At a snail’s pace beneath the railway
The suspense at Andermatt train station on Tuesday morning is nearly palpable. The crew from the Hebag company is in position, and any second now the nearly 1,600 tonnes of mass of the prefabricated concrete underpass will begin moving toward the railroad tracks. At least that’s the hope. “The big challenge is that we have no chance to do a trial run. I have 20 years of experience, but every construction site is different”, says Technical Manager Balz Girsberger, without once taking his eyes off his work. He is standing at the control computer. In spite of this technical support instrument, the task requires an extremely delicate touch. Then everyone holds their breath: The underpass makes a small jolt and begins its journey. It advances slowly, millimetre by millimetre.
The underpass at Andermatt poses an additional challenge: Measuring 35 metres, it is very long and must be translated a total of 45 metres. Urs Herger, Project Manager Destination Planning at Andermatt Swiss Alps AG, is also charged with tension: “Of course I’m used to all types of building projects, but this insertion is really very spectacular.” Completely absorbed, he watches as the massive concrete structure advances constantly and ever so slowly. And the way was not at all easy, because first the underpass had to be lifted with hydraulic jacks. Only then could the mighty thrust cylinders push it forward – at a rate of 4 to 6 metres per hour.
Hectic flurry suddenly breaks out; the men in orange safety vests check the various critical points. Because the steel bedding plates are wet, the underpass is not moving as well as it would if everything were dry. The trickiest thing that could happen would be if the underpass were to become wedged tight. “The membrane underlay caused us several problems, but now everything is progressing according to plan”, tells Balz Girsberger.
After six hours, everyone takes a sigh of relief. The first 20 metres are done; the underpass has reached the planned point. The next 25 metres will be taken one night at the end of October. But first the tracks of the Oberalp Railway must be dismantled.
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