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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.
Keywords
railway systems; tunnels & tunnelling
Woolwich Arsenal is an urban area in south-east London, UK. From 1671 it was home to the Royal Arsenal's weapons and ammunition factories. These finally closed in 1994, since when the area has been subject to extensive urban regeneration. The objective of the Docklands Light Railway (DLR) extension was to improve public transport connections between Woolwich Arsenal and the financial and commercial centres of London and hence support regeneration (Figure 1). The project also provides an important transport link across the River Thames, an historical barrier to local movement.
Powers to construct the project were obtained through an application to the UK Parliament under the Transport and Works Act 1992, supported by an environmental impact assessment. The resulting Docklands Light Railway (Woolwich Arsenal Extension) Order (HMG, 2004) was granted in March 2004, providing the necessary powers and including the ability to acquire land and construct the works within the limits of deviation. Outline planning permission was also granted with the order, but design details still needed to be submitted to the local authorities for approval and the powers were subject to a number of conditions relating to environmental protection. The order provided protection to third parties which may be affected by the works, particularly the obligation to protect third parties from tunnelling-induced ground movements, noise and vibration, and electromagnetic interference.
The project was delivered under a private finance initiative. Docklands Light Railway Ltd (DLRL) is the client and transport operator and let a 30-year design, build, finance and maintain concession to Woolwich Arsenal Rail Enterprises Ltd (Ware, now a Semperian?Royal Bank...