The paper discusses how the empirical relationship can be conservative when estimating helical pile capacity in compression, and load testing can result in more efficient designs. Click here to read this paper.

Full Abstract:

Several analytical methods can be used to estimate the ultimate capacity of a helical pile.  These methods involve calculations and the need for detailed information about the in situ soils.  Alternatively, the most reliable method involves an empirical relationship between installation torque and ultimate capacity, and only requires soil types and blow counts (SPT N-values) to estimate installation depths.  The results of several axial compression load tests in various soil types are examined to demonstrate that this empirical relationship can be conservative when estimating helical pile capacity in compression, and load testing can result in more efficient designs.