Why there are nearly 10,000 sandbags on the A7
Strange face
It’s a strange sight, a highway full of sandbags. Across the entire width of the A7 near the Frisian village of Uitwellingerga, 1,700 sandbags were placed on December 14 on behalf of the Department of Public Works. A few days later, another 550 were added. But it still appears to be far from enough.
Tunneling
The sandbags should prevent the road from breaking down near the Princess Margriet Tunnel. Indeed, in early December, it was found that part of the tunnel trench had risen and the asphalt was crumbling. According to the Department of Public Works, it is due to the high pressure of groundwater.
What do the sandbags do?
With the sandbags, the Department of Public Works is trying to stabilize the so-called tunnel legs. The tunnel legs together form the tunnel box and are secured with dozens of ground anchors. High pressure from groundwater caused the anchors of one tunnel leg to break off, raising a road section.
More sandbags
To prevent other ditches from moving as well, a businessman is now placing 7,500 additional sandbags, spread across all the other tunnel ditches. The sandbags create a pressure four times greater than the pressure from below due to groundwater. The highway section may remain closed for months. Traffic between Sneek and Joure will be diverted via the A7, A32 and N31