A successful year for the NRLA on the Gotthard and Ceneri

The year 2008 was highly successful for AlpTransit Gotthard Ltd. The work continues as scheduled and as things stand today, there is nothing to prevent the opening of the Gotthard Base Tunnel at the end of 2017 and the Ceneri Base Tunnel in 2019 as planned.

The Gotthard Base Tunnel is being constructed from five construction sites simultaneously. On the Amsteg and Bodio sections, the excavation work is already complete, and on 16 June 2009, the first breakthrough between Amsteg and Erstfeld was celebrated. In the east tunnel, a total of slightly over 6km of rock remains to be cut through.
At the beginning of June 2009, of the 153.3km total length of the tunnel system of the Gotthard Base Tunnel, 133km or (87%) had been excavated.

Also at the beginning of June 2009, 6.2km (15.4%) of the 40km of passages and tunnels of the Ceneri Base Tunnel had been excavated.

Status of work on the Gotthard Base Tunnel

Overground section Altdorf – Rynächt

This section from the north portal at Erstfeld to the junction at Rynächt-Altdorf links the base tunnel to the existing main line of Swiss Federal Railways.

In the first months of 2008, the belt conveyor and silo systems were installed from the Erstfeld surface installations site to the construction site at Rynächt. A total of 18km of conveyor belts ensure that the material excavated from the drives at Erstfeld is transported to Altdorf-Rynächt.

Laying of the ballast material in the future trackbed of the new transit line is progressing according to plan. The trackbed is also being used as a temporary material store.

Erstfeld section

The Erstfeld section is the most northerly section of the Gotthard Base Tunnel. It also includes an underground branch-off to allow future extension of the tunnel to the north without interrupting train services.

Full-speed driving at Erstfeld began in the west tunnel in June 2008, and in the east tunnel in April 2008. About six months ahead of schedule, breakthrough in the east tunnel was celebrated on 16 June 2009. In only a few months, the tunnel boring machine covered a distance of 7.2km. Breakthrough between the tunnels took place with very high accuracy – the deviation of less than 1cm horizontally and vertically was extremely small.

The first approximately 600m of the Gotthard Base Tunnel at Erstfeld are being constructed by the cut-and-cover method. Work on the cut-and-cover tunnel started in the northern section of the surface installations site in April 2008. To date, 230m of the east tunnel have already been concreted, and 180m of the west tunnel.

Amsteg section

The Amsteg section is the second section from the north. A 1.8km adit and a construction tunnel were driven by drilling and blasting to the position of the railway tunnels where assembly caverns were excavated. The two tunnel boring machines that set out from the caverns towards Sedrun in 2003 reached their destination in 2006. The last 185m to the boundary of the Sedrun section were excavated by drilling and blasting. The breakthrough between Amsteg and Sedrun was celebrated by AlpTransit Gotthard Ltd. along with the contractors in October 2007.

Currently in the west tunnel, installation of the prefabricated elements of the side benches is in progress. Concreting of the inner lining in the east tunnel is already complete.

Sedrun section

The Sedrun section is reached from the surface through a 1km-long access tunnel and two vertical shafts 800m deep. This section is also the site of one of the two multifunction stations, which will accommodate technical installations, emergency stop stations, and track crossovers. Excavation of the railway tunnels to the north and south from the bottom of the shafts began in 2004 using drilling and blasting. Because of the geological conditions, tunnel boring machines cannot be used.

In June 2008, in the drive south from Sedrun towards Faido, an unexpectedly long interference zone was struck. Since then, in the east tunnel, the interference zone has been mastered and driving rates are increasing again. The drive in the west tunnel, which lags behind the east tunnel by a distance of approximately 50m, is still in the demanding boundary area of the interference zone.

Driving northwards was already completed in October 2007 and November 2007 respectively. To optimise the concreting work, in November 2008 two additional lining wagons were installed to allow four vault-concreting wagons to be in operation simultaneously. As a result, up to 600m3 of concrete can be applied per day. Prefabricated side-bench elements are also being installed here.

Faido section

The Faido section is reached from the surface through a 2.7km-long access tunnel with a gradient of up to 13%. For construction logistical purposes, it is linked to the Bodio section. The second multifunction station is located at Faido. When the two tunnel boring machines cutting from Bodio arrived here they were repaired and modified before continuing towards Sedrun in summer 2007.

In view of the geological conditions that were actually encountered, and the daily advance rates, the forecast breakthrough points between Faido and Sedrun had to be revised. The Transco Sedrun consortium is now expected to reach the Faido section boundary at the end of 2009. The tunnel boring machines from Faido will only reach this section boundary one or two years later – which would naturally have a corresponding effect on the opening date of the Gotthard Base Tunnel.

To avoid this, the Sedrun section boundary was moved southwards. With the resulting gain in time, the planned opening date of the Gotthard Base Tunnel at the end of 2017 can be maintained.

Last year in October, the tunnel boring machine in the east tunnel successfully mastered the feared Piora zone. On 3 February 2009, the tunnel boring machine in the west tunnel of the Gotthard Base Tunnel also cut through the last meters of the Piora syncline and reached the Medels granite.

The remaining 4.5km to the boundary of the Faido section are the part of the Gotthard Base Tunnel with the greatest overburden and very high rock temperatures of up to 50 degrees Celsius. For this reason, prior to driving, horizontal bores are drilled in both tunnels. Depending on the results of the bores, the necessary safety measures are defined.

