Grand opening of the world’s longest and deepest traffic tunnel
Nearly all of the highest Alpine peaks are found in Switzerland. The country’s central position has always made it an important, albeit time-consuming route across the Alps. Today, June 1, is the official opening of the long-awaited Gotthard Base Tunnel. The tunnel will shave off many hours for both passengers and goods transportation. It took 23 years to complete but, measuring 57 kilometers from portal to portal, it is also the world’s longest and deepest traffic tunnel ever built.
The Sedrun section was the most demanding part to construct due to a combination of a two-kilometer-deep rock layer and very poor rock stability. Sandvik drills, loaders and breakers were selected to overcome the challenges. The construction site could only be accessed through a horizontal access tunnel and two vertical 800-meter-deep blind shafts. All equipment, material, machines and workers were transported through these two shafts.
“All machines had to be dismantled for the shaft, including the instrumented drilling jumbos. It was a very complicated procedure,” says Pekka Nieminen, who was Global Tunneling Business Line Manager at the time. Nieminen managed equipment development for the project together with the engineering and sales departments, and Avesco, the distributor.
Demanding situation resulted in innovative solutions
The combination of depth and weak rock presented an even more problematic issue: safety for the workers.
“The Sedrun excavation site was situated two kilometers down, so compression of the rock down there was massive. Safety was always top priority. The challenging conditions required innovative thinking and close cooperation with both the customer and our distributor,” Nieminen says.
He says that the 60 ton drilling equipment Sandvik developed for the Sedrun project was like a Swiss army knife that could basically handle all drilling needs using either a rock drill or a rotary head.
“We’ve never made anything like it. But that special drilling equipment generated a lot of business for standard equipment,” he says.
The project started in 2003. At that time, the competition dominated the construction market in Switzerland, so the contract was very important for Sandvik. Thanks to its successful execution, other projects followed, such as the 15.4-kilometer Ceneri Base Tunnel that is scheduled to open in 2020. The Gotthard Base Tunnel and the Ceneri Base Tunnel are both part of the New Railway Link through the Alps (NRLA).
“Although the Gotthard Base Tunnel forms the heart of the NRLA, it only provides a continuous flat route together with the Ceneri Base Tunnel,” says Nieminen. “The Sedrun section was shorter than Ceneri, but far more complex,” he concludes.
The picture above shows Axera T12-Sedrun drilling jumbo in action in the tunnel.