C-TEC AG • 800-345-2832 • http://www.ctecag.com
Reprinted from Grain Journal January/February 2019 Issue
Grain Bin Settling
Unstable soils underneath a 150,000-bushel, 90-diameter steel grain bin caused half of the slab to settle six inches after it had been built in 2010.
The tank foundation’s geopiers had been inserted at a depth of 15 feet but did not have enough strength to support the filled grain bin. The slab had been constructed with a ring footing foundation on a six-inch floor over a six-inch base of granular fill. At full storage capacity of 4,600 tons, the grain load for the bin could not be supported.
Alternative bids to fix the problem exceeded $1 million and would have taken months, which would have interfered with the approaching fall harvest.
Polyurethane Foam Injection
By using geotechnical reports, CTEC AG, York, NE (800-345-2832), designed a plan to stabilize the subgrade and also to lift the settled slab.
To stabilize the soil, a four-foot grid pattern of 106 points was used to install HydroFoam (HF) 402, a high-strength polyurethane foam, at a depth of 12 to 15 feet. Each injection point accepted 15 to 75 pounds of material. A total of 4,500 pounds of HF402 foam was installed to stabilize the subgrade.
After the soil was stabilized, 62 5/8-inch holes were drilled to pump material through injection ports for lifting the slab. A five-inch lift was achieved using 4,500 pounds of HF 402 Fast and 1,000 pounds of RR 401, another high-strength foam. At five inches, the slab showed no signs of stress, and the customer was pleased to conclude the project.
It took five days to drill, stabilize, lift, and complete the project, which saved the owners months of downtime and hundreds of thousands of dollars.
