Engineering-geological modelling as a tool for archaeological site preservation strategies

Abstract

Traditionally, cultural heritage (CH) site conservation strategies have mostly focused on the employment of procedures to protect archaeological exhibits from weathering processes. However, CH-sites are often located in areas affected by geological hazards, which can threaten the conservation of the site itself. For these cases, engineering-geological modelling is an essential tool to design conservation strategies for geohazards management in the framework of CH-site preservation. The research here proposed is focused on the Punta Eolo promontory at Ventotene island (Italy) where the remnant of the roman “Villa Giulia” emperor palace is hosted. Detailed engineering-geological surveying has been carried out at Punta Eolo. In particular, engineering-geological investigations have been coupled with remote investigation of the area of interest. Thanks to the engineering-geological surveys, a detailed engineering-geological map was drafted, also highlighting the geomechanical setting of the Parata Grande Tuff formation (hereinafter, PGT). The presence of a superficial deposit, mainly composed of archaeological material overlaying a tuffaceous unit, was evidenced. To bound this layer’s thickness more effectively, 52 single-station seismic noise measurements were carried out. Seismic ambient noise measurements show significant horizontal-to-vertical spectral ratio (HVSR) resonance peaks at 3 Hz, a variable secondary peak ranging from 9 to 19 14 Hz, respectively related with the contact between the PGT and the underlying lavas and the superficial deposits and PGT units. The measurements conducted at the edge of the promontory show evidence of polarization of the particle motion potentially related to the vibrational behavior of the unstable rock blocks that bound all the site. A 3D model of the cliff, reconstructed by drone photogrammetry technique, allowed to perform the rock mass joints surveying along the not-accessible cliff faces, as well as to visualize the superficial deposits thickness all around the perimeter of the promontory. Additionally, a 3D geological model was made using the RockWorks 16 program to facilitate a more direct visualization of site-specific features. The engineering-geological model here presented enables the development of an efficient conservation strategy for the Villa Giulia archeological site, as a critical tool for mitigating geological risks. Furthermore, future archaeological excavation will be driven by the reconstructed geological model of Punta Eolo.