Sandflow tunnel foundation

Sand foundation 1.0 – sand jetting
The sand jetting method was developed by the Danish company Christiani & Nielsen. When plans were made for an immersed tunnel in the Western Scheldt in 1972, this method proved unsuitable due to the great depth and strong currents. 

Sand foundation 2.0 – sand flowing
As a result, Ballast Nedam investigated an alternative approach: placing foundation sand through pipes integrated into the tunnel floor. Full‑scale trials demonstrated the effectiveness of this solution. The sand flow method was patented and first applied in the construction of the Vlaketunnel in 1975, and later, in almost every immersed tunnel in The Netherlands.This technique is known as “sand flowing” rather than “sand jetting.”

The sandflow operation is a continuous process directly starting after immersion. It requires craftmanship to operate the sandflow process. A minor mistake can cause a blow-up of the tunnel element. It is not without a reason that our experienced specialists perform the sandflow operations.