Delicate piling job in Germany

First, a quick lesson in conductor piling for beginners. The conductors are made up of tubes - in this case over 12 meters in length. A special pile-driving hammer is used to drive the tubes into the ground at right angles. When the tube is still about 2.5 meters above the ground, the Foxdrill specialists use a special piling trailer to place the next tube on top of it and weld the tubes together. Then it's  the piling hammers' turn again. Depending on the geology of the subsoil, depths of 30 to 100 meters can be achieved.

Bruins: "We can preset the piling hammer to a certain energy level per number of hits. If a pipe has not been driven any further into the ground after 200 hits every 25 centimeters, that is the signal to finish."

So much for the standard. So how do you create a deflection that deep into the ground? "We do it with the first piece of pipe that goes into the ground, called the 'deflection shoe'," explains Bruins. "This is a piece of pipe with a slightly thicker wall. We weld this section to the first pipe at an angle of 0.5 degrees so that it bends slightly into the ground, in this case at a depth of 85 metres. In this way, we ensure that the borehole itself also deflects slightly to the desired location".

The pipes also had to be driven exactly parallel to each other. Bruins continues: "Soon there will be a drilling tower above the pipes to carry out the drilling. Such a tower is not very maneuverable. By stacking the three pipes exactly parallel to each other, it will be much easier for the customer to move the drilling derrick from one conductor to another".

During the project, measurements were taken to map vibrations and noise. "We measured vibrations at the customer's request because there was an old water pipe nearby. Fortunately, this did not cause any problems. We also measured the noise level as a test in cooperation with the pile hammer manufacturer. They developed a prototype hammer that was less noisy. We tested it here."