Mirko Francioni

Geological Application of UAV Photogrammetry and Terrestrial Laser Scanning in Marble Quarrying (Apuan Alps, Italy)

Workplace safety in quarries can be evaluated and improved through an accurate risk assessment of mining activities. Rock slopes stability is dominantly influenced by the structural setting which, in combination with exploitation methods, affects the risk. This paper describes studies carried out in the Apuan Alps, where several quarry walls reach hundreds of meters in height and are dominated by natural slopes with complex morphology. Aim of the present paper is to determine the detailed structural-geological setting of a quarry wall and to identify potentially unstable zones. In such an environmental context, data obtained from engineering-geological surveys, collected at the foot of the slope and along the wall by climbing technicians, may be used for rock mass characterization. This data, which holds important statistical value, has been integrated with other info coming from a terrestrial photogrammetric survey, that was realized using an unmanned aerial vehicle, and from terrestrial laser scanning. The stereoscopic and high resolution images and the 3D model from point clouds have been processed and interpreted in order to provide a deterministic information of the complete slope setting. The geometrical and geo-engineering data was utilized for a stability analysis carried out through a 2D numerical modelling based on the distinct element method. Results of this study have been used to assess the safety conditions necessary to continue the exploitation activities and, eventually, to plan for proper remediation.

Integration of Geotechnical and Remote Monitoring Systems for the Analysis and Control of Ground Deformation in Marble Quarrying (Apuan Alps, Italy)

Workplace safety in quarry sites can be evaluated and established through an accurate monitoring of mining activities and slope stability. This last is dominantly influenced by the structural setting which, in combination with exploitation methods, affects the risk. The present paper shows the applied methodologies and the preliminary results obtained from an integrated monitoring system implemented in the Apuan Alps, within a quarry characterized by a buttress shaped remnant of previous excavation activities and accessible from 3 sides. In 1997, a rock fall event occurred in a neighbouring area of the buttress causing the interruption of quarrying activities. With the purpose of controlling the buttress stability, preserving safety conditions, planning proper remediation works and continuing exploitation activities, various monitoring systems have been installed during the years: this paper describes the 3 more recent systems that have been operating for more than 1 year. The instrumentation consists of geotechnical monitoring sensors composed by extensometers and crack-meters, and two topographic systems represented by a terrestrial interferometer and a robotic total station. Results from the 3 monitoring systems highlighted few critical zones whose presence was already known and precautionary measures had already been adopted; their geo-mechanical character is still under study with the aim of establishing the thresholds of risk that separate the natural rock behaviour from any probability of failure.

Topographic and geological mapping in the prehistoric area of Melka Kunture (Ethiopia)

This paper describes the results of topographical and geological surveys carried out at the prehistoric area of Melka Kunture (Ethiopia) in order to produce new detailed maps at a scale of 1:10,000 for supporting archaeological investigations and providing good reference cartography during fieldwork. The topographic support was created from the stereorestitution of two pairs of Standard Stereo IKONOS-2, 1m pan-sharpened satellite imageries covering an area of about 100km2. The topographic map was utilized both for the geological survey and for the interpretation of the palaeo-environmental evolution of the site based on present geomorphological features. The aerial triangulation of satellite images, performed using ground control points measured using differential GPS surveys, allowed the stereoscopic visualization of the area and the creation of a digital elevation model and orthophotos. These results were a useful cartographic aid during the geological survey when all the outcrops along gullies, streams, roads and rivers were inspected and documented through additional in-depth field checks. The geological map was created and refined using the digital elevation model and photointerpretation of stereo and orthoimageries, making it possible to fully identify the geological boundaries between formations and recognize geomorphological features.

A new approach for defining Slope Mass Rating in heterogeneous sedimentary rocks using a combined remote sensing GIS approach

Engineering rock mass classification is usually the first stage in the analysis and characterization of rock slopes. However, when dealing with sedimentary/heterogeneous rock masses, the use of existing classification methods can be difficult and often misleading, especially when used to define rockfall risk areas and appropriate slope mitigation works. In this research, we describe a novel approach for geomechanical rock slope analysis based on the combined use of remote sensing, geographic information systems (GIS), and the Slope Mass Rating (SMR) classification system. The Montagna dei Fiori area (Italian central Apennines), which is characterized by the sedimentary rocks of the Umbria Marche heterogeneous succession, is used as a case study to demonstrate the application of the proposed approach. Conventional geomechanical scanlines are integrated with photogrammetric techniques to increase the amount of data collected, especially in inaccessible areas. In particular, a new fast and low-cost method of georeferencing 3D photogrammetric models is presented. GIS are used to manage all the data acquired using remote sensing techniques and geomechanical analyses, and a semi-automatic tool developed to allow calculation of the SMR along a major highway, the SP52, which crosses the study area. Finally, a modification of the SMR procedure is proposed to enable definition of the most appropriate mitigation works in folded heterogeneous sedimentary rock masses comprising alternating marls and limestones.