High Capacity Drilled Displacement Piles as an Alternative to Conventional Driven Methods-Paper

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The Red Hook Houses in Brooklyn, damaged by flooding during Superstorm Sandy, underwent rehabilitation to improve resilience to future storms. Difficult ground conditions—including deep fill, loose sands, organic deposits, and soft soils—initially led designers to specify conventional driven steel piles.<br /><br />As a bidding alternative, the project team proposed pressure-grouted drilled displacement piles with double steel casing, designed using micropile and helical-pile methods. Grout injected during installation displaced surrounding soil and formed a composite steel, grout, and soil-mix pile. The alternative aimed to meet substantial axial and lateral loads while reducing installation time, noise, vibration, and cost.<br /><br />Seven test piles were installed at the east and west building sites. Static compression tests recorded ultimate capacities of 128 tons for several piles and 420 tons for higher-capacity piles. Lateral tests showed deflections under approximately 0.5 inch at the tested loads, consistent with design analyses. The results supported the piles’ suitability for the project’s requirements.<br /><br />The authors conclude that drilled displacement piles can provide high capacity with shallower embedment than conventional driven piles, and may be an economical option in soft or loose ground. At Red Hook, the method generated little spoil, reduced vibration, accelerated construction, and was estimated to save about $1 million. The approach was accepted by the New York City Housing Authority. The paper notes that alternative foundation systems may require additional testing and design documentation to address uncertainty among project teams.

Keywords

Red Hook Houses

Brooklyn

Superstorm Sandy

flood resilience

foundation rehabilitation

drilled displacement piles

pressure-grouted piles

micropile methods

lateral load testing

construction cost savings