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Helical piles for a residential retaining wall

When the Techno Metal Post dealer in Iowa, Corey DePenning, was approached by a customer for a retaining wall, he remembered seeing an original stained wood and steel retaining wall project carried out by another Techno Metal Post dealer near Toronto, Canada. He submitted the idea to the customer, and without further ado the design was accepted. Retaining walls of this type are more commonly seen in commercial projects, but helical piles can be used at any size scale, which makes a residential retaining wall on helical piles an effective and durable solution. The wall, being 100’ long and 6’ to 10’ tall, depending on the section, turned out to be a challenge because of the time frame allotted for this job and the difficult area to work in, but very well worth it seeing the great looking end results.

The WF Beams, Channels, Plates, and Techno Metal Post helical products had to be 50 KSI minimum. The project was supervised by a certified engineer from the state of Iowa who recommended the use of P5 (5.563″ x 0.258″ O.D shaft) piles for the wall, every 6’, as well as P3’s (3.5″ x 0.216″ O.D shaft), installed at a 15-degree angle for the tie backs. The design was based upon SM-SC-ML type backfill with a prescriptive 85 PCF lateral earth pressure per ASCE 7 Table 3.2-1. The piles were driven by the EM-1 machine, in black dirt, clay and even shale at 14’ below ground.

  • Location: Des Moines, Iowa
  • Obstacles: Existing retaining wall and Tree roots
  • Soil type: Black dirt and Clay Mixed and shale roughly 14’ below
  • Advantage: Less cost than driven beams and much less time.  Completed the entire wall in a week.
  • Materials: P5 (563″ x 0.258” O.D shaft) for the wall and P3-10’(3.5″ x 0.216″ O.D shaft) tie backs
  • Equipment: EM-1
  • Bearing Capacity: 20K
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