Axial Resistance Gain of Piles Driven into Artesian Soils: Case Studies
Tony Sangiuliano, Kevin J. Bentley, Lisa Coyne, Murty Devata
In the proceedings of: GeoEdmonton 2018: 71st Canadian Geotechnical Conference; 13th joint with IAH-CNCSession: Transportation Geotechnics II
ABSTRACT: This paper presents two case studies that describe the results of static pile load tests at two bridge replacement sites for Ministry of Transportation Ontario (MTO) contracts in southern Ontario, Canada. Site #1 is located at Highway 401 and York. Both contracts involve the removal of existing structures and replacement with new bridges, under multi-year construction staging. The design of the new bridges included steel H-piles driven to refusal in cohesionless silty sand to sandy silt and sand and gravel till deposits under artesian groundwater conditions. Full-scale static pile load tests were conducted during construction, several months after the installation of the test pile at each of the sites. The purpose of the full-scale pile load tests was to compare the actual geotechnical resistance achieved in the full-scale tests to the estimated design geotechnical resistance value, as well as to resistance values measured on initial driving and retap using dynamic formula (Hiley) and/or pile dynamic analyzer (PDA) testing. The results of the full-scale static pile load tests are evaluated to assess set-up or strength gain over time, and examine whether higher geotechnical resistances can be achieved for piles driven to or into multi-layered soils under artesian conditions, for applicability at these and other highway bridge sites in similar conditions. Specifically, at the test sites, in view of the construction staging and the length of time between pile driving and bridge deck construction, the pile load test results have been used to optimize the design and construction of the next stage of pile foundations.
RÉSUMÉ: Cet article présente deux études de cas qui décrivent les résultats d'essais de charge statique de pieux sur deux sites de remplacement de ponts pour des contrats du ministère des Transports de l'Ontario (MTO) dans le sud de l'Ontario, au Canada. Le site n400 au South Canal dans la municipalité régionale de York. Les deux contrats prévoient l'enlèvement des structures existantes et leur remplacement paconception des nouveaux ponts comprenait des pieux en H en acier foncés dans des silts sableux non-cohérant et des dépôts de till et de sable et gravier dans des conditions artésiennes. Des essais de charge statique à pleine échelle ont essais de charge à pleine échelle était de comparer les résistances géotechniques de conception prévues aux valeurs de résistance géotechniques mesurées lors du fonçage initial et du retapage des pieux au moyen de la formule dynamique (Hiley) et / ou d'analyseur dynamique de pieu (PDA), et les résistances géotechniques réelles obtenues dans les essais de charge statique plusieurs mois après l'installation des pieux, afin d'évaluer le gain de résistance avec le temps. Les résultats des essais de charge statique à pleine échelle sont examinés pour déterminer si des résistances géotechniques plus élevées peuvent être obtenues pour des pieux foncés dans des conditions artésiennes, pour appliquer ces résultats ats des n de pieux, en tenant compte du temps écoulé entre la construction des pieux et la construction du tablier. INTRODUCTION Many water-crossing sites in Ontario are underlain by multi-layered soils under artesian conditions. Typically, these aquifer soils are comprised of silts, sands and gravels overlain by a thickness of a lower permeability or cohesive soil (i.e., an aquitard). Where the near-surface soils do not permit the use of shallow foundations due to inadequate bearing resistance, the preferred foundation option is frequently low-displacement driven piles such as steel H-piles. Other deep foundation options such as drilled shafts are considered to have higher risks around basal and sidewall instability in these conditions. The determination of the axial resistance for piles driven to refusal within artesian zones is challenging due to the existing porewater pressure regime and the additional porewater pressures generated during driving. To account for the low level of understanding and the typical to high consequence for these highway bridges, empirical methods that are commonly used are considered to produce conservative axial pile resistances, and hence foundation designs that may be more expensive than required. Recognizing the value that full-scale pile load tests can provide in optimizing foundation design in these conditions, the Ministry of Transportation Ontario (MTO)
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Tony Sangiuliano; Kevin J. Bentley; Lisa Coyne; Murty Devata (2018) Axial Resistance Gain of Piles Driven into Artesian Soils: Case Studies in GEO2018. Ottawa, Ontario: Canadian Geotechnical Society.
@article{geo2018Paper357,author = Tony Sangiuliano; Kevin J. Bentley; Lisa Coyne; Murty Devata,title = Axial Resistance Gain of Piles Driven into Artesian Soils: Case Studies,year = 2018}