Dora Francesca Barbolla

Electrical resistivity tomography (ERT) is one of the most commonly used geophysical methods for imaging the distribution of electrical resistivity in the subsurface. It is often employed to characterise heterogeneity in karst regions and locate cavities and conduits below the surface. The resistivity contrast between the host rock and the cavity depends on the material filling the cavity. Air has a high electrical resistivity and should therefore produce strong reflections and refractions off cavity walls. However, cavities are not always easily detectable. A decrease in resistivity contrast at the interface between rock and air may result from different physical conditions relating to pore saturation, fracturing and stress near the cavity walls. Our first goal is to understand how extensive fracturing and hydrogeological conditions in the first subsurface layers can affect electric current flow in the presence of a karst tunnel. We use the commercial Res2Dmod software 3.0 to simulate an ERT on several ground models. The results, which are based on hydrogeological models, are presented for several conditions of a karst conduit: empty; full of water within a homogeneous background; and below the groundwater level in the presence of extensive fractures in the shallow layer above it.

The castle of Ceglie Messapica was originally born as a fortification – a lookout point. According to some hypotheses, the construction of the central core, consisting of a Norman tower alongside the square tower that was built in the following centuries, dates back to around 1070-1100. The first family to live there was the Pagano family.The castle was abandoned for several years, and a restoration project was presented in 2019. Before the restoration, geophysical investigations were carried out to identify the presence of metal reinforcement bars in the structure of the castle. 58 corbels were analysed using Ground – Penetrating radar (GPR), method. GPR data were acquired along parallel profiles 5 cm spaced using the Ris Hi-Mod georadar system with the 2000MHz antenna. GPR data were processed in a 3D mode using Gpr-slice software. Results well evidenced the 3D distribution of the metal bars and their advanced corrosion that causes stability problems.

Geophysics is a fundamental tool to detect buried structures of archaeological interest through non-destructive techniques. The Messapian city walls in Ugento (Puglia, southern Italy) are of great archaeological importance, and some sections are still visible. In order to locate a stretch of the city walls, geophysical prospections were performed using the low-frequency electromagnetic method and ground-penetrating radar. The surveys were carried out in a peripheral area of Ugento, near a visible section of the city walls. The analysis and interpretation of the measured data revealed clear anomalies that could be ascribed to the city walls that aligned with an adjacent section of the visible walls. Archaeological excavation campaigns found a part of the walls and some important elements, as identified by the geophysical data interpretation.

An important geological risk to which many towns in Puglia are exposed is sinking cavities in urban areas. For urban centers, studying, mapping, providing geological and speleological descriptions, classifying, and cataloging the forms and types of cavities is essential because cavities are linked to past local anthropic and natural processes at different sites. These circumstances could lead to the enhancement of existing underground cavities in urban areas through conservation and continuous monitoring. Unfortunately, in many cases, these underground cavities have been used as landfills and subsequently abandoned. In late March 2007, one of these cavities collapsed inside Gallipoli’s inhabited center, causing damage to the structures but fortunately not human lives. In the area surrounding the collapsed cavity, a series of geophysical investigations were undertaken using ground penetrating radar in an attempt to delimit the area of collapse and develop possible interventions for restoration. In the same area, these measures were repeated 16 years later in December 2022 due to another collapse. The comparison between data acquired in these two periods shows that there were no strong changes apart from an increased presence of subsoil moisture in 2022.

The condition of the wood structure and its components should be carefully recorded before considering any action. The diagnosis of wood structures in heritage should precede any intervention. It is important to know preliminarily the construction and structural system, the decay condition and the causes. Furthermore, damage or structural failure should be considered. The diagnosis must be based principally on measurements of physical parameters using non-destructive testing, and if necessary on laboratory testing. Water is one of the principal causes of wood decay. In this study, ground-penetrating radar and time domain reflectometry were used to estimate the dielectric permittivity and successively the volumetric water content of several types of wood. An empirical relationship was found between the dielectric constant and volumetric water content. Results were applied to two case studies: the Cathedral of Foggia and the Castle of Carosino.

The sinking of cavities in urban areas is a very important geological risk to which many towns in Puglia are exposed. The study, mapping, geological and speleological description, classification and cataloging of forms and types of cavities is of fundamental importance for each urban center because it is linked to past local anthropic and natural processes, unique to each site. All this could lead to an enhancement of existing underground cavities in urban areas through conservation and continuous monitoring. Unfortunately in many cases these underground cavities have been used as landfills and subsequently abandoned. One of these cavities at the end of March 2007 collapsed in the inhabited center of Gallipoli causing damage to the structures and fortunately not to human lives. In the area relating to the collapsed cavity, a series of geophysical investigations were undertaken with the use of ground penetrating radar methodology in an attempt to delimit the area of collapse and understand the possible types of interventions for restoring the area. In the same area the measures were repeated 16 years later (December 2022) due to another collapse. The results show a much more widespread danger situation.

The church of Santa Chiara with its adjacent convent, whose foundations date back to the 13th century, is a monastic complex in the city of Nardò in the province of Lecce. The current church was built ex novo between the 17th and 18th centuries under the direction of Bishop Orazio Fortunato. Currently, there is no information about the presence of crypts or burials in the church and in the adjacent area. For this reason, a campaign of geophysical investigations was undertaken using electromagnetic, electrical resistivity and ground-penetrating radar methods. Geophysical investigations were carried out both inside and in the courtyard of the church. The results showed the presence of a series of anomalies, whose interpretation suggests important structures of probable archaeological interest.