The soil in the road trace consist of peat and soft clay layers. To create a stable and loadbearing foundation, soil improvement is required to prevent excessive settlements during the lifespan. Wicks is carrying out the soil improvement by installing Prefabricated Vertical Drains (PVD) for De Groene Boog consortium.

Due to the presence of an intermediate sand layer, there is a special requirement for the PVD installation. The intermediate sand layer is not allowed to come into contact with the Pleistocene lower sand layer. Connecting these two sand layers will create a waterflow that can cause major issues with the water management of the polder.

Prior to PVD installation, extensive soil investigation is being performed to locate the intermediate sand layer. This is done with the PVD installation rigs, by penetrating the road trace at regular intervals. The dataloggers register the penetration forces accurately, and with the data acquisition system the intermediate sand layer can be easily mapped.

With this data, below surface drains are installed in the deeper soft soil layer. These drains terminate in the intermediate sand layer. Separately, drains are installed into the top soft soil layer. These upper drains are terminated in the working platform above ground level.

Wicks’ early involvement in the project assisted our customer with an economic technical solution to meet the special requirements.

Despite stringent Covid19 measures, the project is progressing well. PVD installation is expected to be completed by 2022, while the new motorway is planned to be open for traffic by 2024.