On the Axial Load-Bearing Behavior of Vibrated and Impact Driven Full Displacement Piles-Paper

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The study investigates how installation method and operating parameters affect the axial load-bearing behavior of full-displacement piles in dense, saturated sand. Scaled 1-g model tests compared vibratory-driven piles with impact-driven piles and piles installed by reproducing the vibrator’s movement slowly, without dynamic effects. Additional tests varied vibration amplitude and frequency.<br /><br />In the selected comparison, vibratory- and impact-driven piles showed broadly similar load–settlement behavior and axial resistance. However, the cyclic quasi-static pile developed substantially greater resistance than the vibratory-driven pile, indicating that vibration-related dynamics—not just cyclic installation or friction fatigue—affect pile capacity. The authors suggest that vibration-induced soil weakening or liquefaction around the shaft reduces skin friction.<br /><br />Installation parameters also mattered. Tests comparing amplitudes found that the pile installed at maximum amplitude had about 30% greater resistance at small settlement and 39% greater resistance at larger settlement than the minimum-amplitude pile. Increasing frequency from 37 to 46 Hz produced a smaller increase in resistance: approximately 15% at small settlement and 12% at larger settlement. Thus, the tested results indicate a stronger amplitude effect than frequency effect.<br /><br />Failure behavior differed as well. Vibratory- and impact-driven piles showed more ductile load–settlement responses, whereas the quasi-static pile failed more abruptly. Overall, the findings show that vibratory installation does not necessarily produce lower axial capacity than impact driving: capacity depends on soil conditions and installation settings. The authors recommend further testing to clarify these effects and the mechanisms behind them.

Keywords

full-displacement piles

axial load-bearing behavior

dense saturated sand

vibratory-driven piles

impact-driven piles

installation method

vibration amplitude

vibration frequency

load-settlement response

soil weakening liquefaction