Spanning Denmark’s Great Belt
BY AWAKE! CORRESPONDENT IN DENMARK
LOOKING at Denmark on a map, we can easily understand why the Danes have long been seafarers and bridge builders. Denmark is made up of 483 islands and a peninsula protruding into the sea from the European continent. Traveling around Denmark has thus always involved crossing water.
The Viking forefathers of the Danes knew how to build very seaworthy ships. And it seems that down through the ages, every little Danish coastal town has had a ferry service connecting it to another town on a neighboring island.
Across the Great Belt
Making a passage by ship, however, has always been risky business. This is true of crossing the broad expanse of open water that separates Denmark’s two largest islands, Sjælland and Fyn. This sound, the Store Strait, stretches like a broad watery belt from north to south; hence, it is often called the Great Belt.
To travel between western Denmark and Sjælland, on which Copenhagen, the country’s capital, is situated, you must cross the Great Belt. In the old days, this could mean spending days waiting for winds to change, storms to subside, or ice to break up. The crossing could be long and hazardous. In the 16th century, because of ice, a royal party was stranded for a week on the little island of Sprogø, midway between the two shores.
It is not surprising, therefore, that the idea of a bridge at this spot has long appealed to the Danes. But could any man-made construction span a body of water as wide as the Great Belt? It would have to be at least 11 miles [18 km] long, including the portion built on Sprogø. It would extend farther than one can see with the naked eye in normal weather—and across open sea. San Francisco’s Golden Gate Bridge, by comparison, is less than two miles [3 km] long.
Planners’ Headaches
Actually, the Danish Parliament began debating the subject of such a bridge in the 19th century. Over the years, planners were occupied with questions like these: Do we want a bridge or a tunnel? Should the connection be for trains, cars, or both? What’s wrong with just using ferries?
Thousands of calculations were made, and millions of words were spoken. The expression “Great Belt debate” became synonymous in Denmark with a never-ending discussion. But finally, in 1987, an agreement was reached. The connection, joining the two large islands at their closest points, would be for trains and cars. The project would consist of two bridges and a tunnel—an 11-mile [18 km]-long combination—together called the Great Belt Link.
The Western Bridge
From the island of Fyn—the birthplace of Danish storyteller Hans Christian Andersen—a combination railway and automotive bridge of reinforced concrete was the first part of the project. Completed in January 1994, it forms the western half of the link. It is now Europe’s longest combined rail-and-road bridge. Standing 60 feet [18 m] above the sea, it stretches more than four miles [6 km] eastward from Fyn to Sprogø.
This Western Bridge, resting on concrete pillars in the sea, is composed of dozens of separate road sections, most of which are 360 feet [110 meters] long. These concrete sections were poured and finished ashore. But how did each part get out to sea to be joined to the previous section? For that, one of the world’s largest floating cranes was used. This massive lifting instrument is over 300 feet [90 m] long and can lift a load of 7,100 tons and carry it out to sea. That is more than the weight of a large car ferry plus 1,000 cars!
But building a dual railway and a four-lane highway to the tiny lighthouse island of Sprogø was not enough. From there, it had to connect with the next two parts of the project. At the end of the Western Bridge, the highway separates from the railway and continues eastward over another bridge. The railway, however, dives into a double tunnel and completes its journey under the sea.
The Double Tunnel
The tunnel, the second phase of the project, is a great accomplishment in itself. Twin tubes, each 25 feet [8 m] in diameter, were built for trains. The tubes were bored through 4.6 miles [7.4 km] of clay, rock, and marine deposits. And the tunnel builders were not able to determine in detail the nature of this underground material before they started drilling.
The tunnel lies between 30 [10] and 130 feet [40 m] beneath the seabed, depending on the undersea terrain—the deepest part being 250 feet [75 m] below the water’s surface. The tunnel drilling machines used were each over 600 feet [each approximately 200 meters] long, including support trains. The finished tubes are lined with 60,000 curved concrete segments, each weighing nearly eight tons.
Starting the tunnel simultaneously from both ends, the builders masterfully succeeded in meeting in the middle with a deviation of less than an inch and a half [4 cm]. It was a long-awaited special occasion when, on October 15, 1994, Prince Joachim of Denmark officially connected the two halves of the tunnel by stepping from one boring machine into the other one, which had been digging toward it. From Sprogø in the middle of the Great Belt, the two finished tunnel tubes now extend all the way eastward to the coast of Sjælland. Since the middle of 1997, trains rapidly cross the Great Belt, providing regular service.
Problems Encountered
The drilling of the double tunnel under the seabed was well under way when suddenly the nightmare of all tunnel workers became a reality—water started to rise in the tubes. The tunnel personnel made it out safely, though it was a narrow escape. The two tunnel holes, however, filled completely with seawater, and much equipment was lost. What had happened? The drilling machines encountered an unforeseen pocket of water in the seabed. This chilling experience naturally set the whole project back, and new techniques had to be devised to get around the problem.
