The ancient walls of Santa Croce in the town of Cagliari (Sardinia, Italy), date back to the Middle Age and have had, until the nineteenth century, several interventions with superpositions and modifications. Beyond the historical and archaeological interest, the study of the structure of the ancient walls became necessary in view of building an underground car parking just at the base of the walls itself. With this purpose, in addition to classical archaeological surveys a geophysical non-destructive survey with seismic techniques has been carried out, namely two refraction tomographies aimed at characterizing the rocks at the base of the walls, and four up-hole tomographies across the walls itself. These geophysical surveys provide a good geotechnical information on the foundation condition, the problematic feasibility of the underground parking and, along with the archaeological procedures, on the heterogeneous structure of the walls.
Lo sviluppo di una indagine multidisciplinare finalizzata alla conoscenza dei complessi monumentali storici in ambito urbano assume un ruolo di primaria importanza per la tutela del patrimonio architettonico e paesaggistico. Con tale obiettivo l'integrazione tra metodologie di rilevamento e metodi geofisici si è dimostrata un utile supporto alla ricostruzione delle vicende costruttive del bastione di Santa Croce a Cagliari, sito pluristratificato interessato a partire dal Cinquecento da numerose sovrapposizioni e ricostruzioni. L'impiego combinato di tecniche diagnostiche non distruttive di tipo geofisico particolarmente utili nei casi in cui non sia possibile l'effettuazione di indagine invasive di notevole impatto come scavi e sondaggi, ha difatti permesso di approfondire la conoscenza del sistema costruttivo e funzionale dell'opera militare. Gli esiti dell'indagine hanno consentito di definire le caratteristiche stilistico costruttive dell'opera cinquecentesca, rivelare l'utilizzo di soluzioni differenti da quanto sinora riscontrato nelle piazzeforti spagnole dell'epoca, circoscrivere l'area interessata dalla ricostruzione documentata nelle fonti storiche, utili tasselli conoscitivi anche in vista di nuovi interventi progettuali che prevedono, tra l'altro, la realizzazione di un parcheggio interrato alla base dello stesso bastione. ; Developing a protocol for the multidisciplinary investigation of historical monumental complexes in urban environments covers a paramount role in protecting the architectural and landscape heritage. To this purpose, integrating the investigation methodologies typical of architecture with the geophysical ones has proved useful in assessing the conditions of the places and of the works, so as to identify and represent their modifications. Comparing data from different disciplinary contributions (historical, archaeological and geophysical ones) has specifically allowed the organisation and assessment of an investigating protocol aiming to the representation, protection and valorisation of the bastion layout; in particular, it has contributed to define its stylistic architectural features, and improve knowledge of the military work operation and of its current layout, even in view of any further planning intervention in an area where, furthermore, the realisation of a parking lot buried at the basis of the 16th century bastion is being considered.
This contribution shows some results of a multidisciplinary survey, which includes the integration of architectural surveying methods and geophysical methods. The operative procedure is applied in the portion of the ancient walls between the bastion of Santa Croce and the fourteenth-century Elephant Tower, in the city of Cagliari, Italy. The sector under study consists of 1) the wall curtain of Santa Chiara designed in 1575 by the engineer Giorgio Paleari and 2) the de Cardona wall curtain, a work commissioned by the Viceroy in the 30s of the same century. The archival documents offer precise indications on the extent of the collapses and the reconstructions/expansions that took place in that period, so facilitating a recognition of the events that took place. The work of the sixteenth century -brought to completion by the same Giorgio Paleari in the years 1576-1578- advances the line of defense with respect to the border of medieval matrix by means of a robust embankment, and incorporates two of the fifteenth-century towers described in the drawings of the military technicians of the time. In the eighteenth century the front was completed by the construction of a lowered embankment near the southern side of the bastion of Santa Croce and the curtain of Santa Chiara, and more recently it has been improved by means of several restorations and consolidations that changed the profile of the parapet –in the origin it was inclined - and the static balance of the constructive system, also through the use of reinforced concrete piles. The application of the survey methods and techniques used in this study provides interesting information about the current structure of the bastion system and the presence of vaulted passages functional to the military work. A new study campaign mainly based on seismic geophysical techniques is proposed.
