Boring is scheduled to begin at the beginning of this month on the $72M, 4.1km long Braintree to Weymouth Relief Facilities Project Tunnel in Massachusetts, US. The TBM cutterhead was lowered down the starter shaft in mid-March, with the rest of the machine assembled over the following two weeks.
Tunnelling was due to start in late summer of 2000 but delays occurred when contractor, Modern Continental experienced problems with water and rock type during construction of the North Weymouth shaft. Modern Continental overcame these problems with a system of ribs, lagging and shotcrete for support during sinking.
Now, with the shaft complete, the 4m diameter Wirth TBM, called ‘Laura’, can start excavating the 3.6km long sub-sea bored tunnel drive from King’s Cove shaft to the Nut Island reception shaft through hard argillates at depths of up to 79m. The TBM is equipped to undertake grouting ahead of the face and horizontal core drillings as necessary. The tunnel drives through anticipated sections of faulted rock and, to allow for this, ribs and lagging will be installed to support the unstable areas when encountered. Also included in the contract is a 668m long, 3m x 3m drill and blast drive from King’s Cove shaft. This section has already begun and the contractor reports progress of 80m as T&TI went to press.
Tunnel boring is scheduled to be completed by March 2002.
Related Files
Braintree to Weymouth tunnel
