Barhale tunnel shield overcomes pipe-jack issues

Built 30m deep into the London Clay, the 2.5m-diameter pipe connects the newly constructed CSO drop shaft located at Barn Elms Sports Centre with the main Tideway Tunnel and will be finished with a 2.2m internal-diameter secondary lining.

The project required an innovative solution as difficult conditions were encountered in the early stages of the pipe jack. These resulted in damage to some of the reinforced concrete jacking pipes as they were pushed in behind an open backhoe-type tunnel excavator machine (TEM).

Frank Green, Barhale Tunnelling Operations Manager said: “With the support of the project team, we developed an innovative solution to help us quickly identify and replace any cracked pipes. It saw us design a bespoke recovery shield which we were able to manufacture in-house through our fabrication arm BCS.”

He added: “The recovery shield not only enabled the damaged tunnel [sections] to be replaced but also provided access to the TEM face to enable repairs and enhancements to be conducted. Additionally, the purpose-made TEM was designed to allow complete dismantling at the end of the blind tunnel drive to allow the final connection to the main tunnel to be completed.”

The work was carried out as part of the programme to build the West Putney Storm Relief Combined Sewer Overflow at Barn Elms in Richmond, West London.

Barhale was awarded the main civils package by the BAM Nuttall Morgan Sindall Balfour Beatty (BMB) joint venture which is delivering the 7km west section of the 25km Tideway Tunnel.