Six-metre pipes were inserted in assembly pits arranged at bending points or shaft areas. Click here to enlarge imageUnnecessary shafts without bending points could be driven through, shafts with bending points were replaced by smaller HOBAS shafts or rehabilitated with HOBAS GRP. Prefabricated shafts were coupled on site, others were adapted or laminated on site.
Before putting the pipe into the relining device, the contractor mounted polyethylene (PE) on the pipe ends (respectively some centimetres before) in order to avoid damaging the external pipe wall while inserting them, assure a safe position and minimise the effect of floating when grouting.
The single pipes were connected in the starting shaft. The pipes were inserted into the host pipe section by section. The enlarging new pipeline was pushed ahead one pipe length after the other by a hydraulic device.
The annular space was filled for many reasons. It allows fixing the pipeline in the old line. It avoids penetration of water and soil while ensuring defined bedding, and thus enables an even transfer of outside loads. Furthermore, the filling prevents a collapse of the defective sewer, it secures the pipeline against floating and it helps balance slight temperature-dependent length variations. A special material was used for the controlled filling process. All involved parties were satisfied with the relining project and use of the HOBAS CC-GRP pipe system. The first months of operation showed excellent results.
Author's note
Barbara Osinger works for Hobas Engineering, based in Basel, Switzerland. For more information, visit www.hobas.com