Dragload and downdrag performances of inclined pile group embedded in consolidating soil

Abstract

The performance of inclined pile group embedded in consolidating soil under surcharge load was investigated by experiment in comparison with vertical pile group and single pile under the same conditions; dragload, downdrag, and layered soil settlement were measured. A three-dimensional numerical model was built via FLAC^3D software, and verified by the experimental results. Influence factors, such as consolidation time, pile spacing, and pile tilt angle were analyzed. The results show that dragload of inclined pile group increases with the increase of consolidation time and pile spacing or the decrease of pile tilt angle. Downdrag of inclined pile group increases with the increase of consolidation time, pile spacing and pile tilt angle.

Keywords

pile group / negative skin friction / consolidating soil / downdrag / dragload / neutral plane

References

[1] Fellenius B. H. Results from long-term measurement in piles of dragload and downdrag[J]. Canadian Geotechnical Journal, 2006, 43(4): 409-431.

[2] Toma T. M. A Model Study of Negative Skin Friction on a Fixed Base Pile in Soft Clay[D]. 1989, UK: Department of Civil Engineering, Heriot-Watt University.

[3] Lee C J, Chen H T, Wang W H. Negative skin friction on a pile due to excessive ground water withdrawal[C]. In: Proceedings of International Conference Centrifuge’ 98, Tokyo, 1998. 513–518.

[4] Kong G. Q., Yang Q., Zheng P. Y., et al. Evaluation of group effect of pile group under dragload embedded in clay[J]. Journal of Central South University of Technology, 2009, 16(3): 503-512.

[5] Chow Y. K., Lin C. H., Karunaratne G. P. Numerical modeling of negative skin friction on pile group[J]. Computers and Geotechnics, 1996, 18(3): 201-224.

[6] Lee C. J., Ng W. W. Development of downdrag on piles and pile group in consolidating soil[J]. Journal of Geotechnical and Geoenvironmental Engineering, 2004, 130(9): 905-914.

[7] Comodromos E. M., Bareka S. V. Evaluation of negative skin friction effects in pile foundations using 3D nonlinear analysis[J]. Computers and Geotechnics, 2005, 32(3): 210-221.

[8] Hoque M. A. Coupled Consolidation Model for Negative Skin Friction on Piles in Clay Layers[D]. 2006, California, USA: Concordia University.

[9] Kong G. Q., Yang Q., Luan M. T. Loading sequence effects on dragload and downdrag for pile foundation[J]. Transactions of Tianjin University, 2010, 16(3): 203-208.

[10] Ng C. W. W., Poulos H. G., Chan V. S. H., et al. Effects of tip location and shielding on piles in consolidating ground [J]. Journal of Geotechnical and Geoenvironmental Engineering, 2008, 134(9): 1245-1260.

[11] Lam S. Y., Ng C. W. W., Leung C. F., et al. Centrifuge and numerical modeling of axial load effects on piles in consolidating ground[J]. Canadian Geotechnical Journal, 2009, 46(1): 10-24.

[12] Shibata T., Sekiguchi H., Yukitomo H. Model test and analysis of negative skin friction acting on piles[J]. Soils Foundations, 1982, 22(2): 29-39.

[13] Kong G., Yang Q., Zheng P., et al. Model tests on negative skin friction for inclined pile considering time effect[J]. Chinese Journal of Geotechnical Engineering, 2009, 31(4): 617-621.

[14] Itasca Consulting Group Inc. Fast Lagrangian Analysis of Continua in 3-Dimensions[M]. Version 3. 0. Minnesota, USA, 2000.