The Boring Machine That Dug the 35-Mile-Long Gotthard Base Tunnel Ain't Boring
Excavating five Giza pyramids' worth of rock for the world's longest tunnel takes some serious equipment.
While we may not yet be able to move mountains, we can sure as hell find ways to go through them. Our latest triumph over rock and ice? The Gotthard Base Tunnel, which runs through the Swiss Alps for 35.5 miles, roughly three times the length of Manhattan. Almost a mile-and-a-half deep at its lowest point, Gotthard, which cost $12.5 billion ($220,000 per mile), is the longest, deepest traffic tunnel ever constructed. Workers and their machines removed enough rock to rebuild the Great Pyramid at Giza five times, some 28 million tons in total. The machine they used to accomplish this definitely deserves a second look.
To penetrate the mountain, the engineers used four Herrenknecht Gripper TBMs; each machine is over 1,400 feet long — just over one lap around a track. A Swiss engineer proposed the project 69 years ago, but work on the massive project only began in 1996 largely because of the need for advanced machinery capable of relentless work. The 35-mile main tunnel is only part of the dig, which includes a secondary tunnel and shafts that — taken as a whole — stretch 94 miles.
The Grippers work by powering disc cutters pressed against the face of the tunnel. The pressure on these cutters is extraordinary, some 35 tons. Because of the tremendous energy required to push through rock, the machine and the tunnel head heat up, requiring water jets to cool down the blades and rock chip transferred along a belt towards where they can be collected and transported out of the deepening hole.
The Gotthard Base Tunnel will host both passenger and freight trains, upwards of 300 in total per day. Passenger trains will one day travel as fast as 155 m.p.h., which will trim travel times from Zurich to Milan by almost an hour. Freight trains will also carry huge loads through the tunnel, which will reduce stress on roads and other railways.
Five-hundred lucky travelers took the inaugural ride this week. The real business kicks off in December. You’re welcome to ride — just don’t try to hold your breath until you come out on the other side.