MDD – Maximum Dry Density. MWD – Maximum Wet Density. OMC – Optimum moisture Content.The RIC mainly consists of three impact components: the impact “foot”, the driving cap and the hammer with the falling weight. The impact foot is a steel foot with a diameter of 1.5 m. It remains in contact with the ground the whole time. The driving cap connected to the foot allows for articulation. The impact foot, driving cap and falling weight are connected to a unit, the so-called hammer rig.

Rapid Impact Compaction with the Rapid Impact Compactor (RIC) is an innovative method in the field of near surface and deep compaction techniques. The RIC is a dynamic compaction device based on piling hammer technology. Dynamic energy is imparted by a falling weight dropping from a controlled height onto a patented foot. The foot of the device remains in contact with the ground; thus, the energy is transferred to the ground safely and efficiently. 

The RIC, imparts energy by dropping a 5 to 9 tonne weight from a relatively small height of 1.2 m at a blow rate of 40 to 90 times a minute. Depending on the ram weight, the maximum energy delivered per blow is 59 to 106 kNm. Although the energy per blow is small compared to the conventional DC, the rapid blow frequency amply compensates, resulting in a greater power that varies between 2.4 to 6.4 MNm/min. Thus, a much greater total energy input per unit area of a site can be achieved with RIC. Moreover, the energy transfer of the RIC is far more effective due to its foot which stays in contact with the ground during the impact sequence. 

Typical areas of application could include projects such as low-rise structures like housing and schools, embankments, roads and pavement areas. Having the Rapid Impact Compactor mounted on a tracked machine gives it the versatility to move about in narrow and limited height spaces, such as within existing warehouses. With regard to its mobility, the RIC is able to be transported as a single unit, with the impact foot removed and the front end lowered horizontally on a flat-bed trailer. The machine can be ready to work just a few minutes after off-loading. If road restrictions apply, the unit can be easily split into two loads with the excavator travelling separately from the hammer. Re-assembly is achieved in less than two hours. 

Numerous developments of the last decades provide a broad range of near-surface compaction technologies (such as static and dynamic rollers) and deep compaction techniques (such as deep vibro-compaction, vibro-flotation and deep vibroreplacement, heavy tamping). However, until recently no device was available for middle-deep compaction. The lately introduced Rapid Impact Compactor (RIC) aims at closing the gap between the surface compaction methods and the deep compaction methods, and permitting a middle-deep improvement of the ground up to a depth of 4 to 10 m.

The compaction effect of the Rapid Impact Compactor is characterized by pulse-shaped loading of the ground and is achieved by a specific number of blows. The ground to be improved is both compacted and displaced depending on the soil type, thus, causing plastic deformations in the near-field while elastic waves are generated in the far-field. The nature of vibration excitation (transient or periodic) is one of the limiting factors for the allowable impact on buildings and human beings and has to be taken into account for the assessment of standardized limit values. 

The technique can usually be employed within 10-15m of sound structures with the vibrations significantly less than traditional dynamic compaction. RIC can also be used in shallow granular fills containing contaminants where penetrative ground improvement techniques such as Vibro Stone Columns would risk exposing contaminants to the atmosphere.