LPT2: use of TBMs

LPT2: use of TBMs

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Use of a TBM, or tunnel boring machine, is essential to the success of such large-scale, 21st century tunnelling projects. Interestingly, they are a relatively new technology and hand-mining techniques were still in use for tunnel excavations in the UK in the last 50 years.

The machine consists of gantries, or functional sections (which can include electrical gantries, motor gantries and more), and can total 200m in length. This results in one major problem: how can the machine be used before enough tunnel length has been bored for it to even fit in?

  • The solution is that only one gantry needs to begin in the shaft. The rest remain on the surface, but are connected to the first via a series of ‘umbilical cords’ running down the shaft wall. As drilling progresses, more gantries can be inserted into the tunnel using a crane lift.
^ the structure of the TBM and the two shafts at New Cross can be seen in my sketch here. At this level of progression, only the western TBM has been inserted, with much of it still sitting above ground

The final length of the TBM is about 400m. Once the western TBM is fully inserted, the eastern one will begin a similar process. We are drilling in both directions because this site is the midpoint of the project.

The TBMs are given names; a bit like ships, they tend to be female. Ours above has been named Edith!

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