First Large-Scale Hobas GRP Jacking Project in the World
Hobas made its debut with centrifugally cast GRP jacking pipes in 1982. Before then, the pipes had only been used on some test construction sites in northern Germany for pushes of up to 50 meters. The world‘s first large and technically highly demanding jacking project with GRP products was undertaken at Hamburg‘s customs port.
A sewer was to be installed under a very busy part of the port in the north of Germany. The specifications were challenging: a fire service exit, port railway and federal railway lines were not to be disrupted under any circumstances and settling had to be prevented over the entire length of the pipeline. Given the fact that trenchless construction saves space and is highly accurate, jacking was truly predestined for this application. The Hobas products‘ corrosion resistance also to aggressive wastewater, their smooth outer surface and easy handling persuaded the clients and they ordered jacking pipes with an outside diameter of 752 mm and wall thickness of 50 mm. The pipes were installed six meters under the ground-water table in two drives over a length of 165 meters without any intermediatejacking stations.
Although their outer surface is very smooth, the Hobas pipes were lubricated with bentonite every 30 meters to reduce friction and speed up the jacking work. It is hardly surprising therefore that the greatest jacking force used was only 1700 kN, which is far less than the limit for the pipes. What is also remarkable is the great precision with which the Hobas pipes were jacked through the silt and clay soil under the groundwater table at that time: the pipeline only deviated 15 mm from the planned route over a length of more than 100 meters, thus remaining well below the specified tolerance.
The facts sounded spectacular then but are now exceeded many times over. In 2009, Hobas supplied De 3000 jacking pipes that were installed without using the intermediate jacking stations in sections of almost a kilometer. And in 2021, Amiblu delivered GRP jacking pipes De 2047 for a spectacular project in Rome that – with a thrust section of 1,235 meters – marked a new trenchless record.