Contribution à l’évaluation du risque d’éboulement sur les falaises rocheuses de la région de Béjaïa

Abstract

Rock falls are common in mountainous road corridors. Because of its sudden and rapid nature, it often has a significant socio-economic impact. This phenomenon occurs commonly on the national road between Kherrata and Bejaia, which characterized by highly vulnerable sections and often affected, such as the slope of Cap Aokas, the Talus opposite the tourist complex Safsaf and the slopes north of the town of Derguina. The risk assessment of this phenomenon in this research is based on the identification of predisposition and trigger factors, and the combination of multi-approaches such as structural, and photogrammetric. The assessment methods are chosen according to the nature of the starting hazard (diffuse or localized). At the Aokas cliff, we combined kinematic analysis and MATTEROCKING. The slope of the Safsaf complex is assessed with alpine technique, while the slope of Derguina is assessed with a global method. The propagation hazard is assessed by a 3D trajectory study. The risk of falling blocks is assessed qualitatively by adopting the RHRA method for the slope of Cap Aokas and the RHRS method for the slopes of Safsaf and Derguina. This study has shown a close relationship between the structural aspect of the rock masses and the trigger zones; the risk in the sites studied is mainly medium to high, and parades according to the morphological conditions of the site and the intensity of the phenomenon are suggested. This methodology can be applied to other sites to reduce and manage à rock fall risk.