Engineers from contractor MVB, a joint venture partnership between Morgan Sindall, Vinci and Bachy Soletanche, spent 29 days continuously pouring concrete into the slip form shutter of the shaft on behalf of client, Thames Water.
Three cranes were used to deliver the concrete to three skips to pour into the 80m deep shaft demanding a total of 11,000m3 of concrete to the scheme. The concrete was batched on-site and placed at a rate of 100-150mm (shutter rise) per hour.
A bespoke C50/60 concrete was designed using a number of admixture blends to control setting times including Isoflex superplasticiser MR 800D retarder. The concrete also contained 500 tonnes of steel fibres as reinforcement.
“This was a tremendous achievement with nine concrete mixes of different levels of retardation supplied on a regular and continuous basis to form an integral part of this vital structure. The materials have been developed using the latest technology and challenge our expertise, to ensure that we can meet the structural requirements of the tunnel. Such developments are key to helping to build a greater Britain,” said Chris Leese, Cemex vice president, readymix and mortars.
The Lee Tunnel is first of two tunnels that will capture an average of 39 million tonnes of London’s sewage and by itself prevent more than 16 million tonnes of sewage mixed with rainwater overflowing into the River Lee each year.