Tunnel and worm

Alvaro Siza’s recently completed snaking path museum in Brazil  might be of interest to KNOT people.

The French engineer  Marc Brunel revolutionized tunneling with an invention based on the observation of nature. He studied the tunneling of the ship worm Teredo Navalis – a pest that ate the wooden hulls of ships. He noticed the tough shell on the end of this worm, used to cut through wood, and that the rest of the worm was a long tube used to dispose of the wood shavings. Brunel conceived of a “tunnel shield” that turned miners into a huge human worm digging under the Thames. He devised a 120 ton cast iron structure, twenty-two feet tall, nine feet wide and divided into nine areas, on each of the squares Brunel attached iron sides three feet deep. A miner stood in each of these opening, which were closed with fourteen three inch thick boards. The miner removed a board, dug four and a half inches into the soil, replaced the board, then removed the board below and dug four and a half inches again. When the miners were finished, workers standing behind the shield turned huge screws and drive it forward four and one half inches. As the miners began digging bricklayers covered the newly exposed earth, building a permanent tunnel. Brunel hoped his human worm would burrow three feet a day, but he had to settle for one foot a day and it took eighteen years to build the Thames tunnel completed in 1843. The tunnel is still in use as part of the London Underground system.



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