High-Capacity Pipe Piles for the Marquette Interchange Reconstruction

The confluence of Interstate Highways I-94, I-43, and I-794 immediately southwest of downtown Milwaukee, Wisconsin, comprises the Marquette Interchange. The interchange covers a large area with highly variable soil conditions. A design-phase test program consisting of 88 test piles was undertaken to quantify both the time rate and magnitude of soil set-up. The test program included 51 indicator piles, 6 axial compression load test piles, 7 companion piles, and 24 reaction piles. Multiple restrike dynamic tests were performed with the last restrike typically conducted between 27 and 56 days after initial driving. Significant increases in shaft resistance occurred, with the poorest soil conditions exhibiting nearly a five-fold increase. Based on the test program results, 324 mm, 356 mm, and 406 mm O.D., closed-end pipe piles with maximum design loads of 1,334, 1,779, and 2,224 kN, respectively were used for the interchange foundations. These high-capacity pipe pile foundations were chosen because of reduced substructure size, reduced utility impact, and the associated cost savings provided by high-capacity foundation units. During interchange reconstruction, the construction schedule could not accommodate long-term restrikes. Therefore, a select number of test piles were dynamically tested during installation and during a short-term restrike at each of the 261 substructure locations. The capacity at the end of driving and the short-term set-up information was compared to the soil set-up magnitude and time rate of set-up quantified in the design-phase test program, and was used to develop pile installation criteria for the cost-effective, high-capacity pile foundations. Depth-variable driving criteria were used which incorporated the reduced end of driving capacity required with increasing pile penetration depth due to the increased soil set-up that occurred with deeper pile penetration depths.