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Geo-Joint: The Gotthard Tunnel

Posted on August 09 2016

The world has a new longest tunnel. The Swiss have spent the last 17 years planning and grinding out twin tunnels forty meters apart through the Gotthard Mountains in the Alps. The pair of tunnels pass through 35.4 miles (57 km) of rock for not only record length, but record depth as well. With nearly a mile and a half of mountain overhead at some points, the interior heat climbs to 115 degrees F. Ventilation systems kept the tunnel diggers from roasting, and cool air driven by transiting trains will keep the temperature down to reasonable levels when the tunnel is under full operation. Besides the heat, drillers had to contend with the threat of groundwater entering the tube under enormous pressure. Waterproof liners and special drainages were added to channel water safely away.
The project is full of impressive statistics. Work on the tunnels cost 12.4 Swiss francs, which is 13.2 billion dollars. The spoil, the waste rock of the drilling, came in at 28.2 million tonnes. Remember, each tonne is a metric ton – 240 pounds heavier than the 2000-pound American ton! 2,600 people worked on the project, 700 at a given time, racking up four million person-hours. Nine workers died in accidents during construction. The Gotthard Base Tunnel, or GBT, so called because of its path of nearly constant elevation, edged out Japan for the crown on length. Japan’s tunnel between the islands of Hokkaido and Honshu is three kilometers shorter, and the GBT beats the Channel Tunnel between England and France by seven kilometers. Perhaps most astounding, all this record-breaking construction was completed a year ahead of schedule and only modestly over budget.
This isn’t the first tunnel the Swiss have cut through the Alps, of course. Way back in the 1880s, the original Gotthard tunnel was cut through a much shorter route, but a lot of climbing into the mountains on loops and switchbacks preceded the trip through the tunnel. The new GBT starts lower and stays level, allowing faster train speeds, which shaves 45 minutes off the old transit time. And in addition to time saved, more freight will now go by electrically-powered trains instead of by diesel truck over Alpine roads. It is estimated that whereas 180 trains a day went on the old route, 240 per day will head through the new tunnel. All this more efficient travel will save fuel and cut CO2 emmissions, a big goal of the Swiss government. The greatest benefits of the route will come in a few more years when another segment of the rail line into Italy is completed. That piece, the Ceneri Base Tunnel, will allow high-speed trains to travel the entire distance at their full velocity.
Recording-holding fame may be fleeting for the GBT, though. The Chinese have plans to build a tunnel between the ports of Yantai and Dalian beneath the Bohai Strait, a distance of over 76 miles (123 km), which is double the length of Switzerland’s new tunnel.

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