The definitive version is available at: La versione definitiva è disponibile alla URL: http://ac.els-cdn.com/S0098300412002695/1-s2.0-S0098300412002695-main.pdf?_tid=fbc6b396-aa86-11e3-b387- ABSTRACT:A new automatic method for discontinuity traces mapping and sampling on a rock mass digital model is described in this work. The implemented procedure allows one to automatically identify discontinuity traces on a Digital Surface Model: traces are detected directly as surface breaklines, by means of maximum and minimum principal curvature values of the vertices that constitute the model surface. Color influence and user errors, that usually characterize the trace mapping on images, are eliminated. Also trace sampling procedures based on circular windows and circular scanlines have been implemented: they are used to infer trace data and to calculate values of mean trace length, expected 3 discontinuity diameter and intensity of rock discontinuities. The method is tested on a case study: results obtained applying the automatic procedure on the DSM of a rock face are compared to those obtained performing a manual sampling on the orthophotograph of the same rock face.

Bogoslovsky and Ogilvy (1977), Jongmans and Garambois (2007) and in Maurer et al. (2010). Successful results are documented from seismic methods, such as reflection, refraction, tomography and ambient noise measurements, electrical methods, such as electrical resistivity tomography (ERT) and spontaneous potential (SP), and electromagnetic methods, such as ground-penetrating radar (GPR).Electrical methods provide important information about the water/fluid saturation, since electrical resistivity is strongly influenced by the water content and its conductivity,

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When studying rockfall phenomena, a single value of the block volume is not sufficient to take into account the natural variability of the geometrical features (orientation, spacing, persistence) of the discontinuity sets. Different approaches for obtaining cumulative distributions of potentially detachable block volumes are compared. A highly fractured rock mass outcropping along the western Lake Garda (Italy), consisting of prevailing limestone and interbedded marls, is studied in detail from geological and geostructural points of view. Then, a representative rock face has been selected and analyzed with traditional and non-contact survey methods to identify the main discontinuity sets and to collect spacing samples. Based on these data, in situ block size distributions for different combinations of sets are built following statistically-based approaches, without the use of a Discrete Fracture Network (DFN) generator. The validation of the obtained distributions is attempted based on the detached block surveyed at the foot of the slope. However, in this particular case study, the detached blocks cover only a minimal volume range compared to both theoretical values and visible rockfall scars. The fallen rock blocks have a marginal role in design block determination, since their volume depends on geological discontinuities (bedding and fractures) and could be affected by other processes after the detachment (e.g., fragmentation). The procedure here described should be standard practice in the study of rockfall events, and it should be uniform in European standards such as Eurocodes. Future developments should involve the scientific community for setting the percentiles of the probability distribution to be considered for block design definition.

Several high altitude slope instability phenomena involving rock block of different volumes have been observed in recent years. The increase in these phenomena could be correlated with climatic variations and a general increase in temperature that induces both ice melt with consequent water seepage and glacial lowering with consequent loss of support of the rock face. The degradation of the high altitude thermal layer, which is known as "permafrost", can determine the formation of highly fractured rock slopes where instabilities can concentrate. The present research develops a methodology to improve the understanding and assessment of rock slope stability conditions in high mountain environments where access is difficult. The observed instabilities are controlled by the presence of discontinuities that can determine block detachments. Consequently, a detailed survey of the rock faces is necessary, both in terms of topography and geological structure, in order to locate the discontinuities on the slope for a better geometric reconstruction and subsequent stability analysis of the blocky rock mass. Photogrammetrical surveys performed at different times, allow the geostructure of the rock mass to be determined and for the rock block volumes and detachment mechanisms to be estimated, in order to assess stability conditions and potential triggering mechanisms. Photogrammetrical surveys facilitate both the characterisation of the rock mass and the monitoring of slope instabilities over time.The methodology has been applied in a case study, the North Face of Aiguilles Marbrées in the Mont Blanc massif, which suffers from frequent instability phenomena. A slope failure, which occurred in 2007, has been back-analysed using both, the Limit Equilibrium Method (LEM) and 3D Distinct Element Modelling (DEM). The method has been supported and validated with traditional in situ surveys and measurements of the discontinuity orientation and other rock mass features. The present research develops a methodology to improve the understanding and assessment of rock slope stability conditions in high mountain environments where access is difficult. The observed instabilities are controlled by the presence of discontinuities that can determine block detachments. Powered by Editorial Manager® and Preprint Manager® from Aries Systems CorporationConsequently, a detailed survey of the rock faces is necessary, both in terms of topography and geological structure, in order to locate the discontinuities on the slope for a better geometric reconstruction and subsequent stability analysis of the blocky rock mass. Photogrammetrical surveys performed at different times, allow the geostructure of the rock mass to be determined and for the rock block volumes and detachment mechanisms to be estimated, in order to assess stability conditions and Manuscript Click here to download Manuscript: Terrestrial photogrammetry and numerical modelling with pictures. doc 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 2...