Fit to burst

The town sewage company Eigenbetrieb Stadtentwässerung (EBS) of Tuttlingen, Germany recently increased sewage canal capacity underneath a 120 m stretch of pavement using the Grundoburst pipe bursting system.

Trenchless specialists Uhrig Kanaltechnik used the pipe bursting system because the footpath above the sewage canal had only recently been renewed and the 2 m installation depth would have required extensive groundwork.

The project necessitated a cross section enlargement of the existing bore path from a nominal diameter (ND) of 300 mm - outer diameter (OD) of 350 mm - to a ND of 450 mm (OD of 500 mm).

A Grundoburst spokesperson said, "It was quite a challenge to increase the old pipe diameter by +150% and the project required a high penetration force.

"The ground conditions close to the bore path featured clay and gravel with high compaction, so these conditions asked even more of the system."

Uhrig elected to use its 250 tonne class Grundoburst 2500 G, which is capable of bursting old pipes of between 250 and 1000 mm in diameter. The bursting head consisted of three expander units assembled consecutively. The centering sleeve with an OD of 295 mm was followed by the burst sleeve of OD 445 mm and then the expander with an OD of 550 mm.

The bursting process, along with the simultaneous new pipe installation was completed in just a few hours and jobsite clearance only took half a day.

"The execution of this sophisticated task in very tight working conditions was carried out quickly and professionally," said Axel Salzmann of the Tuttlingen engineering office.

Mr Zimmermann from EBS said, "The cost of this project saved us about +20% on the more traditional open-trench method. Furthermore, the short construction time demonstrated the advantages of using this type of technology."