Impact Stresses During Dynamic Compaction

The development of an analytical model for describing ground behavior during dynamic compaction requires that the magnitude of impact stresses be known. Although several theoretical methods for calculating dynamic stresses have been proposed, very few field measurements from full-scale operations have been made available for checking their validity. This technical note presents measured peak dynamic stresses at the ground surface obtained from an accelerometer mounted on the falling weight. The field testing program investigated a range of drop heights up to 19 meters using a constant weight of 20.9 tonnes. A simple analytical model derived from the conservation of momentum is shown to provide reasonable estimates of the magnitude and duration of impact stresses during dynamic compaction.