Solving Variable Bedrock Challenges with Ductile Iron Piles-Video

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The presentation describes a 370-foot pedestrian bridge connecting an existing Tampa clinic to a new hospital tower across a busy road. Heavy compression, tension, and lateral loads, restricted access, variable limestone, and weak soil layers made foundation design challenging. The team selected externally grouted ductile iron piles, installed with an excavator-mounted percussion hammer, as a faster, less costly alternative to driven steel piles. The grout helped provide skin friction and capacity despite uncertainty about bedrock depth, grout loss, and potential pile necking. A site-specific load-test program confirmed the design, with piles tested to several times their required loads. During construction, the crew installed about 20 piles per day, monitored vibrations near the clinic, and completed the work in roughly 75% of the scheduled time. The project also demonstrated the system’s adaptability to variable pile lengths, limited overhead clearance, and equipment relocation across the road.

Keywords

pedestrian bridge

ductile iron piles

foundation design

externally grouted piles

load testing

limestone soil conditions