Comparative Numerical Study of Constitutive Models for Pile Foundations in Liquefiable Soils under Seismic Loading
Amr ME Abdelaal, Mourad Karray 
Dans les comptes rendus d’articles de la conférence: GeoManitoba 2025: 78th Canadian Geotechnical Conference & 9th Canadian Permafrost ConferenceSession: Numerical Analysis Modeling 1
RÉSUMÉ: Le comportement des pieux en sols liquéfiables dépend de la façon dont la loi constitutive représente contractance, dilation et surpressions interstitielles. Avec FLAC3D, nous avons comparé trois modèles (Finn, P2PSand, NorSand) calibrés pour le sable d’Ottawa (Dr ≈ 40 %) sur un pieu de 0,5 m soumis à l’accélogramme de Nahanni amplifié (×7). P2PSand a généré Ru ≈ 1,0 à 6–8 m, réduisant σ′v à ~5 kPa ; Finn a produit un ramollissement de 25 %, tandis que NorSand est resté principalement dilatant. Les affaissements en tête de pieu étaient de −0,18 m (Finn), −0,05 m (NorSand) et −0,03 m (P2PSand). Le choix et la calibration du modèle peuvent donc déplacer la profondeur de liquéfaction de plusieurs mètres et multiplier par six le tassement prévu, d’où l’importance de valider les paramètres par des essais cycliques propres au site.
ABSTRACT: Pile behaviour in liquefiable ground depends strongly on how the soil constitutive law represents contractancy, dilation, and pore-pressure build-up. Using FLAC3D, we compared three models—Finn, P2PSand, and NorSand—calibrated for loose Ottawa Sand (Dr ≈ 40 %). A single 0.5 m diameter reinforced-concrete pile embedded 6 m into a 10 m × 10 m × 10 m domain was shaken by the 1985 Nahanni acceleration record, scaled by a factor of seven. P2PSand generated the highest excess porewater pressures, reaching Ru ≈ 1.0 at 6–8 m depths and driving effective vertical stress to within 5 kPa of zero. Finn produced moderate softening (σ′v reduction ≈ 25 %), while NorSand remained dilative and largely preserved effective stress. These contrasts translated into very different serviceability responses: pile-head settlement was −0.18 m with Finn, −0.05 m with NorSand, and −0.03 m with P2PSand. The findings show that the constitutive model's choice and calibration can shift predicted liquefaction depth by several metres and alter settlement by a factor of six. Designers should therefore validate model parameters against site-specific cyclic tests whenever piles are sited in potentially liquefiable deposits.
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Abdelaal, Amr ME, Karray, Mourad (2025) Comparative Numerical Study of Constitutive Models for Pile Foundations in Liquefiable Soils under Seismic Loading in GEO2025. Ottawa, Ontario: Canadian Geotechnical Society.
@inproceedings{Abdelaal_GEO2025_198,
author = {{Abdelaal, Amr ME}, {Karray, Mourad}}
title = {Comparative Numerical Study of Constitutive Models for Pile Foundations in Liquefiable Soils under Seismic Loading }
booktitle = {Proceedings of the 78th Canadian Geotechnical Conference & 9th Canadian Permafrost Conference}
year = {2025}
organization = {The Canadian Geotechnical Society},
address = {Ottawa, Canada} }
title = {Comparative Numerical Study of Constitutive Models for Pile Foundations in Liquefiable Soils under Seismic Loading }
booktitle = {Proceedings of the 78th Canadian Geotechnical Conference & 9th Canadian Permafrost Conference}
year = {2025}
organization = {The Canadian Geotechnical Society},
address = {Ottawa, Canada} }