Milestones for Swiss road and rail projects 22 Mar 2018

Patrick Reynolds for TunnelTalk

Two Swiss projects have recorded major milestones in efforts to remove the transport bottlenecks at the Gubrist tunnel on the Zurich ring road and on the Eppenberg rail project.

Advance of third tube for the Gubrist highway tunnel
Advance of third tube for the Gubrist highway tunnel

The Gubrist project involves adding a third tube to the northern section of the city’s ring road for client Swiss Federal Roads Office (FEDRO).

Contractor Marti began second heading drill+blast excavation from the Weiningen portal at the start of March. Initial tunnel excavation on the 3.3km long project began late last year (2017) at the Affoltern portal. Cut-and-cover transitions will link to the main 3km drill+blast excavation of the route.

The new, three lane road tunnel runs parallel to the two exiting tubes, to which it will be linked by 12 cross passages at intervals of 300m, eight of 19m2 for pedestrians and four at a larger 39m2 size for vehicles. The tunnel is to be opened to traffic in 2022.

A third three-lane tube is needed as part of Zurich ring road
A third three-lane tube is needed as part of Zurich ring road

With an excavation area of almost 180m2, the tunnel has cover varying from 8m to 180m along the alignment. Geology consists of interbedded sandstones, siltstones and marl. Construction of the existing tunnels suggests that little by way of groundwater is to be encountered.

Loose rock at the Meiningen portal, together with close proximity of a residential area, required installation of pipe roof and spiling support for the first 100m. A thicker layer of concrete will reinforce and control swelling pressure in the tunnel invert reaches through marl deposits.

A JV of Marti AG and Marti Tunnelbau is building the tunnel as Lot 201 on the Zurich Northern Ring Road improvement scheme. The contract was awarded for SF190 million in 2016 with the JV beating five other bidders. Tender documents allowed for drill+blast, TBM or machine excavation and supported with pilot tunnels. Engineers for the project is a JV of Amberg Engineering, Meichtry & Widmer and BHAteam Ingenieure.

Last TBM breakthrough at Eppenberg
Last TBM breakthrough at Eppenberg
Eppenberg is a twin tube rail project
Eppenberg is a twin tube rail project

At the twin-tube Eppenberg rail tunnel project, the 12.75m diameter Herrenknecht Mixshield achieved its second and final breakthrough in February 2017 onf the 2.6km long underground section of the 3.1km rail project for Swiss rail authority SBB.

The Marti Tunnelbau/Wayss & Freytag JV began excavation of the Eppenberg tunnel in January 2017. The client specified bored tunnelling for the project due to the geology and mandated also the type of TBM to be used.

About two-thirds of the drives were completed by the TBM in dry mode, achieving about 17m/day, before a planned switch to the slurry Mixshield mode in mid 2017 for the final 770m stretch.

Other underground structures on the contract include two 6m diameter escape/emergency shafts of 22m and 62m deep, and a 95m long escape tunnel.

The Eppenberg project is the key part of a reconfiguration and expansion of the busiest Swiss rail route at a cost of SF855 million. The tunnel project has a total budget of SF550 million. Studies began in 2007, preliminary works were underway by 2014 and in 2015 the main construction began. The JV’s construction contract value is SF273 million. Consultants on the scheme are a JV of ILF, Aegerter & Bosshardt, ACE-Partner and TUV SUD Schweiz.

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