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Model Behaviour

Building Information Modelling is being used to manage the design and construction risks involved in enlarging and modernising one of London Underground’s busiest stations. GE reports.

London Underground’s (LUL’s) £700M Victoria Station Upgrade is a congestion busting project.

The station currently handles 80M passengers per year and capacity will be increased by more than 50% when the project is complete.

Victoria underground station serves the Victoria, District and Circle lines with two ticket halls.

The upgrade will double the size of the existing Victoria line ticket hall - known as the South ticket hall.

A new entrance and third ticket hall will be created on the north of Victoria Street, linked to the platform tunnels, the South ticket hall and the District & Circle line ticket hall by new passenger tunnels.

Seven new lifts will provide step-free access from street to platform levels.

Emergency evacuation and access for the emergency services are also being improved.

Station boxes will be 15m deep. In short, it’s a complex project.

“We’re enlarging predominantly Victorian infrastructure, working in a very restricted area alongside a live railway and with passengers continuing to use the station,” says LUL CAD manager Paul Clark-Edwards.

“Our priorities are first the safety of our customers and second the smooth running of the railway.” But, surrounded by businesses and government offices, and with myriad buried services to contend with, LUL also has complex stakeholder relationships to manage.

“The model was an LUL engineering requirement”

To manage risk, LUL is using building information modelling (BIM) on a scale that is unprecedented in the UK.

BIM is a process that incorporates 3D design, simulation and analysis, quantity surveying, cost and carbon modelling, scheduling and a host of other tools, and provides a platform for collaboration and co-ordination, right across the project team, from project inception to completion, operation and maintenance.

“We initiated this approach because, without a spatially accurate, fully co-ordinated 3D model, it would be near impossible to visualise and co-ordinate this project,” Clark-Edwards explains. “The model was an LUL engineering requirement.”

“Conventionally you’d model the tricky areas of a project to check your design works. Here all areas and disciplines have been modelled. We have a fully integrated design and you can see how the entire project fits together,” adds Deryck Povey, LUL principal project engineer.

Secant piles forming the walls of the new North ticket hall will be within 3m of the culvert carrying the River Tyburn.

The passenger tunnel linking the new ticket hall to the Victoria line ducks under the culvert and scrapes over the southbound Victoria line platform tunnel with only millimetres to spare.

An escalator squeezes between the twin bores of the north and southbound platform tunnels, with just 300mm clearance.

“BIM is being used to resolve an incredibly complex spatial puzzle so that the new and old come together seamlessly - so everything fits first time,” says Mott MacDonald project manager Rob Dickson.

South_Tickethall

To minimise the chance of new infrastructure clashing with old, Mott MacDonald created a 3D record of existing LUL and third party assets.

This drew on accurate “as built” records, “but we had to create a substantial amount of information by doing laser surveys”, says Dickson. “It was labour intensive but provided an amazingly clear picture of the underground environment we are working in.”

This 3D record formed the basis for a central BIM model incorporating 18 different engineering disciplines.

The model has been used to plan and log the relocation of services and co-ordinate station upgrade works.

“It enables the contractor to dig with minimised risk of encountering unidentified structures,” says Dickson.

Time and cost savings are being delivered by using the integrated BIM model to check for structural, architectural and building services clashes within the station.

On design of the ticket halls, automation within the model has yielded time savings on structural recalculations required following architectural changes.

“We are building intelligence into our modelled objects. So, for example, when we have to move openings in structural slabs that already have the reinforcement laid out, the model will calculate the new load paths and regenerate itself around the new opening with minimal rework,” explains Clark-Edwards.

Materials quantities are automatically calculated by the model, giving visibility to the cost impacts of design changes.

“We’re looking to take the benefits further and feed reinforcement data from the model directly into the fabricator’s steel bending machine,” says Dickson.

“By running construction sequencing scenarios we can co-ordinate site delivery, storage, site containment, traffic management and passenger flows”

“The BIM model is being used to position the jet grout sleeves - to set out the length, orientation and co-ordinates of every column - and check that we’re getting the 100% coverage needed,” Povey adds.

It also enables Keller to ensure that drill strings will not hit buried infrastructure.

The contractor is planning to use the BIM model to control its grouting rigs, which will help reduce setting out time on site.

The richness of information contained within the 3D model will improve the contractor’s ability to understand and resolve details.

It will also enable LUL to check the contractor’s work against its specification, Clark-Edwards says. “With an integrated single model approach we’re able to continuously review and test the design for constructability, and potentially for maintenance and operation of the asset. By using viewing tools like 3D pdfs we can greatly increase our level of engagement in the process and therefore have a higher level of confidence that our requirements are being met.”

BIM will also be used to plan construction. “It enables us to better schedule the myriad activities required,” says Clark-Edwards. “By running construction sequencing scenarios we can co-ordinate site delivery, storage, site containment, traffic management and passenger flows. And we can do virtual ‘dry runs’ on critical activities to see how best to carry them out within the constraints of an operational railway.”

“We’ve used the model to involve LUL’s future maintainers and think about how to get plant in and out,” adds Povey. “Traditionally the operations and maintenance guys aren’t involved in design and, after handover, remedial works are often required to improve access and provide space to handle plant.”

Post-completion, the detailed model will also provide LUL with an accurate record of assets belonging to third parties as well as its own.

The model contains spatial, technical and procurement information and will help LUL manage the station through its 150-year design life.

BIM: VICTORIA STATION Upgrade

Information from across the supply chain is combined to provide the clearest possible picture of the project and the constraints it will face during construction and operation.

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