What is Rapid Impact Compaction and why do we use it?

A compaction plate is placed on the ground to be treated. A hydraulic hammer, generally weighing less than 10 to 15 tonnes, is fitted to an excavator and used to transmit compaction energy to the soil via repeated impact. Without specific site precautions, a safe working distance to sensitive structures can usually be defined on the order of 8 to 10 m, as a distance of 5 to 6 m can usually be adopted for classical structures. At that distance, noise levels are lower than 90 dBA.

The Rapid Impact Compaction technology is the modern approach for compacting existing soils that would otherwise be excavated and compacted using a conventional roller compactor in layers of 15 to 30cm.

Energy is transferred to the underlying loose granular soils rearranging the particles into a denser formation. Rapid Impact Compaction can effectively densify up to 4-5m of soils without excavation, adding water or dewatering. It can also be used for fill compaction, which can place in bulk fill materials and compact it accordingly without adding any water.

For large infrastructure developments, Rapid Impact Compaction takes the lead due to its speed of execution that makes it much more cost effective than other alternatives.

Rapid Impact Compaction is a technique allied to Dynamic Compaction that can be used to increase the bearing capacity of soils through controlled Impact. The treatment is effective in the top layers of soil, typically up to 6m depth, though improvements up to a depth of 9m have been seen in some conditions.

Drop weights of 10 tonnes are used on our HC150 machines respectively and are dropped from heights of 1.2m – 1.5m onto a special foot assembly at 30 – 80 times per minute. The foot remains in contact with the ground at all times.

Control: the machine is accurately controlled from the excavator cab and the degree of compaction is electronically monitored,

Safety: the impact foot is in contact with the ground at all times and eliminates the risk of flying debris. Unlike conventional dynamic compaction, other activities can take place in close proximity,

Quality assurance: the impact energy and soil deflection are recorded by an on-board computer for presentation of compaction data to site managers. Results can verify work done to the client. The data can also highlight weak zones where extra fill is required, or zones where underground obstructions were present (eg. previously hidden old foundations),

Mobilisation: the Rapid Impact Compaction units are mounted on CAT 45 ton and CAT 85 ton excavators and can be mobilised within minutes of arrival on site,

Speed & cost: due to the fast ground coverage and the compaction efficiency, Rapid Impact Compaction generates a significant cost and time saving over conventional dynamic compaction methods with up to 75% cost and 100% time savings.

The compaction in the Rapid Impact Compaction technology is usually preceded by creating a test plot where the compaction is performed for various spacing and rates of blows. Then, the local compaction of the improved soil is tested and the optimal grid spacing and the number of blows per one point is determined. Depending on the soils, the number of blows varies between 10 and 40 per one point.