Specification of Minimum Pile Hammer Energy

We often see minimum hammer energy ratings listed in plans for piling projects. Unfortunately, it appears that most of these energy requirements were not made on the basis of WEAP (wave equation) analysis. Often the specified hammer energies are vastly lower than those needed to meet constructability requirements or to develop sufficient pile movement to fully mobilize the geotechnical resistance of a pile subject to dynamic testing (PDA).

In our view, this often creates the situation where the contractor may be misled about the size of hammer (and often the size of crane needed to support the hammer and leads) at bid time

The best approach for determining pile hammer requirements would be to leave this up to the contractor as part of their means and methods. Alternatively the designer, owner or a pile testing consultant engaged by them could perform the WEAP analysis to determine minimum hammer energy requirements to satisfy pile constructability.