A CLOSER LOOK: STUDIES OF INTERACTIONS BETWEEN LINE C AND MONUMENTS
Along its route, Line C interacts with highly prized historic buildings and monuments, from the Colosseum to Palazzo della Cancelleria and Palazzo Venezia. To safeguard a heritage that is unique to the world and protected by UNESCO, the Customer Roma Metropolitane tasked the General Contractor with preparing, before drawing up the Final Design of Sections T2 and T3, a study of the interaction with the monumental heritage and with the historic buildings affected by the construction of Line C.
The Line/Monuments interaction study provided sound technical and scientific support for defining the measures to safeguard the monuments, and the corresponding monitoring project.
In the study, for each of the 56 monuments, monumental areas, and historic buildings, the following activities were performed:
- Reconstructing the buildings’ “architectural history” by means of a broad research campaign at the properties and in the archives, while verifying how the structural interventions performed in the past may have modified their static behaviour;
- Survey and photographic documentation, with a high degree of detail, of the cracking situation currently present;
- Defining, by onsite surveys, the types and geometries of the ground structures;
- Analysing, using the most modern diagnostic survey techniques, the mechanical properties and constitutive bonds of the structural elements and of the materials used for the construction;
- Constructing complex mathematical models, thanks to special software, capable of faithfully reproducing the historic monument/building;
- Calculating, based on the design data, the subsidence basins induced by the excavations, and of induced stress situation in correspondence with the structural elements;
- Designing an adequate monitoring system;
- Designing safeguarding measures aimed at minimising the induced effects.
The aforementioned activities were entrusted to the most qualified operators of those operating in the sector, organised in 7 Specialist Working Groups.
Moreover, precisely in consideration of the value of the heritage to be protected, on the strength of the previous consolidation experience of the Tower of Pisa, a multidisciplinary Scientific Technical Committee was set up, composed of the most authoritative experts on the European landscape in designing underground works in urban settings.
The Scientific Technical Committee
This multidisciplinary specialist body is formed by a small and selected group of university instructors who are experts in various disciplines:
The SCIENTIFIC TECHNICAL COMMITTEE performs a function of high consulting for Metro C S.c.p.A. and the Customer for all aspects of Line/monument interaction, during the design of the new Line C, in the section involving the Historic Centre.
The Scientific Technical Committee’s essential function is that of ensuring a high methodological level of the studies and checks performed by highly specialised structures, in order to minimise the risks derived from building tunnels that interact with the historic/artistic heritage above.
The Scientific Technical Committee coordinates, with guidance and control functions, the working groups of the following disciplines:
These studies are aimed at analysing the interaction between the excavation of the tunnels and the pre-existing buildings, taking into account their state of conservation, the geotechnical conditions of the subsoil, and the excavation method adopted.
The results make it possible to draw up a monitoring scheme of the buildings affected by the phenomena of interaction with tunnels, identifying the monuments and the historic buildings that might require safeguarding measures, preferably of a temporary and reversible nature.
In carrying out its activities, the Scientific Technical Committee interacts on a regular basis with the Roma Metropolitane customer project manager and with all the institutions tasked with protecting the archaeological and the historic/artistic heritage.
CHECK UP PHASES
Phase One: selection
In Phase One, the preliminary Line/monuments interaction verifications are done, in order to identify the most sensitive points to be analysed in the area between Ponte Vittorio and the Colosseum. Phase One involves mainly the geotechnical engineering working group.
Phase Two: historical reconstruction
In Phase Two, a historical/architectural and structural analysis is done of 40 buildings and 11 monuments, with topographical surveys of both the foundations and of the portion on the surface.
This phase examines cadastral maps and verifies the type and depth of the foundations and restorations that succeeded one another over time, and that might have altered the building’s statics.
If necessary, supplementary probing is done (core sampling or tomography) for comparison with paper documents.
The result of these surveys is a genuine x-ray of the building, which is indispensable for drawing up a historical study for each monument or building.
Phase Three: risks map
Once all the elements on the condition/conservation of the buildings are determined, each building’s vulnerability indices are identified, in order to draw up a risks map.
Phase Four: structural simulation
In Phase Four, based on what was verified in the field, 3D models of the state of the buildings are made, and the tunnel excavation’s effect on the foundations is simulated. At this point, there are two possible scenarios:
1 – The excavation does not present a risk, and therefore the building can absorb the stresses derived from it.
2 – The building’s structure does not tolerate the vibrations/stresses caused by the excavation of the line tunnels, and in this case specific safeguarding measures must be adopted.
Phase Five: safeguarding measures
The possible safeguarding measures are:
1 – Revision of the design solutions, with modification of the route
2 – Preventive defence on the ground, for example with protection works like retaining minipiles
3 – Preventive structural consolidation of the building.
Phase Six: monitoring
The sixth and final phase consists of preparing a sophisticated monitoring system (in operation for Section T3) that supervises continuously for the entire duration of the works in order to verify, “live,” every small change from the previous situation as the tunnels advance underground.
The monitoring is performed using laser and optical techniques, inclinometers, electrical meters, thermometers and accelerometers to check vibrations.
The results of the monitoring go into a specially created database and allow all the interested parties to follow, in real time, the deformation phenomena as they evolve. Moreover, they permit prompt signalling of the need for any modifications to the tunnel excavation process.
Monumental buildings and monuments subjected to the entire monitoring phase:
- Aurelian Walls at Porta Metronia
- Aurelian Walls at Porta Asinaria
- Church of Santa Maria in Domnica
- Church of Santo Stefano Rotondo
- Celimontano Aqueduct
- Basilica of Maxentius
- Columns of Forum of Nerva
- Forum of Caesar
- National Monument to Victor Emmanuel II
- Trajan’s Column
- Palazzo Venezia and Museum
- Church of Saint Mark
- Church of Santa Maria di Loreto
- Palazzo Valentini and Santissimo Nome di Maria Church
- Palazzo of the old mint
- Palazzo Bonaparte
- Doria Pamphilj administration
- Church of the stigmata and its appurtenances
- Palazzo Grazioli
- Palazzo Altieri
- Appurtenances of Palazzo Altieri
- Palazzo Origo
- Palazzo Datti
- Palazzo Pescatori Serventi
- Palazzo Vidoni Caffarelli
- Palazzo Bufalo della Valle
- Convent and Church of Sant’Andrea della Valle
- Palazzo dei Santi XII Apostoli
- Palazzo Massimo Istoriato
- Palazzo Massimo alle Colonne
- Palazzo Massimo di Pirro
- Palazzo Massimo di Camillo
- Church of San Pantaleo
- Convent of San Pantaleo
- Palazzo Braschi
- Palazzo Strozzi Besso
- Palazzo della Cancelleria and Church of San Lorenzo in Damaso
- Palazzo Fieschi Sora
- Palazzo Avogadro Martel
- Church of Santa Maria in Vallicella
- Oratory of Saint Phillip Neri and convent
- Palazzo Sforza Cesarini
For the following monumental buildings, the interaction analyses went no further than the first selection phase as they were subsequently deemed as not interacting with the Line’s construction:
- Palazzo Nobili Vitelleschi
- Palazzo Celsi and Palazzo Ruggeri
- Palazzo Cenci Bolognetti
- Church of the Gesù
- Casa Professa
- Palazzo Venezia
- Palazzo Capranica del Grillo – Teatro della Valle
- Church of Sant’Ivo alla Sapienza
- Palazzo della Sapienza
- Holy area of Largo Argentina
- Church of Santo Stefano del Cacco
- Church of Santa Maria in Via Lata
- Palazzo Doria Pamphilj
- Church of San Giovanni dei Fiorentini