Remediation shaft Beerenbosch I

About shaft Beerenbosch I

Construction of Schacht Beerenbosch I began in 1905, and in 1928 the shaft reached its final depth of 428 meters. 

The first part of the shaft is a circular tunnel with a diameter of 2.15 m. The wall of the tunnel is made of masonry 30 centimeters thick. This tunnel goes 60 meters straight down into the ground. After this, the diameter widens to 2.60 meters. 

In 1969, people stopped using the shaft. Therefore, the shaft was rehabilitated (closed) by placing a concrete plug in the tunnel. This concrete plug is 6 meters thick and is located 60 meters below ground where the shaft widens. The tunnel above the plug was also filled with concrete and this layer is about two meters below ground level. 

Why are we remediating the shaft?

In 2016, the Ministry of Economy released the results of a study of remediated mine shafts. That study showed that mine shafts used to be remediated in a way that is safe today. But in recent years we have learned many new things about shaft sealing. New ways that remain safe well into the future.  

In order to keep the shafts solid in the future, we will have to take extra measures with a number of shafts.

This is also the case with the Beerenbosch I shaft. The concrete plug in the shaft is not far and deep enough into the ground to ensure that it remains firmly in place in the future. Therefore, the German company Daldrup & Söhne AG is now making the plug longer at the bottom. They can do this kind of special work. This company also did the rehabilitation of the Willem II shaft of the Domaniale mine. 

How do we remediate the shaft ? 

This is done in the same way as for the Willem II shaft. To keep the shaft solid for the long future, Daldrup & Söhne AG drills an opening in the concrete plug. Through this opening, they then inject waterproof and lightweight foam into the shaft. This foam floats and forms a layer on the mine water at the bottom of the shaft. 

There is then an empty space between the layer of foam on the water and the bottom of the concrete plug. They fill this by spraying concrete down through the drilled opening. Just as much until the space is completely filled with concrete. After this, the plug is a lot longer. 

Why are we having this done now? 

We are having this done now because the mine water is rising about 2 meters per year. The water is now about 32 meters below the concrete plug. The layer of foam glass is 10 meters high. That means 22 meters of concrete can spray into the space. If we wait too long, there won't be enough room left to make the concrete plug long enough. 

How long will the work take? 

Daldrup & Söhne AG has already begun preparations. They have already cleared the entrance to the shaft.

We expect the work to continue for another 3 to 4 months. 

Do we use the mine water from the shaft as an energy source? 

No, we don't do that here. So the work also has nothing to do with using mine water as an energy source.