Drilled Displacement Piles – Current Practice and Design-Article

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Drilled displacement (DD) piles are cast-in-place foundations installed with specialized augers that push soil laterally, producing little spoil and generally less noise and vibration than driven piles. Their capacity typically falls between that of comparable bored piles and full-displacement driven piles, though it varies with soil conditions, tool design, and installation method. Common systems include Atlas, De Waal, Fundex, Olivier, Omega, pressure-grouted displacement (PGD), and SVV piles. Their tools and extraction procedures create either smooth or screw-shaped shafts.<br /><br />The paper reviews installation, construction monitoring, and three empirical design methods based mainly on cone penetration, standard penetration, or pressuremeter test data. Automated monitoring can record drilling depth, torque, penetration rate, and grout or concrete delivery, supporting quality control but not replacing field inspection.<br /><br />Comparisons with load tests at Belgium’s Limelette site show that design predictions vary: one method generally overestimated measured capacities, while another was closer for some pile types but underestimated others. For a Georgia residual-soil profile, predicted DD pile capacity also varied substantially by method. These results emphasize that existing methods are site-specific and cannot reliably capture installation-induced changes in soil behavior.<br /><br />The authors recommend improving design methods to account for pile type, installation effects, and soil response. Progress requires well-characterized sites, instrumented load tests extending beyond 10% of pile diameter, systematic installation monitoring, and a broader database combining pre- and post-installation soil tests with load-test results.

Keywords

drilled displacement piles

cast-in-place foundations

soil displacement

empirical design methods

cone penetration test

standard penetration test

pressuremeter test

installation monitoring

pile load tests

site-specific design