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evolutionsummer2013

INfrasTrucTure Paul Ebbutt, Principal Client Engineer - Civils & Stations, London Underground discusses the challenge of maintaining a 150 year construction adventure. The London Undergro ndU A 150 yeAr consTrUcTion AdvenTUre Introduction The Victorian era – the subsurface act in tension with imposed loads. There The first section of the current London railway, 1860s to 1880s have been several cast iron failures over Underground (LU) network was opened Victorian engineers made extensive use of the years across the LU network and LU to customers 150 years ago when steam brick and masonry structures, which have has a special inspection regime to monitor trains ran over what is now part of proved to be remarkably durable. The cast iron elements. LU also has an ongoing the Circle Line between Paddington original route of the Metropolitan Railway policy of strengthening or replacing all and Farringdon. The LU network then opened in 1863 and was constructed such members. All major highway loaded expanded over the following decades below ground level. It consisted of many structures had been strengthened or making use of the various technical brick retained cuttings and brick tunnels replaced by the 1970s and since then LU advances in materials, plant and constructed mainly by the ‘cut-and-cover’ has had a policy to strengthen or replace construction methods available to the method with large brick underground other spanning structures as opportunities designers and constructors. This has stations at Baker Street, Great Portland and funds permit. LU has been a great left the LU operators and engineers of Street and Gower St (Euston Square). promoter in the use of carbon fire plates today numerous challenges in maintaining There is impressive early use of wrought bonded to the soffits of cast iron members reliable services and ensuring an ongoing iron at the Praed Street junction covered and over the last 15 years it has been comfortable environment for the way (Paddington). applying this technique. customers while ‘balancing the books’. The Circle line was finally completed in The Metropolitan District Railway opened History of construction a section of subsurface railway from South 1884 with the last section being between The construction of the LU network took Kensington to Westminster in 1868. Mansion House and Tower Hill, and there place in several phases with each period The construction of later sections of the is a noticeable advance of materials with providing new techniques and materials that subsurface railway is markedly different much use of riveted steel structures. The have left their challenges and legacies. The from the original 1863 construction in subsurface railway eventually converted to construction phases can be summarised as so much as there was significant use of electric traction in stages from 1905. follows: cast iron. This trend was replicated on Over the last 10 years LU has had a Victorian – subsurface railways 1860s other extensions of the Metropolitan programme of replacement of drains 1870s and 1880s – Metropolitan, Circle and Metropolitan District plus the East and track in the subsurface tunnels and and District lines London Line. The poor qualities of cast covered ways that has been a significant 1890s – early ‘tube’ railways – City & iron in tension soon demonstrated challenge with the potential for disturbing South London and Waterloo & City the material to be unsuitable for track the ‘equilibrium’ of the long established supporting dynamically loaded structures early 20th century ‘tube’ railways – the formation and structures constructed in and there is now only one track supporting core of the Central, Bakerloo, Piccadilly the Victorian era. LU is investigating options structure that contains cast iron elements and Northern lines for alternative modern track forms for on the network. There are many cast 1920s and 1930s expansion – the iron elements remaining that span over the subsurface railway that provides the Underground Group and the the railway in particular in cut-and-cover benefits of durability, low maintenance, Metropolitan Railway subsurface covered ways, which were improved customer comfort and control of noise and vibrations. 1960s/1970s – Victoria line/Jubilee line/ constructed as a cheaper alternative to Piccadilly line to Heathrow the more traditional brick arch covered Management of water ingress has always 1990s Jubilee line extension. way. These covered ways contain cast been a problem on the subsurface railway iron beams spanning between masonry along with the effects of vegetation on walls with brick jack arches between these the walls and structures in the open beams, and these spanning elements often 2


evolutionsummer2013
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