A Costain-Skanska joint venture (JV) has completed construction work on Royal Oak portal in west London and handed it over to Crossrail, UK's major rail infrastructure project.
The portal near Paddington will be the transition ramp for trains entering and exiting the central London tunnel.
Trains will traverse along a gradual gradient for several hundred yards prior to entering the tunnel.
The Costain-Skanska JV excavated a total of 25,000m3 of ground to construct the portal, and constructed a concrete headwall with a pair of 7.24m-diameter tunnel 'eyes' at the deepest end of the ramp.
The Royal Oak tunnel portal will act as an entry point for the tunnel boring machines that will start constructing the Crossrail tunnels next year.
The tunnel portal is the first of five to be completed on the Crossrail route, which is a new 118km high-frequency rail route that will run from Maidenhead and Heathrow in the west to Stepney Green, for Shenfield near Brentwood and Abbey Wood, in south-east London.
The contract for the Royal Oak portal was awarded to Costain-Skanska in 2010 as part of an advanced works civils framework contract totalling £100m.