Dynamic Compaction/Compression

Definition

A class of soil improvement methods that involves application of repeated impulsive loading onto the ground surface.

Dynamic compaction (DC) was originally developed for densifying loose granular fills and its effectiveness for such materials is well documented. The most common method of applying impulsive loading is by dropping a disk-shaped heavy mass with a weight of between 10 and 40 tonnes and a radius of between 2 and 4 m, from a height of between 5 and 30 m (Lee and Gu 2004).

The primary mechanism causing densification are compressional (P-) waves generated by the impact of the falling weight on the ground. The passage of these waves causes a large, transient increase in effective stress, resulting in densification and plastic volumetric change of the soil (Gu and Lee 2002). The passage of shear (S-) waves causing cyclic shearing may also have a secondary effect, but this is likely to be much less significant, since the number of cycles due to impulsive loading is...