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Silbury's structural integrity
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Pilgrim
Pilgrim
597 posts

Edited Aug 23, 2007, 06:47
Re: Silbury's structural integrity
Aug 23, 2007, 06:45
Pilgrim wrote:

Update 14 is here:

http://www.english-heritage.org.uk/upload/pdf/Silbury_Hill_web_update_14.pdf



I’m a bit concerned about Figure 2. There is an awful lot of ironmongery in that shot. Corrugated iron, Atkinson's supports etc. Comparing it with other tunnel shots like those in Update 10 and 9 seems to indicate that its taken in the narrow part of the tunnel. If that is Atkinson's ‘59’ on the leaning support, then this isn't far off from where the roadstone fill ended (‘57’). Above the ‘59’ the small numerals on the yellow patch on the ring are identical in style to one being marked by an archaeologist in Update 9. The caption in Update 14 says:

Figure 2 shows the old Atkinson tunnel arches where they have moved and settled as a direct result of the mass of loose chalk pushing these arches. These are being removed progressively and securely.

Given that this leaning arch bears a small yellow panel and a number which is identical to others used in this conservation project, I would surmise that the arch was marked some time in the last few weeks and has moved since. The caption in the Update is ambiguous; it gives no indication of the timing of the movement of the loose mass of chalk which surrounds the leaning arch. I can only perceive that this is a recent event, and I’m concerned that for this arch to be displaced in this manner (and by this much) would need a distinct lateral force. I would therefore question the statement in Update 14:

Otherwise, the geotechnical conditions within the hill remain unchanged, with the
3 separate voids all remaining stable and the remainder of the tunnel standing
without any observed movements or structural changes.

I think that the last two arches beyond the fluorescent are different in curvature to the ones directly above it, and they may well be the beginning of the widened section before the central chamber. I think the two pieces of wood on the spoil are noggins; similar noggins can be seen between the rings in the first photograph in Update 10. They are being presumably used to maintain the relationship between the ring supports. Again, I presume that these noggins were moved by the lateral force of the loose chalk? I'd like to know this:

From where exactly did this loose chalk originate?

When was this damage caused?

And

How Much of this 'loose chalk' is there?


Peace

Pilgrim

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