Design and Load Testing of Large Diameter Helical Piles for Terminal Railroad MacArthur Bridge Project in Downtown St. Louis-Video

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Jessica Harper of Almeida Piling presented a case study on using high-capacity helical piles for replacement piers on St. Louis’s MacArthur Bridge. The federally funded rail project faced tight space, nearby existing foundations, overhead restrictions, and variable geology, making battered helical piles a practical alternative to micropiles.<br /><br />Piles were designed to bear on limestone bedrock. Load testing revealed substantial variation in bedrock depth and no anticipated gravel layer. West-side tension capacity fell short of the original 115-kip target, so the team conservatively adopted 40 kips; grouting was also incorporated into the design. Compression performance exceeded expectations: a test pile reached 713 kips with 0.64 inches of displacement.<br /><br />Final design capacities were 213 kips compression and 21 kips tension for the east pier, and 356 kips compression and 40 kips tension for the west pier. Despite geological and groundwater challenges, the team concluded helical piles were the best solution for constructability and cost, and considered the project a milestone for railroad bridge foundations.

Keywords

helical piles

MacArthur Bridge

replacement piers

limestone bedrock

load testing

railroad bridge foundations