Journal of the Korean Geotechnical Society (한국지반공학회논문집)

Korean Geotechnical Society (한국지반공학회)
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Skin Friction and End Bearing Resistances of Rock-socketed Piles Observed in Bi-directional Pile Load Tests

양방향 재하시험 결과를 이용한 암반소켓 현장타설말뚝의 주면 마찰력과 선단 지지력

  • Song, Myung-Jun (R&D Division, Hyundai Engrg. and Construction Co. Ltd.) ;
  • Park, Yung-Ho (R&D Division, Hyundai Engrg. and Construction Co. Ltd.) ;
  • Kim, Myoung-Mo (Dept. of Civil and Environmental Engrg., Seoul National Univ.)
  • 송명준 (현대건설 연구개발본부) ;
  • 박영호 (현대건설 연구개발본부) ;
  • 김명모 (서울대학교 공과대학 건설환경공학부)
  • Received : 2013.03.06
  • Accepted : 2013.07.02
  • Published : 2013.07.31
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Abstract

In this paper, the empirical relations of skin friction and end bearing resistance with the results of site investigation in soft rock are proposed through the analysis of bi-directional pile load tests of rock socketed drilled shafts performed at large offshore bridge foundations and high-rise building projects (13 test piles in 4 projects). The site investigation and drilling for bi-directional pile load tests were performed at the centers of test piles, and f-w curves for skin friction and q-w curves for end bearing were plotted based on load-transfer measurements. From the above curves, the empirical relations of skin friction and end bearing resistance with the results of site investigation depending on the mobilized displacement are determined by multiple regression analysis and compared with previous studies. Since the f-w and q-w curves of rock-socketed piles in Korea show hardening behavior according to mobilized displacement, the developed empirical relations by the mobilized displacement are more reasonable than those of previous studies which could not consider the mobilized displacement and suggested the ultimate capacity with unconfined compressive strength only. Particularly, the developed equations correlated with unconfined compressive strength show the best correlations among the equations correlated with other parameters.

본 연구에서는 해상 교량 현장과 초고층빌딩 현장에서 실시한 암반에 근입된 대구경 현장타설말뚝의 양방향 재하시험(총 4개 현장, 13개 말뚝) 결과를 분석하여 연암에서의 주면마찰력과 선단지지력 산정을 위한 경험식을 제안하였다. 양방향 재하시험을 위하여 각 시험 말뚝의 정 중앙 위치에서 시추 및 지반조사가 이루어졌으며, 각 말뚝에 부착한 계측장치로부터 얻은 데이터를 이용하여 주면의 f-w 곡선과 선단의 q-w 곡선을 작성하였다. 이 곡선들로부터 - 지반조사결과들과 주면마찰력 및 선단지지력에 대한 다중회귀분석을 실시하여 - 변위에 따른 극한 주면마찰력과 선단지지력 산정식을 제안하였으며, 이 결과를 기존의 경험식들과 비교 분석하였다. 변위가 증가할수록 지지력이 증가하는 국내 암반의 f-w 곡선과 q-w 곡선의 특성상, 다양한 말뚝 변위기준에 따라 제안한 경험식들이 변위와 무관하게 일정한 극한값으로 제안된 기존의 경험식들보다 더 합리적인 것으로 판단된다. 본 연구의 제안식들 중에서 일축압축강도의 함수로 나타낸 주면마찰력 및 선단지지력에 대한 제안식이 다른 지반정수들에 의한 경험식보다 좋은 상관관계를 보여주는 것으로 나타났다.

