Dynamic Replacement improves the strength of saturated cohesive soils and soft organic soils, when dynamic consolidation is not effective due to the high fines content of the in-situ soils.

Dynamic Replacement was selected as an alternative to piles with extremely stringent settlement specifications for the foundation of the tracks bearing Ariane rocket carrier (2000 tons) in the French Guyana. Full-scale kentledge test was performed and confirmed the quality of soil improvement.

The determination of soil parameters of the large volume inclusions and between those inclusions, has enabled the application of Dynamic Replacement as a foundation system. Large diameter (2.5 to 4 meters) columns are driven to depth up to 7 meters and behave as mushroom pillars.

Dynamic Replacement Columns are driven into the soil by pounding with a 15 to 30 ton pounder dropped from 10 to 30 meters. The position of the Columns is prepared by a pre-excavation which is partially filled by granular material. The pounding enforces the material to the desired depth. Alternative phases of filling of the Column and Compaction of the material are performed until completion of DR-Column.

TSING-YI Oil Tanks (Hong-Kong)

The shortage of land has left no choice to CHINA PETROLEUM to reclaim land from the sea thanks to hydraulic backfill in successive stages. The period required for each consolidation stage being very important, Menard has proposed a technical solution based on Dynamic Replacement pillars, Dynamic Compaction and Preloading together with a guarantee in terms of absolute settlement (<10cm) and differential settlement (<3‰) for the tanks. A tripod capable of releasing a pounder weighing 40 tons with a height of 40 meters has been used to prepare the seating of 26 tanks in 4 months. After treatment, the tanks have been loaded with water, before being put into service for the fuels.

The settlements measured under the skirts of large tanks of 45 meters diameter and 22 meters high are ranging from 1.7 to 6.5 cm during the hydrotest which has shown rebounds between 0.5 and 2.5 cm for the same tanks.