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NIRE Annual Report
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1997

System Safety Approaches for Utilization of Underground Space in Urban Area

System Safety Division
Safety Engineering Department
Objectives
Because of the lack of land spaces in urban areas in Japan, deep under ground space is expected for public use. To realise the underground space utilization, a national project was started in 1989 from many aspects such as geological survey method, construction way, machinery development, etc. A pilot underground space, called "Geo-dome", was constructed in 1996 and many kinds of observation for the evaluation of the space have been conducted. System safety division of NIRE has been involved in the project from system safety side. The project was ceased at the end of March 1997 and the results are under preparation of papers. The outline of them are as follows.
Underground Space Climate
To establish comfortable and safety underground environment, air velocity distribution, temperature, humidity, carbon dioxide concentration, atmospheric pressure, etc. have been continuously measured. Temperature layers were observed during summer season. Humidity was supplied by atmosphere and not by underground water in case of Geo-dome wall condition.
Alarm Messages Propagation
To investigate speech transmission characteristics in Geo-dome, measurements on some objective physical indices and speech intelligibility by subjects were carried out. From analyses of the experiments, it was found that the physical indices and intelligibilities fluctuate much due to arrangements of sound source and receiver. On the other hand, speech intelligibilities had high correlation with values of RASTI, t60, C60 and D60. Except for psychological evaluations on speech hearings, the values of these physical indices have to be kept high, at least, to realise better speech communication environment in the dome.
Evacuation
To know the effect of underground spaces to human behaviours, we carried out questionnaires about psychological effect (STAI test) and experiments of way finding at Geo-dome. As the result of STAI test, human subjects obviously indicated anxiety (average 5 points) when they arrived at the bottom of Geo-dome (-80m level). As for way finding problem, we settled a round shaped and line symmetrical maze at the bottom of Geo-dome. Without any signs to exit, some of human subjects completely lost their way, because they were prevented to recognise location by the shape of maze. With visual or sound signs, they promptly travelled to the exit. Some of human subjects mentioned about "panic." These results suggest that the most necessary point at the utilization phase of the deeper underground opening spaces. It will be helpful to people that plans for the easy evacuation, easy perceptible guide systems, and convenient design of spaces, especially in the deep underground spaces.

Selected Publication
1) Speech Intelligibility in the Underground Dome without Absorption Treatment, Tech. Rep. Archit. Acoust., Acoust. Soc. Jpn., AA96-39(1996)

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