Keywords: rigid pile, side friction, lateral loading, numerical model, p-y curve, ultimate soil resistance.

Piles are subjected to lateral loading in their application as bridge foundations, foundations of offshore platforms or wind turbines. The design of piles is commonly performed by employing the beam on elastic foundation model, where soil-pile interaction is dictated by p-y curves [1]. The latter represents the soil pressure exerted on the pile due to lateral (horizontal) pile displacement, along the depth of the pile. Even though the current design procedure [2] is simple in its application, the proposed p-y curves have been calibrated to the response of flexible piles, while the accuracy of the ultimate soil resistance has been widely questioned [3].

The current study investigates the lateral response of rigid piles in cohesionless soils subjected to load with high eccentricity. Hence advanced three-dimensional finite element models were developed and the soil nonlinearity, the soil layering, and the geometric nonlinearity induced by sliding along the soil-pile interface and gap formation are taken into account. The effects of pile stiffness and friction resistance are analysed. The results indicate that the induced failure mechanism is complex, including the development of both slip displacements along the pile interface (circumferential and vertical) and plastic soil deformations. The generated failure mechanism closely resembles the one reported in the literature.

The effect of the pile stiffness in the lateral capacity of the pile and the p-y curves was found to be negligible, as long as the flexibility criteria for a rigid pile are met. Nevertheless the effect of the increase of the interface shear strength was shown to be significant, affecting thus the pile lateral response by:

• increasing the lateral load capacity of the pile
• increasing the distance of the rotation point from the pile tip
• increasing the stiffness of the p-ycurves
• increasing the ultimate soil resistance
• increasing the pile displacement at ultimate soil resistance

The code provisions [2] neglect the side shear resistance, thus underestimating the normalized ultimate soil resistance while the stiffness of the p-y curves is overestimated especially at significant depths.

1

L.C. Reese, W.F. Van Impe, "Single piles and pile groups under lateral loading", A.A. Balkema, Rotterdam, 2001. doi:10.1115/1.1445326

2

American Petroleum Institute, "Recommended Practice for Planning, Designing and Constructing Fixed Offshore Platforms - Working Stress Design", API RP-2A-WSD, 2000.

3

C.-C. Fan, J.H. Long, "Assessment of existing methods for predicting soil response of laterally loaded piles in sand", Computers and Geotechnics, 32(4), 274-289, 2005. doi:10.1016/j.compgeo.2005.02.004

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