3D MODELING RELIEVED THE HEAVY TUNNEL CONSTRUCTION IN STOCKHOLM

To think differently and innovatively was a need when building a tunnel over a railway line by the new Norra Station in Stockholm. To save both time and space CN3 build a parametric model of the tunnel in 3D and visualized the building process’s phases digitally. This made it a solid and effective building process and, in the end, created a tunnel of higher quality.

The vision for the NS20-project in Stockholm was to expand the infrastructure around the town district Norra Station. The plan was to build a tunnel over a railway line. Furthermore, the space was to be exploited for building valuable housing square meters on top of the actual tunnel.

This demanded tunnel construction of high quality.

The contractor Züblin worked with CN3 in building the tunnel. By developing an optimized design, the intention was to create security in the time plan, good risk management and accelerated construction rate. In this way, the design supported that the building process to become more solid and profitable.

CN3’s job was to deliver innovative solutions by building parametric 3D models of the design. CN3 not only delivered the computational engineering part but also acted as a link between Züblin and the client-advisor of the project.

Savings through automation in the tunnel construction

“How can we build the tunnel so as many repetitions as possible in the process is obtained?”

This was one of the questions, CN3’s project leader of the tunnel project in Stockholm Jens Fobian-Larsen asked himself and his team. As a civil engineer with wide execution experience from building processes, Jens had the building expertise to understand the contractor’s wishes and needs. He also had the digital competencies and a project team in Copenhagen that could support the process with both specific project deliveries as well as software solutions for the automation of building processes.

“I think it is an extremely interesting work field we find ourselves in. We take the static design and we model it fast with automated methods and come with solutions that add value. Large savings are to be drawn both from   the contractor and the developer by optimizing the construction through iterations,” Jens explains, and he goes on:

“The intelligence we can add to a building project concerns the fact that we have a great understanding of construction technology and automation while using digital tools to execute the design.”

35-40 percent time savings with digital visualization and planning

Tommy Axelsson was site manager on the tunnel project at Züblin in Sweden. He has long experience with concrete, and at the tunnel project, he collaborated with Jens and CN3 regarding the reinforcement, reinforcement design, and which lifting points the construction had.

It was planned for there to be a turn in the tunnel which required the construction to be built in a way, where every reinforcement curve was moved some centimeters compared to the previous resulting in an unbroken curve.

“We left everything to CN3 acquiring a parametric model of the building we could show and use. The most important factor is to work great together in the process,“ Tommy Axelsson says and continues.

“I could propose solutions in a meeting and then CN3 went home and coded the 3D model fast and effectively. It could be that my proposal was wrong but then we could discover it and change it beforehand. It’s like having a Lego house to build on when you have a 3D visualization build on a digital twin. You may be 35-40 percent of the time at the actual construction site working with digital 3D-models in advance.

Tommy Axelsson has worked with CN3 multiple times, and appreciate that CN3’s people are both technologically skilled and easy to work with:

“The team at CN3 can translate ideas into usable models and solutions, and they are fast at returning. If anything must be clarified they respond immediately. They are quite simple top professionals, “ he explains.

Due diligence based on a technological platform

CN3’s team used their self-developed software platform Vitus to incorporate agility in the NS20-project and in this way obtaining a solid building process. Vitus is an open BIM platform which in combination with other digital tools was used to set up a tailored IT platform for the project in Stockholm.

One of the advantages of the tailored platform is working with algorithms that not only consider the factors which currently are known but also the matter that factors change along the way. Due diligence is made possible through the adapted IT platform.

CN3’s technical construction competencies also include prefabrication and automation. The optimal is often to obtain a repetition effect and at the same time have the opportunity for variation in the construction. Repetition creates quality and is an effective way to obtain a solid building process.

Quality in the building process is also delivery before time

Along the way, in the building process, geotechnical challenges were faced which otherwise could have delayed the project significantly. Nevertheless, the tunnel was finished two weeks before promised. Jens Fobian-Larsen says:

“On the plane on the way home from the last meeting I had a great feeling that this was quite good. We had kept our deadlines and been part of delivering a tunnel of high quality. And because the tunnel is better executed it will last for longer. The developer received extra value, and at CN3 we took with us great learning from the project which we can use in future tunnel projects.”