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Numerical Analysis of Thermal Effect on Axial Load and Pile Settlements in PHC Energy Piles

PHC 에너지파일의 열응력에 따른 축하중-침하 수치해석

  • Received : 2012.10.24
  • Accepted : 2013.05.02
  • Published : 2013.05.31

Abstract

This study investigates the effect of thermal stress on axial load and pile settlement of PHC energy piles. A series of numerical analyses were performed by controlling major influencing parameters such as pile arrangement, pile spacing, end-bearing condition, soil condition and pile cap stiffness. It is found that the characteristics of pile-load transfer are significantly affected by seasonal operation mode (i.e., cooling and heating) throughout the year. Also, the axial load under thermal loading increases with increasing the pile spacing. The settlement of the pile in sand is larger than that in clay because of the thermal stress generated. It is also found that thermal stress highly influences on the end-bearing pile, corner pile and rigidity of pile cap.

본 논문에서는 열응력에 따른 PHC 에너지파일의 축하중과 침하량의 변화를 수치해석을 통하여 분석하였다. 이를 위해 $3{\times}3$, $5{\times}5$ 배열 군말뚝 형태의 에너지파일을 말뚝 간격과 배치, 지반조건, 말뚝의 선단지지조건 및 말뚝 캡의 강성도 등의 조건으로 구분하여 수치해석을 수행하였다. 본 연구 결과 말뚝 중심 간격이 클수록 온도변화에 따른 말뚝의 축하중 차이가 크게 나타났고, 사질토지반이 점성토지반 보다 온도변화에 의한 침하량의 변화가 크게 나타났다. 또한, 에너지파일이 모서리부에 위치할 때 말뚝의 축하중 차이가 가장 크게 나타났으며, 말뚝의 선단이 암반에 지지된 경우 온도변화에 의한 축하중 변화가 더 크게 발생하여 침하량이 감소하는 것을 확인하였다. 말뚝 캡의 강성도에 대한 영향은 말뚝 캡의 강성이 커질수록 온도변화에 의한 침하량이 감소하는 것으로 나타났다.

Keywords

References

  1. Baek, S.K. (2004), A Study on geothermal heat pump system utilizing hollow piles, Doctoral Dissertation, Pusan National University.
  2. Bourne-Webb, B. Amatya, K. Soga, T. Amis, C. Davidson, and P. Payne (2009), "Energy pile test at Lambeth College, London: geotechnical and thermodynamic aspects of pile response to heat cycles", Geotechnique, Vol.59, Issue 3, pp.237-248. https://doi.org/10.1680/geot.2009.59.3.237
  3. COMSOL Multiphysics user's guide (2011), COMSOL Multiphysics version 4.2a.
  4. Knellwolf, C., Peron, H., and Laloui. L. (2011), "Geotechnical analysis of heat exchanger piles", Journal of Geotechnical And Geoenvironmental Engineering, Vol.137, No.10, pp.890-902. https://doi.org/10.1061/(ASCE)GT.1943-5606.0000513
  5. Engineeringtoolbox.com, 2005.
  6. Environmental Protection Agency (1993), Health Effects of Passive Smoking : Lung Cancer and Other Disorders.
  7. Hamada, Y., Saitoh, H., Nakamura, M., Kubota, H., and Ochifuji. K. (2007), "Field performance of an energy pile system for space heating", Energy and Buildings 39, pp.517-524. https://doi.org/10.1016/j.enbuild.2006.09.006
  8. Horikoshi, K. and Randolph, M.F. (1997), "On the definition of raft-soil stiffness ratio", Geotechnique, Vol.47, No.5, pp.1055-1061. https://doi.org/10.1680/geot.1997.47.5.1055
  9. Jeong, S.S. (1993), "Downdrag on a single pile and pile groups", Journal of the Korea Civil Engineers Society, Vol.13, No.4, pp. 259-268.
  10. Jeong, S.S., Song, J.Y., Min, H.S., and Lee, S.J. (2010), "Thermal influential factors of energy pile", Journal of the Korea Civil Engineers Society, Vol.30, No.6C, pp.231-239.
  11. Kim, Y.H. and Jeong, S.S. (2011), "Analysis of soil resistance on laterally loaded piles based on 3D soil-pile interaction", Computers and Geothechnics, Vol.38, No.2, pp.248-257. https://doi.org/10.1016/j.compgeo.2010.12.001
  12. Laloui, L., Moreni, M., Fromentin, A., Pahud, D., and Vulliet, L. (1999), "In-situ thermo-mechanical load test on a heat exchanger pile", 4th International Conference on DEEP FOUNDATION PRACTICE, pp.273-279.
  13. Ministry of Land, Infrastructure and Transport (2010), Development of closed vertical loop ground heat exchanger systems for utilizing geothermal heating and cooling system, Ministry of Land, Infrastructure and Transport.
  14. Ministry of Trade, Industry and Energy (2006), The Development of Ground Heat Exchangers that are More Efficiency and Lower Price, Ministry of Trade, Industry and Energy.
  15. Min, H.S., Yun, T.S., and Jeong, S.S. (2011), "Effect of group spacing of energy piles on thermal analysis", Journal of the Korean Geotechnical Society, Vol.27, No.8, pp.39-50. https://doi.org/10.7843/kgs.2011.27.8.039
  16. Min, S.H., Lee, C.H., Park, M.S., Koh, H.S., and Choi, H.S. (2010), "Numerical study of heat transfer efficiency, performance and mechanical behavior induced by thermal stress of energy Pile", Journal of Korea Society of Geothermal Energy Engineers, Vol.6, No.2, pp.9-13.
  17. Paek, J.Y., Cho, J.Y., Jeong, S.S., and Hwang, T.J. (2012), "Shaft group efficiency of friction pile groups in deep soft clay", Journal of the Korea Civil Engineers Society, Vol.32, No.2C, pp.49-60.
  18. Song, J.Y. (2011), A Study on the Influence Factors of PHC Energy Piles based on Thermal and Structural Characteristics, Master's Dissertation, Yonsei University.
  19. Wallace, J. W., Fox, P. J., and Stewart, J. P. (2002), "A simplified approach for settlement analysis of single pile and pile groups considering interaction between identical piles in multilayered soils", Computers and Geotechnics, Vol.27, No.8, pp.969-976.
  20. Woo, S.W., Kim, J.H., Shin, S.H., and Hwang, K.I. (2007), "The Comparison of the EWT and LWT between Field Measurement and CFD of Vertical-type Geothermal Heat Exchanger", Journal of Korea Society of Geothermal Energy Engineers, Vol.3, No.1, pp.11-16.
  21. Yu, H.K. (2008), "Development and Performance Evaluation of Ground Heat Exchanger Utilizing PHC Pile Foundation of Building", Journal of the Korean Solar Energy Society, Vol.28, No.5, pp. 56-64.

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