Kemroc cutter attachments successfully pave the way for key construction project
THE Königsteiner Höfe is a new residential and commercial quarter being constructed in the middle of Königstein im Taunus in the German state of Hesse. Acting as a subcontractor to general contractor Köster Group, Höfling Erdbau were engaged to complete the site preparation work. Using two excavators with cutter attachments from Kemroc, the contractor put all the bored pile walls in place and put in the drainage systems efficiently and to the required accuracy.
The 9,000 sq m site offers enough space for a total of eight buildings with around 75 apartments providing 7,000 sq m of residential space, as well as facilities, offices, a bistro, and an organic market. Köster and Höfling Erdbau have started the first phase of this ambitious project which is scheduled for completion by June 2024. This stage of work will involve excavating the site and installing all the required ground support.
Initial works began with excavations to a depth of 15m on the slope side and to a depth of 7m on the valley side, while shoring was erected as a contiguous bored pile wall. Around 185 piles had to be anchored and lined by filling the space between each pile with steel mesh and shotcrete.
To help keep costs down, the shoring wall had to be profiled back beforehand with a surface to be as flat as possible. Achieving the surface finish required would have been impossible in the difficult quartzite ground conditions, using an excavator with breaker/ripper attachment.
For this reason, Höfling Erdbau specified a different excavator attachment – a rotary drum cutter. After initial trials with a different brand that did not yield the desired results, Enrico Trender, sales manager at Kemroc, was approached by Höfling Erdbau and he recommended the combination of a 25-tonne excavator and Kemroc KR 120 rotary drum cutter (120kW) to complete the task.
Kemroc’s KR range comprises 19 transverse cutters with spur gears. They are particularly robust, and wear-resistant, and serve as suitable attachments for carriers with short booms in confined spaces – especially in demolition, tunneling, trenching, pipeline work, concrete renovation, quarrying, and underwater/profiling work.
Won over by Kemroc’s cutter attachments, Daniel Korn, site manager at Gerhard Höfling, rented a KR 120 drum cutter for use on the company's own 25-tonne excavator for profiling work. With this combination, it was possible to mill the ground containing quartzite from between the bored piles with a smooth surface finish and line it with shotcrete in what would have previously been classed as soil class 6 to 7 material.
The subcontractor also had to excavate a drainage trench up to 60cm deep, 50cm wide inside, and at the foot of the shored wall for its entire length. Mr Korn decided to carry out this work using a combination of a 9-tonne short-tail excavator and Kemroc EK 40 chain cutter (44kW).
Kemroc’s EK range of chain cutters is equipped with a unique cutter chain running between the outer cutter drums. They loosen the material along the entire width of the cutter head without leaving a central spur as would be the case when using conventional drum cutters without any sideways movement. This allowed the Kemroc EK 40 chain cutter to excavate trenches with a precisely defined width. This operating characteristic saves time and up to 40% energy and produces fine-grained milled material that can often be used immediately as backfill.
On the Königsteiner Höfe residential project, the milled material was transported away for recycling. Backfill was not required because the sloping drainage trench was to be lined with a fleece material and filled with special drainage gravel so that when it rained, the rainwater collected would flow down to the pump shafts.
Following successful completion, Mr Korn was delighted with the use and immediate impact of the Kemroc cutter attachments. ‘In view of the difficult soil conditions with the presence of quartzite prevailing on our construction site, the choice of equipment was almost perfect for this task,’ he concluded.