Helsinki, Finland

Development along the coastline North of Helsinki centre will provide much needed accommodation and living facilities in the area.

Reclamation of this land was started after WWII using a variety of fill material over unstable glacial deposits. The area suffers continuous settlement. Mix in place ground treatment has been used in some areas and a variety of driven pile types and sizes installed.

Pile design has been carried out relying on end bearing, but with the such significant consolidation, ensuring long term suitability of the base capacity was the ambition of the static load testing program.

Loadtest & Skanska Tekra OY came up with a solution using bi-directional testing. The pile could be tested after installation and then re-tested at intervals of 6 months to determine the change in the ground conditions with time, without interrupting progress on site.

Two 530mm driven steel piles were selected as the test piles. These were driven to set with a loose driving shoe that would allow the 330mm O-cell® to load the soil directly below the base.

Geotechnical conference carried out beside piles under test

The testing was to coincide with a seminar on ground improvement techniques. The seminar marquis was to cover the whole test area and provide seating and facilities for the seminar.

As the seminar progressed, one of the piles was tested ‘live’ and the delegates were kept informed of the test results with real time updates.

Bi-directional testing provided a solution to a testing problem even where the reaction in friction was insufficient. Due to the small testing footprint, testing and retesting could take place after the structure was completed without disruption to construction program.

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Helsinki, Finland