A tunnel that led through a dam had to be enlarged.
A concrete layer exactly 0.5 m thick had to be removed from each of the floor, walls and ceiling.
This layer was not allowed to be thicker than 0.5 m under any circumstances, which meant that precision was required. Very strong vibrations inside the tunnel also had to be avoided so as not to endanger the dam.
The tunnel was about 18 m long, 6 m wide and 5 m high and reinforced with 16 mm thick iron. First, diamond saws were used to cut through the entire length of the tunnel with saw cuts exactly 0.5 m deep. Cross sections were made every 2 m. A hole was drilled in each piece after 1 m, i.e. halfway along the length. Two Darda C9 N splitting cylinders and a portable Darda high-pressure hydraulic unit with electric motor then simply split out the pieces. The saw cuts ensured that no pieces thicker than 0.5 m broke out.