The first two tunnel boring machines (TBMs) to be used on the Tideway project in London have been lowered in to the shaft at Kirtling Street.
The two 800t 25m long TBM heads, Ursula and Millicent, were lifted into the shaft last week in a staged operation.
Self-propelled modular transporters (SPMT) lifted the TBMs together with their 200t supporting chassis and transported them one by one to the shaft location.
There, they were transferred to strand jacks and lowered 55m down to the bottom of the 30m diameter shaft. In total six TBMs will be used on the project.
The TBMs were lowered down in increments of around 400mm to 500mm at a time.
At the base of the shaft, the TBMs landed on SPMTs which were lifted down the shaft in a previous operation. These will allow the TBMs to be swivelled around and moved to the start of the tunnels.
“Shove” frames already cast into the sprayed concrete lining of the shaft, will provide the initial thrust block to allow the TBMs to push off and start boring into the ground.
Tunnelling is due to start by the end of the year.