Tuesday, January 30, 2007 at 11:39 am

A Rail Tunnel Across the Strait of Gibraltar?

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The Washington Post reports that Spain and Morocco are working on plans to build a high-speed rail tunnel across the Strait of Gibraltar. But the project faces much more serious engineering challenges than the Channel Tunnel did.

For starters, the water is exponentially deeper: nearly 3,000 feet at the shortest route across the strait, compared with just 200 feet in the channel. As a result, engineers have mapped out a different path, from Cape Malabata, Morocco, to Punta Paloma, Spain, that would run twice as far across the strait but through shallower water — a still daunting 985 feet below sea level.

Compounding the problem is that the seabed around Gibraltar is much more permeable than the hard-chalk rock under the channel, which would require engineers to push the tunnel down by another 300 feet or so. The water pressure at that depth means the tunnel would leak heavily, no matter how well it was constructed, said Andrea Panciera, chief project engineer with Lombardi Engineering Ltd., the Swiss firm that is designing the Gibraltar link.

“This is the biggest difficulty,” he said. “We have to go deep into the seabed, which is very, very soft, with a lot of water pressure on top of that.”

Via About.com Geography.

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