Construction of Sweden’s Hallandsås Tunnel has been dogged by technical issues but early use of Building Information Modelling methods by Sweden’s transport administration has helped maximise efficiency.
Most engineers think of Building Information Modelling (BIM) as being a relatively new concept, but Swedish transport administration body Trafikverkethas been using BIM methods for 20 years. According to Trafikverket, this approach and adoption of the latest BIM technology has played a key part in bringing the Hallandsås Tunnel project close to completion.
“Trafikverket has been using BIM techniques for rail schemes since 1994, but we concluded that increasing its level of BIM adoption would help improve productivity and reduce reworking on the Hallandsås project,” said Trafikverket technology strategist for major projects Leif Malm.
This drive for efficiency on the Hallandsås scheme was considered vital in order to overcome the issues the project had in its early stages.
Work on the rail link, which will create a six-fold increase in rail capacity between MalmÖ and Gothenburg, was started in 1992 by Kraftbyggarna but halted after five years due to environmental issues. In 1996 Trafikverket brought in Skanska to work on the scheme, however, issues with high levels of water leakage containing acrylamide above trigger concentrations led to the decision to stop the project again and focus on decontamination and sealing the tunnel.
A joint venture of Skanska and Vinci restarted work on the scheme in 2005 and completed the first bore between Bastad and Forslov in 2010. Work on the second bore was completed last year and the new rail link is now expected to be opened in 2015.
The tunnels have been driven by a Herrenknecht tunnel boring machine through unstable ground formed of gneiss, amphibolites and dolerite. As a result, Vinci and Skanska undertook a 230m section of ground freezing to take the route through the waterbearing fissured Molleback zone.
Given the challenges experienced with the ground conditions, Trafikverket was keen to ensure the rest of the project went smoothly.
As the project progressed, and Trafikverket realised that planning and detailed engineering design of track and related infrastructure would need to happen in parallel with the tunnelling, it sought to increase its use of BIM to keep the work on schedule.
Sweco was given the responsibility for all BIM-related strategy and coordination of the Hallandsås project, including helping the project team implement effective BIM processes to optimise production, develop integrated 3D models through a collaborative design process, and use that information throughout the project lifecycle. According to Sweco, use of Bentley Systems’ BIM software on the scheme has resulted in innovative methods, reusable resources, a reduction in costs and productivity improvements that are helping to keep the project on schedule.
Bentley Navigator is being used to visualise and inspect the 3D digital model, while Project Wise is the hub for document management and administration. “Bentley’s products can manage large amounts of data with ‘real-world’ coordinates, which is important on infrastructure projects,” says Sweco BIM strategist
Sweco worked with Trafikverket to create an integrated 3D object library, as well as automated scripts for when objects are inserted into the CAD models. Every object is specified with detailed information such as type, codes, part number, description, and web links. This standardised library ensures project quality for the Hallandsås project, and means that every 3D object can be reused by Trafikverket on future projects. The 3D model allows design and function to be visualised and it enables automatic generation of drawings and reports, and facilitates simulation and analysis.
Reusability has been a key benefit for the Hallandsås project in terms of functionality and methodology. Recurring items are modelled, attached with attributes, and compiled into a 3D object library. These objects can be linked to different processes, including time management, logistics, and procurement planning.
As tunnelling progressed, by continuously feeding the “as-built” data from the tunnelling production into the 3D model, integrating it with the latest design and engineering information, the team can effectively manage the changing conditions. The shared information empowers the design engineers to analyse the effect of, and react to, changes immediately, avoiding the risk of costly surprises during the construction as a result.
“We call that ‘Live BIM’ - to use information from the ongoing production as basis for impact assessments and adjustment of the engineering,” explains Ahnsjö.
“The most important contribution is our coordination process, which efficiently reduces design errors and increases quality. We have monthly coordination meetings with all involved engineering consultants. Before the meeting, all current design files are loaded into a digital model and pre-inspected using the clash detection functionality in Bentley Navigator.
“Thanks to the pre-inspection, which highlights design problems and obvious errors, affected parties can discuss and solve issues in advance. At the coordination meeting, the entire design is reviewed using dynamic views and section cuts of the digital model. The day after, results are published and made easily available as 3D pdf files,” adds Ahnsjö.
Thanks to the coordination process, 200 non-constructible conflicts and 3,000 unique collisions have been detected on the Hallandsås scheme. By resolving these at the design stage, the production cost of correcting the problems and additional work caused by design faults has been reduced by 50%. For the Hallandsås project, with a contract sum of SEK700M (£63.4M) for the work embraced by BIM, the cost saving is estimated to be up to
“The BIM methodology obviously constitutes a great potential for improvements in project efficiency,” says Ahnsjö. “BIM is all about building and adapting information to its purpose.”
Another BIM objective has been to enable, enhance and reuse engineering design information in downstream processes.In addition to providing the construction layout and geometrical drawings, the 3D design model has been prepared to supply data for machine control and guidance, survey layout, quantities and specifications, time management, cost control, analysis, as-built models, and more.
“Reinforced by the basic features of Bentley software, and especially the clash detection inside Navigator, we have shown a very positive effect in terms of increased quality of the construction documentation, reduced production cost for correctional and additional work, and more efficient risk management, which means we can secure the production schedule,” says Ahnsjö.
Long-term, the model will eventually be used in operations and maintenance to provide up-to-date asset management data.
Hallandsås is the first and most advanced of a group of official BIM pilot projects within Trafikverket. As a result of the progress made, technology used, and benefits achieved on the project, Hallandsås will set the standard for all future projects, with Trafikverket mandating the use of BIM in all investment projects by 2015.
1994 Year when Trafikverket started using BIM methods
200 Number of nonconstructable conflicts picked up at design stage
£4.5M Cost saving on Hallandsås project resulting from use of BIM