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

Crossrail is one of the most significant infrastructure projects ever undertaken in the UK. With a £14.8bn funding envelope, Crossrail will provide a high frequency, high capacity train service serving 40 stations and linking Reading and Heathrow in the west of London, to Shenfield and Abbey Wood in the east. These above ground sections of the route will be linked via twin, 21km tunnels up to 40m deep under central London. This requires the excavation of circa 8M m3 of soil, which is being recycled to create a new bird sanctuary on the coast of Essex. The central London tunneled 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 (Figure 1) is within the sediments of the Lambeth Group and more than 10,700 tests have been undertaken specifically on these sediments alone – more than any previous project. Six Earth Pressure Balance Tunnel Boring Machines (EPBMs) are being used for the main tunnel sections, while two slurry TBMs are being used for the most easterly tunnel sections which are primarily in Chalk.