All Issue

2018 Vol.20, Issue 2 Preview Page
Estimation of the amount of refrigerant in artificial ground freezing for subsea tunnel

해저터널 인공 동결공법에서의 냉매 사용량 산정

Youngjin Son1
,
Hangseok Choi2
,
Tae Young Ko3*
손 영진1
,
최 항석2
,
고 태영3*
1General Manager, Infra Eng’g Team 2, SK E&C
2Professor, Dept. of Civil, Environmental and Architectural Engineering, Korea University
3General Manager, TBM Team, SK E&C
1SK건설 Infra Eng’g2팀 부장
2고려대학교 건축사회환경공학과 정교수
3SK건설 TBM팀 부장
*교신저자. *Corresponding Author. 
31 March 2018. pp. 255-268
PDF XML Citation
Abstract

Subsea tunnel can be highly vulnerable to seawater intrusion due to unexpected high-water pressure during construction. An artificial ground freezing (AGF) will be a promising alternative to conventional reinforcement or water-tightening technology under high-water pressure conditions. In this study, the freezing energy and required time was calculated by the theoretical model of the heat flow to estimate the total amount of refrigerant required for the artificial ground freezing. A lab-scale freezing chamber was devised to investigate changes in the thermal and mechanical properties of sandy soil corresponding to the variation of the salinity and water pressure. The freezing time was measured with different conditions during the chamber freezing tests. Its validity was evaluated by comparing the results between the freezing chamber experiment and the numerical analysis. In particular, the freezing time showed no significant difference between the theoretical model and the numerical analysis. The amount of refrigerant for artificial ground freezing was estimated from the numerical analysis and the freezing efficiency obtained from the chamber test. In addition, the energy ratio for maintaining frozen status was calculated by the proposed formula. It is believed that the energy ratio for freezing will depend on the depth of rock cover in the subsea tunnels and the water temperature on the sea floor.

Keywords
Artificial ground freezing
Freezing efficiency
Freezing time
Liquid air
The amount of refrigerant

해저터널은 시공중 예측치 못한 고수압으로 인한 해수 침투가 발생할 가능성이 매우 크다. 이에 고수압조건에서 차수 및 보강효과가 탁월한 인공 동결 공법의 적용이 대두되고 있다. 본 연구에서는 인공 동결 공법에 필요한 냉매량을 산정하기 위해 열흐름 에너지 이론 모델에 의한 이론적인 값을 계산하고, 동결 챔버 실험결과 및 수치해석결과와의 비교를 통해 적 정성을 검증하였다. 염분과 수압에 따른 열적․역학적 특성 변화를 규명하기 위해 동결용 챔버를 제작하여 염분과 수압 조 건에 따라 사질토의 동결 시간을 파악하였다. 또한, 이론값과 수치해석 결과의 동결 시간은 유사한 경향을 확인하였다. 동결공법의 냉매량은 수치해석의 결과를 기반으로, 동결 챔버 실험을 통해 동결 효율의 결과와 이론식을 통한 동결 유지 를 위한 에너지 비율을 적용하여 산정하였다. 동결유지를 위한 에너지 비율은 해저터널의 토피고와 해저면의 수온에 따 라 좌우될 것으로 판단된다.

키워드
인공 동결 공법
동결 효율
동결 시간
액화 공기
냉매 사용량
References
1
Andersland, O. B., Ladanyi, B. (2004), Frozen Ground Engineering (Second edition). Chichester: John Wiley & Sons, Hoboken, New Jersey,  pp. 363.
2
Colombo, G., Lunardi, P., Cavagna, B., Cassani, G., Manassero, V. (2008), “The artificial ground freezing technique application for the Naples underground”, Proceedings of the World Tunnel Congress 2008 on Underground Facilities for Better Environment and Safety, Agra, India, pp. 910-921.
3
Handbook of Chemistry and Physics (84th Ed, 2004), Boca Raton, FL : CRC-Press/ Taylor and Francis.
4
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.
5
Heijboer, J., Hoonaard, J., Linde, F.W.J. (2004), The Westerschelde tunnel: approaching limits, A.A. Balkema, The Netherlands, pp. 292
6
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.
7
Pimentel, E., Papakonstantinou, S., Anagnostou, G. (2011), “Case studies of artificial ground freezing simulations for urban tunnels”, Proceedings of the Word Tunnel Congress 2011 on Underground Spaces in the Service of a Sustainable Society, Helsinki, Finland, pp. 459-468.
8
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, No. 1, pp. 57-69.
9
Sanger, F. J., Sayles, F. H. (1979), “Thermal and rheological computations for artificially frozen ground construction”, Engineering Geology, Vol. 13, No. 1-4, pp. 311-337
10
Stoss, K., Valk, J. (1979), “Uses and limitations of ground freezing with liquid nitrogen”, Engineering Geology, Vol. 13, No. 1-4, pp. 485-494.
11
Son, Y.J., Lee, K.W., Ko, T.Y. (2014), “Studies of application of artificial ground freezing for a subsea tunnel under high water pressure - focused on case histories”, Journal of Korean Tunnelling and Underground Space Association, Vol. 16, No. 5, pp. 431-443.
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 : 20
  • No :2
  • Pages :255-268
  • Received Date : 2018-01-02
  • Revised Date : 2018-02-21
  • Accepted Date : 2018-02-26
  • DOI :https://doi.org/10.9711/KTAJ.2018.20.2.255
Journal Informaiton Journal of Korean Tunnelling and Underground Space Association Journal of Korean Tunnelling and Underground Space Association
Online Submission & Review System
  • NRF
  • KOFST
  • KISTI Current Status
  • KISTI Cited-by
  • crosscheck
  • orcid
  • open access
  • ccl
Journal Informaiton Journal Informaiton - close