Menard proposed to treat the whole site (housing plots, retaining walls, roads and gardens) using the Dynamic Compaction/Dynamic Replacement (DC/DR) techniques in order to increase the bearing capacity of the soil and ensure long term settlements performance (25 mm beneath the housing plots and 50 mm elsewhere). This solution presented significant advantages over a traditional piling scheme: no issues with the obstructions within the made ground, reduced overall costs and significant reduction of carbon footprint of the whole project.
A specific sequence of works had to be devised because of to the numerous different plateau levels with associated retaining walls required on the site because of the topography. An extensive testing regime had been put in place to demonstrate the effectiveness of the DC/DR works for all areas. This comprised Cone Penetration Tests (CPT) prior and after the ground improvement in the made ground, CPT inside the DR pillars, as well as dummy footing tests. Vibration monitoring had also been put in place for the duration of the DC/DR works.
The use of Dynamic Compaction/Dynamic Replacement (DC/DR) significantly reduced the carbon footprint of the project as no supply of material was required for DC and only aggregates (no concrete or cement) for DR. In addition, the aggregates were sourced locally, taken directly from the cut areas of the site. DC/DR represents overall a very eco-friendly ground improvement alternative to traditional piling for brownfield remediation.