Reconstruction of a Segment of the UNESCO World Heritage Hadrian’s Villa Tunnel Network by Integrated GPR, Magnetic–Paleomagnetic, and Electric Resistivity Prospections

Abstract

Hadrian’s Villa is an ancient Roman archaeological site built over an ignimbritic tuff and characterized by abundant iron oxides, strong remnant magnetization, and elevated magnetic susceptibility. These properties account for the high-amplitude magnetic anomalies observed in this site and were used as a primary tool to detect deep archaeological features consisting of air-filled and soil-filled cavities of the tuff. An integrated magnetic, paleomagnetic, radar, and electric resistivity survey was performed in the Plutonium-Inferi sector of Hadrian’s Villa to outline a segment of the underground system of tunnels that link different zones of the villa. A preliminary paleomagnetic analysis of the bedrock unit and a high-resolution topographic survey by aerial photogrammetry allowed us to perform a computer-assisted modelling of the observed magnetic anomalies, with respect to the archaeological sources. The intrinsic ambiguity of this procedure was reduced through the analysis of ground penetrating radar and electric resistivity profiles, while a comprehensive picture of the buried archaeological features was built by integration of the magnetization model with radar amplitude maps. The final subsurface model of the Plutonium-Inferi complex shows that the observed anomalies are mostly due to the presence of tunnels, skylights, and a system of ditches excavated in the tuff.

Multi-Parametric Imaging of Etruscan Chamber Tombs: Grotte Di Castro Case Study (Italy)

“…The "E"starting value was calculated by measuring the two-way travel time (TWT) of the reflections generated from the top of the EB1 excavated burial (Figure 3). This value was integrated using velocity analyses on diffraction hyperbolas occurring along the profiles and was found to be consistent with those proposed in the literature for the same soil type [42,43].…”

The sediment at the end of the tunnel: Geophysical research to locate the Pleistocene entrance of Gruta da Companheira (Algarve, Southern Portugal)

“…These reflectors seem to delimit an irregularly shaped depression, which become shallower to the west, up to a minimum depth of 2 m (Figure 11c). Given the expected lithology of the above GPR‐b, the sudden increase in velocity of GPR‐d most likely reflects the transition from these clayish sediments to the underlying limestone bedrock, which delimits the bottom of the ERT‐F feature (Carbonel et al, 2014; Ghezzi et al, 2019; Gutiérrez et al, 2011).…”

Developments in 3D Visualisation of the Rail Tunnel Subsurface for Inspection and Monitoring

“…Aforementioned NDI methods are most commonly deployed in routine RTSSI surveys based on encountered literature, motivating distinction from (i) more antiquated methods (e.g., invasive, inefficient, overly localised), (ii) less established experimental practices and (iii) schemes for real-time subsurface monitoring. In (i), we group: Borehole/Drill Core Sampling [190,191], Electrical Resistivity Tomography (ERT) [192][193][194][195], Endoscopic Probing [196,197] and Schmidt Hammer Strength Testing [53,198]. In group (ii), we gather: Radiography/Muon Tomography [199,200] and multiple additional prototype robotic RTSSI systems [14,166,[201][202][203][204].…”