E6 Jaktøyen-Storler, construction plan

NGI's responsibility was detailed geotechnical and geoenvironmental design for construction of four-lane motorway E6 south of Trondheim, in Mid-Norway. The Project involved large structures, high embankments and deep cuttings and excavations in areas with challenging ground conditions with several hundred metres to bedrock and extensive presence of quick clay. Also, contaminated soil and effluence of surface water.

The project has included essential detailed design and production of drawings and specifications for tender documents for development of the New E6 from Jaktøyen to Storler South of Trondheim.

Challenges

Major interventions in areas with challenging ground conditions.
The tasks were to design a direct shallow foundation of structures in quick clay, a 10 m high embankment with associated settlements over extended periods (including creep), a 14 m deep excavation within the quick clay zone with requirement for earthquake design. There is also a risk of differential settlements on a bridge structure due to creep settlements. And, finally, there is evidence of contamination along major parts of the existing motorway, and re-use of contaminated soil requires approval.

Geotechnical advice

A geotechnical test site was established to investigate the strength properties of clay which had undergone ground improvement by the lime-cement dry mixing Method. Also, the test set-up allowed to investigate the capacity of open-ended steel core piles by performing tension (pull-out) tests. Preloading and extensive use of a (prefabricated) vertical drain and cement-lime stabilization was undertaken to ensure acceptable settlements on structures.

Adequate safety for the stability and bearing capacity of structures and excavations was achieved through cement-lime stabilization and terrain intervention. Advanced earthquake analysis has also been necessary, as the estimates provided by simplified methods were too conservative. Preparation of action plan for contaminated soil takes into account regulatory requirements regarding environmental assessment.

Optimal solutions for a demanding project

The first bridge structure across the motorway, shall have a direct foundation on clay and quick stabilised by the clay cement-lime method. Extensive use of cement-lime stabilization, terrain intervention and rise in elevation of a river course will be carried out to ensure stability. Clean-up of contaminated soil will provide improved conditions for biodiversity. Planned start-up for construction of the new E6 parcel is early 2016.