The Downdrag Response of a Driven Pile Bridge Foundation in Minnesota

A Budge

In the proceedings of: GeoVancouver 2016: 69th Canadian Geotechnical Conference

Session: CASE HISTORIES - IV Miscellaneous

ABSTRACT: The Minnesota Department of Transportation (MnDOT) is engaged in several performance monitoring projects to evaluate the soil-pile interaction phenomenon of dragload and downdrag as new design guidance is being developed by the United States FHWA and AASHTO agencies. This paper describes a project where a new bridge approach embankment was constructed over a soft soil layer overlying bedrock. The soils below the bridge abutment embankment experienced consolidation settlement and the bridge piling was subject to dragload. The abutment embankment was monitored for deformation performance and two steel H-type piles, within the production pile group, were instrumented and subsequently monitored during construction and several years into service. Sensor response showed that the piles continued to accumulate load following construction as soils continued to consolidate. A computational model of the soil pile system was also developed to assist with the understanding of the field measurements and extrapolate performance behavior under different conditions. Lessons learned on this and related recent case-study projects relative to the downdrag phenomenon are presented.

RÉSUMÉ: Le Départment des Transports du Minnesota (MnDOT) est engagé dans plusieurs projets de contrôle de la -pieu de dragload et de downdrag pendant que nouvelles directives de conception sont développés par les organismes des États-Unis FHWA et AASHTO. Cet article décrit un projet où un sols sous le remblai de culée du pont ont connu des tassements de la consolidation et les pieux du pont one été pris par le dragload. Le remblai de la culée a été surveillé pour déformation et deux pieux en acier de type H, au milieu du groupe de pieux de production, ont été instrumenté et surveillé par la suite durant la construction et de plusieurs années en service. La réponse des capteurs a moles sols a continué de consolider. Un modèle informatique du système sol-pieu a été également développé pour aider à la r le comportement de la performance dans des conditions différentes. Des leçons là-

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