Geomechanical Characterization of a Rock Cliff Hosting a Cultural Heritage through Ground and UAV Rock Mass Surveys for Its Sustainable Fruition

Abstract

In mountainous areas around the world, dealing with rockfalls means facing some technical survey difficulties due to the low accessibility of areas and the height of slopes. If a cultural heritage is also threatened by such mass movement, the need of specific survey solutions, even in a combined asset, is required. This paper deals with the integration of ground and UAV rock mass surveys aimed at defining the rockfall attitude of an unstable rock cliff sector hosting an example of cultural heritage in tourist area of southern Italy, whose fruition has already been threatened by the occurrence of rockfalls. As an example of the defensive architecture of XII and XIII centuries, the Saracen Castle in Taormina is reached by hundreds of visitors each year, but its access path and the surrounding area are threatened by the unstable condition of the cliff, hosting unstable rock volumes on kinematically critical planes. In order to achieve a reliable geostructural setting of the cliff, aiming at its possible securing through proper mitigation works, ground rock mass surveys could not provide enough information due to the bad accessibility of the rock faces. Therefore, a survey by an Unmanned Aerial Vehicle, with a reliable verified accuracy, was carried out to map the discontinuity planes especially occurring at the highest portions of the cliff, achieving geostructural data of different fronts of the cliff. Ground and aerial data were combined and statistically analyzed to define the main kinematic failure patterns. In this perspective, a critical comparison between the two employed surveying methodologies is proposed herein, highlighting that both approaches are affected by potential and limitations and that the integration of the mutual dataset represents a suitable solution for a complete rock mass characterization in this type of areas. Furthermore, rockfall simulations allowed ascertaining that potential falling blocks would cross the access path to the castle, thus representing a natural threat to the fruition of cultural heritage, thus proving the need of mitigation measures to ensure the safe fruition of the cultural heritage.

UAV-Based Photogrammetry and Infrared Thermography Applied to Rock Mass Survey for Geomechanical Purposes

“…Field remote survey methodologies applied to rock masses are enhanced by technological development, which is in turn favored by the increasing scientific casuistry. Among the remote surveying technologies, Unmanned Aerial Vehicles (UAV) systems, originally used for military scopes [1], can be addressed as a reference for photogrammetric applications in rockfall stability studies, e.g., [2][3][4][5]. In fact, UAV photogrammetry integrated with Structure from Motion (SfM) [6], allowing the reconstruction of reliable three-dimensional models of exposed rock mass planes, offers a low-budget, lightweight, time-saving, and user-friendly remote sensing solution [7].…”

The Use of Innovative Techniques for Management of High-Risk Coastal Areas, Mitigation of Earthquake-Triggered Landslide Risk and Responsible Coastal Development

“…It stops splitting when the points in one node achieve the given maximum count [99]. In this case study, the Kd-tree method has been used for the extraction of the orientation at each discontinuity located on the slopes under investigation [100,101]. Since the original data are points, the Kd-tree was used to organize them in k-dimensional space, searching for the neighboring points.…”

Drones in hospitality and tourism: a literature review and research agenda

“…This cluster highlights the potential application of drones to prevent or mitigate the effects of natural disasters, such as damage caused by faults and landslides in sensitive areas, heritage sites and tourist areas. UAVs can be used to find fault patterns in unstable rocky cliffs Garrill et al, 2021;Mineo, Pappalardo and Onorato, 2021), as well as identify hazards and the risk of rock falls on roads in tourism areas (Li et al, 2019;. The cluster identified novel and effective uses of UAVs in tourism search and rescue (SAR) operations.…”