Argentieri, Alessio

We present the results of a combined analysis of remote sensing and geophysical ‐ geotechnical data carried out in the Acque Albule Basin, a sinkhole prone area located close to the city of Roma, where a wide travertine wedge is present. We carried out geophysical measurements and borehole drillings over two test areas to image the subsoil where paroxysmal sur fi cial dynamics occur. One site is marked by subsidence occurring at least since the early 2000s, whereas the other site hosts the “ La Regina ” and “ Colonnelle ” sinkhole lakes, which discharge sulfur ‐ carbonated waters. The stability of these two sites threatens highway, railway, and airport facilities, and this study helps to assess the geological hazard. For example, InSAR and LiDAR data helped de fi ne wide scale subsidence over the last 20 years and previously undetected small ‐ scale morphologies. Geophysical measurements of the latter revealed shallow and deep dissolution affecting the travertine and driving sur fi cial paroxysmal events. Both study sites were found to lie inside a large depression located at the junction between Jurassic carbonate and Plio ‐ Pleistocene units in association with paleo karst morphologies in the travertine deposits and affected by the present ‐ past spillage of sulfurous waters. Given these elements, multidisciplinary geophysical observations are crucial for assessing and mitigating the geological risk and guiding land use planning and management.

Negli ultimi anni l’incremento di fenomeni di sprofondamento nel territorio di Roma Capitale e nella sua area metropolitana costituisce un rischio sempre maggiore per la popolazione e per le infrastrutture. Il verifi - carsi di questi eventi è in gran parte dei casi connesso alla presenza di sistemi caveali di origine antropica e diversa età e funzione. Un fattore di elevata criticità per l’assetto del territorio è rappresentato dalle reti ipogee non censite in aree di intensa urbanizzazione. La Città Metropolitana di Roma Capitale, in continuità con l’esperienza amministrativa della Provincia di Roma, ha da alcuni anni concentrato l’attenzione sul monitoraggio di edifi ci strategici come quelli scolastici in aree potenzialmente a rischio di sprofondamenti e/o collassi improvvisi. Nell’ambito di un progetto di collaborazione sono stati eseguiti studi geofi sici integrati su due edifi ci scolastici di competenza della Città Metropolitana di Roma Capitale, ubicati in Municipi della Città, noti per essere interessati da un complesso sviluppo di sistemi ipogei; le indagini hanno consentito di individuare anomalie nelle caratteristiche del sottosuolo imputabili alla presenza di possibili cavità non ancora note e/o esplorate. Le indagini eseguite presso il plesso scolastico di Via Asmara (Municipio II), realizzato nel 1939, sono funzionali al corretto posizionamento delle scale di emergenza nel cortile dell’edifi cio per prevenire cedimenti e/o crolli legati alla possibile presenza di una catacomba. Il secondo caso di studio si riferisce all’Istituto Jean Piaget di via Diana (Municipio V), costruito intorno al 1932, in prossimità del quale sono noti crolli e sprofondamenti negli anni passati. Da ultimo nel 2013, a qualche decina di metri dall’edifi cio scolastico ed in prossimità del muro di recinzione, si è verifi cata l’apertura di una grossa voragine che ha coinvolto un’abitazione privata. Per tale ragione è stata programmata un’apposita campagna di indagini geofi siche preventive presso l’Istituto. Il presente studio ha permesso di perfezionare un protocollo speditivo di utilizzo integrato di alcuni metodi geofi sici (microgravimetrico, georadar e sismico) funzionale all’individuazione di cavità nel sottosuolo in area urbana, che permette di mappare dimensioni, distribuzione spaziale e profondità. Tale base informativa risulta imprescindibile per una gestione e messa in sicurezza degli edifi ci scolastici esistenti e per la progettazione di nuovi interventi.

