Dynamic compaction uses the energy from a falling weight in a pre-determined grid pattern to improve granular soils and fills.
Dynamic compaction is a ground improvement technique that densifies soils and fill materials by using a drop weight. The drop weight, typically steel, is lifted by a crane and repeatedly dropped onto the ground surface. Vibrations transmitted below the surface improve soils at depth. The drop locations are typically located on a grid pattern, the spacing of which is determined by the subsurface conditions and foundation loading and geometry.
Treated granular soils and fills have increased density, friction angle, and stiffness. In shallow karst geologies, dynamic compaction has been used to collapse voids before construction to reduce sinkhole potential. It has also been used to compact construction debris and urban fill as well as sanitary landfills before construction of parking lots, roadways, and embankments. The removal of compressible, contaminated fills can sometimes be avoided.
Typically, in situ testing by borehole or static cone penetrometer, allied with measurement of print volume and site surface settlement is performed during the dynamic deep compaction.
The treatment pattern, energy level, number of passes, and phasing of passes must be designed to take into account the soil conditions, type of development and required bearing capacity, and settlement characteristics. It is essential to have a thorough understanding of the soils before treatment and to maintain very close control during all phases of the work. Typically, in situ testing by borehole or static cone penetrometer, allied with measurement of print volume and site surface settlement is performed during the dynamic deep compaction contract.