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Ground investigations for new Thames tunnel | BUILDING MAGAZINE

Ground investigations for new Thames tunnel

An extensive programme of ground investigations will get under way this week along the route of the proposed Lower Thames Crossing road tunnel in London.

Highways England is commissioning more than 700 individual investigations at sites in Kent, Essex and Thurrock to give engineers a clear picture of the soils, rock and groundwater along the entire 14.5 mile road. The project will include the longest road tunnel in the country as well as bridges, embankments and cuttings.

Tim Jones, project director for the Lower Thames Crossing said: “The complex programme of tests and surveys we’re embarking on here will enable us to better understand the ground conditions, and help us build it safely, in a way that protects us to better understand the ground conditions, and help us build it safely, in a way that protects the environment, while keeping costs down. This preliminary work will help us to give the clearest possible picture of what will be involved in building the new crossing when we apply for planning consent and help ensure our construction programme can get the new road open for 2027”.

Key areas of interest for the project team include: the protected wetland in Kent; under the river itself where the tunnel will be and historical land development in the north. The scheduled tests includes over 400 boreholes – some of which will be up to 100m deep – nine pump tests and about 85 trial pits and geophysical surveys.

The programme will start this month with tests on land, followed by ones on the Thames later this summer. Investigations are likely to carry on until the end of the year.

The most common of the main ground investigations being used will be cable percussion boreholes involving a 7m-tall frame lowering drilling tools up to 60m deep. There will also be rotary core boreholes, cone penetration testing, dynamic sampling, trial pits, surface water sampling, pump tests, laboratory testing and geophysical surveying.