Then one day an explosive fire broke out, and one of the tubes quickly filled with smoke. As a foreman put it, “the smoke got so thick that Pinocchio couldn’t have seen his own nose.” The site was cleared, the fire extinguished, and the work stopped until the cause was determined—hydraulic oil had caught fire. These and other troubles meant that the whole project was delayed time after time.
The Suspension Bridge
The third and crowning piece of the Great Belt Link is the beautiful 4.2-mile [6.8 km]-long automotive suspension bridge. The bridge includes a free span of approximately one mile [of over 1.5 km], making it one of the world’s longest suspension bridges. The roadway of this eastern part of the Great Belt Link is suspended 220 feet [67 m] above the sea. Such a height is necessary because the Great Belt, one of the world’s busiest international waterways, must be kept open for oceangoing vessels.
The two gigantic bridge towers, or pylons, each about 830 feet [254 m] high, are now the tallest structures in Denmark. In comparison, the Statue of Liberty, in New York Harbor, is 151 feet high, not including its base. Naturally, these enormous towers in the sea need a solid foundation. To provide this, the seabed was carefully leveled and covered with a stone “cushion” that serves as a base for caissons, huge concrete boxes on which the towers stand. Each of the caissons measures 256 feet [78 m] long, 115 feet [35 m] wide, and 62 feet [19 m] high and weighs 35,000 tons.
For the erection of the pylons, a special movable scaffolding form was used. Concrete was poured in sections—13 feet [4 m] vertically at a time. When one portion was finished, the form was moved upward, and 13 feet [14 m] more were added on top. It took 58 steps upward to finish each tower.
A fascinating feature of suspension-bridge construction is the spinning of the strong cables used for support. These cables are a carefully assembled bundle of 169 smaller cables, each of which, in turn, is made of 127 steel wires that are each two tenths of an inch in diameter. How did those heavy bundles get hoisted up in the air? They did not! Rather, they were assembled in place. Each individual wire was attached to a special trolley that drew it up to the top of the tower, back down the other side, then up the other tower, and finally on down to the base. Each trip made the cable a fraction thicker. After one year and about 20,000 of such roller-coaster rides, the cable was finally complete.
The Opening
Finally, in June 1998, all the parts of the link were ready for the official opening. The Great Belt Link was a bold and costly enterprise for a small nation, and the Danes followed the construction with fascination. For this reason the opening was planned as a festival for all who wanted to share in it.
Before the bridges were handed over to automotive traffic, pedestrians and cyclists got a never-to-be-repeated opportunity to cross them. On a sunny day in June, more than 250,000 people, including pedestrians, skateboarders, roller skaters, and cyclists, streamed through the colorful ‘opening village’ of hot-dog stands, bandstands, and souvenir shops and out onto the bridges to enjoy the exhilarating view of the sea and the coastline.
During the festivities, the Danish queen pointed out in a speech that the term “bridge builder” is one of the most beautiful expressions that can be used about any person. Jet planes in formation crossed the sky above the bridge. The newly composed work “Bridge Cantata” was played. It included a farewell salute from one of the old ferries. As part of the music, when the conductor pointed his baton at a TV camera, a ferry waiting a mile out in the sea picked up the signal and sounded its loud foghorn for all to hear.
On the evening after the opening, the now superfluous ferries gathered beneath the suspension bridge and sounded their horns to lament that they were members of a dying species.
What the Link Means
Now that the efforts of the thousands of planners and workers are finished, what is the result? Certainly, Denmark has gained another attraction for visitors, since the bridges are indeed a beautiful sight from the land or from the sea. By car, it is a remarkable experience to roll across a bridge that is so big that one or both ends are often out of sight! And, of course, the crossing time has really been shortened. Whereas the ferry took over an hour, a train now zips across in just seven minutes!
The link is already changing several patterns in the population. Many more Danes are visiting friends, doing business, or seeking entertainment across the water. Urbanization and business development are being affected because it is now possible to have your job on one side of the belt and your home on the other. And goods can be moved across the country much faster than before.
But something has also been lost. The ferries that plied these waters represented a tradition that was centuries old, and many travelers rather liked the break a ferry ride gave them. “I shall miss the ferries,” lamented one businessman. “Water and big boats are fascinating. I enjoy the feeling of being windblown on the deck.” Still, there is no doubt that the new link will draw the different parts of the Danish island kingdom closer together and make traveling to and from northern Europe much easier.
[Maps on page 25]
(For fully formatted text, see publication)
DENMARK
FYN
SJÆLLAND
FYN
WESTERN BRIDGE
SPROGØ
TUNNEL
SUSPENSION BRIDGE
SJÆLLAND
RAILWAY
MOTOR HIGHWAY
[Picture on page 26]
Opening evening for the completed suspension bridge
[Credit Line]
Nordfoto, Liselotte Sabroe