Examination of the evaluation of negative skin friction on production piles for a major bridge structure

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dc.contributor.authorChalajour, Sepehr
dc.contributor.examiningcommitteeAlfaro, Marolo (Civil Engineering)
dc.contributor.examiningcommitteeFiorillo, Graziano (Civil Engineering)
dc.contributor.examiningcommitteeWang, BingChen (Mechanical Engineering)
dc.contributor.examiningcommitteeEl Naggar, Hesham (Civil Engineering, Western University)
dc.contributor.supervisorBlatz, James
dc.date.accessioned2025-03-21T14:29:46Z
dc.date.available2025-03-21T14:29:46Z
dc.date.issued2025-03-20
dc.date.submitted2025-03-19T19:23:57Zen_US
dc.date.submitted2025-03-21T03:56:23Zen_US
dc.degree.disciplineCivil Engineering
dc.degree.levelDoctor of Philosophy (Ph.D.)
dc.description.abstractRelative settlement of soil and pile generates negative skin friction (NSF), creating a downward shearing force along the pile’s shaft. The resulting axial force and settlement are called drag force (DF) and downdrag (DD), respectively. The pile's downward movement starts at the top and reaches equilibrium at the neutral plane (NP), where relative settlement is zero. The NP’s location determines the pile’s maximum axial force (MAF). Excessive settlement from external loads, such as embankment filling, can induce DF on the pile in compressible soils. A full-scale field study was conducted on a production H-pile at a bridge construction site in Manitoba, Canada. The pile was driven into clay till to evaluate the NSF and its associated DF and DD under service loads. Field monitoring showed that the pile installation into cooler ground reduced compressive strain along the shaft. Loading and unloading during pile driving create compressive residual stresses in the middle and lower shaft and tensile stresses at the pile top. Ignoring these forces might lead to underestimating the applied loads on the pile. Five code provisions for ultimate limit state (ULS) design of piles subjected to NSF were evaluated. The findings indicated that design codes that include DF in ULS design, such as AASHTO and CEN, tend to result in more conservative and potentially costly designs compared to codes that do not account for DF in ULS design, such as CHBDC, AS2159, and FHWA. Numerical modeling revealed that MAF, NSF, DF, and DD vary among piles within a group due to the geometry of the applied load. The pile in the most critical location experienced 65% higher MAF, 25% more DF, 37.5% more DD, and 32% more NSF compared to the least critical pile. Parametric studies showed that increasing surcharge load, shortening pile length, reducing pile cross-section and decreasing soil-pile friction reduced DF and MAF at the NP. Applying bitumen coating along the shaft reduced MAF and DF by 70% and 90%, respectively, and construction in high plastic clays leads to an increase in MAF and DF. Replacing traditional granular embankment with lightweight cellular concrete reduced by up to 60%. It also DD by 65% to 70%, DF by 35% to 44%, and NSF by 50% to 70%, depending on the pile’s location within the cap. Comparing between the Unified Design Method (UDM) and the obtained results showed that UDM overestimated MAF at the NP, DF and DD for both pile scenarios, however the NP position was almost identical. Additionally, the pile resistance based on this method may not account for the setup effect, leading to a more conservative design. Considering pile capacity derived from restrike measurements versus end of initial driving in dynamic analysis provides higher resistance in geotechnical ULS design in soil with shaft setup potential.
dc.description.noteMay 2025
dc.identifier.urihttp://hdl.handle.net/1993/38940
dc.language.isoeng
dc.subjectPiles
dc.subjectnegative skin friction
dc.subjectdrag force
dc.subjectdowndrag
dc.subjectneutral plane
dc.subjectinstrumentation
dc.subjectnumerical modeling
dc.titleExamination of the evaluation of negative skin friction on production piles for a major bridge structure
local.subject.manitobano
project.funder.nameMitacs - Government of Manitoba
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