The Connaught Tunnel Project was situated in East London and comprised the construction of approximately 2km of overground railway on the site of an abandoned branch of the former North London Railway Line. Approximately 550m of new railway was located in the existing Connaught Tunnel which was constructed in 1878 to allow diversion of the railway line beneath the ‘Connaught Passage’, the water link connecting the Victoria and Albert Docks. To accommodate the new larger Crossrail trains and the overhead line equipment, the tunnel was to be carefully reconstructed, which involved lowering of the tunnel invert and widening of central twin tunnel sections beneath the dock passage to form a single box tunnel.
The original Connaught Tunnel
From 2011 to 2013, I was a site engineer at Connaught Tunnel, my first piece of work was to write a proposal to Crossrail for the method of tunnel construction. This was to install cofferdams in order to drain the dock passage and allow access to the tunnel from above. The proposal was accepted and the Connaught tunnel was constructed using this method.
The below BBC London News and Crossrail videos will explain more
Crossrail recycles disused Connaught Tunnel
Breathing new life into Connaught Tunnel
Surface rail works
I worked primarily on the surface section of the Connaught Tunnel project and managed surveys to identify potential UXO, unexploded ordnance remaining in the ground from the London Blitz of 1940. The method of testing was a magnetometer cone penetration (MagCone) test. This test uses a standard cone penetration testing (CPT) rig which hydraulically pushes a 32mm diameter magnetometer probe into the ground to a defined refusal criterion pressure. The probe takes readings of the amplitude of the magnetic field of the ground. Buried ferrous items within the detection radius distort the magnetic field and can be clearly identified on the software data graphs within the CPT rig which are then identified as ‘anomalies’ by specialist UXO analysts.
Anomalies are rarely UXO itself, yet I worked closely with the UXO specialist engineers to define procedures for excavating around an anomaly and evacuation procedures if necessary. At Connaught Tunnel, it was important to work closely with key stakeholder London City Airport to demonstrate that I was managing the package of works suitably in close proximity to their assets.
No UXO were discovered along the Connaught Tunnel route, but the package of works was fantastically interesting to be involved with. The works also grabbed the attention of BBC news. Click the links below to find out more.