FP MCCANN PRECAST CONCRETE SEGMENTAL SHAFTS INSTALLED ON HS2 TUNNELS
Project: HS2 Mandeville Rd Ventilation/Intervention Shaft
Client: HS2
Main Contractor: Skanska Costain STRABAG Joint Venture (SCS JV)
Shaft Sinking Contractor: Joseph Gallagher
FP McCann Product Supplied: 20m Diameter Precast Concrete Segmental Shaft
Three FP McCann precast concrete segmental shafts have been sunk on a key section of HS2 in northwest London. The Mandeville Rd, Greenpark Way and Victoria Rd Ancillary ventilation and intervention shafts will play a major role in the Northolt Tunnels section of the high-speed rail link
At 3km intervals, the shafts help to regulate air quality and temperature within the two tunnels, as well as providing dedicated and continuously available points of entry for emergency services. The Northolt Tunnels consist of four such ventilation/ intervention shafts, design of which has been determined by location and topography.
The 20m diameter Mandeville Rd shaft is the last of the three precast concrete segmental shafts supplied
by FP McCann to the Skanska Costain STRABAG Joint Venture (SCS JV) constructing the London tunnels section of HS2, with shaft sinking specialist Joseph Gallagher undertaking the work as sub-contract partner to the SCS JV
The shaft is positioned on a steep embankment for the London Underground Central Line formerly the site of the old Affinity Water pumping station. A number of shaft sinking options were considered at design stage however, the smaller footprint required over other methods determined the final specification of the precast concrete segmental shaft. The Mandeville Rd shaft consists of 12 rings 20m in diameter and has been sunk by the Joseph Gallagher team using the underpinning method of construction. This is an extremely efficient and structurally sound process.
The precast concrete segments were delivered on a just-in-time basis thereby limiting traffic disruption in the surrounding residential area. Environmental benefits are further achieved through the reduction in excavated material associated with this type of shaft build. In turn, this helps to lower the carbon footprint.
On completion in 2024, the Mandeville Rd vent shaft will feature an above ground integrated headhouse; a building containing fire control and
ventilation systems for the tunnels below.
Commenting on the precast concrete shaft sinking at Mandeville Rd, Sam Lucas Project Manager for Joseph Gallagher says, “The use of this process to sink the ventilation/ intervention shaft is a tried and tested method. Construction is simple and allows for ease of ground excavation. The smaller footprint over other options helps to reduce the volume of material to be removed thereby minimising the environmental impact. From the installation of the first ring, the precast concrete shaft sinking continued uninterrupted throughout”.
FP McCann’s smoothbore shaft segments are all factory fitted with EPDM rubber gaskets which provide an immediate water-tight seal upon construction. Cross segment connections are made by passing a spear bolt through a pocket in one segment and screwing it into a threaded plastic socket in the adjacent segment. Circle joint connections are made using a ‘T’ bolt passing through a hole in one segment into a ‘T’ box in the adjacent segment. Bolts are designed to fully compress the gasket.
For further information on FP McCann’s Smoothbore Shaft Linings, contact the sales team Sales@fpmccann.co.uk:
