Figure 1 : The TBM breakthrough precisely to the design!

The challenge in the Tunnelling Industry is how the TBM can mine underground exactly as per the design so that it can breakthrough at the right location at the end of the journey. This can be understood with the principle of 3D coordinate Geometry.

There are many tunnelling projects in the UK depending on the requirements of the country such as traffic, sewerage diversion, power cable diversion, fertiliser mining…etc.

Please see the following examples for the Uk’s ongoing and upcoming tunnelling projects:

  •  Crossrail 2 – Rail tunnel to minimise the traffic
    • This Rail Tunnel recently opened as ‘Queen Elizabeth II’ Line
  • Thames Tideway – sewerage diversion tunnel
    • This will help to avoid diverting London’s sewerage to the Thames River, instead the sewage will be taken to the Sewage Treatment Plant in Beckton. The Thames River will be purified in the future.
  •  HS2 (High speed 2) – Railway tunnel runs from London to the North part of the UK via Birmingham; this project includes tunnelling in London.
  •  London power Tunnels 2 – LPT2 (high voltage power cable diversion)
  • This involves diverting all the surface high voltage cable to the underground, especially from South-West London (Wimbledon) to South-East London (Hurst and Crayford).
  • Potash mine Tunnel-  Collect Minerals (North UK) 1500 m below ground
  • This project mainly involves mining and transporting minerals from below ground.
  • Hinkley Point C, Sea Tunnel– Nuclear Power Energy Generation Project – Electricity for 500,000 houses
  • Silvertown Tunnel – This is a road tunnel running underneath the Thames River near Blackwall Tunnel.
  •  Stonehenge Tunnel – Road Traffic Diversion (Upcoming)
  •  Lower Thames Crossing– This helps minimise Dartford bridge Traffic(Upcoming)

Hence, it can be understood that the Tunnelling Industry plays a vital role in construction Industry.

Tunnelling Design Alignment concept includes vertical and Horizontal Alignment to follow straight lines, curves (e.g 250 m, 400 m radius and left or right curves) and transition(left or right) :

Vertical Alignment details with the gradient (pitch)

Horizontal Alignment details Coordinates X (Eastings) and Y(Northings)

The engineers in Tunnelling track the location of the TBM with the help of GPS monitoring (Global Positioning System) and the EDM (electronic distance measurement) inside the TBM.

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Figure 2 : Tunnelling Boring Machine(TBM) Navigation throughout Tunnelling

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Figure 3 : Plan View of  a Tunnel Horizontal Alignment

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Figure 4 : Longitudinal Section of a Tunnel

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Figure 5 : Ground Formation below London

There can be London Geology starting from the surface; London  Clay, Lambeth Group(Sandy-Clay), Thanet Sand and Chalk.

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Figure 6  : Precast concrete segments complete a ring

During Tunnelling, the vertical and horizontal directions can be changed using the different ring selection, which is the precast segmental ring , different ring types can be used for different driving directions - for example, it can be twelve ring types to define the geometry of TBM direction. One ring may be made up of 6,8 or more precast segments

Figure 7 : Navigation Window to the TBM operator

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Currently, Heavy Civil Engineering Tunnels with different diameters varies from  3m up to 14m running in the UK for many kilometres starting 1km to 35 km, ending up breaking though accurately at the design location using the Navigation technology. It is remarkably interesting to see that track and monitoring of the TBM location using 3D Geometry.