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SPECIAL REPORT BSEE


Heidi Merikukka M Eng, Project Manager, Underground Structures and Shelters Department, Pöyry, believes that more cities need to look below the surface to find space for parking and even the transportation of goods. Here, she cites Helsinki as a prime example of underground applications.


travel to the centre for employment and services. Despite more and more people using public transportation, private transportation in the form of vehicles is still growing. This means higher traffic in the city centre and also a growing need for parking places.


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In most cities it is difficult to find spaces for new parking facilities since remaining free space is prioritised for commercial and residential buildings. Lorries and delivery vans are transporting more and more goods to various department stores and shops. This adds to congestion in the city centre. In Finland, a demanding climate also affects the infrastructure since above ground parking facilities often have an open construction and the climate affects both the structure and cars.


Cities around the world have to address these problems which affect the everyday lives of locals. One solution is to move the parking facilities, as well as the transportation of goods, underground. This solution means less traffic above ground and


WHAT LIES BENEATH Underground solutions


xpanding cities creates more demand for services and businesses in city centres. Most people live in the suburbs but need to


better conditions for both cars and goods handling.


Helsinki is an excellent example of underground applications, with the rock spaces being in use for a long time. Beneath the city, a world of many layers of service spaces, parking facilities and private operations has developed. Initially every project was developed only for its own needs but now, future projects are also considered when developing a new project. Helsinki has in fact an official underground master plan in place.


Design solutions for parking facilities


When starting the design of an underground parking and shelter facility there are a several issues to be considered. These are based around finding a: uSuitable rock resource with acceptable rock quality


uOptimal location for the access tunnel or tunnels


uSuitable above ground locations for pedestrian shafts


uSuitable above ground locations for technical shafts


uDeciding if the parking facility shall be single or multi-storey


Finding an optimal location for the


access tunnel is a significant aspect of the parking facility’s design. The access tunnel entrance must be located in a logistically favorable place so that users can easily find it. It must also be easy to drive in without creating traffic jams. The access tunnel must also be as short as possible in order to save costs and construction time.


Underground parking facilities have several vertical shafts for different purposes. These are pedestrian, ventilation and technical shafts. Optimal location of the shafts is a main issue when designing them. Pedestrian vertical shafts must be located where the people will want to go above ground. The distance to walk above ground will therefore be minimised. The shaft can also go directly into a shopping centre or concert hall, for example. This means pedestrians do not need to go into the open air which is favourable during winter time in harsher climates. The ventilation shaft must be located in a place where exhaust air can be discharged without harming surroundings.


The exhaust shaft can be located, for example, in a building and discharge the exhausted air above the roof level. The technical shaft must be located where the intersections of electricity, heat and water connections are located. Usually the surrounding environment is very demanding in the city area and the above ground architecture of vertical shafts has to be integrated to the surroundings.


uEntrance from Karamzin Street pedestrian tunnel at the parking level.


Service and storage space design is also demanding because the access shaft will usually go into an existing building. Also, the access to the storage spaces must be designed in a way that minimises disruption to the traffic and parking spaces that are underground. Important matters to be considered during the design are reservation of space for loading docks, height and load of using vehicles, required turning radius for


the vehicles and turning locations for larger vehicles.


Underground civil defence shelters are an economical solution due to the rock roof and rock walls that can resist pressure shocks. This means pressure structures are only required for the openings. Shelter in rock consists of several blast and gas tight walls. And it is very important to minimise the number of pressure structures in the layout design because this directly affects the costs. The location of pressure structures must be designed such that the impact on traffic is a minimum.


Conclusions


Considering the above, when we approached the project of the location of the Töölönlahti parking facility, the only possible solution was to put it underground. The Parliament Building, Helsinki Music Centre, Finlandia Hall, Finland’s National Museum and Helsinki City Museum are all situated in the area. A parking facility above ground would impact the architectural image of the whole area. The city would have been reluctant to grant planning permission to construct such a structure within these surroundings.


Taking the cars underground allows the space around these building to be used for pedestrians and recreation. The area functions as a comfortable meeting place for locals and highlights that ultimately the city centre is for citizens and not vehicles. In addition, since the cars are underground, they are not affected by the often harsh weather in Helsinki. Constructing car park facilities underground is expensive. The price for one car park space is about 50,000 to 70,000 euro (£42,600 to £59,600). However, benefits that cannot be measured in financial terms make the underground construction profitable.


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