Metro – where engineering meets art

tender estimate of €2.5bn and there Rome’s Metro is a fascinating project on many levels. was talk of the whole line being As the two TBMs mining the latest section were preparing commissioned early in 2013, rather than in 2015 as expected. to pass by the city’s famed Colosseum, Kristina Smith took a The earliest ambition for Line C was that it would cross the tour round site. city from the northwest to the southeast with almost 40 stations. One of the first signs of the of Line C on behalf of the City Intersecting twice with the existing tunnelling works underway of Rome. “The Colosseum has metro and once with Line beneath the centre of Rome been completely monitored with B, it would reduce congestion in are the huge metal braces sensors for horizonal and vertical the city centre and improve air supporting some of the city’s displacement and vibration since quality and passenger journeys. The historic monuments. The Aurelian 2015.” line is Rome’s first driverless one Walls are braced either side This latest section of Line C and features technology such as with a system of shoring in two consists of just two stations, Fori . locations. Similar support is visible Imperiali and Amba Aradam, 3km Metro C’s package of works on the Church of Santa Maria of parallel tunnels and two shafts. encompassed six sections of line – in Dominica and the Pilot of Known as Section T3, it runs right T2 through to T7 (see Figure 1) and Aqueduct Celimontano. There are under – and through - Rome’s 30 stations, 19 underground. The others too. historical heart. original plan envisaged sections T4 Contractor Metro C, a The technical and logistical and T5 opening first, followed by consortium of companies challenges encountered here the remaining sections, although led by Astaldi, is mining two illustrate some of the difficulties the sequence has been revised over 6.7m-diameter metro tunnels the wider program of works has the course of the programme. 35m below the surface using faced: the need to protect Rome’s Sections T7 and T6a, running Herrenknecht EPB machines. ancient monuments; hugely from Monte Compatri in the When TJ visited site in early May, significant – and disruptive - southeast up to Parco di Centocelle one of the two machines had archaeological finds; a variety of opened first, in November 2014. stopped for a thorough health ground treatment; and changes to The second section – T5 and most check, 350m before it would pass the design. of T4 – from Parco di Centocelle closest to the Colosseum at a to opened in June 2015. distance of 15m in plan. And San Giovanni station, the first Rome’s Line C Ambitious plans is operational “We expect potential When the Metro C consortium interchange with Line A, opened in as far as San movements of a few millimetre,” won the contract for Line C back May 2018. Giovanni. The says Andrea Sciotti, director in early 2006, it offered both Currently section T3 is expected stretch from there of operations for Roma the lowest bid and the shortest to be open by 2021, according to to Fori Imperiali is now under Metropolitane, the organisation potential programme. Its bid price Sciotti. To date, funding for the construction. set up to manage the construction was €2.17bn compared to the line only as far as Fori Imperiali, the station close to the Colosseum has been secured, with design up to Venezia Station given the go-ahead. Metro C has submitted project finance proposals for a further section. As for Section T1, which T3 Stretch was never part of Metro C’s works, that has been on hold for a long time. According to Sciotti, the cost for the line so far to Fori Imperiali will be €3bn, €800m of which will be spent on Section T3. Sciotti suggests that some of the reasons for the price escalation compared to the time of contract award include archaeological problems

20 Tunnelling Journal – WHERE ENGINEERING MEETS ART

and changes to the standard covering seismic design. Both San Giovanni and Amba Aradam stations, which is currently under construction as part of T3, have been moved to a greater depth and the alignment of tunnels to and from them changed accordingly since the early designs. This is because the archaeological layer of ground, containing multiple artefacts from Rome’s long history, was found to be deeper than expected here. These two stations have also been redesigned so that they can double as museums. San Giovani, which is already open, features archaeological finds from multiple depths and periods of history in glass cases which are part of the station. “San Giovanni gives the public the story of the site. We can take the train passing between the old strata. We can read the depth and historical age of different cultures, so we can read the story of the site from ground level to prehistoric age,” explains Sciotti. Amba Aradam station has around 2.5 bar at the bottom of supplied by H+E, have brought the Section T3 of moved location since the the excavations. Both the station muck out. Rome’s metro Line C runs though the preliminary design. It was first boxes, which are formed with As well as the visible above- historical heart of placed in Largo dell-Ambra diaphragm walls, and the shafts ground support to some of the city. Aradam and is now in Piazzale have been waterproofed. Shaft 3.3 Rome’s historic buildings and Ipponio, a public garden. The will provide space for a crossover structures, various sections of The depth of San ground treatment have been Giovanni and revised design sees the whole as well as access for maintenance Amba Aradam station contained in one box, and emergencies while shaft 3.2 deployed along different parts stations were rather than two boxes linked by will be a ventilation shaft. of the T3 section. Where the lowered to avoid tunnels. The linked design became “If there is trouble during tunnels pass under the Aurelian the layer of impossible when archaeologists operation of the train, the system Walls, which were built in the 3rd archaeological interest, shown vetoed the use of jet grouting is designed to automatically take century to protect Rome against here in red. because it could damage the train to the nearest station attacks, compensation grouting underground artefacts. and the ventilation system starts has been used to firm up the Ironically, the new position to push the smoke and the heat ground beneath the structures. was assessed to have lower in the opposite direction,” says The protection measures were archaeological risk, but once Sciotti. successful, reports Sciotti, with excavations were underway this The stretch of tunnel between around 5mm of settlement and no location revealed perhaps the shaft 3.3 and San Giovani station damage to the walls. most exciting finds of the whole was constructed using traditional Compensation grouting will also route. methods rather than by TBM. “We be used where Line C underpasses did a 3.3m micro tunnel first, did the Station for . Archaeological surprises radial injections to increase the Originally, the plan was for Line Metro C began construction of strength of the ground and then A to link directly into this station, the T3 section in 2013, with the enlarged the tunnel,” explains with a new section of station construction of Ambra Aradam engineer Daniele Ricci, who works constructed directly under the Station and shaft 3.3, which lies for Roma Metropolitane and is existing one. However, this design between San Giovani and Ambra responsible for the civil works. was rejected for two reasons, says Aradan stations. It began work on The two TBMs, Herrenknecht Sciotti. the second shaft, 3.2, between machines which have been busy First it would have caused Ambra Aradan and Fori Imperali building Line C since 2009, started extended disruption to Line B. stations and then excavation for boring in 2018 having been And second, the new site for the the station subsequently. refurbished. The stretch between station does not have any risk The water table in this area shaft 3.3 and Amba Aradam was or archaeological discoveries. is 6 or 7m below ground level, mucked with trains. From Amba “In ancient times, there was a leading to a water pressure of Aradam onwards conveyors, little hill in this area, the Velian

