Tapiola metro station and central parking garage are under construction into the bedrock under the Tapiola Center. The Tapiola central parking facility is the biggest underground parking hall in the Finland. The Tapiola Metro station is parallel with the parking halls. Due to the horizontal rock stress, the whole complex may behave as one unit with 160 m span. The movements of the rock mass were monitored during the whole excavation period with extensometers. In October 2013, during routine inspections it was found out that numerous cracks have appeared into the shotcrete in the roof arc of the southern parking hall. The original simulations, the monitoring results and the back-analysis based on monitoring results were compared with each other. As a result, an acceptable explanation was achieved, but due to the complexity of the geology, geometry of the facilities and simultaneous excavation works in the caverns, the basic reason of the phenomenon remains unknown.
1 Underground Facilities
Tapiola, an area in the City of Espoo, has been one of the most famous areas in the Helsinki metropolitan area. Earlier the Tapiola region was also a remarkable commercial center but during the past two decades other regions around Tapiola have increased their commercial capacity.
To restore the attractiveness of the area, it was concluded that Tapiola must become functionally and commercially stronger. The main task was to draw up a modern development plan for the commercial heart of Tapiola. When the decisions on the West Line underground and the location of the respective Tapiola station were made, a momentum for the design of the underground part of the development plan was created. This underground part consists of central parking for 3,000 cars, service facilities for the stores and Tapiola metro station (Figure 1). All of these are constructed into the bedrock.
The Tapiola central parking garage consists of two approximately 450 m long three-storey halls and four 100 to 200 m long two-storey halls offering initially 1,500 parking spaces with an option to expand up to 3,000 spaces. The span of the parking halls is 17–22 m and the height 10–18 m. This underground parking facility, along with its 21 vertical shafts, is the biggest underground parking hall in Finland.