Nydalsbrua in Trondheim

Nydalsbrua is a 183 meters long cable-stayed bridge over the Nidelva in Trondheim that will replace the existing Sluppen bridge. The project includes approximately 1.2 km with new road and 1.7 km of bicycle paths, Nydalsbrua, two smaller bridges over Leirelva and a tunnel portal and 80 meters of future tunnel up to Byåsen.

The project is under the auspices of the Norwegian Public Roads Administration, with Skanska as the executing contractor. NGI has been responsible for geotechnical and environmental geological design as a sub-consultant to Aas-Jakobsen Trondheim. The assignment includes consultancy and model-based design for the preparation of a zoning plan, technical plan and detailed construction plan with a complete tender basis and working drawings. NGI also assists the Norwegian Public Roads Administration with follow-up in the construction phase.

Many structures

There are many structures included in the project, such as a new carriageway (Nydalsbrua) which crosses the Nidelva north of the existing Sluppen bridge. The bridge is a cable-stayed bridge with one tower and one centric cable plane.

The landing areas for Nydalsbrua are located in steep terrain. On the west side of the river is also the Dovre railway line above the construction area. Nydalsbrua has its back anchorage just below Dovrebanen. In addition to Nydalsbrua, two bridges over the Leirelva are included in the project.

Geotechnical challenges

The foundation for Nydalsbrua bridge itself is built on 800 mm drilled steel pipe piles to rock, while the ramp bridges are founded on a combination of drilled steel pipe piles, steel core piles and direct foundations on rock. Just above the anchoring chamber for the bridge cables runs the Dovre railway line, which in the construction phase is supported by an approximately 80 meters long temporary pipe wall which is anchored with lace stays to rock.

For the foundation of the use axes, three sheet pile constructions are established with a support height of 4 to 9 meters. The project is complex and challenging with steep slopes and proximity to the Dovre railway line, quick clay deposits and challenging construction conditions.