Crown Bridges alliance, Helsinki
We have built Länsimetro tunnels and stations in a number of projects with the aim to streamline traffic between Helsinki and Espoo and to help the cities reduce their greenhouse gas emissions. Good transport links facilitate urban development around the stations.
We have been involved in the construction of Länsimetro since the beginning and are its single largest builder. We have been responsible for most of the tunneling of Länsimetro and the construction of the busiest metro stations. People live and work next to the construction sites, which is why special attention has to be paid to safety and traffic flow. The environmental permit sets conditions for noise, dust and process water treatment, as well as for the impact on groundwater.
In the first phase of the Länsimetro project, jointly developed by the cities of Helsinki and Espoo, the metro expanded from Ruoholahti towards Matinkylä in Espoo, including eight new metro stations and 14 kilometres of new metro tracks. Traffic on the new section started in 2017.
In the first phase, we built the Aalto University, Tapiola, Niittykumpu and Matinkylä stations, as well as the Urheilupuisto–Matinkylä tunnel.
We carried out excavation and reinforcement of tunnels and stations in Ruoholahti, Lauttasaari, Koivusaari, Keilaniemi, Urheilupuisto and Niittykumpu. In addition, we were involved in the building of the foundations for the station building in Finnoo. We also built waterproof structures for the Lauttasaarensalmi rail tunnel and were involved in providing the furnishings for the tunnels.
We excavated the access tunnels in Otaniemi and Matinkylä and carried out the excavation contract for Tapiola’s eastern access tunnel.
We used a conventional drilling and blasting method to carry out the excavation. The tunnels were systematically sealed by means of pre-injection in accordance with the requirements of the environmental permit. The structures are designed for a lifetime of 100 years.
In the second phase of the metro, we were responsible for the Finnoo station excavation and reinforcement project, completed in October 2017. We are also building the Soukka and Kaitaa stations, expected to be completed in 2022.
The Finnoo excavation and reinforcement contract included the excavation and reinforcement of the Finnoo station and railway tunnels, as well as sewer tunnels in the area. We constructed 1,380 metres of new metro line and 771 metres of sewer tunnels. In 2017, our construction site won the Länsimetro Safest Construction Site award for the period January 1 – June 30.
The Soukka and Kaitaa station contracts were awarded on the basis of a tender, in which the decisive criteria were quality and price. Tenderers were awarded points based on strict criteria specified in the invitation to tender. The consortium YIT–ARE received the highest score and was thus selected.
“The purpose of the selection criteria in the invitation to tender was to find the best professional know-how and the best proposal for a cost-efficient implementation of a logistically and technically challenging construction project,” explains Aku Kallio, Director of Construction at Länsimetro.
In both station projects, an underground station is to be built in previously excavated premises. The contracts also include entrance buildings and yards, as well as technical spaces, shafts, a civil defence shelter and a service tunnel with its connecting tunnels.
Each station has a different theme, which is also reflected in the station architecture. At Kaitaa, the theme is “lush courtyards” with pine forest shades. The Soukka station is inspired by the modernist building stock of the 1960s, the key words being modernism, precision and sharpness.
The buildings carefully reflect the respective themes, which have been improved in cooperation with the different stakeholders.
An interactive working method called Big Room has been actively used in the project in order to facilitate problem solving, among other things.
“Big Room is very useful, as it helps us solve problems face to face with the client at very short notice. It is a very modern approach and also helps to create a better community spirit when people get to know each other,” says Ari Larikka, foreman at the Kaitaa construction site.
The site also supports work progress through a model called the Last Planner. In the model, the steps of the project and the required tasks are placed on a timeline. The timeline is attached to a wall where the project personnel can see it at all times. The aim is to facilitate successful execution of the tasks right from the outset. Daily schedules drawn up at the construction sites have been very helpful in overcoming occasional problems. The Last Planner has been a useful tool for preventing knock-on effects.
Building information modelling is also a tool that comes in very handy when you want to explain the construction status to people other than the personnel.
“As a contractor, we strive to support our client in advancing the project. At the Aalto University Station, we were the first to solve many of the construction problems. We were then able to take that experience to the other stations and make use of the lessons learned. We used building information modelling in the management of production volumes and design status. With the model’s 3D visualisation functionality, we were able to illustrate the construction status for the client, designers, subcontractors and our own people,” explains Anne Piiparinen, Senior Vice President, YIT Industrial and Structural Engineering Division.
The goal of the project is to build a metro that will make commuters’ daily life easier. For example, the stations are located near the services that people use every day. Länsimetro is entirely underground. This solution has minimised the inconvenience caused by construction to traffic and has also minimised disruption to people’s lives. It has also left terrestrial areas free for other uses, such as further urban development.
The construction of Länsimetro will accelerate the growth of the whole of Finland, while at the same time aiming to significantly reduce greenhouse gas emissions and improve air quality. A single metro train carries as many passengers as 700 cars.
Length of the first phase: 14 km
Length of the second phase: 7 km
Total volume of concrete cast during the second phase: 70,000 m3
Number of tunnel retaining wall elements installed in the second phase: 2,700
Number of elements installed in the second phase: 9,800