Back-calculations of Centrifuge Tests on Pile Groups Subjected to High-cyclic LoadingÂ-PPT Presentation

PPT Presentation

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The study evaluates whether numerical methods developed for offshore monopiles can predict the response of pile groups under high-cycle lateral loading. It back-calculates centrifuge tests by Niemann et al., conducted at 100 g on medium-dense dry silica sand. The tests included monotonic loading of a single pile and 500-cycle loading of single piles and pile groups.<br /><br />Finite-element simulations used numgeo, with geometrically nonlinear analysis, frictional pile–soil contact, and either hypoplasticity with intergranular strain or an enhanced High-Cycle Accumulation (HCA) model. Soil parameters were calibrated using laboratory compression and triaxial-test data, with automated calibration methods.<br /><br />The simulations reproduced the monotonic single-pile response well, although the analysis did not converge at higher loading. For cyclic single-pile loading, the HCA model matched accumulated pile-head displacement during roughly the first 20 cycles but overpredicted displacement at larger cycle counts. In contrast, it predicted the pile-group response to high-cyclic loading well.<br /><br />The results suggest that the HCA approach can be applied to pile groups, but its performance depends on the loading conditions and parameter calibration. In particular, the study notes that large strain-amplitude regions may require specific consideration during calibration.

Keywords

offshore monopiles

pile groups

high-cycle lateral loading

centrifuge tests

finite-element simulations

numgeo

hypoplasticity

intergranular strain

High-Cycle Accumulation model

pile-soil interaction