Jet Grout Columns in Mixed Profile to Control Foundation Settlement Gerald Ratner Athletics Center

The signature feature of the Gerald Ratner Athletics Center at The University of Chicago is the roof—a flattened S-curve, which appears to float in the air, suspended by cables attached to five masts that peak 30 to 36 m (100 to 120 ft) from the ground. The masts are inclined at 10 degrees from vertical. Each mast supports several stranded steel cables. As with any suspension structure, displacements of the mast could significantly affect cable length and tension and unfavorably redistribute loads through the superstructure. Consequently, control of foundation settlement was key to the success of this project. Consolidation settlement of stiff silty clay, underlying a medium dense sand layer, was computed to lead to total settlement in excess of the project requirements for the masts. Ground improvement, consisting of triple-fluid jet grouting, was selected to reduce the compressibility of the silty clay, increase the stiffness of the sand deposit and maintain the viability of the shallow foundation system. This case history presents the subsurface conditions at the site, structure and foundation design development and the jet grout ground improvement.