NATM

Contract C305 is the biggest design-bid-build construction contract of the Crossrail (CRL) project and includes the eastern running tunnels of CRL's central section with launch shafts and SCL launch adits for TBMs at Limmo Peninsula, SCL caverns and launch adits for TBMs at Stepney Green and 10 SCL cross passages between the running tunnels with lengths up to 30m. At the Limmo Peninsula site a 40m deep and 30m diameter SCL shaft was built. At the shaft bottom in Stepney Green, two 30m long and up to 10m wide SCL launch adits were constructed followed by two 14m high and up to 18m wide, SCL caverns with single sidedrift and double sidedrift cross sections.

Farringdon station is now one of London's major rail interchange stations, providing connections between three networks. During the construction of the Crossrail project, it also received four earth pressure balanced tunnel boring machines (TBMs): the two Drive X TBMs, running from Royal Oak to Farringdon and the two Drive Y TBMs, running from Limmo to Farringdon. The complete station layout will comprise two ticket halls, two platform tunnels, connecting cross passages, escape and ventilation adits, two escalator - inclines and two concourse tunnels constructed using mainly SCL tunnelling.

Farringdon station is situated at the heart of London's rail network and will be one of its major rail interchange stations, which will link Crossrail, Thameslink services and London Underground trains. The station layout includes two ticket halls, two escalator inclines, two platform tunnels, connecting cross passages, concourse tunnels and ventilation adits. The chosen tunnelling system for Farringdon Station was sprayed concrete lining (SCL). The station comprised a total of 1km of SCL tunnels at depths of up to 35m below ground level and excavation cross-sections varying from 25m² to 110m².

The project was part of the extension of Glenmont Route north into Maryland and included Wheaton Station and two approx. 2500 m long running tunnels as well as ventilation shafts and a cross-adit. Ilbau America, advised by Dr. Sauer & Partners, recommended changes to the existing conventional design and introduced the New Austrian Tunnelling Method (NATM), which was then used to construct the station tunnels, running tunnels and ancillary structures. The shaft at Hildarose Drive was constructed in conjunction with a large double cross-over.

The Russia Wharf segment is the last, but most challenging section of the Silverline Phase II construction for the Massachusetts Bay Transportation Authority (MBTA). The line is designed to provide a dualmode bus rapid transit connection between the central business district in South Boston to the new Convention Center. The tunnel passes diagonally under the 100 year old Russia Wharf complex, which comprises three seven-story buildings with steel frames and brick facades listed in the National Register of Historic Places. The chosen construction method was NATM in conjunction with ground freezing, for the first time in the US. Steel fibre reinforced concrete was used for temporary and permanent lining.

The Santiago Metro network comprises five lines. The Linea 2 South extension included 2.5km dual track running tunnels and two stations with a maximum span of 16.2m. Further, an excavation of 60-65m2 running tunnel in combined top heading/bench with a subsequent invert excavation. Reinforcement consisted of lattice girders, welded wire fabric for initial lining and welded wire fabric for final shotcrete lining. Dr. Sauer and Partners assisted in the production of design criteria for the final design and produced finite element structural computations for the large station caverns.

The Beacon Hill Tunnels and Station are part of the 22.5km initial segment of the Sound Transit Central Link Light Rail Line that will establish a high capacity commuter connection from downtown Seattle to Tacoma. The 1300m running tunnel under Beacon Hill will be mined by Earth Pressure Balance Machine (EPB), while the deep mined Station will be constructed using slurry walls and the New Austrian Tunneling Method (NATM), referred to as Sequential Excavation Method (SEM) for this project.