Natural soil deposits and undocumented fills can be densified by dropping large weights from great heights repeatedly on the ground surface. Because the energy imparted is considerable, compaction can be achieved at significant depths below the ground surface.
This mass of concrete, weighing about 12,000 pounds, was used for deep dynamic compaction at the site of an oil storage tank farm on Hokkaido, in Japan.
Here the mass has been lifted to a height of about 50 feet, and is ready to be dropped. When it hits the surface of the ground, the blow will impart about 600,000 foot-pounds of energy.
These craters are the result of dropping the weight.
The craters were surveyed to determine the effects of the treatment.