Silecroft FTS, Millom, Cumbria
Donegan Civil Engineering recently carried out this specialist tunnelling sub-contract for Daniel Contractors on a United Utilities scheme.
The scope of works included sinking by caisson a 5.50m internal diameter segmental drive shaft, as can be seen here, approx 8m deep through clays, sands and gravels with tidal water pressure.
Sinking by caisson a 4.00m internal diameter reception shaft, approx 5m deep in similar conditions to the drive shaft.
Carry out a 1000mm micro-tunnel drive approx 100m in length with a Herrenknecht TBM, which would act as a sleeve pipe through which a smaller gravity main could be installed.
As per Network Rails requirements the shafts were constructed outside the ‘zone of influence’ and during the pipejacking works operatives double shifted through the night until the TBM was recovered from the reception shaft.
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