Ceneri Base Tunnel Visit - Week 24

During the Week 24 (30th June - 4th July) of our Tunnelling course, we had a visit to the Herrenknecht HQ and a visit to the Switzerland's third largest tunnel - Ceneri Base Tunnel. This blog post presents some of the details of the latter.

Ceneri Base Tunnel © AlpTransit Gotthard Ltd. Retrieved 4th July '14

The 15.4 km Ceneri Base Tunnel completes the link between Zurich and Milan (passing through the Gotthard Base Tunnel) with overburden varying from 800m to 100m. The project is managed by Alptransit Gotthard Ltd and the contractor is Condotte Cossi Consortium.

Location of Ceneri Base Tunnel [1]

Based on the Pini Swiss Engineer's presentation (during Week 18 of our course), we had an overview of the project's technical and geological challenges. Our visit was more focussed to learn the operational and logistical challenges and how innovatively, the Alptransit has been managing it. This tunnel construction site, probably, has the most mechanized form of Drill and Blast tunnelling.

The tunnel face

The tunnel face can be seen in the picture above. There is no problem in the stability of face and hence no additional measures are taken. The support system can be seen - rockbolts with shotcrete. No steel arches are used. Second layer of shotcreting is done after installing the rockbolts.

Three boom drilling jumbo (suspended logistic platform can be seen at crown)

Crusher at the starting of belt conveyor.

The tunnel is excavated using Drill and Blast technique. Two drilling jumbos are available at the site. One of them is used for tunnel advancing and the other one is used for cross tunnels. After each round of blasting, the muck is loaded in to the crusher using a back hoe loader. The crusher is connected to the belt conveyor and the muck is taken away to the portal. The whole system of belt conveyor and ventilation is hanging from the crown using a logistic platform and could be extended as the tunnel advances (like in a TBM).

One of its kind - Concrete batching plant inside the tunnel (special cavern)

Special cavern is built to accommodate the batching plant inside the tunnel itself.

Provision for future expansion

Complete muck handling system is using belt conveyor.

Nonel detonators

Sliding form work for Tunnel side walls in preparation

Sliding formwork for the tunnel side wall can be seen in the above picture. This is at a cavern location. The complete crown is going to be concreted using shotcrete (no formwork is used at cavern's crown). Lattice girder type assembly is used in steel cage work to optimise the rebar cage assembly time.

References:
[1] European International Contractors (EIC) newsletter (link), retrieved on July 5th, 2014.