Completed primary Sprayed Concrete Lining (SCL) works for Tottenham Court Road Station Upgrade Project (TCRSUP), London, UK

Tottenham Court Road Station (TCRS) is a London Underground (LU) station situated in central London. The station serves as an interchange between the Central and Northern Lines.

Over 150,000 passengers use the station daily and with the completion of Crossrail in 2017, passenger numbers are expected to increase to over 200,000.

Improvements to the Tube station will provide: step-free access from street level to all platforms and interchanges via the enlarged and new ticket halls, additional access points to the Northern and Central Line platforms to reduce congestion, additional escalators serving the Northern Line and five new lifts, as well as future connections to the Tottenham Court Road Crossrail Station.

Main construction started in 2010 with completion expected in 2016.

DSP Design Services

Dr. Sauer & Partners Ltd. (DSP) were initially employed as the specialist sub-consultant to Halcrow for producing the Sprayed Concrete Lining (SCL) design for the primary lining of the new tunnel structures. The original design incorporated the use of lattice girders and mesh reinforcement within the primary lining. Design drawings for construction tender were produced up to Stage F of the RIBA (Royal Institute of British Architects) Plan of Work.

Tunnel diameters vary between 4.0m for cross passages and 11.0m for the Northern Line Concourse Tunnel. Multiple transitions and interfaces to existing LU structures make for a challenging design and construction project under the busy streets of central London.

The winning tender for construction was made by the joint venture of Taylor Woodrow and BAM Nuttall.

Halcrow has remained the lead design organisation with DSP as the specialist sub-consultant for the tunnelling works. Since the time that contract was awarded, the contractor has requested three SCL re-design packages which DSP has led:

1. As part of the original tender package two interchange tunnels and two lift shafts were designed with Spheroidal Graphite Iron (SGI) lining. For cost and time savings DSP has re-designed these structures using Fibre Reinforced (FR) primary sprayed concrete lining.

2. This re-design package involved taking the original SCL geometries based upon lattice girders and mesh reinforcement and re-designing them using a FR primary sprayed concrete lining. Additionally, the waterproofing system was re-designed to use spray applied waterproof membrane.

3. This re-design package saw the re-design of two overbridges to the Central Line. The overbridges were originally designed to be excavated and constructed using traditional timbering techniques. The contractor requested DSP to re-design the overbridges with a primary lining of FR sprayed concrete. DSP also produced the waterproofing design.

SCL overbridges have previously been designed in the UK but this is the first time a design has been accepted as fit for construction. It is also the first time an SCL overbridge has been constructed on the LU network.

DSP Construction Services

The powers to construct the LU Tottenham Court Road Station Upgrade Project were provided under the Crossrail Bill. Crossrail’s Information Paper D23 – Sprayed Concrete Lining requests the SCL designer to provide 24/7 cover on site to ensure the construction of the works is in accordance with the design.

DSP provided the requested site support services during the construction phase for two years between November 2010 and November 2012. These services comprised of SCL engineering and inspection.

All primary SCL works designed for TCRSUP have now been completed.

Figure 1: Overview of new tunnel works

Figure 2: Northern Line Concourse Tunnel with cross passages and stub adits for connections to new staircases. All structures designed with FR primary sprayed concrete lining.

Figure 3: General arrangement of SCL Overbridge No. 2 (No. 1 similar).

Figure 4: Excavation and support of the Northern Line Concourse Tunnel: single sidewall drift.

Figure 5: First step after SCL Overbridge No. 2 completion: installation of transfer beam.

Figure 6: Excavation and support of Northern Line Escape Tunnel and removal of existing cast iron passageway.