Field testing demonstrates time-dependent bearing capacity gains in extra-long concrete pipe piles, suggesting initial driving metrics can reliably predict foundation strength.
Key Points
To investigate the vertical compressive bearing behavior, settlement characteristics, and load-transfer mechanics of ultra-long pretensioned prestressed concrete pipe piles.
Conducted high-strain dynamic testing and static load tests on four 0.9 m diameter extra-long pretensioned prestressed high-strength concrete pipe piles.
Measured concrete modulus, side friction resistance, and end-bearing load distribution under static loading conditions up to 2.1 times the design load.
Pile bearing capacity exhibited time-dependent growth, increasing by 27% to 66% between initial driving and the conclusion of dynamic testing.
Under 2.1 times the design load, concrete modulus ranged from 37.5 GPa to 52 GPa, side friction resistance ranged from 0 kPa to 97 kPa, and pile end load ratios ranged from 0% to 7.54%.
Static load tests validated the restitution coefficient for predicting ultimate bearing capacity, while revealing incomplete mobilization of shaft friction and end resistance in the lower pile section.