Case Study – Deep Soil Stabilization in City Creek Mall in Salt Lake City, UT
City Creek Center is an up-scale shopping center in downtown Salt Lake City. While under construction, a five-foot wide trench between two underground parking garages was back-filled with pea gravel and a sidewalk was built on top of it.
About ten years later, the gravel began to settle enough to cause underground power lines to stretch and finally tear, knocking the power out for many of the local businesses. Engineers determined that the trench needed to be stabilized by injecting polyurethane grout down to about 35 feet below the surface to strengthen and stabilize the gravelly soil.
PolyFoam Solutions, a local geotechnical services contractor, was called in to perform the work. A single-component polyurethane, AP 700, was chosen as the grout to be injected due to its ability to permeate through the soil, fill the voids between the rocks, and provide excellent strength and stability.
PolyFoam Solutions developed an injection plan and detailed where each of the injection points would be located. The plan was communicated to the engineer, and approval was given to move forward with the project. PolyFoam Solutions installed 10 injection tubes down to 35 feet below the surface. They pumped approximately 1 gallon of polyurethane grout (foam) while upstaging the tubes 1 foot at a time. The injection points were spaced about 36” apart.
After only two days, the site work was completed, and the general contractor was able to move forward with filling the trench and repairing the sidewalk.
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