George E Ramey and Roy C Johnson Jr. This paper was first published in GE’s September 1979 edition.
Pile capacity prediction equations are widely used for predicting capacities, writing pile-driving specifications, est’mating pile length requirements, interpolating between and extrapolating beyond load test results, etc. The most common categories of these equations are:
(a) dynamic impact equations,
(b) dynamic wave equations, and
(c) static soil mechanics equations.
The first two equation categories give estimates of pile capacity at the time of driving based on the pile behaviour under the last hammer blow. They do not profess to estimate increases or decreases from that capacity with time as the moulded soil restabilises. The soil mechanics approach provides capacity estimates based on undisturbed soiI conditions.