The Victoria Station Upgrade (VSU) project in central London provides perhaps the best example to date of how BIM can be used in ground engineering.
This £700m scheme (above) is delivered by a BAM Nuttall-Taylor Woodrow (BNTW) joint venture and includes a new and an enlarged ticket hall, plus 400m of connecting tunnels between the two, 7m below ground level.
It is a complex project on a congested site, crisscrossed by pipelines, sewers, and power and communications cables, with tube tunnels and the culverted River Tyburn close by.
London Underground pushed for the use of BIM as far back as 2006 when planning the project, believing it would be near impossible without a 3D record of existing and third-party assets. This drew on “as built” records, plus data from laser surveys.
Additionally, BNTW excavated and removed all services in the ground, surveyed their condition, and put them back – adding data about the services to the model. Information from trial drill holes was also added.
“This got around the problem of a lack of visibility underground,” explains Taylor Woodrow project manager Craig Prangley. “We were having to work under Tube tunnels and the Victoria Palace Theatre, and the BIM model allowed us to drill with confidence.”
BIM was also used to coordinate the design of 2,500 jet grout columns, injected to stabilise the water-bearing river terrace gravels on the site and create an impermeable barrier to the new station box. These are raked in numerous directions, because of the complexity of the existing infrastructure. The position and orientation of every drill string is uniquely identified in the BIM model.
“As the job progressed, all the as-built data on the grout columns was fed back into the model, and this helped us understand where the gaps were between the columns when we started the tunnel,” says Prangley.
“The result is that the tunnel construction productivity has doubled – compared with similar tunnel jobs at Tottenham Court Road and King’s Cross stations, where we would typically proceed at a metre a day; here we have achieved two metres,” he says.
The model has also helped with clash detection among structural, architectural and building services packages, and saved time on the structural design recalculations; when changes were made to the position of openings in structural slabs, the model calculated new load paths and regenerated the reinforcement design with minimal rework.
The project has even been extended to 5D and 6D BIM. Quantities of materials have been calculated, giving visibility to the cost impacts of design changes. Post-completion, the model will provide London Underground with an accurate record of assets, to manage the station throughout its life.
