Installed with a torque drive mounted on a mini hydraulic excavator, this viable approach to foundation support requires pre excavation to the bot tom of a structure’s existing footings. The approach is best suited for one to 2 story structures.
As in the case of mini piles, if no foundation exists, one must be installed. Helical anchors are advanced to refusal, the depth of which will vary greatly from site to site. The 7" to 12" diameter anchors are best suited for sites with silty to gravelly soil, with relatively shallow excavation depths. As with mini piles, a bracket is fitted to the top of anchor 2.75" diameter shaft. This bracket grabs the edge of the footing or angle iron (if required) and is affixed to the footing. The bracket has two tensioning bolts which are tightened to transfer the structural load onto the piles.
Pile spans are typically 5-8′ and allow adequate width to pass conveyors and mini excavators. On completion of contaminated soil dig out, the foundation must be replaced. This approach is priced at $1,800 – $2,000 per helical pile plus the $3,000 – $8,000 cost of pre excavation work depending on site specific details.
|Design Capacities||48,000 lbs|
|Diameter (inside) Nominal||3 in|
|Wall Thickness||0.216 in|
|Diameter (outside) Nominal||3.432 in|
|R – Radius (outside) Nominal||1.716 in|
|r – Radius of Gyration||1.16 in|
|I – Moment of Inertia||3.02 in(4)|
|B – Bending Factor||1.29|
|K – Effective Length Factor (theoretical)||0.7|
|K – Effective Length Factor (recommended design value)||0.8|
International Building Code Allowable Capacity
Fully Supported Column – 48,000 lbs
Soft Soil 5′ Unbraced Column – 48,000 lbs
Liquid Soil 10′ Unbraced Column – 28,000 lba