한국지반공학회논문집 (Journal of the Korean Geotechnical Society)

  • 제32권4호
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  • Pages.41-49
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  • 2016
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  • 1229-2427(pISSN)
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  • 2288-646X(eISSN)
한국지반공학회 (Korean Geotechnical Society)
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모래지반의 상대밀도에 따른 횡방향 반복재하 시 말뚝의 극한지지력 평가

Effect of Relative Density on Lateral Load Capacity of a Cyclic Laterally Loaded Pile in Sandy Soil

  • 백성하 (서울대학교 건설환경공학부) ;
  • 김준영 (서울대학교 공학연구소) ;
  • 이승환 (서울대학교 건설환경공학부) ;
  • 정충기 (서울대학교 건설환경공학부)
  • 투고 : 2016.03.04
  • 심사 : 2016.04.16
  • 발행 : 2016.04.29
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초록

해상구조물을 지지하는 말뚝기초는 바람, 조류, 파랑 등의 영향으로 횡방향 반복하중을 지배적으로 받는다. 본 연구에서는 횡방향 반복하중이 말뚝의 횡방향 극한지지력에 미치는 영향을 평가하기 위하여, 서로 다른 세 가지 상대밀도(40%, 70%, 90%)로 조성된 모래지반에서 모형말뚝시험을 수행하였다. 상대밀도 40%로 조성 된 모래지반에서는 횡방향 반복재하 시 말뚝 주변 지반이 조밀해짐에 따라 횡방향 극한지지력이 증가하였다. 반면, 상대밀도 70%와 90%로 조성 된 모래지반에서는 횡방향 반복재하 시 말뚝 주변 지반의 교란효과로 인하여 횡방향 극한지지력이 감소하였다. 이러한 횡방향 극한지지력의 증가 및 감소효과는 횡방향 반복하중의 크기가 커질수록 더욱 명확하게 나타났으며, 모래지반의 포화 여부에는 큰 영향을 받지 않았다. 모형시험 결과를 활용하여 모래지반의 상대밀도, 횡방향 반복하중의 크기에 따른 말뚝의 횡방향 극한지지력 산정 식을 제안하였고, 이를 횡방향 반복하중을 지배적으로 받는 말뚝의 설계 시 활용 가능하도록 하였다.

Pile foundations used as offshore support structures are dominantly subjected to cyclic lateral loads due to wind and waves. In this study, a series of cyclic lateral load tests were performed on a pre-installed aluminum flexible pile in sandy soil with three different relative densities (40%, 70% and 90%) in order to evaluate the effect of cyclic lateral loads on lateral load capacity of a pile. The cyclic lateral loads increased the lateral load capacity of a pile at 40% relative density, whereas they decreased it at 70% and 90% relative densities. This can be explained by the fact that the cyclic lateral loads slightly densified the surrounding soil in relatively loose sand (40%), while the surrounding soil was disturbed in relatively dense sand (70% and 90%). These effects were more obvious as the cyclic lateral load amplitude increased, being independent with the saturation. Also, from the test results, an empirical equation for the lateral load capacity of a cyclic laterally loaded pile in sandy soil was developed in terms of relative density of the soil and the cyclic lateral load amplitude.

키워드

참고문헌

  1. Baek, S.H., Kim, J.Y., Lee, S.H., and Chung, C.K. (2014), "Effect of Relative Density of p-y Backbone Curves for Cyclic Lateral Load on Pile Foundations in Sandy Soil", Proceeding of 33rd OMAE conference, San Francisco, Vol.3, pp.1-6.
  2. Barton, Y.O. (1979), "Lateral Loading of Model Piles in the Centrifuge", M.Phil. Thesis, University of Cambridge.
  3. Barton, Y.O. (1982), "Laterally Loaded Model Piles in Sand: Centrifuge Tests and Finite Element Analyses", Ph.D. Thesis, University of Cambridge.
  4. Broms, B.B. (1964), "Lateral Resistnace of Piles in Cohesive Soils", J. of Soil Mechanics and Foundation Division, ASCE, Vol. 90, No.2, pp.27-64
  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. 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.
  8. 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.
  9. 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
  10. 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.
  11. 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
  12. 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.
  13. 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.
  14. 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).
  15. Paik, K.H., Kim, Y.J., and Lee, S.Y. (2011), "Effects of Loading Method on the behavior of Laterally Cyclic Loaded Piles in Sand", J. of the Korean Geotechnical Society, Vol.27, No.3, pp.63-73 (in Korean). https://doi.org/10.7843/kgs.2011.27.3.063
  16. Parry, R.H.G. and Sanglamer, A. (1977), Laterally load tests on single model piles with radiographic observations, Cambridge University Interim Report, CUED.C, Soils TR 36.
  17. Poulos, H.G. and Davis, E.H. (1980), Piling foundation analysis and design, John Wiley and Sons Inc., New York.
  18. 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)
  19. Zhang, L., Silva, F., and Grismala, R. (2005), "Ultimate Lateral Resistance to Pile in Cohesionless Soils", J. of Geotechnical and Geoenvironmental Engineering, ASCE, Vol.131, No.1, pp.78-83. https://doi.org/10.1061/(ASCE)1090-0241(2005)131:1(78)