Negli ultimi anni l'incremento di fenomeni di sprofondamento nel territorio di Roma Capitale e nella sua area metropolitana costituisce un rischio sempre maggiore per la popolazione e per le infrastrutture. Il verificarsi di questi eventi è in gran parte dei casi connesso alla presenza di sistemi caveali di origine antropica e diversa età e funzione. Il presente studio ha permesso di perfezionare un protocollo speditivo di utilizzo integrato di alcuni metodi geofisici (microgravimetrico, georadar e sismico) funzionale all’individuazione di cavità nel sottosuolo, che permette di mappare dimensioni, distribuzione spaziale e profondità. Tale base informativa risulta imprescindibile per una gestione in sicurezza degli edifici scolastici esistenti e per la progettazione di nuovi interventi.

We present the results of multidisciplinary investigations of two significant sites, located in the Acque Albule Basin (AAB), 25 km Northeast of Rome (Italy). This basin has been interpreted as a transtensional structure, lying in the western margin of the Apennine range and affecting the Plio-Pleistocene sedimentary and volcanic sequences. During late Pleistocene times, AAB has been filled in with thermogenic travertine of variable thickness. Since historical time, lithoid travertine has been quarried, becoming the main building material during the Roman period (Lapis Tiburtinus). At present, the mining activity still represents the main economic resource of the region together with thermal baths. After the end of the II World War this area has experienced a strong urbanization and marshy lands were transformed into densely populated areas affected by subsidence and sinkhole phenomena. In order to characterize these environmental hazards from the geophysical and geotechnical point of view, we chose two test sites close to relevant anthropic infrastructures. Site A, located at the southern side of the Guidonia military airport and beside an important road; site B, a few kilometers South-East of site A, lies next to the Regina and Colonnelle Lakes and close to the Roma- Pescara railway. The former feature is a large sinkhole depression, hundreds of meters in width, characterized by ongoing subsidence, whereas the latter consists of two sinkholes actually acting as springs. Both sites lie in proximity of inferred faults, which would affect the AAB in the N-S and NE-SW– directions respectively. The aim of this study is to compare the two cases by collecting geological, geomorphological and geophysical parameters and thus testing the variable controlling their formation and development. We also extended the geophysical campaign in the surrounding area using a multidisciplinary approach to image both surface and subsurface features. We carried out stratigraphic and geomorphological survey, 2 and 3D Geoelectrical Tomography (ERT), differential GPS altimetry, gravity, magnetic, seismic, and soil gas measurements. Moreover, two drillings have been bored inside and outside the depression area of the Site A, reaching depths of 60 and 20 meter, respectively. Geotechnical parameters of the recovered stratigraphy were also measured by laboratory tests. In general, the approach we propose could provide key elements to recognize similar situations in sinkhole prone areas. Moreover, comparative analysis together with the monitoring of the A site can represent useful tools to understand the genesis and dynamics of phenomena and hopefully to forecast their evolution, particularly in the parts of the basin where active movements caused fractures and damages to buildings and infrastructures.

In Rome urban area, within the garden dedicated to Ytzhak Rabin (a portion of the Villa Ada park), occurrence of a few collapses has been observed for the first time in September 2012. In the surroundings, presence of underground cavities- mainly catacombs- is conversely well documented by previous studies. Local authorities were immediately informed of sinkholes formation, because collapses occurred very close to a playground located in a highly frequented sector of the garden. Propagation processes of the phenomena, periodically monitored since their first observation, significantly fastened after a period of heavy rainfalls on Rome area in January- February 2014. Thus, multidisciplinary geophysical investigations have been started in agreement with Civil Protection of Rome Municipality, who has taken preliminary safety measures (installation of fences and danger signals). Hitherto, 28 sinkholes have been identified, aligned along a WNW-ESE trending zone, testifying localized collapses of the roof of underground cavities, probably belonging to the palaeocristian catacomb systems dug nearby Via Salaria. Preliminary geophysical prospections have been performed in a small test area, in order to verify methods applicability and thus program a systematic survey of the whole garden. Drillings, and direct exploration of the accessible galleries, will complete the reconstruction of underground geometry and conservation state of vaults and pillars. Once completed the hazard assessment, the planning of urgent works is expected in order to restore the complete use of the garden.

