Centrifuge and numerical modeling of axial load effects on piles in consolidating ground

Lam, S. Y.; Ng, Charles Wang Wai; Leung, C.F.; Chan, S.H.

doi:10.1139/t08-095

Cited by 78 publications

(26 citation statements)

References 13 publications

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“…The process of the dragload elimination is slightly influenced by the presence of the sacrificing piles but heavily governed by the tip location (Lam et al 2009). The larger the distance between the pile toe and the stiff bottom soil, the easier it is for the dragload induced on floating piles to be completely eliminated (Lv et al 2013).…”

Section: Introductionmentioning

confidence: 99%

Comparative study of Y-shaped and circular floating piles in consolidating clay

Lam

et al. 2016

Can. Geotech. J.

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Although engineers often make use of pile geometry to improve the axial load capacity of piles, geometrical effects on floating piles in consolidating clay are still not fully understood. This paper reports two centrifuge model tests to investigate the responses of a Y-shaped pile and a circular pile subjected to an induced dragload and applied axial loads. Three-dimensional numerical back-analyses were performed considering the elasto-plastic slip. The Y-shaped and circular piles developed similar downdrag but the dragload induced on the Y-shaped pile was larger than that induced on the circular pile. As the axial load increased, the neutral plane shifted upward along a nonlinear path which gradient of the Y-shaped pile was gentler. The ultimate bearing capacity of the Y-shaped pile was 1.73 times that of the circular pile. The dragload on the Y-shaped and circular piles was eventually eliminated at approximately 0.56 and 0.83 times the corresponding ultimate pile capacities, respectively. Three flanges of the Y-shaped pile "hung-up" adjacent soil which settled together with the pile shaft. The lateral extent of vertically non-uniform trapped soil decreased with increasing axial load. Even though the Y-shaped and circular piles encountered a similar serviceability limit state, Y-shaped pile had advantages in bearing capacity.

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Section: Introductionmentioning

confidence: 99%

Comparative study of Y-shaped and circular floating piles in consolidating clay

Lam

et al. 2016

Can. Geotech. J.

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“…Lam et al [29] conducted four centrifuge model tests on single isolated pile and shielded single pile, to investigate the behaviour of floating piles subjected to negative skin friction and also to study the effects of axial load on the loadtransfer mechanisms along the pile. The authors carried out also, three-dimensional numerical analysis of the centrifuge model tests.…”

Section: Introductionmentioning

confidence: 99%

Behaviour of single pile in consolidating soil

Abdrabbo

Ali

2015

Alexandria Engineering Journal

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Piles located in consolidating soil are subjected to indirect loading resulted from the settlement of adjacent soil. Both pile and soil undergo downward movements caused by the axial pile load and surcharge loading on surrounding area. Both dragload and downdrag imposed on the pile are time dependent. The purpose of this research was to analyse and quantify the dragload and down drag imposed on single pile. Effect of pile head load was considered. Shielded and unshielded piles are analysed. Three dimensional nonlinear analyses using ABAQUS 6.12 have been utilised. The research investigates the size of the surcharge loaded area, location of the pile tip and pile head load on the dragload and down drag imposed on the pile. Based on numerical results the study revealed that sacrificing piles, which are unloaded piles, ''hang up'' the soil between the piles in the group and, thus, the vertical effective stress around the shielded pile is reduced. Numerical results proved that an average value of the shear stress mobilisation factor b mobilised along unloaded shielded central pile varies between zero at neutral plane (NP) and 0.27. The long term dragload of the shielded floating pile is about 67% of the long term dragload of unshielded floating single pile. ª 2015 Production and hosting by Elsevier B.V. on behalf of Faculty of Engineering, Alexandria University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).

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“…Fellenius (2006) and Poulos (2008) pointed out that downdrag (excessive pile top settlement caused by NSF) should be included in the design of piles in consolidating soils. Field tests and centrifuge model tests focused on downdrag of piles under surcharge load were carried out (Little, 1994;Ng et al, 2008;Lam et al, 2009Lam et al, , 2013EI-Mossallamy et al, 2013). Numerical analyses focused on downdrag of a group of piles under surcharge loads were carried out (Chow et al, 1990;Lee, 1993;Teh and Wong, 1995;Lee et al, 2004;Yao et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

Group effect of dragload in pile groups embedded in consolidating soil under embankment load

2015

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In this paper, model tests and numerical simulations on 3 × 3 pile group embedded in consolidating soil under embankment load with different pile spacings are carried out. Single pile and 2 × 2 pile group are studied for comparative analyses. The performances of dragload versus relative displacement of pile-soil, load sequence and load rate, and the group effects of dragload and downdrag versus pile spacing are analyzed. A case study on dragload of a pile group considering with or without couple effect is also presented. It is worth pointing out that in this experimental condition, when pile-soil relative displacements reach 2 mm, dragload will reaches nearly 75-95% of the maximum values; When consolidation time reaches 240 h, the neutral plane becomes stable approximately at 0.95H (H is the thickness of compression soil). The dragload and downdrag are influenced by load sequence of pile head load versus surcharge load.

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Centrifuge and numerical modeling of axial load effects on piles in consolidating ground

Cited by 78 publications

References 13 publications

Comparative study of Y-shaped and circular floating piles in consolidating clay

Comparative study of Y-shaped and circular floating piles in consolidating clay

Behaviour of single pile in consolidating soil

Group effect of dragload in pile groups embedded in consolidating soil under embankment load

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