Sweco had to think innovative on the light rail project in Bergen to overcome complex planning and paperless construction by efficiently transferring models to the contractor’s machine control system.
Sweco was awarded the major contract and responsibility for construction phase 4: the 9 km line running from Nonneseter to Spelhaugen. The project includes a tunnel that presented challenging ground conditions at its entrance on the Kristianborg side. That required new ways of thinking to enable the intricate planning work and sharing models with the contractor.
Advantageous for everyone to work from the same model
Gemini Terrain is a widespread tool used in most infrastructure projects in Norway. In recent years, Sweco has used Gemini on several projects to ensure streamlined collaboration with contractors.
"There are great advantages if consultants, developers, and contractors are all using the same software. This makes it easier to understand each other's challenges," says Kine Sjøberg, BIM Coordinator. She adds:
"Gemini Terrain includes powerful features that make tunnel planning and design more dynamic and quicker to use than other solutions available on the market," she says.
Model-based construction projects require new methods for collaboration
The project is based on a design-bid-build contract, where the developer is responsible for all or the vast majority of planning work. Therefore, the contractor needs to place orders, extract quantities, and use the consultant's models efficiently and accurately.
"A handful of our consultants had to learn Gemini Terrain, which ensured a better communication with the contractor. We've learned a great deal through this process. Not least, how we can adapt our models, so they're easy to use for the contractor," says Sjøberg.
She refers to the model used by personnel in the drilling rig.
"Our transparency models have to be highly detailed, but they were too much for the contractor. We had to simplify the models considerably so that they could work in practice," she says.
Developed new working methods on the go
The construction of phase four from Bergen city center via Haukeland University Hospital to Fyllingsdalen started in 2018. The new line will open at the end of 2022 or in early 2023. Sweco's job is to plan and design this construction phase.
"There have been several challenges encountered during its implementation. At the tunnel entrance in Kristianborg, the cross-section is large in addition to the rock cover being thin and the rock mass being of poor quality. As a consequence, we had to redesign parts of the tunnel," she says.
The rock supports were redesigned, including lattice girders, steel piping, and 500 bolts that run nine meters into the rock. Since bolts were running in multiple directions, this had to be planned and designed with great care.
“We used Gemini to plan the rock supports and blasting profiles. We had to request help from Powel’s consultants to design the lattice girders so that the contractor could generate DWGs with the correct geometry. This is important in terms of acquiring data that is of a high enough quality to ensure correct prefabricated arches, geometrically correct design, and construction by the stated tolerances,” says Sjøberg.
Powel is working continuously on further developing the software.
"We are very satisfied with our partnership with Sweco. The Bergen project demonstrates the importance of a close collaboration between consultant and contractor. We firmly believe that more and more consultants will start using Gemini Terrain,' says Kjetil Gjesdal, Presale Manager at Powel Construction.