On May 2010, due to heavy rainfall, a sinkhole developed in correspondence of the S.P. Carolano roadway (1+200 km, Montelibretti, Roma), in the southernmost sector of the Sabina area. The collapse is located in correspondence of a “U like” shaped profile of the roadway crossing the central sector of a NNW trending valley. In order to obtain a more complete geological characterization of the sinkhole phenomenon, gravity, seismic and electrical investigations have been carried out on the base of previous detailed studies, historical sources and maps. Due to recent propagation of the sinkhole, probably related to the anthropogenic alteration of the superficial drainage network in previous times and recently triggered by heavy rains, local authorities decided to promptly fill the sinkhole with arid material, in order to preserve public safety. In this study is suggested the restoration of the natural runoff of the water flow in the area.

The Plio-Quaternary Acque Albule Basin is already known for the occurrence of sinkholes; since the spring 2014, it has been ongoing the study of an active subsidence process, which formed a depressed area near the Guidonia village. During the last year, the phenomenon has become more intense giving rise to two collapses along the eastern rim of the depression. Thus, geophysical and geogeochemical investigation campaigns started in order to understand the genesis and evolution of the phenomenon. Survey results allowed a geological and structural characterization, showing the presence of “travertino” at the depression margins and its absence therein. It has been recognized, by the geophysics, features with NW-SE and NNE-SSW direction ascribable to a possible depression fracturing and consistent with regional structural trends. Thus, it has been possible to plan and perform geognostic investigation consisting in two drillings aimed to define the stratigraphy of the marginal and inner part of the depression.

Sinkhole occurrence along the Tyrrhenian margin of the Central Apennines is of great importance for applied research, land management and civil protection. This study reports on GPS-altimetry magnetic, gravity, geoelectric, seismic, and soil gas measurements of a rapidly developing sinkhole near the Guidonia military airport. The measurements revealed an elliptical 2-m depression elongated 220 m in the NNE-SSW direction with the minor axis of 110 m. In spring of 2013, two vertical cavities formed in the eastern and northeastern flanks of the depression whose depths and shapes are rapidly evolving with the formation of widespread fracturing along the same side. The geophysical observations image the developing sinkhole to a depth of some 50 m, the presence of the Travertino lithotype around the depression (down to at least 40 m), and the lack of this lithotype below the lowered area. The sinkhole's evolution appears to be structurally controlled by local and regional faulting. These results are useful for designing further geophysical, geotechnical and geochemical studies to monitor the sinkhole's evolution and to assess the hazard it presents in densely urbanized area.

Vengono mostrati i primi risultati dei rilievi geofisici e geochimici nella zona di Guidonia che hanno consentito una caratterizzazione geologica e strutturale preliminare fornendo elementi utili per la comprensione della genesi del fenomeno di sprofondamento in atto e della sua evoluzione.

Il Servizio Difesa del Suolo- Provincia di Roma e l’Istituto Nazionale di Geofisica e Vulcanologia, nell’ambito di un protocollo d’intesa finalizzato alla “Caratterizzazione geologico-tecnica e geofisica di siti interessati da Sinkholes e da eventi franosi nell’ambito del territorio della Provincia di Roma” hanno avviato congiuntamente al Dipartimento di Scienze della Terra- Sapienza- Università di Roma una campagna di indagini multidisciplinari in siti soggetti a sprofondamenti sia naturali, sia di origine antropica. Un caso di particolare rilevanza è quello del parco Ytzhak Rabin, nell’area urbana di Roma, dove nel Settembre 2012 è stata rilevata la prima evidenza di due sprofondamenti, sino ad allora non censiti nell’area. Il parco Ytzhak Rabin si trova nel Municipio II, tra via Panama e via Salaria, ed è contiguo a Villa Ada. Il fenomeno, segnalato tempestivamente alle autorità competenti, merita particolare attenzione in quanto la villa è intensamente frequentata e gli sprofondamenti sono ubicati a breve distanza da un’area giochi attrezzata. Nei mesi successivi è stata osservata l’evoluzione tramite sopralluoghi periodici, constatando l’ampliamento delle prime voragini di forma allungata e la formazione di nuove lungo un allineamento circa WNW-ESE, censendone ad oggi 15, di cui almeno 5 con oltre 2 m diametro.