Europe’s largest infrastructure project, Crossrail will dramatically change the way people travel around the capital.
For the first time, a direct connection between all of London’s main employment centres will be achieved; reducing journey times, easing congestion and improving connections. With up to 24 trains every hour, each carrying 1,500 passengers, the project covers over 100km of track from reading to Heathrow.
When it came to solving a difficult dewatering problem at the crucial Stepney Green Junction, Crossrail naturally came to WJ Groundwater.
Regarded as one of the most challenging sections of the project, the track divides at Stepney; heading NE to Shenfield via Stratford and SE to Abbey Wood via Canary Wharf. The diaphragm wall shafts boast tunnels up to 17m wide by 15m high of sprayed concrete lining and although the junction predominantly formed towards the base of the London Clay, the invert reaches into the Lambeth Group, which at Stepney includes extensive water bearing sand horizons with an excess pressure <1 bar.
WJ’s design team got to work analysing the geotechnical conditions and provided fully detailed specification plans, giving Crossrail the confidence they needed to commission our proposals. To achieve the required depressurization, our highly skilled on-site team used a combination of surface ejector wells supplemented by in-tunnel wellpoints, several of which were expertly inclined to a steep 30º from vertical to overcome the restricted access and ensure minimal disruption to other infrastructure works. Our innovative surface ejector scheme succeeded in targeting deeper areas of evident overbleed, achieving the majority of drawdown with tunnel wellpoints.
Crossrail already delivers social benefits across the UK with thousands of jobs and business opportunities for companies of all sizes. Once it opens in 2018, it will increase London’s rail-based transport network capacity by more than 10% and dramatically cut journey times across the city. WJ are proud to be a part of this life-changing project and we value the trust Crossrail placed in us to deliver the right solutions to a challenging problem.
- LOCATION: Stepney Green, London
- CLIENT: Crossrail
- MAIN CONTRACTOR: DSJV (Dragados Sisk JV)