Foundation Supportworks of Wisconsin Case Studies: Helical Piles Installed for Hi-Tower Farms in Valders, WI

In 2010, Keller, Inc. began construction of a free stall milking complex designed to handle up to 380 head of cattle at a dairy farm operation. The exterior foundation consisted of 4-foot deep, 16-inch diameter concrete piles spaced 6 feet 8 inches apart. On top of each piling was a 2 to 6-inch thick footing (concrete “mud mat”) and a 12- inch thick foundation wall ranging from 2 to 4 feet in height.

The foundation wall was designed as a grade beam to span between the pile locations. During the site grading operations, vibratory compaction equipment was used to compact fill soils and prepare the subgrade around the manure pit. However, following construction, sections of the exterior foundation walls and interior knee walls around the pit settled as much as 4 inches, reportedly due to improper soil compaction.

Foundation Supportworks of Wisconsin was contacted to provide a system to stabilize and then lift the settled walls back toward their original elevations. Both push pier and helical pier systems were considered, but due to the relatively light loads of the structure, it was apparent that helical piers would be the better option. A soils investigation identified bedrock at depths of about 12 feet.

A hydraulic jack hammer was used to break up and remove frozen soil down to the bottom of the foundation walls. Ten Model 288 helical piers at 6-foot spacings were advanced to bear on or within the bedrock.

The helical pier configuration consisted of 2 7/8-inch OD by 0.276-inch wall hollow round shaft with 12-inch diameter single-helix leads. L-shaped retrofit brackets were placed at the tops of the piers and positioned below and against the footing. Hydraulic lift cylinders, one at each pier location, were connected in series to uniformly lift the wall sections as much as 4 inches. The 10 piers were installed in two days despite the muddy working conditions caused by thawing ground, snow melt and precipitation.