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Silbury Hill

Silbury's structural integrity

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whipangel W
whipangel Aug 1, 2007 19:16:26
Replying to nigelswift

nigelswift wrote:
...In the first half of the tunnel the voiding is said to be no more than 0.5 metres above Atkinson’s steel support arches...
I thought 0.5m was the 'overbreak', the waterlogged crumbly material which 0.5m above would become solid roof again. Not that they should go breaking it off!

http://www.english-heritage.org.uk/upload/pdf/Silbury_Hill_web_update_11.pdf

nigelswift wrote:
...One thing that makes me think “big” might mean “very big” is that I’ve heard, rightly or wrongly, that the Atkinson rings far in (of which no account or photographs have been provided) are badly distorted. To me, that suggests massive forces. Confirmation that I have been misinformed would be very helpful...
I can confirm from my own phone call to EH that mention was made of the Atkinson supports being distorted under the pressures - they were going to have to add their own safety measures as they could no longer rely on these to protect those working on the project.


http://www.themodernantiquarian.com/forum/?thread=41033&message=530317

N nigelswift
nigelswift Aug 1, 2007 20:27:24
Replying to whipangel

"I thought 0.5m was the 'overbreak', the waterlogged crumbly material which 0.5m above would become solid roof again."

You may be right but the wording isn't clear. I took it to me that the overbreak STARTED 0.5 metres above the rings, not that the overbreak was 0.5 metres thick. The latter interpretation seems consistent with the photograph, where there seems tobe a gap of about that size as well as rubble below.

In any case, the information that the overbreak terminates at the point there is clean rock is itself confusing since many feet above that we know there is surface settlement. So whilst there may be material above the overbreak that hasn't suffered "in situ" deterioration, it doesn't seem to be the case that it's still in the same situ... Tricky. To work it all out I mean.