Use of Nondestructive Testing To Establish Installation Disturbance Zone Criteria For Adjacent Continuous Flight Auger Pile Installation on Design Build Project-Paper

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The study evaluated whether continuous flight auger (CFA) piles could be installed closer together and sooner than required by the project’s specifications without compromising pile integrity. The Jamaica Bus Depot Expansion in Queens, New York, required a 15 ft separation from grouted piles less than 24 hours old. For its 24 in diameter piles, this was more conservative than the six-diameter spacing and 12-hour curing guidance in the New York City Building Code and Deep Foundations Institute manual.<br /><br />During a test program at three site locations, the team installed piles 12 ft apart within the same work shift, and others 6 ft apart after approximately 16 hours. They assessed the piles using Thermal Integrity Profiling (TIP), Sonic Echo (SE) testing, and construction observations and records.<br /><br />Testing found no evidence that adjacent drilling affected previously installed piles at either spacing and curing interval. Two piles showed anomalies, but the evidence attributed them to construction issues unrelated to neighboring pile installation: one likely resulted from reinforcement cage misalignment, while the other had necking associated with withdrawal resistance and reduced grout placement.<br /><br />The results supported adopting 12 ft spacing beside freshly grouted piles and 6 ft spacing after about 16 hours of curing, improving construction efficiency without detected integrity impacts. The project demonstrates how time-based TIP measurements, combined with SE testing and installation records, can help establish site-specific installation criteria. The authors recommend further research across different soils, pile sizes, spacings, and curing times.

Keywords

continuous flight auger piles

CFA piles

pile spacing

grout curing time

pile integrity

Thermal Integrity Profiling

Sonic Echo testing

deep foundations

construction efficiency

Jamaica Bus Depot Expansion