Test Pile Program to Determine Axial Capacity and Pile Setup for the Biloxi Bay Bridge-Article

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Hurricane Katrina destroyed the U.S. 90 bridge over Biloxi Bay, prompting construction of a replacement under a demanding schedule. To reduce foundation-design and construction risks, the project team conducted a comprehensive driven-pile testing program before production installation.<br /><br />The team installed 22 indicator piles—18-, 24-, and 30-inch square precast concrete piles—and monitored driving and restrikes with a Pile Driving Analyzer. Five load tests were performed: one static axial test, two axial Statnamic tests, and two lateral Statnamic tests. The program assessed pile drivability, driving stresses, axial and lateral capacity, and the increase in capacity over time after driving (“setup”).<br /><br />Setup varied with soil conditions. Resistance generally increased more in clay (setup factors of about 1.8–3.0) than in sand (about 1.0–1.4), with mixed clay-and-sand profiles typically between these ranges. The results informed pier-specific driving criteria, including hammer operation, minimum tip elevations, end-of-drive resistance, and when restrike testing or further driving would be needed. Load-test results agreed well with dynamic measurements, supporting the design capacity estimates.<br /><br />The findings allowed the team to shorten estimated lengths of some 24-inch piles by 5–25 feet, confirm the planned capacity of 30-inch piles, and validate the lateral-response model. Accounting for setup in the driving criteria reduced uncertainty and the anticipated need for production restrikes. The program helped pile installation begin ahead of schedule and remain on schedule.

Keywords

Hurricane Katrina

U.S. 90 bridge

Biloxi Bay

driven-pile testing

precast concrete piles

Pile Driving Analyzer

Statnamic tests

pile setup

axial and lateral capacity

foundation design