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Effect of pore-water salinity on freezing rate in application of rapid artificial ground freezing to deep subsea tunnel: concentration of laboratory freezing chamber test

고수압 해저터널에 급속 인공동결공법 적용시 간극수의 염분 농도가 동결속도에 미치는 영향 평가: 실내 동결챔버시험 위주로

  • Oh, Mintaek (Seoul Housing & Communities Corporation) ;
  • Lee, Dongseop (School of Civil, Environmental and Architectural Engineering, Korea University) ;
  • Son, Young-Jin (SK Engineering & Construction) ;
  • Lee, In-Mo (School of Civil, Environmental and Architectural Engineering, Korea University) ;
  • Choi, Hangseok (School of Civil, Environmental and Architectural Engineering, Korea University)
  • 오민택 (서울주택도시공사 토목기술부) ;
  • 이동섭 (고려대학교 건축사회환경공학부) ;
  • 손영진 (SK건설) ;
  • 이인모 (고려대학교 건축사회환경공학부) ;
  • 최항석 (고려대학교 건축사회환경공학부)
  • Received : 2016.08.16
  • Accepted : 2016.09.06
  • Published : 2016.09.30

Abstract

It is extremely difficult to apply conventional grouting methods to subsea tunnelling construction in the high water pressure condition. In such a condition, the rapid artificial freezing method can be an alternative to grouting to form a watertight zone around freezing pipes. For a proper design of the artificial freezing method, the influence of salinity on the freezing process has to be considered. However, there are few domestic tunnel construction that adopted the artificial freezing method, and influential factors on the freezing of the soil are not clearly identified. In this paper, a series of laboratory experiments were performed to identify the physical characteristics of frozen soil. Thermal conductivity of the frozen and unfrozen soil samples was measured through the thermal sensor adopting transient hot-wire method. Moreover, a lab-scale freezing chamber was devised to simulate freezing process of silica sand with consideration of the salinity of pore-water. The temperature in the silica sand sample was measured during the freezing process to evaluate the effect of pore-water salinity on the frozen rate that is one of the key parameters in designing the artificial freezing method in subsea tunnelling. In case of unfrozen soil, the soil samples saturated with fresh water (salinity of 0%) and brine water (salinity of 3.5%) showed a similar value of thermal conductivity. However, the frozen soil sample saturated with brine water led to the thermal conductivity notably higher than that of fresh water, which corresponds to the fact that the freezing rate of brine water was greater than that of fresh water in the freezing chamber test.

Acknowledgement

Grant : 고수압 초장대 해저터널 기술 자립을 위한 핵심요소 기술개발

Supported by : 건설교통과학기술진흥원, 한국연구재단

References

  1. Kang, J.M., Lee, J.G., Lee, J., Kim, Y. (2013), "Analysis of the Relationship between Unconfined Compression Strength and Shear Strength of Frozen Soils", Journal of the Korean geosynthetics society, Vol. 12, No. 3, pp. 23-29. https://doi.org/10.12814/jkgss.2013.12.3.023
  2. Kim, Y.C. (2003), "Experimental Studies on the Uniaxial Compression Strength Unfrozen Water Content and Ultrasonic Wave Velocity of Frozen Soils", Journal of The Korean Society of Civil Engineers, Vol. 23, No. 5-C, pp. 309-317.
  3. Seo, Y.K., Kang, H.S., Kim, E.S. (2008), "A Study of Cold Room Experiments for Strength Properties of Frozen Soil", Journal of Ocean Engineering and Technology, Vol. 22, No. 2, pp. 42-49.
  4. Andersland, O.B., Ladanyi, B. (2004), Frozen Ground Engineering (Second edition). Chichester: John Willey & Sons., p. 363.
  5. Blackwell, J.K. (1956), "A transient-flow method for determination of thermal constants of insulating material in Bulk", Journal of Applied Physics, Vol. 25, No. 2, pp. 137-144. https://doi.org/10.1063/1.1721592
  6. Carlslaw, H.S., Jaeger, J.C. (1959), "Conduction of heat in soilds", 2nd Edition, Oxford University Press, New York.
  7. Da Re, G., Germaine, J., Ladd, C. (2003), "Triaxial Testing of Frozen Sand: Equipment and Example Results", Journal of Cold Regions Engineering, Vol. 17, pp. 90-118. https://doi.org/10.1061/(ASCE)0887-381X(2003)17:3(90)
  8. De Vries, D.A. (1963), "Thermal properties of soils. In Physics of plant environment", Edited by W.R. Van Wijk. North-Holland Publishing Company, Amsterdam, The Netherlands, pp. 210-235.
  9. Germant, A. (1950), "The thermal conductivity of soil", J. Apll. Phys, pp. 750-752.
  10. Ishikawa, T., Miura, S. (2008), "Numerical modeling for mechanical behavior of granular materials subjected to freeze-thaw action with DEM", 12th International Conference on Computer Methods and Advances in Geomechanics, Vol. 2, pp. 1219-1226.
  11. Johansen, O. (1975), "Thermal conductivity of soils", Ph.D. thesis, University of Trondheim, Trondheim, Norway. CRREL Draft English Translation 637, US Army Corps of Engineers, Cold Regions Research and Engineering Laboratory, Hanover, N.H.
  12. Kersten, M.S. (1949), "Laboratory research for the determination of the thermal properties of soils", Research Laboratory Investigations, Engineering Experiment Station, Technical Report 23, University of Minnesota, Minneapolis, Minn.
  13. Li, S., Lai, Y., Zhang, M., Zhang, S. (2006), "Minimum ground pre-freezing time before excavation of Guangzhou subway tunnel", Cold Regions Science and Technology, Vol. 46, pp. 181-191. https://doi.org/10.1016/j.coldregions.2006.09.001
  14. Mickley, A.S. (1951), "Thermal conductivity of moist soil", American Institute of Electrical Engineers Transactions, 70, pp. 1789-1797. https://doi.org/10.1109/T-AIEE.1951.5060631
  15. Nishimura, S., Gens, A., Olivella, S., Jardine, R.J. (2009), "Thm-coupled finite element analysis of frozen soil: Formulation and application", Geotechnique, Vol. 59, pp. 159-171. https://doi.org/10.1680/geot.2009.59.3.159
  16. Shannon, W.L., Wells, W.A. (1947), "Test for thermal diffusivity of granular materials", Proceedings of ASTM, Vol. 47, pp. 1044-1055.
  17. Xu, X., Lai, Y., Dong, Y., Qi, J. (2011), "Laboratory investigation on strength and deformation characteristics of ice-saturated frozen sandy soil", Cold Regions Science and Technology, Vol. 69, pp. 98-104. https://doi.org/10.1016/j.coldregions.2011.07.005
  18. Yang, Y., Lai, Y., Dong, Y., Li, S. (2010), "The strength criterion and elastoplastic constitutive model of frozen soil under high confining pressures", Cold Regions Science and Technology, Vol. 60, pp. 154-160. https://doi.org/10.1016/j.coldregions.2009.09.001