Modification of P-Y Curves to Account for Group Effects on Laterally Loaded Piles

by Dan A. Brown, Auburn Univ, United States,
Chine-Feng Shie, Auburn Univ, United States,

Document Type: Proceeding Paper

Part of: Geotechnical Engineering Congress?1991


The response of piles in a rectangular group subjected to lateral loading has been analyzed using a three-dimensional finite element model to evaluate the effect of pile spacing on lateral load resistance. The model uses 27-noded solid elements to model the piles and soil and includes interface elements to simulate slippage and gapping around the piles. Two different constitutive models for soil have been used; a simple elastic-plastic constant yield strength material for a total stress analysis in clays, and a modified Drucker-Prager model with nonassociated flow for sands. A graphical presentation of stress changes in the soil and zones of yielding in the area around the piles provides some insight for understanding group pile behavior. The potential yield zone overlap and shadowing effects are compared with observations in physical tests. Group effects are seen to be most significant on piles which are in trailing rows (i.e. 'shadowed' by leading row piles). In order to evaluate group effects in a meaningful way which allows comparison to field test results, p-y curves are derived from the pile stresses. The effect of pile group spacing is expressed in terms of scaling factors to be applied to single pile p-y curves. Scaling factors derived from the finite element model are compared with those back calculated from the relatively few large scale experiments, and recommendations for design are proposed.

Subject Headings: Piles | Lateral loads | Finite element method | Soil stress | Soil analysis | Load factors | Simulation models

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