KSCE Journal of Civil and Environmental Engineering Research (대한토목학회논문집)

Korean Society of Civil Engeneers (대한토목학회)
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Evaluation of Freezing Rate of Marine Clay by Artificial Ground Freezing Method with Liquid Nitrogen

액화질소를 이용한 인공동결공법 적용시 해성 점토지반의 동결속도 평가

  • 최현준 (고려대학교 건축사회환경공학부) ;
  • 이동섭 (고려대학교 건축사회환경공학부) ;
  • 이효범 (고려대학교 건축사회환경공학부) ;
  • 최항석 (고려대학교 건축사회환경공학부)
  • Received : 2018.02.26
  • Accepted : 2018.04.20
  • Published : 2018.08.01
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Abstract

Nowadays, the artificial ground freezing (AGF) method has been used in many geotechnical engineering applications such as temporary excavation support, underpinning, and groundwater cutoff. The AGF method conducts the freezing process by employing a refrigerant circulating through a set of embedded freezing pipes to form frozen walls serving as an excavation support and cutoff wall. Two refrigerants of brine with the freezing temperature of $-20{\sim}-40^{\circ}C$ and liquid nitrogen with the freezing (evaporating) temperature of $-196^{\circ}C$ are commonly being used in geotechnical applications. This paper performed a series of field experiments to evaluate the freezing rate of marine clay in application of the AGF method. The field experiments consisted of the single freezing-pipe test and the frozen-wall formation test by circulating liquid nitrogen, which is a cryogenic refrigerant, into freezing pipes constructed at a depth of 3.2 m in the ground. The temperature of discharged liquid nitrogen was maintained through the automatic valve, and the temperature change induced by AGF method was measured at the freezing pipes and in the ground with time. According to the experimental results, the single freezing-pipe test consumed about 11.9 tons of liquid nitrogen for 3.5 days to form a cylindrical frozen body with the volume of about $2.12m^3$. In addition, the frozen-wall formation test used about 18 tons of liquid nitrogen for 4.1 days to form a frozen wall with the volume of about $7.04m^3$. The radial freezing rate decreased with increasing the radius of frozen body because the frozen area at a certain depth is proportional to the square of the radius. The radial freezing rate was formulated as a simple equation.

최근 임시 지보, 보강 및 지하수 차수와 같은 다양한 지질공학분야에서 차수 및 지반보강 공법으로 인공동결공법(artificial ground freezing method)이 적용되고 있다. 인공동결공법은 지중에 매설된 동결관 내로 냉매를 순환시켜 대상 지반에 차수벽 및 지지체의 역할을 할 수 있는 동결벽체(frozen wall)를 형성한다. 본 연구에서는 해성 점토지반(marine clay)에 대한 인공동결공법 현장실증시험을 수행함으로서 인공동결공법에 따른 해성 점토지반에서의 동결속도(freezing rate)를 평가하였다. 현장실증시험은 지중에 3.2m 깊이로 매설된 동결관 내로 초저온 냉매인 액화질소를 순환시키는 방법으로 단일공 시험과 동결벽체 형성 시험을 수행하였다. 자동밸브를 통해 유출되는 액화질소의 온도를 일정하게 유지시켰으며, 동결과정에서 동결관 외벽 및 지중의 온도변화를 측정하였다. 시험결과, 단일공 시험은 부피가 약 $2.12m^3$인 원기둥 모양의 동결체를 형성하는데 총 3.5일 동안 약 11.9ton의 액화질소가 소요되었고, 동결벽체 형성 시험은 부피 약 $7.04m^3$의 동결벽체를 형성하는데 총 4.1일 동안 약 18ton의 액화질소가 소요된 것으로 산정되었다. 임의의 깊이에서 동결면적이 동결반경의 제곱에 비례하기 때문에 동결반경이 증가할수록 방사방향 1차원 동결속도가 감소하였고, 이를 바탕으로 방사방향 1차원 동결속도 예측식을 제시하였다.

