What we’ve done so far: Tunnelling
The Tunnel Boring Machine (TBM) Lilly Rose has now completed the first of its two drives, and is progressing well, having completed more than 50 per cent of the 54 metre second drive. We have also recently completed the hand drives (hand excavated tunnel sections) towards the upstream and downstream tie in manholes.
Our tunnelling contractors, Active Tunnelling, uses two different methods of tunnelling for our sewer diversion tunnel. The methods are:
- Tunnel Boring Machine (TBM): A TBM excavates the tunnel, and concrete tunnel sections are jacked into place at the back of the TBM. Material is removed using a series of conveyor belts and muck skips that are pulled along on trolleys within the tunnel. In the accompanying photograph, you can see the TBM breaking through into the shaft.
- Hand shield: The hand shield is a effectively a steel tunnel section – miners excavate the ground at the front of the hand shield and the concrete tunnel sections are then pushed forward which in turn pushes forward the hand shield. Muck is excavated by miners using hand tools and placed within skips which are removed from the tunnel on trolleys and lifted to the surface by crane. The miners can dig five metres per day using this method.
- A new sewer is required to replace an existing section of the brick sewer that runs underneath Pinkston Road, to provide for the new sewer we are currently preparing for tunnelling by a Tunnel Boring Machine
- The Sighthill Tunnel Boring Machine (TBM), named Lilly Rose, has been craned down to the bottom of an access shaft to commence her journey on the first of two drives. The first drive of some 120 metres is expected to be completed in five weeks. The tunnelling operation consists of two drives totalling 265 metres at a depth of 21 metres
- The TBM has now commenced the first of its two drives to create the tunnel for the new sewer. The TBM is driven by a miner sat within the machine as it digs its way forward.