Keywords

References

  1. Abdelrazaq, A., Poulos, H. G., Badelow, F., and Kim, S. H. (2011), Foundation Design and Pile Testing Program for the 151 Story Incheon Tower in Reclamation Area, Proceedings of the 7th International Conference on Tall Buildings, Incheon, Korea, pp.815-823.
  2. AASHTO (1996), Standard Specifications for Highway Bridges. (16th Ed.), American Association of State Highway and Transportation Officials, Washington, D.C.
  3. CGS (1992), Canadian Foundation Engineering Manual. (3nd Ed.), Canadian Geotechnical Society, Ottawa, Canada.
  4. GEO (2006), Foundation Design and Construction, Geotechnical Engineering Office, Hong Kong.
  5. Horvath, R. G. and Kenney, T. C. (1979), "Shaft Resistance of Rock-Socketed Drilled Piers", Proceedings, Symposium on Deep Foundations, ASCE, Atlanta, Georgia, pp.182-214.
  6. Kim, M. M. (2007), "The Bi-directional Pile Load Test", Workshop in commemoration of the establishment of the ATC-18 Mega foundation, KGS pile foundation committee, Seoul, Korea, pp.89-98.
  7. Korean Geotechnical Society (2003), Korea structure and foundation design specification (KSFDS), pp.348-350.
  8. Kwon, O. S. (2004), Effect of rock mass weathering on resistant behavior of drilled shaft socketed into weathered rock, Ph.D. Dissertation, Seoul University, Seoul.
  9. Ng, C.W.W., Yau, T.L.Y., Li, J.H.M., and Tang, W. H. (2001), "Side resistance of large diameter bored piles socketed into decomposed rocks", Journal of Geotechnical and Geoenvironmental Engineering, American Society of Civil Engineers, 127(8), pp.642-657. https://doi.org/10.1061/(ASCE)1090-0241(2001)127:8(642)
  10. Osterberg, J.O. (1998), "The Osterberg load test method for bored and driven piles the first ten years", Proceedings of the 7th International Conference on Piling and Deep Foundations, Vienna, pp.1-11.
  11. Osterberg, J.O. (2001), "Load testing high capacity piles what have we learned?", Proceedings of the 5th international conference on deep foundation practice, Singapore.
  12. Peck, R. B., Hanson, W. E., and Thornburn, T. H. (1974), Foundation Engineering (2nd ed.), John Wiley and Sons, New York, pp.361-374.
  13. Rosenberg, P. and Journeaux, N. L. (1976), "Friction and End Bearing Tests on Bedrock for High Capacity Socket Design", Canadian Geotechnical Journal, Vol.13, pp.324-333. https://doi.org/10.1139/t76-033
  14. Rowe, R. K. and Armitage, H. H. (1987), "A Design Method for Drilled Piers in Soft Rock", Canadian Geotechnical Journal, Vol.24, pp.126-142. https://doi.org/10.1139/t87-011
  15. Seol, H.I. (2007), Load Transfer Analysis of Rock-Socketed Drilled Shafts by considering Coupled Soil Resistance, Ph.D. Dissertation, The Graduate School Yonsei University Department of Civil Engineering, Seoul, Korea, pp.93-95.
  16. Serrano, A. and Olalla, C. (2002), "Ultimate bearing capacity at the tip of a pile in rock - part 1: theory", International Journal of Rock Mechanics and Mining Science & Geomechanics Abstracts, 39(7), pp.883-846.
  17. Song, M. J., Park, Y. H., and Kim, D. J. (2005), "Preliminary Load Tests for the Design of Large Diameter Drilled Shaft by Bi-directional Loading Method at Toe", KGS Spring Conference, Jeju, Korea, pp.89-98.
  18. Song, M. J., Kim, D. J., Park, Y. H., and Cho, S. (2006), "Joint Pile Load Tests by Multi Level Bi-directional Test Method for Incheon Bridge", KGS Fall Conference, Daegu, Korea, pp.689-697.
  19. Williams, A. F. and Pells, P. J. N. (1981), "Side Resistance of Rock Sockets in Sandstone, Mudstone, and Shale", Canadian Geotechnical Journal, Vol.18, pp.502-513. https://doi.org/10.1139/t81-061
  20. Vipulanandan, C., Hussain, A., and Usluogulari, O. (2007), "Parametric study of open core-hole on the behavior of drilled shafts socketed in soft rock", In Contemporary Issues in Deep Foundations: Proceedings of Geo-Denver 2007, Geotechnical Special Publication No.158, pp.18-21.
  21. Zhang, L. and Einstein, H. H. (1998), "End Bearing Capacity of Drilled Shafts in Rock", Journal of the Geotechnical and Geoenvironmental Engineering, ASCE, Vol.124, No.7, pp.574-584. https://doi.org/10.1061/(ASCE)1090-0241(1998)124:7(574)

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