Parking Garage Supported on Re-Used Caissons and Composite Caisson Micropiles-Video

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The presentation described foundation work for a replacement parking garage at St. Francis Hospital in Hartford, Connecticut. The existing garage’s drilled shafts had limited installation records, making their capacity uncertain, while soft clay ruled out shallow foundations and vibration-sensitive hospital operations made driven piles unsuitable.<br /><br />The team developed composite foundations: a drilled shaft to resist lateral loads, combined with a micropile socketed into bedrock to carry axial loads. This approach cost about 30% less than full-length caissons. To verify that existing shafts could be reused, the team used drop-weight dynamic testing on 12 shafts, meeting or exceeding the required test loads with minimal movement. A micropile load test also demonstrated higher-than-assumed rock bond strength, allowing shorter sockets.<br /><br />The design and construction required careful coordination, load-distribution analyses, and collaboration among the owner, designers, contractors, and testing specialists. Reusing foundations and adopting the composite solution saved more than $3 million, shortened the schedule, and reduced the project’s carbon footprint.

Keywords

replacement parking garage

composite foundations

micropiles

drilled shafts

dynamic load testing

Hartford Connecticut