Structure Support on Laterally Swept Piles-Paper

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The paper examines how lateral sweep affects the axial performance of driven pipe piles, using static load tests from two projects.<br /><br />At the University of North Dakota School of Medicine and Health Sciences in Grand Forks, 9.625-inch-diameter piles, 153.5–164.5 feet long, had measured toe offsets of about 12–17 inches. Although their sweep was less than typical construction tolerances, the piles showed substantial axial movement: at 400 kips, pile-top deflection was about 1.0–1.1 inches. They plunged at 504–525 kips, below the project’s 600-kip target ultimate resistance.<br /><br />At the Mystic Hotel and Convention Center in Minnesota, two piles about 80 feet long had much larger toe offsets—about 51 and 63 inches. Despite exceeding typical sweep tolerances, they supported the required 400-kip ultimate resistance with only 0.52–0.60 inch of pile-top movement. They were not tested to failure.<br /><br />The results suggest that customary plumbness limits of 0.25–0.50 inches per foot may not reliably predict pile performance. The more slender UND piles deflected roughly twice as much as the shorter Mystic piles at comparable loads, despite having less curvature. This indicates that slenderness may influence deformation, and perhaps capacity, more strongly than curvature alone. However, the limited number of tests—and the absence of failure testing at Mystic—means the findings cannot establish a general relationship between sweep and capacity. Further research is needed to develop appropriate project-specific tolerances.

Keywords

lateral sweep

axial performance

driven pipe piles

static load tests

toe offset

pile deflection

pile capacity

plumbness tolerances

slenderness ratio

geotechnical engineering