Länsimetro is applying the Kuivaketju (dry chain) method to the construction of the Matinkylä-Kivenlahti phase. This is a moisture management operating model, adopted for the construction process in spring 2017, which reduces the risk of moisture damage throughout a building’s lifecycle.
“The system was originally developed for the construction of buildings, but we have tailored it to the needs of the West Metro. Construction of the Metro has involved special features compared to buildings; this is a long-term project, with the same work phases repeated several times. The construction of different stations and shafts is highly similar,” says Design Manager Hans Wilkman Ramboll.
After a building has been commissioned, the internal conditions tend to be warm and dry, while those on a railway are very humid.
“Special attention must be paid to the protection of sensitive service equipment and to ventilation and heat control. Stations have very high moisture management requirements, because they have even more technical equipment than the track. A station is a cold, segregated space where conditions vary as you move underground from the surface,” says Lead Consultant Leif Wirtanen of Ramboll.
Moisture is controlled by protecting machines and equipment with the help of protective coverings, for example, but the key issue is ensuring good ventilation. In an operational metro, moving trains change the air naturally, but ventilation has to be based on means such as fans when a metro is still under construction. Humidity is measured continuously.
The Länsimetro project is a pioneer in using the Kuivaketju10 method, since this is the first time that it has been used in a project combining building technology and infra on this scale.
“The City of Espoo’s building inspection authorities require that the West Metro ensure moisture management, and Kuivaketju10 is a good way of doing so. The overall process is still under development, but we already have many good experiences of using Kuivaketju10. Kuivaketju10 resembles the cold chain principle from the food sector; steps are taken to ensure moisture management at every stage from procurement to commissioning,” says Wirtanen.