Continuous Flight Auger Cast Piles for Bridge Foundations-Video

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The presentation describes a value-engineered foundation for the MD-152 interchange reconstruction on I-95 in Maryland. To replace 107 battered micropiles beneath Abutment B, the team designed 119 plumb, 18-inch continuous flight auger (CFA) piles, each approximately 40 feet long. The alternative maintained the existing abutment footprint and limited lateral deflection while avoiding vibration risks to a nearby 108-inch water main.<br /><br />Because AASHTO provides little CFA-specific guidance, the team followed FHWA’s GEC No. 8 and used a factor of safety of two. Subsurface conditions included silt over saprolite; CPT and SPT data informed capacity estimates. Group analysis evaluated 82 load cases across four construction phases, including lateral pile-group effects. A test pile failed at 574 kips, supporting an estimated capacity of about 490 kips versus the 400-kip design value.<br /><br />Structural design required checking steel casing strength, pile fixity, and footing reinforcement. Wing walls required a different, larger CFA design because of spacing and load constraints.

Keywords

MD-152 interchange

continuous flight auger piles

foundation redesign

Abutment B

FHWA GEC No. 8

pile group analysis