Dynamic Compaction is a compaction method which has been around for more than 60 years. It is a simple method with a great impact. A pounder is dropped in free fall from a specified height onto the surface to compact the soil. Cofra uses this technique in situations where our other compaction systems do not meet the criteria in an economical way or where our other methods are not allowed. With a depth of influence of over 12 meters, the technique has a larger depth of influence when compared to our CDC compaction hammers. Cofra uses the dynamic compaction with state of art monitoring systems to make the process as controlled as possible.
Dynamic Compaction (DC) is a technique that densifies loose granular materials up to a depth of 10 to 12 meters below the surface by repeatedly dropping a pounder of 10 to 20 tons from a height of 10 to 25m onto the surface.
The compaction of the underground is initiated by vibrations, which lead to the rearrangement of the particles. These vibrations are generated from the impact of a weight onto the surface.
With the impact of the pounder densification is achieved and a large depression is created. The depression should not extend into the watertable, blocking an effect transfer of the impact energy into the ground. Depending on the requirements, 4 to 10 blows are given on each location. A wide compaction grid is used in several phases.
The compaction results are, amongst others, dependent on the soil type, fines content and requirements. An assessment of the local soil by a compaction expert is therefore highly recommended. The depth of influence can be limited by density differences in the subsoil. If the situation is ideal, effects can be measured up to 12 meters deep. Improvements of up to qc=30MPa have often been achieved in the top 7-8 meters of the soil column
Compaction is required to mitigate liquefaction risks or improve the bearing capacity and settlement behavior under loading of the underground. Dynamic compaction is often used on new reclamations to compact the subsoil up to requirements to avoid liquefaction under an earthquake. The solution is also in high demand to improve the bearing and settlement characteristics of the top layers .
Applying Dynamic Compaction will result in the following effects:
Dynamic Compaction is used in the following markets (click on the specific market for more information):
The following soil types are suitable for the use of DC:
The operational process of Dynamic Compaction consists of placing the pounder on the marked location. After positioning, the pounder is lifted and released from the predetermined height. After impact the pounder is lifted for a following drop. This process is repeated until the stop criteria set by our geotechnical engineer are met. These stop criteria are determined during field trials investigating the the number of blows by print, the drop height, the pounder weight and the number of phases.
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