A conservative ratio of 10:1 capacity versus torque is recommended for the square shaft series of piers. An example would be if a pier or tieback has a specified ultimate load of 50,000 lbs. using the square shaft series, an installation torque of 5,000 ft. lbs. would be specified.

With the slender design, buckling has always caused concern among engineers with little history in Helical-Piers. Full-scale load testing and experience has shown buckling of the A.B. Chance Helical steel piers is not a concern at the rated capacity when the pier is installed in a soil of 5 blow counts or more. The soil has been proven sufficient for support against lateral movement.

The design engineer can utilize the same design approach in designing the helical steel pier as with any other bearing end pile. The helix size(s) is determined by using basic soil mechanics for end bearing piles. The shaft size specified is based upon the rated load carrying capacities for the shaft size and installation torque required to install the pier. The shaft sizes range from 1-1/2 x 1-1/2 to 2 x 2 inch, 80 ksi, solid steel. Arizona Helical-Piers, L.L.C. and our engineering support are available to aid the engineer in determining the most appropriate shaft size for the application. Additional design considerations are as follows:

An existing retail building has exhibited settlement. The design engineer has determined best pier spacing would result in a design load of 32 kips per pier. Soil conditions consist of 10' of uncontrollable fill overlying a sandy clay with and average cohesion value of 5,000 psf.
Determined helix size(s) and shaft size to carry the design load of 32 kips.