The Lambeth Group in the Crossrail Project of London, UK - the geological model

摘要

Crossrail will provide a high frequency, high capacity train service serving 40 stations and linking Reading and Heathrow in the west of London, to Shen field and Abbey Wood in the east. Over-ground sections of the route will be linked via twin, 21km tunnels up to 40m below central London and involving the excavation of circa 8M m3 of soil. The central London tunnelled section of this project has involved, since 2000, the specification for, drilling and interpretation of 1,043 new ground investigation boreholes. Information from a further 653 boreholes by third parties or historic sources have also been incorporated into the ground model. Approximately 10 km of the tunnel route is within the sediments of the Lambeth Group and more than 10,700 tests have been undertaken on these sediments alone. This paper summarises the Lambeth Group ground model for the project including new interpretations. It highlights geological risks that were identified and quantified beforehand so that mitigation measures could be adequately integrated into the design and construction processes. It also highlights areas where project cost and programme optimisation could be implemented as a result of the detailed ground information available. The paper, therefore, provides invaluable information for other projects within these complex sediments. A sister paper by Menkiti et al. (in preparation) will provide an update of the advanced geotechnical behaviour and properties of the Lambeth Group soils.