The Saarbrücken civil engineering contractor SaarGrundbau has successfully completed a tunnelling project using a Herrenknecht AVN 1200 C micro boring machine running on biodegradable hydraulic fluid from the Kamen-based company Fluid Competence. This particularly challenging engineering project involved driving a 96 m-long tunnel with simultaneous casing at a gradient angle of 34.60°.
One particular section along the route of the new gas pipeline being laid in NRW had to negotiate a height difference of 31.4 m. The extreme incline meant that pipe brakes had to be used for the tunnelling phase in order to prevent pipeline settlement both during the excavation work and over the subsequent lifetime of the service pipe. The entire pipe structure weighs around 188 t, which gives some idea of the kind of loads involved. During the construction phase the individual casing pipes lowered into place behind the cutter head of the machine (Figure 1) were continuously inched forward under thrust from the pipejacking cylinders. The pipes are 1,760 mm in diameter.
The project ended with the cutter head breaking through at the surface reception point. It was then secured in place by a heavy-duty crane before being lifted from the end pit and prepared for transport off-site (Figure 2).
Project manager Michele Rossi of SaarGrundbau was delighted that the project had been successfully delivered incident-free. ‘We are confident of our expertise in microtunnelling. When working at construction sites in nature-sensitive areas it is important that we can also count on the performance of the service fluids that we use in our machines. So we value the hydraulic fluids supplied by Fluid Competence (in this case Lubesave) for their biodegradable properties and for the enhanced health and safety standards that they offer both in use and when being handled by our site personnel.’
‘This was an ambitious and successful operation with our fluids running in a Herrenknecht microtunnelling machine. It will open the way for further assignments in much larger machines with greater boring diameters’, explains Dieter Mantwill, who is managing director of Fluid Competence, speaking at the conclusion of the project.
Fluid Competence GmbH