Journal of the Korean GEO-environmental Society (한국지반환경공학회 논문집)

Korean Geo-Environmental Society (한국지반환경공학회)
권호 표지
DOI QR코드

DOI QR Code

A Study on the Negative Skin Friction based on Measurements from Existing Works Analysed by 3D Finite Element Analyses

기발표 실측치 분석을 기반으로 한 3차원 유한요소해석 수행을 통한 부마찰에 관한 연구

  • Jeon, Sang Joon (Department of Civil Engineering, Kangwon National University) ;
  • Jeon, Young Jin (Department of Civil Engineering, Kangwon National University) ;
  • Jeon, Seung Chan (Civil Engineering Division, Dongbu Engineering & Construction Corporation) ;
  • Lee, Cheol Ju (Department of Civil Engineering, Kangwon National University)
  • Received : 2020.05.11
  • Accepted : 2020.07.13
  • Published : 2020.08.01
Download PDF
⟨ Previous Next ⟩

Abstract

In the current paper, a series of advanced 3D finite element analyses have been performed on existing pieces of work of negative skin friction from a geotechnical centrifuge test and full-scale field measurements. From these analyses, key features of pile behaviour under the influence of negative skin friction which, previously, were not fully understood in existing studies, have been meticulously discussed. As such, it has been possible to successfully address several numerical modelling issues such as negative skin friction induced pile settlements and group effects (the shielding effect), the effect of sacrificial piles in groups and the interaction between the pile head and the cap, the effect of interface elements at the pile-soil interface and the time-dependent pile behaviour. During a geotechnical centrifuge test, substantial amounts of negative skin frictions were mobilised when centrifugal acceleration increased from 1g to a certain g-level due to an increase in the self-weight of soil. The behaviour of piles inside a group were heavily affected by the sacrificial piles and the connectivity between the pile head and the pile cap. In particular, as negative skin friction has time dependent qualities associated with consolidation, it was logical to perform coupled analyses when analysing piles in consolidating grounds. From the current work, several insufficiencies of previous researches have been addressed, and the engineering pile behaviour subjected to negative skin friction has been clarified.

본 연구에서는 말뚝에 작용하는 부마찰과 관련된 원심모형실험 및 실규모 현장실험 등 기발표 자료에 대한 고등3차원 유한요소해석을 수행하였다. 이를 통해 기존연구에서는 충분히 고려되지 못했던 부마찰이 작용하는 말뚝의 거동 특성을 상세히 분석하였다. 즉 수치해석을 통해 기존연구에서는 고려하지 못했던 부마찰에 의한 말뚝의 침하와 군효과, 군말뚝에서 희생말뚝의 영향과 말뚝두부와 기초판 사이의 상호거동, 말뚝-인접지반의 경계면 요소(interface element)의 유무 및 시간 의존적인 부마찰의 발생특성 등 다양한 요소들을 분석할 수 있었다. 원심모형실험의 경우 중력가속도가 1g에서 특정한 값으로 증가하는 경우 흙의 자중 증가로 인해 말뚝에 비교적 큰 부마찰이 발생하는 것을 확인하였다. 군말뚝의 경우 희생말뚝 유무 및 말뚝두부와 기초판과의 연결여부에 따라 말뚝의 거동이 크게 영향을 받는 것으로 나타났다. 특히 부마찰은 압밀과 관련된 시간의존적 특성을 가지므로 압밀이 진행 중인 말뚝의 거동을 분석할 경우 압밀을 고려한 해석을 수행하는 것이 합리적인 것으로 분석되었다. 이러한 일련의 고찰을 통하여 기존연구의 한계를 적절하게 보완하면서 부마찰을 받는 말뚝의 거동을 명확히 분석할 수 있었다.

Keywords

References

  1. Brinkgreve, R. B. J., Kumarswamy, S. and Swolfs, W. M. (2015), Reference Manual, Plaxis 3D 2015 user's manual (Edited by Brinkgreve, R. B. J., Kumarswamy, S. and Swolfs, W. M.), pp. 1-248.
  2. Craig, W. H. (1984), Installation studies for model piles, Proc. The application of Centrifuge Modelling to Geotechnical Design, pp. 440-455.
  3. Combarieu, O. (1985), Frottement negatif sur les pieux, Rapport de recherche LPCN 136, Laboratire Centrale Des Ponts et Chaussees, pp. 1-151.
  4. Fioravante, V., Jamiolkowski, M. and Pedroni, S. (1994), Modelling the behaviour of piles in sand subjected to axial load. Proc. International Conference, Centrifuge 94, Rotterdam: Balkema, pp. 455-460.
  5. Kim, S. H. (2017), A study on the Engineering Characteristics of Negative Skin Friction and Prebored Precast Piles by Considering the Interactions at the Pile-Soil Interface, Mater's thesis, Kangwon National University, pp. 1-103 (In Korean).
  6. Lee, C. J., Chen, H. T. and Wong, W. H. (1998), Negative skin friction on a pile due to excessive ground water withrawal, Centrifuge 98, Balkema, Rotterdam, pp. 513-518.
  7. Lee, C. J. (2001), The influence of negative skin friction on piles and in pile groups, PhD thesis, Cambridge University, pp. 1-R13.
  8. Lee, C. J., Bolton, M. D. and Al-Tabbaa, A. (2002), Numerical modelling of group effects on the distribution of dragloads in piles foundations, Geotechnique, Vol. 52, No. 5, pp. 325-335. https://doi.org/10.1680/geot.52.5.325.38704
  9. Lee, C. J. and Charles, W. W. Ng (2004), Development of downdrag on piles and pile groups in consolidation soil, Journal of Geotechnical and Geoenvironmental Engineering, ASCE, Vol. 130, No. 9, pp. 905-914. https://doi.org/10.1061/(ASCE)1090-0241(2004)130:9(905)
  10. Lee, C. J., Lee, J. H. and Jeong, S. S. (2006), The influence of soil slip on negative skin friction in pile groups connected to cap, Geotechnique, Vol. 56, No.1, pp. 53-56. https://doi.org/10.1680/geot.2006.56.1.53
  11. Lee, C. J. (2009a), A study of the influence of negative skin friction on single piles from consolidation analyses, Journal of the Korean Geo-Environmental Society, Vol. 10, No. 2, pp. 29-36 (In Korean).
  12. Lee, C. J. (2009b), The Influence of reduction of vertical stress on the behaviour of piles subjected to negative skin friction, Journal of the Korean Society of Civil Engineers, Vol. 29, No. 1C, pp. 33-39 (In Korean).
  13. Little, J. A. (1994), Downdrag on piles: Review and recent experimentation, Proceedings of settlement 94: Vertical and Horizontal Deformations of Foundations and Embankment, ASCE, pp. 1805-1826.
  14. Ng, C. W. W., Poulos, H. G., Chan, V. S. H., Lam, S. S. Y. and Chan, G. C. Y. (2008), Effects of tip location and shielding on piles in consolidating ground, Journal of Geotechnical & Geoenvironmental Engineering, ASCE, Vol. 134, No. 9, pp. 1245-1260. https://doi.org/10.1061/(ASCE)1090-0241(2008)134:9(1245)
  15. Okabe, T. (1977), Large negative friction and friction-free pile methods, 9th ICSMFE, Tokyo, Japan, Vol. 1, pp. 679-682.
  16. Phamvan, P. (1989), Negative skin friction on driven piles in Bangkok subsoil, Ph.D. Thesis. AIT, Bangkok, Thailand, pp. 1-235.