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Effects of Loading Method on the Behavior of Laterally Cyclic Loaded Piles in Sand

모래지반에서 재하방법이 반복수평하중을 받는 말뚝의 거동에 미치는 영향

  • Received : 2010.10.13
  • Accepted : 2010.11.15
  • Published : 2011.03.31

Abstract

The behavior of laterally cyclic loaded piles is affected by the magnitude and number of cycles of cyclic lateral loads as well as loading method (1-way or 2-way loading). In this study, calibration chamber tests were carried out to investigate the effects of loading method of cyclic lateral loads on the behavior of piles driven into sand. Results of the chamber tests show that the permanent lateral displacement of 1-way cyclic loaded piles is developed in the same direction as the first loading, whereas that of 2-way cyclic loaded piles is developed in the reverse direction of the first loading. 1-way cyclic lateral loads cause a decrease of the ultimate lateral load capacity of piles, and 2-way cyclic lateral loads cause an increase of the ultimate lateral load capacity of piles. The change of ultimate lateral load capacity with loading method of cyclic lateral loads increases with increasing number of cycles. It is also observed that the 1-way cyclic loads generate greater maximum bending moment than 2-way cyclic loads for piles in cyclic loading step and generates smaller maximum bending moment for piles in the ultimate state. It can be attributed to the difference in compaction degree of the soil around the piles with loading method of cyclic lateral loads. In addition, it is founded that 1-way and 2-way cyclic lateral loads cause a decrease in the maximum bending moment of piles in the ultimate state compared with that of piles subjected to only monotonic loads.

반복수평하중을 받는 말뚝의 거동은 반복하중의 크기와 재하횟수 뿐만 아니라 반복하중의 재하방법(한방향 또는 양방향 재하)에도 영향을 받는다. 본 연구에서는 반복수평하중의 재하방법이 모래지반에 타입된 항타말뚝의 거동에 미치는 영향을 조사하기 위해서 가압토조를 이용한 모형말뚝재하시험을 수행하였다. 실험결과에 따르면 반복수평하중을 한방향으로 받는 말뚝의 누적 영구수평변위는 최초 재하방향과 같은 방향으로 발생하지만, 반복하중을 양방향으로 받는 말뚝의 영구수평변위는 최초 재하방향과 반대 방향으로 발생하였다. 그리고 이와 같은 반복하중의 재하방법에 따른 말뚝 영구수평변위의 변화로 인해 한방향 반복재하는 말뚝의 반복극한수평지지력을 감소시키고 양방향 반복 재하는 말뚝의 반복극한수평지지력을 증가시켰으며, 수평하중의 반복재하횟수가 많아질수록 하중의 재하방법에 따른 말뚝의 반복극한수평지지력 차이는 더욱 확대되었다. 또한 반복수평하중의 재하방법에 따른 말뚝 주변지반의 다짐도 차이로 인해 수평하중이 반복재하되는 동안 말뚝에 발생하는 최대 휨모멘트는 반복하중이 양방향보다 한방향으로 재하되는 경우에 더 크게 나타났다. 그러나 극한상태에서 말뚝에 발생한 최대 휨모멘트는 반복하중이 한방향보다 양방향으로 재하된 경우에 그리고 반복재하를 받은 경우보다 그렇지 않은 경우에 더 큰 것으로 조사되었다.

Keywords

Acknowledgement

Supported by : 한국연구재단

References

  1. Barton, Y. O. (1982), Laterally loaded model piles in sand, centrifuge tests and finite element analyses, Ph.D. Thesis, Univ. of Cambridge.
  2. Broms, B. B. (1964), "Lateral resistance of piles in cohesionless soils", J. of Soil Mech. and Found. Eng., ASCE, Vol.90, No.SM3, pp.123-156.
  3. Brown, D. A., Morrison, C. and Reese, L. C. (1988). "Lateral load behavior of pile group in sand", J. of Geotech. Eng., ASCE, Vol.114, No.11, pp.1261-1276. https://doi.org/10.1061/(ASCE)0733-9410(1988)114:11(1261)
  4. Davidson, H. L., Cass, P. G., Khilji, K. H., and McQuade, P. V. (1982), Laterally loaded drilled pier research, Report EL-2197, EPRI, 324p.
  5. Davisson, M. T., and Salley, J. R. (1970), "Model study of laterally loaded piles", J. of Soil Mech. and Found. Eng., ASCE, Vol.96, No.5, pp.1605-1627.
  6. Lin, S. -S., and Liao, J. -C. (1999), "Permanent strains of piles in sand due to cyclic lateral loads", J. of Geotech. and Geoenviron. Eng., ASCE, Vol.125, No.9, pp.798-802. https://doi.org/10.1061/(ASCE)1090-0241(1999)125:9(798)
  7. 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, Geotech. Div., Texas A&M Univ., College Station, Texas, 30p.
  8. Long, J. H., and Vanneste, G. (1994), "Effect of cyclic lateral loads on piles in sand", J. of Geotech. Eng., ASCE, Vol.120, No.1, pp.225-244. https://doi.org/10.1061/(ASCE)0733-9410(1994)120:1(225)
  9. Matlock, H. (1974), "Correlations for design of laterally loaded piles in soft clay", Paper No.1204, Proc. of the 2nd Annual Offshore Technology Conf., Houston, Texas, May, pp.577-594.
  10. 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 J., Vol.18, pp.159-170. https://doi.org/10.1139/t81-021
  11. O'Neill, M. W., and Murchison, J. M. (1983), An evaluation of p-y relationships in sands, Research Report No. GT-DF02-83, Univ. of Houston, Houston, Texas.
  12. Parry, R. H. G., and Sanglamer, A. (1977), Lateral load tests on single model piles with radiographic observations, Cambridge Univ. Interim Report, CUED/C, Soils TR 36.
  13. Prakash, S. (1961), Behavior of pile groups subjected to lateral loads, Thesis, Univ. of Illinois, Urbana, 218p.
  14. Reese, L. C., Cox, W. R., and Koop, F. D. (1974), "Analysis of laterally loaded piles in sand", Paper No.2080, Proc. of the 6th Annual Offshore Technology Conf., Vol. 2, Houston, Texas, pp. 225-244.
  15. Rollins, K. M., Olsen, R. J., Egbert, J. J., Jensen, D. H., Olsen, K. G., and Garrett, B. H. (2006), "Pile spacing effects on lateral pile group behavior: load tests", J. of Geotech. and Geoenviron. Eng., ASCE, Vol.132, No.10, pp.1262-1271. https://doi.org/10.1061/(ASCE)1090-0241(2006)132:10(1262)
  16. Rosquoet, F., Thorel, L., Garnier, J., and Canepa, Y. (2007), "Lateral cyclic loading of sand-installed piles", Soils and Foundations, Vol.47, No.5, pp.821-832. https://doi.org/10.3208/sandf.47.821
  17. Vucetic, M., and Dobry, R. (1988), "Degradation of marine clays under cyclic loading", J. of Geotech. Eng., ASCE, Vol.114, No.2, pp.133-149. https://doi.org/10.1061/(ASCE)0733-9410(1988)114:2(133)