• Question: I know that London's soil is clay, so how can they build skyscrapers on clay?

    Asked by bettaparty2424 to Graham, Luke, Maksim, Ruth on 18 Jun 2014.
    • Photo: Luke Fry

      Luke Fry answered on 18 Jun 2014:

      I am by no means an architect, ground works engineer or civil engineer but I do know that whenever you are building any kind of substantial structure you first dig a BIG hole in the ground or drill a series of really deep pilings and fill it/them with reinforced concrete to form the foundations of that structure. The structure is anchored to this and shouldn’t be going anywhere… imagine it in the same way that the roots of your teeth anchor them in place!

    • Photo: Graham Wiggins

      Graham Wiggins answered on 18 Jun 2014:

      bettaparty2424 – Hi, that’s an interesting question.
      They use piles.
      they drill really deep holes in the ground, insert a steel “basket like cage” to provide the reinforcement, the fill with concrete.
      Lots of those, and you have a solid base to build from, so they usually link the top of all the piles with a “ring beam”.
      If you were not going high, eg single storey, you could use a concrete raft foundation, where the building “floats” on a single “pad” of reinforced concrete.

    • Photo: anon

      anon answered on 19 Jun 2014:

      When building on top of a material like clay first thing you would need is a connection to bed rock (which is the rock surface under ground) this loads that the load from the building is going directly down there and little on the material which is above. In an area like london this will vary but it could be 30m deep. Piles are generally driven into the ground in situ; other deep foundations are typically put in place using excavation and drilling. Deep foundations can be made out of timber, steel, reinforced concrete and pre-stressed concrete.

      thanks

      claire

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