Experts at German demolitioncompany Fischer Weilheim developed a method for the removal of thick concrete tunnel lining in a tram tunnel in Stuttgart.
To begin with, the depth of roughly 1.6 m (5 ft) thick concrete walls was reduced by cutting strips by using a Kemroc rotary drum cutter. A Kemroc cutter wheel was then used to cut the wall into sections at these strips. Finally, the sections were pulled out, broken down and processed.
In the first step, the excavator operator picks up a Kemroc KR 165 rotary drum cutter and grinds a 150 cm (59 in) wide vertical slot into the concrete wall.
This narrows wall to a thickness of 100 cm (39 in), which is the cutting depth of a DMW 220_1000 cutter wheel.
The operator then picks up that tool and cuts through the wall in the just before ground slot. These two steps are then repeated for cutting horizontal slots dividing the tunnel lining into various segments.
The next stage is to use a breaker to weaken the segment at the base of the wall before pulling it down using the excavator bucket. The tunnel lining wall falls to the floor. In this position, each layer of soil, bituminous material and soil can be removed separately leaving a solid piece of concrete which can be broken down using breaker and shear cutter for removal from the site.
Two months after the job started this summer, almost half of the tunnel lining had been removed.