한국지반공학회논문집 (Journal of the Korean Geotechnical Society)

  • 제33권2호
  • /
  • Pages.17-26
  • /
  • 2017
  • /
  • 1229-2427(pISSN)
  • /
  • 2288-646X(eISSN)
한국지반공학회 (Korean Geotechnical Society)
권호 표지
DOI QR코드

DOI QR Code

모래지반에서 횡방향 반복하중을 받는 말뚝의 영구수평변위 평가

Evaluation of Permanent Lateral Displacement of a Cyclic Laterally Loaded Pile in Sandy Soil

  • 백성하 (서울대학교 건설환경공학부) ;
  • 김준영 (서울대학교 공학연구소) ;
  • 이승환 (서울대학교 공학연구소) ;
  • 정충기 (서울대학교 건설환경공학부)
  • 투고 : 2016.11.16
  • 심사 : 2017.01.16
  • 발행 : 2017.02.28
PDF 다운로드
⟨ 이전 논문 다음 논문 ⟩

초록

해상구조물, 송전탑 등을 지지하는 말뚝기초는 바람, 조류, 파랑 등의 영향으로 횡방향 반복하중을 지배적으로 받으며, 이는 말뚝 주변 지반에 영구수평변위를 발생시켜 구조물의 안정성 및 기능성을 저해한다. 본 연구에서는 횡방향 반복하중에 의해 발생하는 말뚝의 영구수평변위를 평가하기 위하여, 서로 다른 세 가지 상대밀도(40%, 70%, 90%)로 조성된 건조 및 포화 모래지반에서 모형말뚝시험을 수행하였다. 모형시험 결과, 모든 시험조건에서 말뚝에 재하 된 횡방향 반복하중은 말뚝 주변 지반에 영구수평변위를 발생시켰다. 누적된 영구수평변위의 크기는 말뚝에 재하되는 횡방향 반복하중의 크기 및 재하횟수가 증가함에 따라 증가하였지만, 1회 재하로 인하여 발생되는 영구수평변위의 증가량은 점차 감소하였다. 또한, 말뚝에 발생하는 영구수평변위는 지반의 상대밀도가 클수록 작게 발생하고, 지반이 포화되면 크게 발생되는 것으로 평가되었다. 추가적으로, 누적 영구수평변위를 최초 재하 시 발생한 영구수평변위로 정규화한 영구수평변위를 평가하였으며, 이를 모래지반의 상대밀도, 횡방향 반복하중의 재하횟수에 관한 식으로 나타내었다.

Pile foundations that support offshore structures or transmission towers are dominantly subjected to cyclic lateral loads due to wind and waves, causing permanent displacement which can severely affect stability of the structures. In this study, a series of cyclic lateral load tests were conducted on a pre-installed aluminum flexible pile in sandy soil with three different relative densities (40%, 70% and 90%) in order to evaluate the permanent displacement of a cyclic laterally loaded pile. Test results showed that the cyclic lateral loads accumulated the irreversible lateral displacement, so-called permanent displacement. As the number of cyclic lateral load increased, accumulated permanent displacement increased, but the permanent displacement due to one loading cycle gradually decreased. In addition, the permanent displacement of a pile increased with decrement of relative density and decreased by soil saturation. From the test results, the normalized permanent displacement defined as the cumulative permanent displacement to the initial permanent displacement ratio was investigated, and empirical equations for predicting the normalized permanent displacement was developed in terms of relative density of the soil and the number of cyclic lateral load.

