Analysis of rock masses belonging to the Apennine-Maghrebide Orogen by means of in situ and remote methodologies applied to rockfall risk assessment

Abstract

The rockfall attitude of rock slopes threatening a strategic spot of eastern Sicily has been studied herein with the aims of testing an innovative methodology for the remote survey of fractured rock outcrops and of assessing the rockfall risk along an important transportation corridor through a quantitative probabilistic approach. The study area, often involved in rockfall events, which cause serious damage to private and public infrastructures, is one of the most relevant places of Sicily due to the great tourism rate recorded every year between the resorts of Taormina and Castelmola, which are also considered an outstanding example of cultural heritage. The innovative procedure of rock mass survey through InfraRed Thermography is tested and proposed herein for the study of the fracturing condition of intensely jointed rock masses, to find out what kind of information can be assessed in this field of rock mechanics. Although this technique is widely used in several scientific fields, its direct application for such purposes is still pioneering. In this thesis, thermal imaging campaigns, carried out under different climatic conditions, are described, and interesting considerations are proposed with reference to a Cooling Rate Index, estimated to study how rock masses, conditioned by their fracture nets, behave during the heat transfer towards the external environment. Such an index was related to the degree of fracturing of the rock masses to find a relationship linking thermal data to one of the main quantitative fracturing indexes. Results return interesting matches between some geostructural features and thermal outputs, demonstrating the reliability of the application of such methodology to bare rock masses. Moreover, new experimental considerations are proposed, laying the foundations for future studies aimed to further validate the InfraRed Thermography as an effective remote survey technique. Risk assessment was carried out through the quantitative approach of the Event Tree Analysis, which was properly customized to take into account the peculiarity of the area and of the road path. Rock mass surveys, trajectory simulations and probabilistic models were taken into account with the aim of calculating the probability related to possible scenarios in case of rockfalls. Achieved outcomes demonstrate that such procedure is a reliable tool, which can be taken as reference to calibrate further risk models in comparable contexts of the world, where rockfall threaten communication routes. This would represent a helpful instrument to the scientific community and to local authorities dealing with one of the most troublesome natural phenomena affecting the public safety.