The Latomiae of Syracuse: A Geotechnical Mapping Through Rock Reflectivity

The archeological site of the Latomia del Paradiso (Syracuse) is endangered by severe instability phenomena due to the shape of walls and underground excava-tion related with the poor mechanical characteristics of the weathered and wet rock. The failure of huge blocks from the ceiling of the underground areas and the detaching of rock "flakes" from the walls surface make the geotechnical zon-ing particularly complex. the zoning is based on the characteristics of the rock wall surface that, in first approximation, can be distinguished in regularized sur-faces because of mining , and in irregular surfaces characterized by fracture prop-agation. The elaboration of reflectivity values obtained from a laser scanner survey pro-vides a quick and reliable method, which can be very useful to assess the localization of alteration processes and their intensity. Alteration processes affect the mechanical characteristics and a decay of a rock mass shear strenght is associated to them. Therefore, it has been possible to obtain a differentiated assessment of the safety conditions of the rock mass walls in areas where a direct assessment was too expensive or difficult because of the wall extension, or impossible. The measurements of reflectivity have been correlated to the Hammer Schmidt rebound values r both in soft rocks, such as those under consideration, and in stone formations of different rock types.