Twin Ports Interchange - Minnesota's Largest Ground Improvement Project-Video

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Video Summary

The Twin Ports Interchange project in Duluth-Superior required ground improvement because very soft, highly variable soils could not support the new embankments. Designers used a three-dimensional numerical model to represent the complex interaction among bridges, retaining walls, utilities, soils, and more than 8,000 ground-improvement elements—mostly concrete rigid inclusions, with some steel H-piles. The system also included load-transfer platforms, concrete caps, and steel reinforcement bars to limit lateral spreading.<br /><br />Extensive soil investigations and a test-fill program informed the model. Its predicted settlement of about 120 millimeters closely matched field measurements. Monitoring also tracked pore pressure, column loads, reinforcement strain, and lateral movement. Installing nearby columns caused an adjacent bridge-supporting pile to move more than two inches at depth, with roughly one inch of permanent footing movement. The project demonstrated the value of integrated modeling and instrumentation for managing complex soil-structure interactions.

Keywords

Twin Ports Interchange

ground improvement

soft soils

three-dimensional numerical model

rigid inclusions

soil-structure interaction