Monitoring activities for the preservation of an Etruscan hypogeum in unsaturated soil mass

Abstract

A geotechnical monitoring campaign and a site investigation have been recently planned and undertaken aiming at the preservation and protection of the “Palazzone” Etruscan necropolis, an archaeological site dated back to Hellenistic period located 4 km from the city of Perugia, along the southeastern margin of the hill where the town is settled. The site includes some beautiful and monumental cavities, among them, the Volumni Hypogeum. The majority of the graves are underground cavities excavated in partially saturated alluvial soil deposits. Their inspection reveals the geological features and the depositional structures. The groundwater table is located about 35 m below the ground surface. Due to the difficulties of soil-sampling inside the ancient cavities, only limited portions of the material were retrieved for conventional laboratory tests, although not enough for a geotechnical characterization. On the other hand, XRD analyses and MIP tests were performed. The obtained results allowed to recognize the relevant contribution of soil suction to the stability conditions of the lateral walls and the ceiling of the cavities, which is complementary to the weak cementation characterizing the soil mass. This important information supports the conservation strategy of the monument, which has as its primary tool the monitoring of environmental conditions, aimed at maintaining the unsaturated conditions of the soil mass.