An Investigation of the Contribution of the Pile Base to the Lateral Response of Monopiles in Sand under Static Loading-Paper

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This study investigates whether pile-base resistance materially affects the lateral response of short, rigid monopiles in sand. Field tests were conducted on 457 mm diameter steel pipe piles embedded 1 m (L/D = 2.2), comparing a pile with its sand plug intact to one with the plug removed, so that no resistance could develop beneath the latter’s tip.<br /><br />The measured load–deflection curves were virtually identical, indicating that the base condition had a negligible effect on the piles’ overall lateral response. A three-dimensional finite-element model using a hardening-soil representation of the sand reproduced the field results, including the similarity between plugged and unplugged piles. The validated model was then applied to monopiles 6, 8 and 10 m in diameter, each embedded 30 m. It likewise predicted little or no influence of the plug on lateral stiffness and load–deflection behaviour.<br /><br />The analyses showed that base shear can develop in plugged piles, but it has limited impact on the overall lateral response. When normalized by plug weight, base-shear behaviour was similar across the modelled diameters; the shear exceeded estimates based on the peak friction angle, likely because of sand dilation.<br /><br />The results suggest that pile-base shear and moment can generally be neglected when designing short, rigid monopiles in sand, including piles up to 10 m in diameter. These conclusions apply to static loading and the conditions examined in the study.

Keywords

monopile

lateral response

pile-base resistance

sand

field tests

finite-element model

hardening-soil model

load-deflection curves

base shear

short rigid piles