Load Tests and Numerical Modeling of Drilled Displacement and Driven Piles in Marl in Savannah, Georgia-Article

Article

Pdf Summary

The study evaluates axial performance of precast prestressed concrete driven piles and drilled displacement piles installed in stiff Miocene marl at an LNG facility in Savannah, Georgia. Load tests at two test areas measured pile-head movement and axial force transfer; the piles exhibited plunging failure, reflecting the marl’s brittle, strain-softening behavior.<br /><br />Conventional CPT-based methods underestimated shaft resistance or overestimated toe resistance. The authors recalibrated the LCPC and Eslami–Fellenius correlations for partial-displacement augered cast-in-place (PACIP), full-displacement augered cast-in-place (DACIP), and driven piles. When checked against tests from a separate area, the revised correlations generally predicted shaft resistance and toe resistance more accurately, though performance varied by pile type and method.<br /><br />The researchers also developed a nonlinear load-transfer model using strain-softening t-z curves for the pile shaft and Q-z curves for the toe. Parameters were calibrated against test results and implemented using a finite-difference procedure. The model reproduced load–settlement behavior and axial-force distributions, including post-peak response; overall predictions were generally within about 10% of test results, with some discrepancies.<br /><br />The findings offer practical tools for estimating pile resistance and deformation in stiff marl, where standard methods may be unreliable. However, the correlations are based on one site, and uncertainties include marl variability, limited CPT coverage, construction-related pile-diameter changes, and model simplifications. The authors recommend validation using data from additional sites.

Keywords

axial performance

precast prestressed concrete piles

drilled displacement piles

stiff Miocene marl

load tests

shaft resistance

toe resistance

CPT correlations

strain-softening model

pile settlement