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Post by zbang on Apr 17, 2022 17:09:03 GMT
As a digression from the "Bank Branch closure" thread-
There was a reference in the project chart to "back-fill tunnels" etc, which I assume is that those tunnels will have no possible further use and will abandoned and then filled to both prevent re-use and to support the earth above. I also assume they're stripped of pretty much everything usable, even for scrap.
How are they filled? Dirt or hoggin fill will settle, leaving an airspace at the top. Foamed concrete would cost a bit. Gravel would cost even more.
Depending on location, they could also fill with water. Is that a consideration?
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rincew1nd
Administrator
Junior Under-wizzard of quiz
Posts: 10,225 
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Post by rincew1nd on Apr 17, 2022 17:22:17 GMT
Other tunnels have had been plugged at each end, with the insides simply left.
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Post by 100andthirty on Apr 17, 2022 18:25:11 GMT
Many of of the LT Museum's Hidden London Hangouts on YouTube have visited disused tunnels. The Angel episode is an example.
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Post by jimbo on Apr 17, 2022 20:04:03 GMT
The plan was to fill the tunnel only at the points of diversion at both ends with foamed concrete, and then to cut the new tunnel route through that. I don't know if this was to reduce earth movement due to the number of listed buildings above the sites. see here Other diversions have constructed step-plate junctions around the existing tunnel, before dismantling that tunnel. This has enabled diversions to be commissioned with little more that a weekend closure, eg Kennington recently. And maybe the old and new route can be connected at the same time if there is not a big height change. But a step-plate junction requires a lot of ground to be excavated, leaving a large cavern remaining. Probably this was too risky beneath the City of London. |
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Post by zbang on Apr 19, 2022 16:32:08 GMT
It certainly makes some sense to basically wall off the disused tunnels, but if they're still hollow they need inspection and probably water pumping (hence access by the Urban Trespassers' Society). I ask because of the earlier reference to "backfilling" and whether old tunnels are ever completely filled or just partially; the link above suggests a complete fill.
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Post by quex on Apr 19, 2022 16:57:37 GMT
Off the top of my head, I can only think of a couple of cases where disused tube running tunnels have been backfilled. These are the original Bakerloo overrun/siding tunnels under the New Kent Road at Elephant & Castle, and parts of the Embankment loop where the new alignment intersected the old. In both cases I think the backfill was a mix of gravel/rubble, weak concrete, and brick.
Parts of the abandoned works for the Oval deep-level shelter were infilled with gravel too - but then the works were abandoned because the gravel soil was difficult to tunnel in.
So far as I know, disused running tunnels at Euston, Angel and London Bridge were never backfilled except perhaps parts near the junctions. Even the King William St tunnels are more or less still walkable.
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Post by jimbo on Apr 19, 2022 21:07:36 GMT
I seem to recall that the Embankment loop was filled at the intersections with the new alignment, as you say, but the majority of the loop was left. During WWII the under-river loop was breached by a bomb and flooded, the only under-Thames tunnel to suffer in that way fortunately! As far as I know, it remains in that state.
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Post by Chris L on Apr 20, 2022 20:53:01 GMT
I seem to recall that the Embankment loop was filled at the intersections with the new alignment, as you say, but the majority of the loop was left. During WWII the under-river loop was breached by a bomb and flooded, the only under-Thames tunnel to suffer in that way fortunately! As far as I know, it remains in that state. The Greenwich Foot Tunnel was also breached by a bomb. |
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Post by Hutch on Apr 21, 2022 13:29:12 GMT
The Greenwich Foot Tunnel was also breached by a bomb. One can see where by the severely reduced diameter of the tunnel some third of the way in. |
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Post by spsmiler on Apr 22, 2022 10:43:28 GMT
I seem to recall that the Embankment loop was filled at the intersections with the new alignment, as you say, but the majority of the loop was left. During WWII the under-river loop was breached by a bomb and flooded, the only under-Thames tunnel to suffer in that way fortunately! As far as I know, it remains in that state. I thought that something was done after the war to help ensure that this flooded tunnel did not become a cause for a future severe flooding event |
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Post by miff on Apr 22, 2022 12:40:53 GMT
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