Innovative Deep Foundation Support using Ductile Iron Piles-Paper

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The paper presents ductile iron piles (DIPs) as a low-vibration, modular deep-foundation option for constrained urban construction. The small-diameter piles are driven in standard 5 m sections using a hydraulic breaker hammer; bell-and-spigot connections join sections without field splicing. Depending on soil conditions and design needs, DIPs can develop capacity through end-bearing on dense soil or rock, or through a grout-bonded shaft that provides compression and tension resistance.<br /><br />The system was used at two Johnson & Wales University projects in Providence, Rhode Island, where limited access, nearby buildings, and vibration concerns influenced foundation selection. At the Center for Physician Assistant Studies, 118/7.5-series piles were driven through urban fill, peat, and sand to bear in glacial till. Designed for 70-kip allowable capacity, they were installed to a set criterion and grouted. A full-scale load test showed 12 mm of movement at the design load of 70 kips and confirmed performance at twice that load.<br /><br />At the School of Engineering & Design, friction DIPs were used near existing buildings as an alternative to conventional drilled micropiles. Grout injected through an oversized conical cap formed a bond zone in sand; selected piles included reinforcing bars for tension resistance. A tension test showed limited movement at the 75-kip design load and maintained resistance at 225% of design load. In total, 66 piles were installed in three working days, with minimal observed vibration.<br /><br />The projects demonstrate that DIPs can be adapted to varied ground conditions and loading requirements. Load tests at both sites supported the design methods and capacities. The authors identify cost-effectiveness, rapid installation, low vibration, and suitability for restricted sites as key advantages.

Keywords

ductile iron piles

deep foundation

low vibration

urban construction

modular piles

grout-bonded shaft

end-bearing

load test

restricted access sites

bell-and-spigot connections