Dynamic Replacement (DR) for Soil Improvement

Dynamic Replacement (DR) is an extremely economical method for improving the overall stiffness of clay, silt and organic soils.

Presentation and key elements

The Dynamic Replacement (DR) columns are formed by a heavy pounder with a weight ranging from 15 to 30 tons drops from a height ranging from 10 to 30 m on a 0.6 to 1.2 m thick working platform prepared on the construction site using non-cohesive soil. A single column is formed by a few series of pounding. Large diameter (1.6 to 3.0 m) columns are driven to a depth ranging from 4 to 7 m.

Following the installation of Dynamic Replacement (DR) columns, the “ironing phase” is executed where the working platform and the top layer of soil is compacted. This process is normally performed by using a flat-shaped pounder with a square base. Single pounds are performed side by side at a distance equal to the external dimension of the pounder base so that the whole improved surface area is covered. Finally, classic compaction with the use of heavy vibratory rollers is conducted to complete the soil treatment.

Dynamic Replacement (DR) columns can act as piles with an extended head for stabilisation of road or rail embankments where the columns improve the stability and increase the safety factor of the embankment. These columns are also successfully applied to reduce the foundation settlement of commercial and industrial buildings and to stabilise landfills.

Dynamic Replacement (DR) columns can be constructed both in loose non-cohesive and firm soils, soft cohesive soils as well as in organic deposits. Natural aggregates, concrete rubble, crushed asphalt and construction rubble can be used to form the Dynamic Replacement (DR) columns

When and why use Dynamic Replacement?

If the ground cannot be dynamically compacted directly due to high fines content within the soil, a granular material must be added. This technique is well suited to highly compressible and weak soils and can be applied to structures with high loading (high embankment, storage tanks, etc.). It improves the bearing capacity of the poor soils and the subsequent reduction and control of total and differential settlements. An additional benefit is that dynamic replacement pillars allow for rapid drainage of the ground.