ALMOST THROUGH

IN THE SEDRUN SECTION OF THE GOTTHARD BASE TUNNEL, MINERS ARE WORKING THEIR WAY FURTHER SOUTH, BLASTING THE TUBES FOR THE WORLD’S LONGEST RAILWAY TUNNEL.

“220200” proclaims a notice on the wall, meaning that we are in tunnel 2, precisely 20.2 kilometers from the northern entrance. A metal barrier blocks the tunnel bore, with an aperture no larger than a chessboard. Volker Kapfhammer slides the bolt and even as he warns, “Mind the wind ....” the air whistles through the opening, tumbling the visitors’ safety helmets from their heads as if a hurricane were blowing beyond the partition in the northern tunnel section. “Without the partition, the suction would blow us away. The Sedrun access shaft acts like a huge chimney,” Kapfhammer explains.

It was at Sedrun that we entered the mountain, first on a narrow gauge railway along a 1,000-meter gallery, then in an elevator down an 800-meter shaft, and fi nally on foot northwards along the future railway tunnel. Now we are facing the metal wall; through the aperture we glimpse an illuminated tube. The walls and floor are freshly concreted, the track bed is recognizable, here the tunnel is finished: Job done for Kapfhammer and the 600 people whose work he organizes. With all his strength, the Bilfinger Berger engineer braces against the wind and closes the aperture. Now only the monotonous hum of the ventilation system fills the void. On this side of the partition the rock walls are only partially coated with shotcrete. Here in the southern part of the Sedrun section, the drilling and blasting continues with the rubble manhandled up and out through the access shaft.

THE HARDEST PART OF THE TUNNEL
“Of the five construction sites undertaken in the Gotthard massif since November 1999, Sedrun is the most demanding,” says Volker Kapfhammer. The village that gave its name to the section lies 800 meters above the tunnel floor, accessible only via two vertical shafts. Men and machines have all had to be brought into the interior of the mountain by elevator. And every lump of excavated rock has to take the same route out: a herculean feat. As one of four partners in the Transco consortium, Bilfinger Berger was awarded the contract to build the Sedrun section in December 2001: In the years that followed, miners were to blast two tunnel tubes each two kilometers northward and four kilometers southward into the mountain at the very heart of the 57-kilometer Gotthard Base Tunnel.

When work first began, the geological zone between Sedrun and Faido to the south was one of the areas least explored by geologists. Because the mountains rise to a height of 2,500 meters above the planned line of the tunnel, exploratory drill holes could not predict what kind of rock to expect. The only thing they did know was that here in the Tavetsch intermediate massif there was everything from hard granite to almost sand-like dolomite. While huge tunnel boring machines chewed their way through the rock from the northern and southern ends of the route, in the Sedrun section there was and is no alternative to conventional blasting. Tunnel boring machines would simply jam and fail for weeks at a time in this, the most difficult section of the Gotthard, where crumbling shale, brittle gneiss and even the feared kakirite are regularly encountered. Still, the Sedrun miners consistently advanced by up to twelve meters per day. They were so successful that four years ago the client, Alptransit Gotthard AG, extended Transco’s contract by a further 1.5 kilometers to the south. Kapfhammer estimates that they will make the final breakthrough and complete the tunnel in autumn 2010.

ROLES REVEALED BY HELMET COLOR
In three shifts a day, seven days a week, the miners, fitters, concreters, mechanics and electricians push forward. They’re all kitted out with headlamps, dust masks, protective goggles and rucksacks containing an oxygen supply that guarantees their survival for at least 20 minutes. Only the color of their helmets distinguishes one orangeoveralled tunneler from another: green for the electricians, blue for the fitters, yellow for the construction teams. Franz Schwinger, a seven-year veteran of Sedrun, wears a yellow hard hat: He is a miner, his job is to stabilize the freshly cleared passage using the shotcrete buffalo, a remotecontrol shotcrete pump. One of Bilfinger Berger’s Austrian employees, he has spent half his working life in tunnels. “But this one is something special,” he says. “It makes you proud to be here.” The Gotthard Base Tunnel will not only enter the Guinness Book of Records as the world’s longest railway tunnel, it will bring the people living north and south of the Alps closer together. It will also be a huge relief to an Alpine region plagued by heavy trucks. Every excavator, every one of the big drilling machines, every narrow gauge locomotive working down here, first had to be laboriously dismantled on the surface, then lowered down the shaft and reassembled.

