The Koivisto Bridge, which crosses the Kokemäenjoki river on Highway 11, has made Finnish piling history. The new bridge under construction is being built with exceptionally long steel tube piles, the deepest of which have been driven to a depth of 92 metres. This is reportedly the longest pile length ever driven in Finland.
The piles consist of 12-14-meter-long steel pipes with a diameter of 1000 mm, welded together on site. A particular challenge is posed by the soft, deltaic soil and the longer than expected length of the piles – factors that have increased the challenge of the work considerably.
– Originally, the longest friction piles were planned to be 60-70 meters long, but the final load-bearing capacity was only found at a much deeper depth. The longest pile was driven a staggering 57 622 times. Pile driving to this depth requires reliable and robust equipment and a high level of professionalism that few in Finland can match,” says Henry Vuorma, KFS Finland’s Pile Driving Manager.
The increased dimensions of the piles have also required a re-evaluation of working methods and careful planning on how to drive the piles efficiently, safely and with quality in mind, and subsequently concrete them to the final depth. Despite all this, the piling has been successful and the required load-bearing capacity has been achieved.
– The most heavily loaded piles have now been driven to the hard bottom and load capacity measurements have reached up to 19 MN. This shows that the piles meet the 16 MN load-bearing capacity requirements perfectly, Vuorma continues.
The new Koivisto bridge will be 130 meters long and 15.3 meters wide, a continuous steel girder bridge with a connector structure. The piling work started in March 2025 with reinforced concrete piles, followed by large diameter piling. To date, a total of 4.5 km of reinforced concrete piles have already been piled on site.
After the Koivisto bridge, KFS will continue the piling work on the Pikkuhaara bridge, where slightly shorter piles will be used. Both the Koivisto and Pikkuhaara bridges were built in the 1950s and no longer meet current load-bearing and safety requirements. The new bridges are important for road safety and to meet today’s standards, and their foundations are built in a sustainable way – by piling deep into the load-bearing soil.
The contractor is the Finnish Transport Agency and the main contractor is Kreate Oy. The piling contractor is KFS Finland Oy.