Crown Bridges alliance, Helsinki
Under contract with Region Stockholm, YIT is a part of the metro extension project at Sockenplan in Stockholm. The work began in August 2020 with a construction period of approximately 2.5 years. The total value of the project is approximately SEK 400 million.
The project is part of a major expansion of Stockholm’s metro system. Over the next 10 years, Region Stockholm will expand the metro system with 18 new stations and approximately 30 kilometres of new track. The expansion plan covers almost 30 separate contracts, and the value of the total investment is approximately EUR 2 billion. Sockenplan is the southernmost part of the new blue line towards Söderort, which will ultimately connect the existing Hagsätra line and the new blue line from Södermalm at Sockenplan.
YIT has pervious experience of similar work in Finland and elsewhere. In the ongoing major expansion to Helsinki's metro system, YIT has been one of the main contractors since 2009 and is thus has a lot of up-to-date experience and knowledge from a major metro project. However, despite relevant experience of similar methods, the Sockenplan project is an demading project. The short construction period means that technical solutions and working methods that use the time more efficiently need to be found. Parts of the contract are designed by the client, while other parts are carried out by the contractor, which requires a clear demarcation. Other challenges that affect the project are strict noise and vibration requirements.
“The noise and vibration requirements affect at what times we can work, as well as what methods and machines we can use. Investigations need to be carried out in order to ensure that we can use the method we planned for,” says Mikael Porsbratt, project manager.
A large part of the project includes the support construction, which shall be designed and then carried out in order to realize the large shaft. The support construction will consist of RD pile walls, Berlin-type retaining walls, polyurethane retaining walls and shoring that crosses the large shaft. This requires specialists in geotechnics, hydrology, support construction and grouting. The rock tunnel that will be built at a later stage of the project will be carried out with the help of wire sawing.
“The support construction is complex, and it is vital that the potential environmental impact is monitored, such as subsidence of the existing buildings and the impact on groundwater. But thanks to our experienced specialists, we will succeed,” concludes Mikael Porsbratt.