The paper reports the described methodology applied to a case study of stability evaluation of a rock slope at high elevation (Monte Bianco) where instability phenomena where observed. Stability analysis were performed using both Limit Equilibrium Method (LEM) and Distinct Element Method (DEM) in 3Dimensional field based on accurate non contact surveys. The surveys are supported and validated by traditional in situ measurements of the discontinuity orientation and other rock mass features. The required discontinuity shear strength has been validated by direct shear tests performed in laboratory on specimens taken on the slope. Furthermore, the paper presents some considerations on the influence of climate changes on the rock mechanical features and examines the effect of temperature variation on the stability conditions of rock slopes; this is done by means of several parametrical analysis of the Aguille Marbrèe rock outcrop carried out modifying the rock discontinuity saturation, persistence and frequency, shear strength etc. These analysis are showing how a different water regime in the rock mass, caused by climate variation, can strongly influence the stability condition of the slope; on the other hand, the DEM analysis are used to better understand the complex and progressive instability phenomenon that was observed on site. The comparison between the shape of the unstable blocks and their volume as computed by DEM and those measured on site at the base of the slope, validate the DEM results.
In the Italian North West alpine region, several instability phenomena involving large rock volumes have been observed in the last years at high elevation (3000 m a.s.l.). The increment of these phenomena occurrences could be related with the registered climate variation and with a general tendency of temperature increment. The research presented in this paper was dedicated to the development of a methodology for a better understanding and forecasting of the rock slope stability condition at high elevations. The evaluation of rock slope stability is based on the geostructural characterization of the rock mass and, therefore, structural surveys are the basic requirement of any stability analysis. Since hiking and climbing are among the most important economic resources for alpine regions, the need to improve the safety condition at high elevation is of primary importance and, consequently, rock slope risk evaluation becomes more and more demanding in terms of objectivity and details. To become a real alternative to a traditional survey (both in terms of productivity and accuracy) the photogrammetric or laser scanner techniques requires interactive or automated software tools to allow the efficient selection of discontinuities or the interpretation of the normal vector pattern. For this reason, the segmentation algorithm of the point cloud in subsets, each made of points measured on a discontinuity plane of the rock face has been implemented in RockScan [1], a software tool developed to facilitate the interaction with the point cloud in the identification of the discontinuities; rather than on the 3D data, selection of regions of interest is performed on oriented images of the rock face.
