Intricate segmental replacement work to create passageway openings on parts of the live tube platforms at London Underground’s (LU) expanding King’s Cross station should be completed this month.
LU has replaced 72 rings across two tube lines, 18 per platform on the Piccadilly Line, working in six 52 hour ‘possessions’, which means non-stopping trains are running slow beside the 6.4m i.d. tunnels. The work has taken three months to execute. Later this year similar ring replacement work will start on sections of the station’s Northern Line platforms.
The cast iron tunnel rings are being replaced with frames as normal but what is unusual is the structural detailing, which has the frames more as segmental arches than lintels, T&TI was told. The design was developed to help counter a number of risk management constraints, including the need for compact pieces to avoid calling for more workspace that would jut into trackbed or the kinematic envelope of trains.
Elsewhere in the station, two passage bores are being advanced, 5m and 6m diameter, respectively. However, the largest excavations will be for escalators with cast iron rings of 8.5m i.d., construction of which will be started in March by joint venture contractor Morgan Est-BEMO. Across all the works being planned, excavated diameters will vary from about 4m to 9.5m with both iron and SCL used in the project (T&TI, June 2006, p7).
The works are planned to be handed over for fit-out by May 2008. However, T&TI understands that the LU project team is under pressure to accelerate the works to have a knock-on benefit for other, later works being scoped for the growing interchange station.
Contractor Balfour Beatty is working on the Northern Ticket Hall box.
