Studies of application of artificial ground freezing for a subsea tunnel under high water pressure - focused on case histories -

Young-Jin Son; Kyu-Won Lee; Tae Young Ko

doi:10.9711/KTAJ.2014.16.5.431

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2014 Vol.16, Issue 5 Next Page

Studies of application of artificial ground freezing for a subsea tunnel under high water pressure - focused on case histories - 고수압 해저터널 건설을 위한 동결공법 적용성에 관한 연구 - 사례를 중심으로 -

30 September 2014. pp. 431-443

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Abstract

In this paper case studies of artificial ground freezing, which have not been applied in Korea, have been investigated for the water cut-off in a subsea tunnel under high water pressure and the most commonly used cooling mediums of brine and liquid nitrogen are examined. Since sea water with pressure has the lower freezing point than pure water, the lower temperature cooling medium is required in the application of subsea tunnel. Also, the cooling medium must have refrigeration safety and is able to reduce executing time. Brine freezing system can reuse cooling medium and is safer than liquid nitrogen freezing. But it takes more time to freeze ground and needs complex circulation plants. On the other hand, liquid nitrogen freezing system can’t recycle cooling medium and may cause breathing problems or asphyxiation through oxygen deficiency. But, freezing with liquid nitrogen is fast and requires simple refrigeration equipment. Principal elements of design for ground freezing in subsea tunnel have been extracted and these elements are needed further research.

Keywords

Artificial ground freezing

Subsea tunnel

Cross-passage

Face

High water pressure

Brine

Liquid nitrogen LN2

본 연구는 고수압 해저터널의 차수를 위한 동결공법 적용성 평가를 위해 국내 적용사례가 없는 동결공법의 해외 시공사례를 조사하였으며, 지반 동결공법에서 보편적으로 사용하는 냉매인 브라인(brine)과 액체질소(LN2)에 대한 분석을 수행하였다. 고수압 조건의 해수는 순수한 물에 비하여 어는 점이 더 낮기 때문에 지상에서보다 동결시간이 더 길 수 있고 해저터널과 같이 폐쇄된 공간에서의 적용 시 냉매는 안정성을 확보할 수 있어야 하고 공기 단축이 가능해야 한다. 브라인은 재사용이 가능하고 독성이 적어 인체에 미치는 영향이 적으나, 동결에 상대적으로 장시간 필요하고 동결장비가 복잡한 특징을 가지고 있으며, 액체질소는 냉매의 재사용이 불가하며 기화 시 공기 중 질소농도 증가로 질식의 위험성이 있으나, 상대적으로 동결시간이 짧으며, 동결장비가 간단한 특징을 가지고 있는 것으로 파악되었다. 또한 향후 추가적인 연구가 필요한 해저터널 연결구 및 막장면 주변 지반에 대한 동결공법의 주요 설계요소를 도출하였다.

키워드

동결공법

해저터널

연결구

막장면

고수압

브라인

액체질소

References

1.Colombo, G., Lunardi, P., Cavagna, B., Cassani, G., Manassero, V. (2008), “The artificial ground freezing technique application for the Naples underground”, Proceedings of Word Tunnel Congress 2008 on Underground Facilities for Better Environment and Safety, Agra, India, pp. 910-921.

2.Haß, H., Schäfers, P. (2005), “Application of ground freezing for underground construction in soft ground”, Proceedings of the 5th International Symposium TC28, Amsterdam, The Netherlands, pp. 405-412.

3.Harris, J.S. (1995), Ground Freezing in Practice, Thomas Telford, London, p. 264.

4.Heijboer, J., Hoonaard, J., Linde, F.W.J. (2004), The Westerschelde Tunnel: Approaching Limits, A.A. Balkema, The Netherlands, p. 292.

5.Itoh, J., Lee, Y.S., Yoo, S.W, Lee. S.D. (2005), “Ground freezing improvement for TBM maintenance in singapore”, Proceedings of the International World Tunnel Congress and the 31st ITA General Assembly, Istanbul, Turkey, pp. 471-476.

6.Pimentel, E., Papakonstantinou, S., Anagnostou, G. (2011), “Case studies of artificial ground freezing simulations for urban tunnels”, Proceedings of Word Tunnel Congress 2011 on Underground spaces in the service of a sustainable society, Helsinki, Finland, pp. 459-468.

7.Pimentel, E., Papakonstantinou, S., Anagnostou, G. (2012), “Numerical interpretation of temperature distributions from three ground freezing applications in urban tunneling”, Tunnelling and Underground Space Technology, Vol. 28, pp. 57-69.

Information

Publisher :Korean Tunneling and Underground Space Association
Publisher(Ko) :한국터널지하공간학회
Journal Title :Journal of Korean Tunnelling and Underground Space Association
Journal Title(Ko) :한국터널지하공간학회 논문집
Volume : 16
No :5
Pages :431-443
Received Date : 2014-07-16
Revised Date : 2014-07-28
Accepted Date : 2014-08-07
DOI :https://doi.org/10.9711/KTAJ.2014.16.5.431

Journal of Korean Tunnelling and Underground Space Association ISSN:2233-8292(Print) 2287-4747(Online) 한국터널지하공간학회 논문집

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