A mammoth jet grouting project has been completed at Victoria’s London Underground (LU) station.
Principal contractor Taylor Woodrow BAM Nuttall (TWBN), designer Mott MacDonald, and specialist contractor Keller installed 2,000 interlocking jet columns to enable safe tunnelling in the challenging ground conditions of water-bearing find sands overlaying London clay.
The construction programme was completed in 24 phases over a 34-month period while maintaining pedestrian and vehicle access through the area.
Building Information Modelling (BIM) was used to plan the positions of the jet columns around existing services.
Existing infrastructure, including sewers, water mains and London Underground tunnels dictated that the tunnels were constructed at shallow depths, with an axis approximately 10m below ground surface and clearances of less than 100mm from essential LU assets in places.
Glenn Keelan, LU’s Victoria Station Upgrade programme manager, said: “We have never used the prescribed techniques in combination on the London Underground estate before.
“The delivery required continuous refinement and improvement, including the ‘leap of faith’ needed to apply BIM to ground treatment techniques.”
Steve Worthington, Keller’s project director, added: “The sequencing of work required careful planning and was driven by a risk review of each individual column. We reviewed criteria such as soil types, column inclination and proximity to sensitive structures to successfully install the network of columns to tunnel through.”
Jet grouting is a construction process which improves the quality of the ground by using a kinetic energy jet. The jet mixes the in-situ soil with a cementitious material to create a homogenous ‘soilcrete’ column which reduces permeability and strengthens the ground.