Keywords

References

  1. Anderson, O. B. and Ladanyi, B. (2004). "Frozen ground engineering (Second edition)." Chichester: John & Wiley Sons., p. 363.
  2. Arenson, L. U. and Sego, D. C. (2006). "The effect of salinity on the freezing of coarse-grained sands." Canadian Geotechnical Journal, Vol. 43, No. 3, pp. 325-337. https://doi.org/10.1139/t06-006
  3. Crippa, C. and Manassero, V. (2006). "Artificial ground freezing at sophiaspoortunnel (The Netherlands) - Freezing parameters: Data acquisition and processing." Geo Congress 2006, Feb 26-Mar 1, Atlanta, Georgia, United States of America.
  4. Geng, P., Yan, Q.-X., He, C. and Wang, B. (2010). "Numerical simulation of underground construction by horizontal ground freezing method," Engineering Mechanics, Vol. 27, No. 5, pp. 122-127.
  5. Han, L., Ye, G., Li, Y., Xia, X. and Wang, J. (2016). "In situ monitoring of frost heave pressure during cross passage construction using ground-freezing method." Canadian Geotechnical Journal, Vol. 53, No. 3, pp. 530-539. https://doi.org/10.1139/cgj-2014-0486
  6. Konrad, J.-M. (2002). "Prediction of freezing-inducced movements for an underground construction project in Japan." Canadian Geotechnical Journal, Vol. 39, No. 6, pp. 1231-1242. https://doi.org/10.1139/t02-077
  7. Li, D. and Wang, H. (2010). "Investigation into artificial ground freezing technique for a cross passage in metro." GeoShanghai International Conference 2010, June 3-June 5, Shanghai, China.
  8. Liu, B., Li, D. and Chen, L. (2010). "Numerical simulation and measurement of freezing method applied to connected asile of subwat tunnels under complex conditions." Journal of Safety Science and Technology, Vol. 6, No. 5, pp. 11-17.
  9. Manassero, V., Salvo, G. D., Giannelli, F. and Colombo, G. (2008). "A combination of artificial ground freezing and grouting for the excavation of a large size tunnel below groundwater." 6th International Conferences on Case Histories in Geotechnical Engineering, Aug 11-Aug 16, Arlington, Virginia, United States of America.
  10. Papakonstantinou, S., Anagnostou, G. and Pimentel, E. (2013). "Evaluation of ground freezing data from the Naples subway." Geotechnical Engineering, Vol. 166, No. 3, pp. 280-298.
  11. Pimentel, E., Papakonstantinou, S. and Anagnostou, G. (2012). "Numerical interpretation of temperature distributions from three ground freezing applications in urban tunnelling." Tunnelling and Underground Space Technology incorporating Trenchless Technology Research, Vol. 28, No. 1, pp. 57-69. https://doi.org/10.1016/j.tust.2011.09.005
  12. Pimentel, E., Sres, A. and Anagnostou, G. (2012). "Large-scale laboratory tests on artificial ground freezing under seepage-flow conditions." Geotechnique, Vol. 62, No. 3, pp. 227-241. https://doi.org/10.1680/geot.9.P.120
  13. Qin, W., Yang, P., Jin, M., Zhang, T. and Wang, H. (2010). "Application and survey analysis of frrezing method applied to ultra-long cross-passage in metro tunnel." Chinese Journal of Underground Space and Engineering, Vol. 6, No. 5, pp. 1065-1071.
  14. Russo, G., Corbo, A., Cavuoto, F. and Autuori, S. (2015). "Artificial ground freezing to excavate a tunnel in sandy soil. Measurements and back analysis." Tunnelling and Underground Space Technology, Vol. 50, pp. 226-238. https://doi.org/10.1016/j.tust.2015.07.008
  15. Song, H., Cai, H., Yao, Z., Rong, C. and Wang, X. (2016). "Finite element analysis on 3D freezing temperature field in metro cross passage construction." Procedia Engineering, Vol. 165, pp. 528-539. https://doi.org/10.1016/j.proeng.2016.11.729
  16. Sun, C.-W. and Qiu, P.-Y. (2012). "Research on the freezing method applied to tunnel cross passage of the Guangzhou metro." Modern Tunnelling Technology, Vol. 49, No. 3, pp. 161-165.
  17. Yan, Q.-X. and Xu, F. (2012). "Thermal-soild coupling analysis of the connected of the cross aisle in metro constructed by horizontal freezing in ground." China Railway Science, Vol. 33, No. 1, pp. 54-59.