Friction Fatigue and Drivability Analysis of Open Ended Pipe Piles Based on Cone Penetration Testing Results-Paper

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The paper examines friction fatigue in driven open-ended pipe piles and its effect on driveability predictions. Friction fatigue is the reduction of unit shaft resistance as a pile is driven deeper, attributed to repeated shearing of the surrounding soil. Conventional driveability analyses often represent driving resistance using empirical soil setup factors, which may not adequately capture this depth-dependent effect.<br /><br />The authors compare two GRLWEAP analyses for a 1,676-mm-diameter offshore pipe pile with 119 m of embedment: a conventional setup-factor approach and the CPT-based Alm and Hamre (A&H) friction-fatigue model. The case-study soils were interbedded carbonate sands, clays, and silts. Both analyses used the same long-term resistance assumptions and standard damping and quake values; internal friction and soil-plug resistance were not included.<br /><br />Predicted blowcounts from each analysis were compared with field driving records. The conventional approach increasingly overpredicted blowcounts at greater depths, particularly in the final 30 m of driving. The A&H model, which predicts shaft resistance decreasing toward a residual value with distance above the pile toe, tracked measured blowcounts more closely at deep penetration. Both approaches showed reasonable agreement over much of the shallower profile, but friction fatigue became increasingly important with depth.<br /><br />The authors recommend considering friction-fatigue models in wave-equation analyses for deeply embedded piles, especially in offshore projects where installation equipment and operations are costly. They also advise conducting both lower- and upper-bound analyses to account for uncertainty.

Keywords

friction fatigue

driven open-ended pipe piles

driveability predictions

shaft resistance

wave-equation analysis

GRLWEAP

Alm and Hamre model

offshore pile foundation

blowcount prediction

pile driving records