Experimental Investigations on the Lateral Bearing Behaviour of Vibratory-Driven Open Steel Pipe Piles-Paper

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The study investigates how vibratory installation affects the lateral load-bearing behavior of open steel pipe piles in saturated sand. Researchers at the University of Stuttgart conducted 1-g model tests using a glass-fibre-reinforced pile, designed to reproduce the flexural rigidity of a steel monopile, in a concrete test container filled with Berlin Sand. They measured pile penetration and acceleration during installation, then applied lateral loads while recording pile displacement, bending, and force. A jacked pile served as a reference.<br /><br />In a representative test in dense sand, penetration slowed substantially as the pile advanced, alongside a reduction in pile-head acceleration. The authors suggest that increasing soil resistance—potentially due to densification around or inside the pile—contributed to this trend.<br /><br />The vibratory-driven pile showed stiffer lateral behavior than the jacked pile: on average, the jacked pile’s lateral displacements were 1.75 times greater. Comparisons with three analytical p-y methods found that the modified approach by Kallehave et al. best matched the vibratory-driven pile’s response over part of the tested load range. However, standard approaches generally overestimated its displacements, while they slightly underestimated those of the jacked pile. Adjusting the soil friction angle improved agreement, but this was presented as a workaround rather than a validated design method.<br /><br />The results indicate that vibratory installation may increase lateral stiffness, an effect not explicitly captured by existing p-y approaches. The authors emphasize that further testing is needed, particularly to assess how vibration frequency, vibrator static moment, and soil density influence pile behavior.

Keywords

vibratory installation

lateral load-bearing

open steel pipe piles

saturated sand

1-g model tests

pile penetration

pile-head acceleration

lateral stiffness

p-y methods

soil densification