LYCOS RETRIEVER 
Channel Tunnel: Chalk Marl
built 645 days ago
There are 5 million cubic metres of soft grey chalk marl making up the hoe, all of which was dug out in the creation of the Channel Tunnel. The feature is approached by a tunnel through the cliffs, and is protected by sea wall and rip rap.
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Beyond the point the tunnel begins to dip downwards, there are a number of chalk falls and the water gets deeper. There is some timber propping on the right hand side. At 180 metres there is a large chalk fall, which can be reached although the water is 3 feet deep at this point. Beyond here the water quickly comes up to roof level and
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Over approximately 50 m of tunnel, the 0.4 m thick tunnel lining was reduced to a mean depth of 0.17 m, with the thinnest area being 0.02 m. The chalk marle showed no signs of failing or collapsing, but colliery arches were subsequently installed to support the ground as a precaution.
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Chalk Marl