The Gotthard Base Tunnel

D76-074

In approximately one year, the Gotthard Base Tunnel will open for transportation to the general public. At 57 km, it will then be the world’s longest railway tunnel equipped with state-of-the-art technology. To ensure smooth operation, it will be necessary to take special safety precautions during maintenance. – An exciting project happening beneath the Saint-Gotthard Massif.

Zurich to Lugano in Less Than 2 Hours

Gaining 60 minutes of time: The train travels up to 2300 meters under the mountain ridge!
Switzerland is centrally located in Europe and thus a well-traveled hub – not only for tourist traffic but for freight traffic as well. According to the AlpTransit Gotthard AG (ATG), 26 million tons of freight is transported through the Swiss Alps every year, 80% of which is transported in transit; this amount is expected to increase further in the coming years. The general public voted in 1992 to shift traffic from the streets to the tracks to protect the Alp region to the greatest extent possible: The new transversal Alp railway (NEAT) project has begun; the Gotthard Base Tunnel is the main structure, which will open in 2016. The Ceneri Base Tunnel is part of the so-called Gotthard Axis, the completion of which is planned for 2020. The tunnels will reduce the driving time between Zurich and Lugano by 60 minutes.

The construction of the tunnel is an immense project. The smooth and continuous operation is a major challenge for the responsible parties as well; thus, the groundwork had to be laid in the planning stage of the project. Two single-track tubes run for 57 km almost completely straight; the route has few gradients, which will allow passenger trains to travel at speeds of up to 250 km/h. The current standard in tunnels is a maximum of 200 km/h. The flat route makes it possible for longer and heavier freight trains to travel through the tunnel, which will make the train route more competitive.

In tunnels, safety plays a central role. The tubes are connected by 178 cross cuts and are equipped with ventilators and emergency and fire safety exits. There are two emergency stops with two lane changes each that allow trains to change tubes; normally these tubes are closed off by gates. The emergency stops are equipped with doors that can serve both as escape doors and doors with which to regulate the fresh air supply.

 

Mobile Maintenance Doors in the Gotthard Base Tunnel

The precise positioning of mobile maintenance doors makes it possible to perform maintenance work in the tunnel.
Walter Brändli, Nencki AG. For the performance of maintenance work in sections of the tunnel, there must be an ample supply of fresh air for workers. For this purpose, fresh air can be conducted into the maintenance sections from the emergency stops; however, this is only possible if the tubes are sealed first. The seal is created using so-called mobile maintenance doors developed by the company Nencki AG for Harsco Rail Europe.

This railbound vehicle, known as the MET, can be anchored at specific positions in the Gotthard Base Tunnel to seal off the tunnel cross-section (Image 1).

Exact Alignment of the Doors is Critical
Construction tolerances lead to unevenness in the tunnel tubes. To ensure that the doors can be used at all intended spots, alignment rings with matching inner dimensions are mounted in the tunnel. To achieve the required tamped degree, the divide between the door and the alignment ring is only a few centimeters. The door must be set up in such a way that the divide is evenly distributed.

The strong forces that occur due to the difference in pressure between the front and the back of the door are transferred to anchors in the tunnel wall across two spread arms. While the spread arms of the MET are only located on one side of the main door, a few anchors are applied to the front and back of the alignment rings each.

Positioning Demands
At four positions with two MET orientations each, the spread arms have to fit into the anchor and the main door into the alignment ring. The time it takes to assemble the doors should be short. Nencki carries out correct alignment with a FLEXPOINT^® cross-hair laser that is built on the main console, which carries the door and the spread arms (Image 2).

There is a board on the tunnel wall with a cut-out Maltese cross (Image 3). If the laser cross hair fits to the target board, the spread arms fit into the anchor and the main door into the alignment ring.

Alignment
The motor vehicle operator drives the module-carrying wagon with the help of the perpendicular laser line to within a few centimeters precisely of the installation site. The parking brake is then pulled and the four outriggers sunken into the tunnel floor.

Afterwards, the MET can be easily rotated along the longitudinal axis with the outriggers of one side of the wagon. The horizontal laser line that rises or falls is crucial. The fine positioning in the longitudinal direction is carried out by shifting the main console on the carrying wagon. The user focuses on the perpendicular laser line. After alignment, the spread arms encompass the anchor (Image 4); the installation of the main door can begin.

Harsco Rail Europe GmbH is a systems supplier and is responsible for the prototype development and series production of the maintenance vehicles. Nencki AG develops the mobile maintenance doors used to seal the tubes.

Laser Modules for Industry and Crafts

In this project, a FLEXPOINT^® FP-HD laser with a wavelength of 635 nm and 10 mW was used that was assembled with an FP-MPT-19 precision mount. The HD series was developed for industrial environments and is particularly robust. It fulfills IP67 requirements; thus, it is dustproof and protected against temporary immersion (DIN EN 60529).

The potential-free housing is made of aluminum, and the laser can be used at surrounding temperatures between -20°C and +50°C; thus, it is ideally suited for the tunnel, which is between +35°C and +40°C.

Nencki AG selected a focusable version of the laser, which can be easily set by hand. The cross-hair is projected using a diffractive element that has a fan angle of 10° and is sealed in a fixed manner in the housing. The lasers were assembled according to customer request.

Datasheet:

Further product information:
Laser Modules for Industrial Applications

Manufacturer:
LASER COMPONENTS Germany / Laser Modules

Contact:

Contact Person:	Stephan Krauß
Company:	Laser Components Germany GmbH
Address:	Werner-von-Siemens-Str. 15
ZIP / City:	82140 Olching
Phone:	+49 (0) 8142 2864-32
Fax:	+49 (0) 8142 2864-11
Email:	stephan.krauss@lasercomponents.com