Tunnelling Journal 21 ROME METRO – WHERE ENGINEERING MEETS ART

Hill, which was removed around 1930,” explains Sciotti. So, the Fori Imperiali station will be 50 or 60m from the existing Colosseo one, with the two stations connected by a foot tunnel. Excavations for the station box for Amba Aradam station have revealed impressive archaeological finds. In March 2016, a 900 sq m barracks dating back to the time of the Emperor Hadrian in the 2nd Century AD were uncovered. This was followed by the further discovery of a luxurious villa belonging to a Roman military commander. The barracks, found 9m below ground level, includes 39 rooms off a long corridor and a central fountain. Some of the well-preserved elements of the Controversy “It’s also very difficult to H+E conveyors in buildings included a mosaic floor, Looking at the mainstream news understand which kind of artefact use on the Rome marble floors and wall frescos. stories relating to Line C, it seems you will find buried in the ground. Metro Line C. There was also a grave alongside that the technical challenges and If you find special things it takes the barracks containing 13 adult achievements of the engineers time to excavate. We did a lot of skeletons. and contractors are sometimes boreholes during investigation While this discovery is exciting overshadowed by its public on the ground to understand for archaeologists, residents profile. One Rome resident, when what might be there, but it’s and visitors to Rome, for the asked what people think of the impossible to understand what is contractor it means that the pace works, replied: “They think it is underground. Not just what you of excavation had to decrease to a taking too long!” find, but the condition of what crawl. The method for excavation It isn’t just the additional time you find.” has all been set down in an that is annoying the public. There Given the huge possibilities ‘Archaeological Handbook’ which are the significant cost overruns. for unknown conditions and the was created after the first part of There have been suggestions of potential for changes of scope, the line had been built. corruption amongst officials, with one has to question whether Metro C used a method called Rome’s public prosecutor carrying design and build is the most ‘modified-top-down’ which it had out a major investigation into an appropriate form of contract. created at San Giovanni station alleged fraud involving millions of When asked why this form of where 4,000 artefacts were Euros. contract was chosen, Sciotti exposed during construction. This Metro C has said that the simply says: “Because the client involves excavating down in 3m huge number of changes – by thinks design and build is better layers and creating slabs between 2016 there had already been 45 for the allocation of the risk.” the diaphragm walls using major changes – has been a big It remains to be seen whether self-supporting prefabricated contributor to the increase in Line C will ever make it to the end segments to avoid casting onto cost. There are also numerous of its originally proposed route at the earth. organisations and different levels the Northeast corner of Rome. If “All the archaeological interest of bureaucracy to navigate and all it doesn’t, critics say it is massively layers must be excavated the archaeological and heritage over-designed, carrying just a with archaeological method interests on top of that. fraction of the passenger numbers of excavation, which involves Roma Metropolitane’s position it was designed for. many people and very low as middle man, sitting between The flip side of the argument production, but we have to adapt client the city of Rome, ATAC is that the line is future-proofed, for the respect of archaeological the operator and Metro C the ready for its last section should artefacts that we find during the contractor, must be a challenging funding become available and excavation,” says Sciotti. one. When asked what the most with the capacity to deal with The parts of the barracks and challenging part of the works changes in modes of transport villa, having been painstakingly have been, Ricci sighs and says: across the capital in the future. excavated and removed will be “Everything I think.” Later he The changes to station design stored and then reassembled in expands: “Technical problems, to accommodate extravagant Amba Aradam station, partitioned whether easy or difficult, we archaeological exhibitions may off from the circulation spaces by can solve them. The problem is seem costly now, but there’s glass screens. This element may when you have a lot of laws and no denying that they will be an not be ready when the line first different authorities in the same impressive addition to the city’s opens. time and the same place. historical heritage.

Tunnelling Journal 23