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It is often necessary to densify loose unconsolidated soils to achieve acceptable foundation performance of structures.
This is particularly required in areas of seismic activity where it is necessary to reduce soil liquefaction and seismic deformation potential. Compaction in unconsolidated soils is achieved by vibration, typically either by insertion of a large vibrating probe into the ground (vibro-compaction) or by frequent free fall drops of a large mass from a substantial height (deep dynamic compaction). Increases in designs for structures in potential seismic areas and the resulting increase in the requirement for densification has led to investigation of the potential for use of explosive compaction as an economic alternative to the more traditional techniques.
Explosive compaction is carried out by setting off explosive charges in the ground at engineered elevations and time delays. The energy released causes liquefaction of the soil close to the blast point.
This causes cyclic loading of the soil remote from the blast point. Liquefaction of the soil followed by repeated applications of explosions using controlled blast sequences causes unconsolidated soil particles to compact and settle into a denser arrangement and reduces any void ratios. As a result, surface settlement and increased soils resistance to cyclic loading will be created by the blasting.