal acceptance.
Compared to a rock fall event, the motion of rock avalanches is more massive and the bulk of rock fragments (dry debris and rock blocks) moves as a semi-coherent flowing mass.
The fact that the stratigraphic set-up is usually not altered during the evolution of the phenomenon suggests that the deformation only affects a thin layer of material in the lower part of the moving mass.
Flow-like movements of rocks are among the most dangerous and damaging of all landslide phenomena. Since it often proves impossible to mitigate their destructive potential by stabilising the area of origin, risk analyses, including predictions of run out, have to be performed. With these predictions losses can be drastically reduced, as they provide means to define the hazardous areas, estimate the intensity of the hazard (which will serve as input for risk studies), and work out the parameters for the identification of appropriate protective measures. At the same time, reliable predictions of run out can help to avoid exceedingly conservative decisions regarding the development of hazardous areas.
In this article the potential of a combined application of two prediction methods is presented through the run out analyses of the Oselitzenbach site (Austrian Alps).
Run out prediction methods can be grouped into two broad classes (Hungr, 2001):
Empirical methods
Analytical methods
