3D numerical analyses of performance of geotextile-reinforced and pile-supported embankment over a soft foundation

Kaiwen Liu, R. Kerry Rowe

In the proceedings of: GeoRegina 2014: 67th Canadian Geotechnical Conference

Session: Geosynthetics

ABSTRACT: al analyses of performance of geotextile-reinforced and pile-supported embankment over a soft foundation Kaiwen Liu & R.Kerry Rowe GeoEngineering Centre at Queen's-RMC, Department of Civil Engineering, Queen's University, Kingston, Ontario, Canada ABSTRACT The combined use of geosynthetic reinforcement and piles can control deformations and also increase the stability of structures. A full-scale field experiment involving a geotextile reinforced piled-embankment constructed on soft soils in France is analyzed using a fully 3D coupled finite element model. This section of embankment was numerically constructed according to the schedule in the field and the results compared with (a) the observed field performance and (b) those for the counterpart embankment without any improvement under similar embankment loading. The synergistic effects of geotextile reinforcement and piles are discussed. The study shows that the final settlement about 150 days after completion of construction was about 68% less for the reinforced-piled than unreinforced embankment and the maximum lateral movement below the toe decreased to approximately 42% of that of the unreinforced embankment. The numerical results are generally in good agreement with field data in terms of stresses on the subsoil, vertical settlement, and horizontal movements under the toe as well as strains in geotextile. RÉSUMÉ L'utilisation combinée de géosynthétiques de renforcement et de pieux peut contrôler les déformations et également augmenter la stabilité des ouvrages. Une expérience de terrain en vraie grandeur impliquant un remblai sur pieux renforcé par un géotextile construit sur des sols mous en France est analysée en utilisant un modèle éléments finis couplé en vrai 3D. Cette section du remblai a été numériquement construite selon le calendrier de réalisation et les résultats comparés : (a) à la performance observée sur le terrain et ( b ) à ceux du remblai témoin sans aucune amélioration sous chargement similaire du remblai. Les effets synergiques du géotextile de renforcement et des pieux sont discutés. L'étude montre que le tassement final 150 jours environ après l'achèvement de la construction était d'environ 68 % inférieur pour le remblai renforcé par pieux par comparaison au remblai non renforcé et le déplacement latéral maximal en crête a diminué d‚environ 42 % par rapport à celui du remblai non renforcé. Les résultats numériques sont généralement en bon accord avec les données de terrain en termes de contraintes dans le sous-sol, de tassement vertical et de mouvements horizontaux en crête ainsi qu'en matière de déformation du géotextile. 1 INTRODUCTION One approach to constructing embankments over soft soils is the combined use of piles and geosynthetic reinforcement. The use of suitable piles can enable stable embankments to be constructed to unrestricted heights at any reasonable construction rate even on very soft soils. Basal geosynthetic reinforcement can allow an increase in pile spacing and/or minimize the size of pile caps or even eliminate the need for pile caps, with associated cost savings. In addition, the horizontal thrust of the embankment fill can be counteracted and the need for raking piles along the extremities of the foundation can be eliminated by the provision of suitable basal reinforcement (BS8006:1995). Recently, numerical analyses of the performance of geosynthetic-reinforced and pile-supported embankments (GRPSE) have been reported by several investigators (Hello and Villard 2009; Huang and Han 2010; Borges and Marques 2011). All these simulations were either two dimensional or quasi-three dimensional (only a unit cell with a single pile was modeled in 3D). When both the pile grid geometry and the lateral slopes are considered, the problem requires a fully 3D analysis. Nevertheless, there have been very few fully 3D, and even fewer coupled mechanical and hydraulic analyses (i.e., by Liu et al. 2007 and Huang and Han 2009). Thus, a numerical study of GRPSE validated by field data is needed to improve understanding of the performance of GRPSE. Nunez et al. (2013) analyzed a well-documented full-scale GRPSE constructed on soft soils in Paris, France (Briançon and Simon 2012) using a finite difference numerical model. However, the maximum settlement of the embankment was underestimated by 37%. Also, there was poor agreement between calculated and observed lateral displacements below the toe of embankment with the predicted displacement being 60% less than observed in the field. The objective of this study is to report the findings of a fully coupled 3D finite element analysis to reexamine the performance of the case study in France discussed above (Briançon and Simon 2012). The calculated results are compared with field monitoring data and simulation of Nunez et al. (2013).

RÉSUMÉ: merical analyses of performance of geotextile-reinforced and pile-supported

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Kaiwen Liu; R. Kerry Rowe (2014) 3D numerical analyses of performance of geotextile-reinforced and pile-supported embankment over a soft foundation in GEO2014. Ottawa, Ontario: Canadian Geotechnical Society.

@article{GeoRegina14Paper256,author = Kaiwen Liu; R. Kerry Rowe,title = 3D numerical analyses of performance of geotextile-reinforced and pile-supported embankment over a soft foundation,year = 2014}