Drilling rig

Ground conditions and installation

Instrumentation and dewatering setup

• Clients
  • Greycoat and Cross London Rail Links
• Main contractors
  • Skanska UK
• Consultants
  • Ove Arup & Partners
• Key contributors
  • GCG and WA Fairhurst
• WJGL roles
  • Instrumentation and dewatering subcontractor
• Project reference
  • J1063 & J1109

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The redevelopment of the site near Moorgate, London, included the construction of a ventilation shaft 8.5 m in diameter and 50 m deep. WJ was responsible for the design and installation of a dewatering system to allow the shaft to be constructed in stable ground. This consisted of six deepwells to reduce the water levels in the lower Thanet Sand aquifer and 11 ejector wells to relieve pore pressures within the Lambeth Group. To monitor the performance of the dewatering system and the construction of the shaft, WJ installed an array of piezometers with triple response zones to monitor water levels, and inclinometers and extensometers to monitor ground movements during shaft construction. All data was fed directly to WJ’s monitoring web site accessible to the whole site team.

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