Rapid Impact Compaction

Rapid Impact Compaction is a shallow ground improvement and densification technique. This method densifies shallow, granular soils, which repeatedly strike an impact plate on the ground surface using a hydraulic hammer. The energy is transferred to the underlying loose soils and regroups the particles into a denser formation. The impact locations are located on a grid pattern and the spacing of those locations is calculated by the subsurface conditions and foundation loading and geometry.

Rapid impact compaction reduces liquefaction and seismic-induced settlement. This compaction involves lower levels of vibration with higher frequencies which are less damaging to existing structures, where dynamic compaction cannot be used.

Process of Rapid impact compaction:

RIC technique is performed at the surface of a terrain and it comprises of a heavy excavator which is equipped with a specially designed arm onto which the hammer is attached. Within the hammer, a 9 to 16 drop weight is hydraulically lifted till a required height after which the weight is dropped using a hydraulic acceleration. This whole process of lifting and dropping of the weight takes place with a frequency of 40 to 80 times a minute.

During the compaction of a location, the foot remains into contact with the soil. The impact of the hammer on to the foot initiates the compaction process. The movement of the foot into the ground, the heavy weight of the equipment and high energy transfer is also causing densification. The dense compaction grid ensures that a homogeneous compaction is reached throughout the area. This is caused because the impact locations are also affected by the compaction of nearby points which results in improving the overall performance.

Advantages of Rapid impact compaction:

• The bearing capacity of the soil is increased after it is treated.
• Minimizes settlement to a greater extent and provides uniform support for a floor slab or foundation footing, while controlling vibrations to 2 inches per second within 30 feet of the drop point.
• Rapid Impact Compaction consolidates the soil immediately instead of using a surcharge to consolidate the soil under a static weight.
• Loose fills or soils can be consolidated immediately without the need to replace the soil.
• When the soil is treated by Rapid impact compaction, the stiffness of the upper 10 feet of soil affects the lateral load capacity of a pile. By densifying the upper layers, the lateral load capacity is greatly increased.

Remarks:

RIC is a great alternative when compared to the time and cost of over-excavation and re-compaction.