June 3 2020 ITS Money: Brian Koch

Brian Koch, P.E., D. GE | Michels Corporation

Bidirectional Load Test – Case Study: I-74 Over the Mississippi River

Utilizing barges, 233 drilled shafts were installed in the Mississippi River for a bridge from Moline, IL to Bettendorf, IA . For each shaft 7 ft. to 10 ft. permanent steel casing was installed into the bedrock and a socket was drilled to depths of 60 ft. for each shaft. A bidirectional load test was then performed in a demonstration shaft to confirm the constructed shafts were meeting designed capacities. Due to the information gained from the load test, 24 drilled shaft rock sockets were reduced substantially, which in turn reduced the schedule and cost of the project.

Findings

Benefits of performing the bidirectional load test on the I-74 Mississippi River Bridge Project.

• Saved money by reducing the length of rock sockets.
• Reduced schedule duration by reducing the length of rock sockets.
• It preserved natural resources by reducing the work required to construct the bridge.

In addition, it saved the design team loss of sleep by providing them with actual capacities to ensure proper design.