Bodio section

The Bodio section is the longest section of the Gotthard Base Tunnel. The first tunnel metres were constructed above ground, then through loose rock, before sufficiently solid rock was reached to allow driving with tunnel boring machines. To allow faster construction of the underground assembly caverns for the tunnel boring machines, a bypass tunnel was dug round the site of the portal. From the assembly caverns, two tunnel boring machines started cutting north towards Faido in 2003. After about 13.5km, both machines reached their destination in 2006.

On 24 June 2008, work on the tunnel lining in Bodio was completed. Since October 2008, fitting out of the shell with the connecting gallery equipment (doors, double floors and ventilation) has been in progress. To date, 30 cross galleries have been completely equipped.

Overground approach line south

The approximately 5km-long overground approach line from the south portal at Bodio to the junction at Giustizia links the Gotthard Base Tunnel to the existing main line of Swiss Federal Railways.

The trackbed of the overground approach line has been completed as far as possible. In the first half of the year, the foundation piles and steel sections for the noise-abatement walls were installed along the approach line. The noise-abatement walls will only be assembled shortly before the new line goes into operation.

The preparations for handover of part of the construction site from the shell contractor to the general contractor for railway infrastructure are in progress.

Status of work on the Ceneri Base Tunnel

The 15.4km-long Ceneri Base Tunnel extends from Camorino to Vezia. Like the Gotthard Base Tunnel, it consists of two single-track tunnels that are linked to each other by connecting galleries.

The major part of the Ceneri Base Tunnel will be cut from the intermediate heading at Sigirino. In the areas around the portals at Camorino and Vezia, parts of which are densely populated, apart from the overground rail sections and portal buildings only a few hundred metres of the tunnel will be constructed.

Of the more than 40km-long tunnel system under the Ceneri, 15.4% had been excavated at the beginning of June 2009.
The Ceneri Base Tunnel is scheduled to become operational to coincide with the railway timetable revision in December 2019.

Camorino/Vigana

The north portal of the Ceneri Base Tunnel will be constructed at Vigana. Some 800m of tunnel will be driven from here towards the south. Shortly after the portal in both tunnels, underground branch-off caverns will be built that have connecting ramps to allow a later crossing of the Magadino plane.

To link the Ceneri Base Tunnel to the existing railway lines, various building works will be constructed at the Camorino junction. In addition to the portal buildings, these include two viaducts, the underpass under the cantonal road, the overpass over the motorway, and the Locarno-Lugano loop.

At the start of October 2008, the installation surfaces for the Tunnel Lot Vigana were handed over to the contractor. After various preparatory works, in spring 2009 the contractor started driving under the A2 motorway. Work on the ‘Canale fugatore’ is in progress. In the future, this drainage tunnel in the area of the construction site in the Magadino plane will protect the agricultural land and neighbouring residential areas from flooding.

Sigirino

At Sigirino, exploratory bores were already excavated between 1997 and 2002 which provided valuable information about the geology to be expected. Subsequently, before starting to cut the main tunnels, the tunnel builders constructed the access adit for the drive of the Ceneri Base Tunnel. At the end of this adit are two underground caverns which are the starting points for the two drives running south and north. Breakthrough of the access adit into the existing caverns was celebrated on 6 November 2008.

On 11 June 2009, the main work of the large tunnel construction lot of the Ceneri Base Tunnel was awarded. The work should begin in spring 2010.

Vezia

Vezia, near Lugano, is the site of the south portal of the Ceneri Base Tunnel. Some 300m of tunnel will be driven from here towards the north. Immediately after the portal, the tunnel section joins the existing railway line. Approximately 2.5km before the portal is the underground branch-off at Sarè. This will allow future extension of the tunnel southwards to Chiasso and Italy.

The construction work at Vezia is particularly demanding because it is taking place in a residential area and in a very confined space. Furthermore, the Ceneri Base Tunnel crosses over the Vedeggio-Casarate road tunnel, which is also under construction, at a distance of only 4m. The preparatory work at Vezia began in mid-March 2008. In mid-June 2008, work began on the construction pit for the portal and the 170m-long cut-and-cover section.

Railway infrastructure

An important milestone in the project year was signing of the work contract for the railway infrastructure equipment of the Gotthard Base Tunnel in April 2008. With a value of around 1.7 billion Swiss francs, this is the largest contract of the entire project and probably one of the world’s largest contracts for railway infrastructure.

The railway infrastructure contractor is responsible for the entire railway infrastructure equipment of the Gotthard Base Tunnel and the immediately adjoining overground sections to the north and south. The contractor is tasked with the execution planning, execution, and commissioning of the railway infrastructure systems.

After a year of intensive planning and project preparations, the first work on the railway infrastructure of the Gotthard Base Tunnel began at Biasca on 18 May 2009. This work involves constructing the access tracks from the railway station at Biasca to the railway infrastructure installation site south of Biasca. As from summer 2009, on the approximately 60,000m2 installation site construction will take place of accommodation for 230 workers, a canteen, assembly workshops for the pre-assembly of the railway installation components, warehouses and open-air storage areas, a control centre to monitor the construction site traffic in the tunnel, and various construction site railway sidings. Installation of the railway installation equipment through the south portal at Bodio will start in May 2010.