Can you compact in the rain?

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 Rapid Impact Compaction for the soil improvement uses a hydraulic hammer mounted on an excavator. The hammer with a weight ranging from 5 up to 12 tons is dropped freely from a height of 1.2 m on a large circular foot. Impacts repeated at a rate ranging from 40 up to 60 blows per minute plunge the steel foot creating a crater.

The control system installed in the operator’s cab allows for controlling the compaction process and recording the parameters such as impact energy or foot penetration. It can also be used to change the height from which the hammer is dropped.

The compaction in the RIC 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.

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.

RIC can be used to improve bearing capacity and reduce liquefaction potential of loose soils. The compaction sequence is designed to work from the outside in, so that compaction of the lower zone soils occurs first followed by compaction of the upper zone. Data monitoring during the compaction process and the online display in the operator’s cab enables compaction control, an economic application of the compaction tool, and a work integrated quality control. The total impact depth of the impact foot, the number of blows, and the final settlement of the impact foot after a blow define the stopping criteria.