Since April 2021, works to expand the high speed broadband network have been carried out in Saxony by a telecom company based in Grimma, Web + Phone GmbH, which was awarded the contract to connect the town of Schneeberg to the fibre optic network. Web + Phone specialise in cloud, IT and communication services, being awarded the contract to lay the 5cm diameter plastic conduit which will carry the fibre optic cables to the local civil engineering company Bautechnik Schödl GmbH in Grimma. Bautechnik Schödl have to lay the conduit through a variety of materials including open terrain, paved roads, concrete and rock and are also responsible for laying the cable to individual houses. 

Around 100 households in Schneeberg are being connected to the fibre optic network under the publicly funded project, while several hundred more will be connected on Web + Phone’s own network. The construction team supporting Enrico Schödl, the site manager for at Bautechnik Schödl, are using a Kemroc cutter wheel mounted to a 16t wheeled excavator to open the trenches before laying the empty conduit. Before starting this project, his father Steffen Schödl had been thinking about the best way to do the trenching and he approached Kemroc to request a trial of a cutter wheel. Following positive test results, Kemroc service manager Marco Schön supplied an SMW 80 to the site, installed it on the excavator, and set up the hydraulics to match the requirements of the cutter wheel attachment.

Grinding, laying, filling and compacting

Kemroc’s SMW range of cutter wheel attachments were designed specifically for the excavation of slots and narrow trenches in soft and medium to hard rock. Available in three sizes, they can be mounted on excavators from 10t to 40t operating weight, being designed to excavate slots and narrow trenches, such as for when for laying cables, to depths of 1m. In practice, when excavating in rock and other hard materials, the wheel is gently worked into the ground until the support frame rests firmly on the ground. The cutter wheel is then pulled towards the excavator or the excavator tracks in reverse. The spoil or cut material is guided out of the trench and deposited along the side of the trench.

Working in this way, a six man team has achieved record progress rates in Schneeberg since April 2021. The excavator opens the trench and makes sure all health and safety measures are in place. Two men lay the empty pipe with specialists being responsible for covering the pipe with a layer of sand, backfilling and compacting. “In this way, we make much better progress than using conventional saws and excavators and compared to another company operating in Schneeberg on the same project using a tractor with a rear mounted cutting attachment, our tool combination has proven to be far more manoeuvrable. We can adjust our cutter attachment with its endless turning rotator to any angle to suit ground conditions without having to move the excavator,” commented Enrico Schödl.

Depending on material and ground conditions, the civil engineering professionals achieved some impressive advance rates. They ranged from 30m/h in standard depth asphalt covered paving to over 80m/h in frost protection layers and up to 100m/h in open topsoil. Enrico Schödl was also impressed with the economics of this excavating method. While excavating the 13cm to 15cm wide trench in asphalt, the cutter wheel produces a finely ground, homogenous material which can be used for backfilling on top of the sand layer covering the pipe. As a result, significant savings are achieved by not having to transport or purchase backfill.

In total, public funding will cover the cost of laying 26km of optic fibre as well as all the associated house connections. From April till September 2021, the Bautechnik Schödl team have already laid around 10km of conduit. Martin Flechsig, managing director of Web + Phone said, “Depending on the conditions, expanding the fibre optic broadband network can involve the use of several different types of equipment and methods including drill rigs, trenchers and/or trenchless technology. Here in mountainous territory, and especially over long distances in natural terrain with soils containing large amounts of rock, you can really see the advantages of using specialist excavator attachments like those from Kemroc.”