The Presidential Palace in February 2015. Copyright The Office of the President of the Republic of Finland.
The renovation project was highly demanding both technically and in terms of project management. The historical value and location of the building also raised the difficulty level.
Sito planned the foundation engineering works, subgrade reinforcement, and piling for the project, in addition to scheduling all the surveys and test repairs. At the early stage, when only subgrade reinforcement work was being carried out, the principal designer of the project was Aku Varsamäki from Sito. He commented on the project as follows: ”The most challenging aspect of the work was the extremely fragile old building. We needed to come up with the gentlest method of constructing the new foundations and to ensure that the building remained undamaged during the subgrade reinforcement works.”
The foundations of the Presidential Palace, completed in 1820, have been repaired in two stages. The last subgrade reinforcement, undertaken in the 1960s using Mega piles, was no longer sufficient, as surveys carried out over the years showed cracks in the walls resulting from the settlement of the foundations. The load bearing capacity of the piles had deteriorated due to factors such as the vibration caused by passing trucks and the impact of groundwater conditions.
Test repairs were carried out by reinforcing the lower sections of the Mega piles by injection and jet grouting. Injection, which would have been the faster and less expensive method, proved to be inefficient, so jet grouting was chosen as the final repair method. In addition to the repairs, approximately one hundred new piles had to constructed under the palace.
”The prize was decided on the basis of two major factors: The demanding location of the Presidential Palace and the test repairs carried out prior to the actual pile reinforcement work. Moreover, the jury believes that this repair method can also be used in the future in other demanding projects in the Helsinki area,” says Veijo Käyhty, Editor-in-Chief of Rakennuslehti magazine, which announced the prize.
”It was obvious that the entire project was meticulously managed: no area was left to guesswork, and the repair method was thoroughly tested in advance. Thanks to this preparation, the schedule and costs could also be accurately outlined in advance.”
The RIL Prize 2015 was announced on 19 November 2015 at the House of Estates in Helsinki.
Designers and contractors involved in the project:
- The Office of the President of the Republic of Finland
Project management consultant
- Indepro Oy/ Matti Kruus, Pekka Romppanen
Principal design office
- LPR Arkkitehdit / Pauno Narjus and, for preparation work, Sito Oy/Aku Varsamäki
- LPR Arkkitehdit/ Pauno Narjus and Tiitta Itkonen
- Ideastructura Oy/ Pentti Aho
- Sito Oy / Aku Varsamäki
- SRV Rakennus Oy/ Site Manager Toivo Mäkeläinen; Area Manager: SRV Rakennus Oy / Alpo Asikainen
- Lemminkäinen Infra / Kimmo Perkiö