Post by ianvisits on Dec 26, 2007 13:02:55 GMT
As part of a history research project into another underground railway in the region of the South Bank I am coming across a lot of info about the Bakerloo Line in that area.
Actually, a bit of a nuisance as it is quite distracting.
Anyhow, one of the documents I came across (Phil. Trans. R. Soc. Lond. A.) was an engineering report into ground strain movements, and how buildings can impact on other structures.
You might think that plonking the massive Shell Towers complex on the South Bank right on top of the Bakerloo Line would push it down into the ground - but in fact, the exact opposite has happened.
According to the report, an area of some 210mx110m was excavated to 12m depth. The Bakerloo Line runs under the new hole and it is only about 1m below the deep piles beneath the basement.
Observations were made to check what effect the removal of all that soil mass from above the railway would have - and indeed, the railway tunnel did start to shift upwards as expected.
However - even after they finished building those two large towers, there is still a net loss of weight above the tunnels (by about 2/3rds), and the Bakerloo Line has continued to shift upwards.
By the time of the completion of the towers, the Bakerloo line had shifted upwards by between 16 and 28 mm in the area - and measurements made in 1970 showed that the center of the southbound tunnel has drifted upwards by over 5cm.
I am not sure what the displacement is today - but I doubt we will wake up one morning to read that the tunnel has suddenly "popped up" over night and burst through the ground ;)
A graph of the displacement is available at www.flickr.com/photos/ianvisits/2138256662/
Actually, a bit of a nuisance as it is quite distracting.
Anyhow, one of the documents I came across (Phil. Trans. R. Soc. Lond. A.) was an engineering report into ground strain movements, and how buildings can impact on other structures.
You might think that plonking the massive Shell Towers complex on the South Bank right on top of the Bakerloo Line would push it down into the ground - but in fact, the exact opposite has happened.
According to the report, an area of some 210mx110m was excavated to 12m depth. The Bakerloo Line runs under the new hole and it is only about 1m below the deep piles beneath the basement.
Observations were made to check what effect the removal of all that soil mass from above the railway would have - and indeed, the railway tunnel did start to shift upwards as expected.
However - even after they finished building those two large towers, there is still a net loss of weight above the tunnels (by about 2/3rds), and the Bakerloo Line has continued to shift upwards.
By the time of the completion of the towers, the Bakerloo line had shifted upwards by between 16 and 28 mm in the area - and measurements made in 1970 showed that the center of the southbound tunnel has drifted upwards by over 5cm.
I am not sure what the displacement is today - but I doubt we will wake up one morning to read that the tunnel has suddenly "popped up" over night and burst through the ground ;)
A graph of the displacement is available at www.flickr.com/photos/ianvisits/2138256662/
