In Tampere, an underground air-raid shelter is being built where two ice-hockey rinks will be placed for civilian use. It consists of a single hall with a span width of 32 m, a maximum height of 9.2 m and a length of 134 m. The Site investigations included different types of geological mapping, diamond core drilling and rock stress measurements. The final cross-sectional profile was chosen on the basis of BEM and FEM calculations. The need for strengthening was mainly determined by the shelter specifications. The Strengthening consists of a combination of rock bolts, steel net and shotcrete. Rock mass Conditions are followed with precise levellings and extensometers during and after the construction stage.
InTampere baut man eine Gebirgsschutzraum, wo zwei Eishockeybahnen fuer Zivilgebrauch liegen werden. Sie ist eine Einzelhalle mit einer Spannweite von 32 m, einer Höhe von 9.2m und einer Lange von 134 m. Die Platzuntersuchungen enthielten geologlsche Kartierung auf verschiedenen Weisen, Kern- bohrundgen Gebirgsspannungsmessungen. Der endgueltige Querdurchschnitt war auf der Grunde der Grenzelement- und Finite-elementberechnungen gewahlt. Das Befestigungsbeduerfnis war hauptsachlich von Schutzraumgebrauch festgesetzt. Die Be- festigung besteht aus einer Kombination von Felsankern, Stahlnetz und Spritzbeton. Die Gebirgsmassenverhaltnisse sind mit genauen Abwagungen und Extensometern unter und nach Abbau gefolgt.
A Tampere on est en train de construire un abri souterrain contenant deux patinoires Pour Ie hockey sur glace. Il embrasse une simple halle avec une portee de 32 m, une hauteur de 9.2 m et une longueur de 134 m. Les investigations in situ embrassont des etudes geologiques variees, des forations au Diamante pour Ie carottage et des mesures de l ' etat de contrainte des roches. La section transversale finale a ete choisie sur la base de calculations par les methodes des ele- ments de bord et finis. Le besoin de renforcer etait principalement determine par l' usage d' abri. Le renforcement consiste en boulons, en filet d' acier et en beton projete combine. Les conditions dans Ie massif rocheux sont observees par 1es mesures geodetiques et par les extensometres pendant et apres la construction.
According to the Finnish legislation a town district of 10 to 30 thousand inhabitants has to have air-raid shelters from 1 to 3 hectares (30 000 m2) altogether. To- day thls is an investment of up to 100 million Finnish marks (25 million USD), only for exceptional use. To utilize these investments more effectively a civilian use is always tried to find'' for these spaces. In larger spaces one has of course more alternatives to choose. Alternative uses Nearby all of the larger air-raid shelters have been built in rock since the beginning of the 1960-es (Vuorela and Tervila,1980). The Finnish bedrock is usually of good quality and the soil cover is thin. The first bedrock shelters were mainly used for storages or car parking. Today there are much more possibilities, e.g. gymnastics and tennis halls, running tracks, swimming halls, cinemas, bowling halls etc., not to speak of training rooms for pop groups. The most important restriction to the civilian use is the demand that the shelter has to be able to be changed to its original purpose in 24 hours.
At the middle of the 1970'es such good experiences had been obtained on bedrock shelters that an idea was arisen to place an ice-hockey rink underground into a bedrock air-raid shelter. After some discussions with the Finnish Ice-hockey Association it was found out that the minimum acceptable width for an ice-hockey rink was 28.5 m. This again supposed a bedrock shelter with a span width of minimum 32 m.
(Figure in full paper)
The planning of the first bedrock shelter with a span width of 32 m was started in 1977 in the town of Turku (Holopainen and Oksanen, 1980). The second one was started a year later in Hervanta, in the town of Tampere (Fig. 1). This one is discussed in more details here. The third one will probably be started this year in the vicinity of Helsinki. The capacity planned for the bedrock shelter of Hervanta is 3 000 persons, which means a hall area of 134 × 32 m in a single hall (Fig. 2).
The investigations in Hervanta were started with aerial photogeological mapping and surface geological mapping in summer 1978. On the basis of the information obtained from these the shelter was preliminary placed in a larger block in the bedrock (Fig. 2). The shortest distance to the nearest fault zone was about 2S0 m (N-NW from the shelter). The shelter axis was in the direction of the bedrock block. The rock type in the block was homogeneous, coarse-grained, unaltered porphyric granite.
