Comparing theoretical predictions and guidelines against pile test data for CFA piles in glauconitic sands in Belgium-PPT Presentation

PPT Presentation

Pdf Summary

This study compares theoretical predictions and Belgian design guidelines with static load-test data for continuous flight auger (CFA) piles installed in glauconitic sands at a Belgian site. The work forms part of a broader project to develop and calibrate soil models for offshore wind turbine monopiles.<br /><br />The site’s Diest Formation contains weathered glauconitic sands, classified as sandy silt by the piling contractor. Glauconite’s distinctive mineral composition and behavior made installation challenging: augering crushed the material and produced sticky, clay-like soils, affecting pile construction and performance. The researchers assessed 0.6 m CFA piles using static load tests and bearing-capacity results based on the 10% displacement criterion.<br /><br />Predictions were compared using Belgian practice, including the approaches in NAD 2008 and Reports 19 and 20, as well as load-settlement methods based on De Cock (2008) and the t-z formulations of Allani and Huybrechts (2022). The comparisons considered different soil classifications and stratigraphic interpretations.<br /><br />The study highlights why settlement and capacity predictions in glauconitic sands are difficult: particle crushing can transform coarse material into finer-grained soil, and existing guidelines may not capture the resulting effects on pile behavior. Prediction accuracy is also constrained by the calibration of design parameters. Reliable model calibration requires test data that distinguish shaft resistance from base resistance.<br /><br />The authors recommend a broader, systematic testing program involving different pile types, together with detailed investigation of glauconitic sand properties. Further research is needed to improve design parameters and predictive methods for piles in these soils.

Keywords

CFA piles

glauconitic sands

static load test

Belgian design guidelines

bearing capacity

pile settlement

Diest Formation

soil classification

shaft resistance

monopile calibration