키워드

참고문헌

  1. Achumus, M., Kuo, Y.S., and Abdel-Rahman, K. (2009), "Behavior of Monopile Foundations under Cyclic Lateral Load", Computer and Geotechnics, Vol.36, pp.725-735. https://doi.org/10.1016/j.compgeo.2008.12.003
  2. Ameircan Petroleum Institute (2007), Recommended practice for planning, designing and constructing fixed offshore platformsworking stress design: API recommended practice 2A-WSD (RP 2A-WSD), API.
  3. Baek, S.H., Kim, J.Y., Lee, S.H., and Chung, C.K. (2016), "Effect of Relative Density on Lateral Load Capacity of a Cyclic Laterally Loaded Pile in Sandy Soil", J. of the Korean Geotechnical Society, Vol.32, No.4, pp.41-49 (in Korean). https://doi.org/10.7843/kgs.2016.32.4.41
  4. Barton, Y.O. (1979), "Lateral Loading of Model Piles in the Centrifuge", M.Phil. Thesis, University of Cambridge.
  5. Davidson, H.L., Cass, P.G., Khilji, K.H., and McQuade, P.V. (1982), Laterally loaded drilled pier research, Report EL-2197, EPRI, 324p.
  6. Fleming, W.G., Weltman, A.J., Randolph, M.F., and Elson, W.K. (1992), Piling Engineering, 2nd ed., John Wiley and Sons Inc., New York.
  7. Hettler, A. (1981), "Verschiebungen Starrer und Elastischer Grundungskorper in Sand bei Monotoner und Zyklischer Belastung", Ph.D. Thesis, University of Karlsruhe.
  8. Hoadley, P.J., Barton, Y.O., and Parry, R.H.G. (1981), "Cyclic Lateral Load on Model Pile in a Centrifuge", 10th International Conference on Soil Mechanics and Foundation Engineering, Stockholm, pp.621-625.
  9. Iai, S. (1989), "Similitude for Shaking Table Tests on Soil-structure-Fluid Model in 1g Gravitational Field", Soil and Foundations, Vol.29, No.1, pp.105-118. https://doi.org/10.3208/sandf1972.29.105
  10. LeBlanc, C., Houlsby, G.T., and Byrne, B.W. (2010), "Response of Stiff Piles in Sand to Long-term Cyclic Lateral Loading", Geotechnique, Vol.60, No.2, pp.79-90. https://doi.org/10.1680/geot.7.00196
  11. Lin, S.S. and Liao, J.C. (1999), "Permanent Strains of Piles in Sand due to Cyclic Lateral Loads", J. of Geotechnical and Geoenvironmental Eng., ASCE, Vol.125, No.9, pp.798-802. https://doi.org/10.1061/(ASCE)1090-0241(1999)125:9(798)
  12. Little, R.L. and Briaud, J.L. (1988), "Full Scale Cyclic Lateral Load Tests on Six Single Piles in Sand", Miscellaneous paper GL-88-27, Geotechnical Division, Texas A&M University, Texas.
  13. Long, J. and Vanneste, G. (1994), "Effect of Cyclic Lateral Loads on Piles in Sand", J. of Soil Mechanics and Foundation Division, ASCE, Vol.120, No.1, pp.225-244.
  14. Meyerhof, G.G., Mathur, S.K., and Valsangkar, A.J. (1981), "Lateral Resistance and Deflection of Rigid Wall and Piles in Layered Soils", Canadian Geotechnical Journal, Vol.18, pp.159-170. https://doi.org/10.1139/t81-021
  15. Nicolai and Ibsen (2014), "Small-scale Testing of Cyclic Laterally Loaded Monopiles in Dense Saturated Sand", J. of Ocean and Wind Energy, Vol.1, No.4, pp.240-245.
  16. Nunez, I.L. (1988), "Driving and Tension Loading of Piles in Sand on a Centrifuge", Proceeding International Conference Centrifuge 88, Paris, Corte, J.K. (ed.), Balkema, Rotterdam, pp.353-362.
  17. Paik, K.H. (2010), "Lateral behavior of Driven Piles Subjected to Cyclic Lateral Loads in Sand", J. of the Korean Geotechnical Society, Vol.26, No.12, pp.41-50 (in Korean).
  18. Paik, K.H. and Park, W.W. (2010), "Permanent Deformation of Piles in Sand under Cyclic Lateral Laods", J. of the Korean Geotechnical Society, Vol.26, No.11, pp.63-73 (in Korean).
  19. Poulos, H.G. and Davis, E.H. (1980), Piling foundation analysis and design, John Wiley and Sons Inc., New York.
  20. Rao, S.N., Ramakrishna, V.G.S.T., and Rao, M.B. (1998), "Influence of Rigidity on Laterally Loaded Pile Groups in Marine Clay", Journal of Geotechnical and Geoenvironmental Engineering, Vol. 124, No.6, pp.542-549. https://doi.org/10.1061/(ASCE)1090-0241(1998)124:6(542)
  21. Rosquoet, F., Thorel, L., Garnier, J., and Canepa, Y. (2007), "Lateral Cyclic Loading of Sand-installed Piles", Soils and Foundations, Vol.46, No.5, pp.821-832.
  22. Yang, E.K. (2009), "Evaluation of Dynamic p-y Curves for a Pile in Sand from 1g Shaking Table Tests", Ph.D. Thesis, Seoul National University.