Torino Extends its MetroConstruction of the Turin metro extension between Porta Nuova and Lingotto has entered a new stage with the official lowering on 28th February, 2008, at Marconi station, of the cutter head of TBM "Caterina", the machine that will dig the tunnel under Nizza Street between Marconi and Lingotto stations (lot 2). Lot 2 is built by Maire Engineering (leader) in joint venture with Ghella on behalf of Gruppo Torinese Trasporti (GTT). The contract amounts to EUR74.6 million (EUR19.2 million for tunnelling). Equipment of the tunnel is not included in the contract. Visit www.maireengineering.it, www.ghella.com and www.comune.torino.it/gttThe TBM officially commenced digging on 9th April. Within a year, the 400-tonne piece of engineering will cross five stations along Nizza Street (Nizza, Dante, Carducci-Molinette, Spezia and Lingotto) and will complete the 3.1 km single bore tunnel that will connect the city centre with Lingotto trade fair district. Working round the clock, the machine will dig and install at the same time the concrete lining, like the three TBMs that previously worked between Fermi and Porta Nuova. As the tunnel is completed, construction of the stations will move to the final phase. The Marconi-Lingotto section also includes five vent shafts excavated by micropiling and six cut-and-cover stations built between diaphragm walls, the first (Marconi) being the start point of the TBM and the last (Lingotto) a yard for train service. View a video (in Italian) at www.youtube.com/watch?v=hFwttQcNAww. Visit www.metrotorino.it/comunicati2008/080228.pdf A system monitors the full tunnelling process and gives technicians plenty of information and visibility on the whole project and provides them with real-time relevant data on the environmental and structural monitoring of the surrounding ground, roads and buildings. The technological system constantly and accurately monitors all of the buildings in Nizza Street.Construction of the 3.7 km Porta Nuova-Lingotto section (red on the map) began in April 2006 and will end in 2010. Click here. The TBM is expected to break through into Lingotto station in December 2009. The stretch between Porta Nuova and Marconi (600 m) is built using the cut-and-cover method (lot 1). The Porta Nuova-Lingotto section will open at the end of 2010. The line will then stretch for 13.2 km serving 21 stations. Construction of Porta Susa station will be completed at the end of the construction of the cross-city railway. Meanwhile, the station will not open until 2009.The earth pressure balance (EPB) TBM from Herrenknecht (machine S-415) features a cutting diameter of 7,750 mm, a shield length of 8.30 m and back-up length of 80 m. The machine is powered with 2,000 kW, the cutting wheel is able to rotate at a speed of 3 rpm, with a 55,750 kN thrust and a 14,648 kNm torque. Visit www.herrenknecht.comThe EPB technology is based on the face support principle which provides continuous support to the tunnel face by balancing the earth pressure against the forward pressure of the machine. The soil excavated by the cutting head is accumulated under pressure in the cutting head chamber. The soil in the cutting head chamber is pressurised at an adecuate level depending on the surrounding ground conditions (geotechnical characteristics of the subsoil, water table level compared to the tunnel axis, hydraulic gradients, ground permeability, possible interference of existing structure, etc.). The push applied to the TBM shield and therefore to the rotating cutting head causes the soil from the tunnel face to fall in the excavation chamber and it is then excavated by a rotating conveyor. The control of the rotation speed of the conveyor allows to regulate the volume extracted with respect to the volume excavated to accumulate sufficient soil and therefore a pressure which is the one that will balance the tunnel face.As the tunnel is being mined by the EPB TBM, the segmented concrete liner is continuously constructed into rings within the tail shield of the machine. The shield advances by pushing through the ground by hydraulic rams on the last installed ring of concrete segments and as the machine moves forward, the rings are grouted in place. A cementitious grout is injected longitudinally to fill the annular space between the ring extrados and the surrounding ground at a certain pressure, the volume of which at least equals the theoretical volume of the annular space. This eliminates the need to re-visit the tunnel for secondary construction making it a one-pass system.The grout injection nozzles positioned in the tail skin at the end of the segmented ring ensure constant continuous pressure grouting through ports. The ring is internally protected by rows of brush seals to prevent the problem of grout flowing out of the cavity following injection. Tail sealant grease is injected into the brushes to seal the gap between the shield and the segments to secure against ingress of water, soil or grout. The equipment for handling the segments and the grout is supplied by De Nicola. Visit www.paolodenicola.comAs the tunnel is driven, the volume of soil that falls into the cutting head chamber i.e. the theoretical volume and the admixtures that may have been injected on the face or within the chamber has to be extracted. It is fundamental to regulate the volume that is extracted with the screw conveyor if an intervention is necessary in case too much soil is excavated (overbreak