Dynamic Compaction involves imparting energy to the ground through the use of a falling weight. This technique is divided into two main areas: Deep Dynamic Compaction and Rapid Impact Compaction. Deep Dynamic Compaction involves repeatedly dropping a large weight (typically 15 - 25 tonne) over a height of in the order of 15 - 20 meters from a crane onto selected grid points to densify or compact the underlying soils. Rapid Impact Compaction involves dropping a smaller weight (7 - 13 tonne) from a much smaller distance (1.2 - 1.5 meters), but doing so repeatedly in very quick succession (40 times per minute) to improve the ground.
The main variation between the methods is the depth of effectiveness. Deep Dynamic Compaction is typically used to improve soils up to 10 - 15 meters in depth, whereas Rapid Impact Compaction typically has a depth of influence range of 4 - 6 meters. Deep Dynamic Compaction generates significant vibration and as such may not be suitable in congested areas.