High-strain dynamic model of large-diameter pipe piles with soil plug for vertical vibration analysis

Abstract

A rigorous analytical model is developed for simulating the vibration behaviors of large-diameter open-ended pipe piles (OEPPs) and surrounding soil undergoing high-strain impact loading. To describe the soil behavior, the soil along pile shaft is divided into slip and nonslip zones and the base soil is modeled as a fictitious-soil pile (FSP) to account for the wave propagation in the soil. True soil properties are adopted and slippage at the pile-soil interface is considered, allowing realistic representation of large-diameter OEPP mechanics. The developed model is validated by comparing with conventional models and finite element method (FEM). It is further used to successfully simulate and interpret the behaviors of a steel OEPP during the offshore field test. It is found that the variation in the vertical vibrations of shaft soil along radial direction is significant for large-diameter OEPPs, and the velocity amplitudes of the internal and external soil attenuate following different patterns. The shaft soil motion may not attenuate with depth due to the soil slippage, while the wave attenuation at base soil indicates an influence depth, with a faster attenuation rate than that in the pile. The findings from the current study should aid in simulating the vibration behaviors of large-diameter OEPP-soil system under high-strain dynamic loading.