PSI - Issue 78

Vincenzo Calvanese et al. / Procedia Structural Integrity 78 (2026) 1134–1142

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3. The interventions on the Insula Meridionalis The design project optimized during work execution in the Insula Meridionalis is a sequence of local interventions that will enhance the capacity of the entire structural system to face degradation and dynamic events such earthquakes. The interventions have been designed according to the approach defined in parag.2, a diagnostic survey, that will have described in the following parag. 3.1, has allowed to have a defined knowledge of the materials and structural details shown in parag. 3.2. The works in the Insula Meridonalis are ongoing, and the diagnostic survey for assessment has been planned, as well as the monitoring that is herein described in parag. 3.3. 3.1. The diagnostic survey In the case of the Insula Meridionalis, during design phase most of these analysis have not been carried out as soon as that most rooms and walls were not accessible to the engineers and architects involved. Some areas have been excavated recently, and a complete knowledge could be refined only during construction. To define the executive interventions, the following diagnostic investigations have been planned: • Continuous core drilling for stratigraphic analysis, using 12 cm diameter cores, subject to a preliminary local assessment of the rock overlay's stability. • Tensile tests on rock-anchored bars used for consolidating the ridge. These tests aim to verify the intervention's effectiveness and allow for calibration of the executive design for the ridge intervention, ensuring its effective while adhering to the principle of minimal intervention. • Thermographic surveys to be conducted on all main masonry surfaces. This will identify moisture and elements with different thermal coefficients for a better characterization of the masonry elements. • Ground-penetrating radar (GPR) surveys to detect voids, and investigations for identifying vertical cracks to better localize drilling points. • Video endoscopies for geometric verification of the masonry and the depth of the foundations. Some interventions that are designed and executed in some part of the Insula are described below, in particular the ones planned the structures identified as the Horrea, because they require further investigation and a specific design. The Horrea are characterized by their masonry load-bearing elements and barrel vaults, the vaults were constructed by pouring a monolithic concrete cast over pre-existing masonry walls. The type of collapse observed in this area is a direct result of the impact sustained by the structures of the Horrea during the impact of pyroclastic flows during the eruption in AD 79. The effect of this impact was particularly evident leading to damage of the original structure and consequently increasing the vulnerability of these elements both in the vaults, and in the keystones at the center of the vaults. The planned intervention (see in Figs. 3, 5, 6 ) aims to consolidate the precarious front section of the Horrea’s vault. It includes the insertion of AISI 304 stainless steel bars into the vault (Fig. 4). The bars measure 200 cm in length, a diameter section ranging from 16 to 18 mm in 20 mm diameter boreholes. The boreholes will then be filled with structural fluid mortar, perfectly compatible with the historical material. Furthermore, prior to the bar insertion, structural fluid lime mortar injections will be spread in to the masonry from the extrados of the vault, and from the intrados if necessary. The injection grid will consist of three boreholes per square metre of extradosal surface. It is crucial that these injections are carried out wherever cracks or micro-cracks are identified on the vaults; therefore, perforations must be made at these points, and the cracks must be filled with the same high-resistance structural mortar. 3.2 The executive design during works