Jubilee Line Extension

At the time, the JLE was the largest extension to the Underground network in decades, and would require the first deep tunnelling undertaken in South East London, previously avoided due to the difficult ground conditions. The tunnel, and its structures such as Stations, Ventilation Shafts, & Cross Passages would have to be built in the water bearing, stratified silts, sands and clays of the Lambeth Group, the very dense silty, Thanet Sands and London’s soft underlying bedrock, the Chalk, which can have water pressure to above ground level.

This was the first example of deep dewatering being undertaken simultaneously across the city of London on a project wide level.

Working for the constructors and tunnelling contractors WJ dewatered 5 stations, 6 ventilation shafts and undertook the first example of in tunnel dewatering for several cross passages. WJ undertook all the design work and in the absence of thorough groundwater pumping tests, we took a carefully considered observational approach, which ensured that the contractors achieved best value and a reliable and predictable drawdown. The data and experience gathered from JLE projects helped to inform decision making for dealing with groundwater for underground construction in London for the next 2 decades.