or extra-excavation) or not enough (underbreak).LiningThe TBM will install 30 cm-thick segments, 1,400 mm long on average (1,380 mm minimum length and 1,420 mm maximum length) to shape a concrete liner featuring an outer diameter of 7.48 m and inner diameter of 6.88 m.The precast segments, produced by IPA, have various sizes and types. Each ring is formed by six segments (A1, B1, C1, E1, C2, B2), 15 Biblock fasteners and six formed grooves on the radial joints. Each ring weighs 23,681.25 kilogrammes and has a volume of 9,4725 cubic metres. The maximum admissible tolerance for the fabrication of the rings is ± 1 mm for the length and ± 0,5 mm for the width. The width is 1,400 mm. Each ring can be rotated at multiple angles of 24°.The sealing of the final lining will be made by T128 - 50 ShA seals placed between each segments and between each ring. Visit www.ipaprecast.itGeologyThe ground investigations carried out in the area of Lot 2 have mapped a geological reference model. This model consists of the following homogenous litostratigraphic deposits, described from top to bottom: Rissiani fluvio-glacial and fluvial deposits (gravels, pebbles, and sands in alluvial matrix, generally soft, with discontinuous cemented layers); Villafranchiano lacustral and fluvio-lacustral deposits (clayey alluvium and gravelish sandy levels, little cohesive); and Pliocene nephritic marine deposits (clayey and sandy alluvium, grey blue sands with fossils, rather cohesive). The typical overburden is 12 m with a maximum of 20 m. Mucking-outA conveyor belt transports the earth from the TBM cutter head to a structure named carrousel where skips are placed to raise the muck from the shaft bottom. Beyond the carrousel is a gantry crane where is located an empty skip. The skips full of spoil are hoisted out to the surface and dumped at ground level in a stockpile awaiting transport to the final dump area. Future extensionsFurther extensions of Line 1 have been mooted from Collegno to Rivoli (west of the line) and to Bengasi Square (south), at the limit with Moncalieri. A second line is also planned. The start and end of works have not been programmed yet.Meanwhile, the possibility of sinking underground part of tram line 4 between Corso Brescia and Corso Sommeiller, is under study. The line currently connects Falchera with Mirafiori.Line 1The TBM could pursue its route to extend the line from Lingotto to Bengasi (green on the map). The interministerial committee for economic planning (CIPE) approved on 31st January the financing of this section. The project will be financed by the city of Turin, the province of Turin, the Piedmont region and GTT, according to an agreement signed in 2002. The estimated cost to construct that stretch amounts to EUR193 million. The CIPE decision stipulates that the Italian government will finance 60%, while the remaining 40% will be covered by these local institutions. The new section will be nearly 2 km long, with two stations at Italia '61 and Bengasi. By the end of the year, GTT will have to prepare the final design of the project.By the end of the year, the planning of the western extension from Fermi to Cascine Vica will also be ready, paving the way to the financing and completion of Line 1. The next commitment from the government will be the first section to Cascine Vica. This is a 4 km extension with four stations (Pastrengo, XXIV Maggio, Leumann and Cascine Vica). At longer term, it is envisaged to extend the line to Rivoli then to Rosta (pink on the map). Line 1 of Torino metro showing the ongoing (red) and planned (green and pink) extensions Line 2Work is also under way to prepare the preliminary project for Line 2 that will follow a north-south corridor. On 28th March, 2008, the agency for metropolitan mobility, the Piedmont region, the province of Turin and the cities of Turin, Orbassano, Rivalta and Beinasco have signed a memorandum of understanding which stipulates that these administrations pledge to support the planning phase of Line 2 of the metro and its extension from Turin to Orbassano. For that purpose, a working group including technicians from the signatories will be in charge of defining the line route to southwest. The route within the boundaries of Turin has already been determined and will soon be submitted for approval to the city council.Starting from Mirafiori, the line will run under Corso Orbassano to connect with the future Zappata station of the cross-city railway and continue to Porta Nuova where it will intersect with Line 1. From there, the path will pass beneath Roma Street, San Carlo Square and Castello Square. Beyond that point, after studying four possible routes, the city of Turin has given priority to the option involving a stop in Vanchiglia and is about to approve the project until the city boundary, while the working group will be responsible for deciding the alignment to Orbassano (southwest). Planned Line 2 of Torino metro (preferred alignment in purple) To the north, the line will also provide service to the university of Turin on the site of the ex-Italgas works, then will head to Vanchiglia and will continue its underground path under Corso Regio Parco until the ex-tobacco plant (another future university premises). After that, the line will take a disused railway track between Sempione Street and Gottardo Street to join Rebaudengo, where an interchange station with the cross-city railway is also planned (purple on the map). Click it/26. 24/08.