Overview

Dynamic formulae have been used since the nineteenth century to estimate the drivability and capacity of driven piles. With the advent of the wave equation analysis, they are certainly no longer "state of the art" and they have many limitations. However, they are found in many specifications and can be used as an initial estimate of the drivability of a given hammer in advance of a wave equation analysis.

This page is an interactive page to enable you to instantly develop the capacity/resistance table vs. blow count for two widely used dynamic formulae:

1. Engineering News Formula: The first dynamic formula to achieve wide currency (in the U.S. at least,) this formula dates back from around the time Vulcan hammers were first introduced. It is still found in many pile driving specifications, especially those for wood piling.
2. Gates Formula: A more advanced formula than the EN formula, it is recommended by the FHWA as an initial estimate of hammer size.

Use of these formulae is discussed in detail in the Vulcanhammer.info Guide to Pile Driving Equipment. All energies used are the rated striking energy of the hammer. By entering the Vulcan hammer size, you can generate this table below.

Important note: all results are in kips. EN formula results are traditionally reported in U.S. Tons; comparison needs to be made on this basis.