For many years, Vulcan included Engineering News Formula charts and data in its literature. Vulcan dropped the EN formula out of its literature in the 1970’s, for two reasons: the wave equation was in the ascendancy, and endorsement of the EN formula was an implied endorsement of the “bearing power” of the piles they drove, an endorsement which Vulcan was justifiably reluctant to make.
Nevertheless, the use of dynamic formulae persists for smaller projects and is embedded in many specifications. For this purpose, the FHWA favours the Modified Gates Formula, and this is discussed in the latest edition of their Design and Construction of Driven Pile Foundations. The section on the Modified Gates Formula is reproduced below:
Copies of the FHWA Design and Construction of Driven Pile Foundations can be obtained by clicking on the cover images to the right.