Extending London's Docklands Light Railway to Woolwich

The £180 million, 2·5 km extension of London's Docklands Light Railway to Woolwich Arsenal has provided the capital with another much-needed cross-river transport link. Completed in January 2009, the project included the construction of twin 5·3 m diameter running tunnels through chalk containing highly abrasive flints under the Thames using an earth-pressure-balance tunnel-boring machine. It also included cut-and-cover approaches, an underground station and an emergency shaft on the river bank. Major challenges included tunnelling under sensitive infrastructure and the Thames, and working adjacent to an existing operational railway at Woolwich Arsenal. This paper describes the design and construction of the project and how the challenges were overcome.