This compaction method is positioned between the conventional shallow compaction and the deep dynamic compaction. Densifies geomaterials by repeatedly dropping a hydraulic hammer mounted on a specially adapted excavator at a fast rate. The weight of the hammer is typically between 5 and 12 tons, which is dropped freely from a height of approximately 1 m on a circular steel footing with 1 to 1.5 m diameter. The equipment can generate up to 60 blows per minute.
This technique has been developed in the UK, and is now in use worldwide.
This method is in general effective for granular geomaterials (gravel, sand, silts, and uncontrolled fills) to a depth of 3 to 4 m.
This compaction method is generally very fast and controlled as it induces less vibrations than other methods due to low impact energy, making it a suitable method to operate closer to existing structures. It can detect weak areas during execution, allowing the increase in compaction energy on those areas.
Rapid Impact Compaction (R.I.C.) is used to increase bearing capacity and stiffness of soils/fills to support building foundations, floor slabs, tanks, highways, railways, parking areas, airport runways. Mitigation liquefaction, reducing collapsible potential, compact granular fills in large lifts (up to 2 to 3 m) are other common applications.
In R.I.C. the soil right underneath the steel plate is compacted by the first blows, further blows push the dense material deeper to densify the underlying soils until no or little further penetration can be done.