Heinz Rieder from the Bernese Oberland is one of 20 or so construction plant mechanics from all over Europe who care for the machines day and night. Like everyone else here, they work ten days at a stretch before finally taking a four-day break with their families in Austria, Italy, Eastern Germany or the Ruhr area. “We’re a well-oiled team,” says Rieder in his Swiss German dialect. “And if words fail us we use hands and feet to get the message across.”

The miners in the Sedrun section constantly run into a type of rock that is extremely fragile: You can crumble kakirite into a heap of dirt between your fingers. Working in these fault zones under the huge pressure of the mountain above is very risky. Boring machines would stand no chance here, and even with conventional mining techniques, extensive safety systems must be implemented.

The idea that saved the day came from the German coal mining industry. Coal miners have long stabilized mining shafts using steel rings made of several components which allows them to be shifted up against each other. They absorb pressure and deflect it away from the tunnel into the surrounding mountain. The steel rings support a maximum load of up to 180 tonnes per square meter and are installed at close intervals one behind the other as soon as each section of rock is removed. Each time the pressure of the mountain acts on the rings, the pressure that is created when they are forced together discharges with a loud crack.

ONLY THE PORTA ALPINA REMAINS A DREAM
Nothing is overlooked: Depending on the mountain above, the temperatures at the work face can reach 50 degrees Celsius. It takes a sophisticated ventilation system to lower the working temperatures to a more bearable 28 degrees. In an emergency, water that suddenly gushes in would have to be pumped out through the shaft. The pumps are ready. If need be they can lift 100 liters per second to the outside world 800 meters above. Everything is taken care of — well almost: Nothing has come of the opportunity the inhabitants of Sedrun dream about. They had hoped that one day in the caverns beneath their village a railway station would be built, the Porta Alpina, where travelers from Milan and Zurich would alight to ski and hike in Sedrun’s picturesque surroundings. Too expensive, said those responsible in Switzerland, and too much of a safety issue. The plans were cancelled. “Maybe one day,” says Volker Kapfhammer as the elevator carries us back up the shaft. “One day the dream will come true. In any case, we have already done the excavation work. The underground chambers are ready for use at any time.” As Kapfhammer steps out of the train that has carried us the thousand meters to the exit, a fresh wind is blowing through the valley. He breathes deeply: Today has brought him another five meters closer to his goal.

ALPTRANSIT PROJECT BRINGS RELIEF - SWITZERLAND IS ACTING TO COUNTER THE GROWING VOLUME OF TRAFFIC
Switzerland’s Federal Office for Spatial Development estimates that by 2030, the volume of traffic moving through the country will increase by between 46 and 104 percent compared to the year 2000. With this in mind, Switzerland has been working for years to transfer freight traffic from road to rail by constantly developing its rail network. The most important transport project is AlpTransit, the new north-south rail link through the Alps. The Zurich – Milan route forms the main axis and is of major importance for through traffic between Germany and Italy. When the 57-kilometer Gotthard Base Tunnel opens in 2017, some 300 passenger and freight trains are expected to pass through every day. Once it is complete, the journey time by high-speed train between Zurich and Milan will be cut from 3:40 to 2:40. Even the airlines will find it hard to compete. (si)

Image: Alpine transit routes

Text: Philipp Mausshardt, Photos: Frank Schultze
Bilfinger Berger Magazine 1/2010