UTILITY TUNNELING | TECHNICAL


Behind the micro TBM were jacked a sequence of 2m (6.5ft) i.d. concrete pipes to form the tunnel culvert passing under the river. The utility pipelines would be carefully fed through the tunnel – while being arranged together but kept separate in the packed bundle. Once fed through, the remaining sections of pipelines within the tunnel would be sealed into place – but only after a testing phase. The tests were needed for the assembly of pipelines


to ensure that none had defects or problems before they were to sit, permanently in place, in the vital new – but difficult to access – underground link in the expanded network of utilities. The project was successfully executed by a joint


venture of Austrian contractor BT Bau GmbH and Smet- Tunnelling nv, part of Dutch contractor Smet Group.


UTILITY PIPELINES Locally, either side of the Danube, EVN has groundwater well fields to tap for potable water supplies. It also has power plants on either side of the river. Connecting each utility together is strategically, and operationally, advantageous. In a statement, EVN spokesperson Stefan Zach, said,


“This can be of essential importance in the event of a well field failure. Especially in challenging times like these, it shows how important regional supply security is.” The new drinking water connector would be two


pipelines supplied by AGRU Kunststofftechnik GmbH. The pipelines are high-performance PE 100-RC of o.d. 560mm SDR 111, able to operate at up to 16 bar pressure. The piping supply package also included fittings. EVN has power plants on each side of the river. Zach said: “The biomass plants on both sides of the


Danube can stand in for the other plant at any time in the event of a breakdown or revision.” He added: “Since we also have large well fields and


springs on both sides of the Danube, the tunnel enables the drinking water reserves to be interconnected.” On the Korneuburg side of the river, therefore,


pipelines were laid from the power plant and from a well field to run toward the river. However, more trenchless tunneling was needed before reaching the river – to pass below a railway line and also the A22 highway. In addition to the two water and two district heating


pipelines, the project also involved carrying a steel, high-pressure natural gas pipeline and also cables for electricity and optical fiber telecoms. AGRU also supplied protective pipelines to house


the electricity cables and telecom optical fiber cables, respectively. Almost 2900m (3171yd) of o.d. 160mm SDR 121 pipelines, plus fittings, were supplied in total to help protect the cables. Each of the water, natural heat and telecom pipes


were welded together with 18m-long (59.1ft) pipe rods of o.d. 560mm, which AGRU says reduced the welding effort which used mechanically manufactured heating coil sleeves in the connection zones.


A variety of different pipelines – by type, size, and


material therefore – had been assembled and aligned together on the banks of the Danube. Their positions were maintained using with carriage (cradle) frames, placed along their length at set intervals. The bundle of pre-welded pipelines, also supported


by the carriages, was then pulled along a rail system that had been specially-installed on the run up to the river bank, passing down the approach cutting and into the pit, from where the pipelines then disappeared into the long culvert tunnel, below the River Danube. Once the utility pipelines were in place in the


tunnel, for the testing phase of the assembly the concrete culvert tunnel was sealed at its portals. The testing process involved filling the sealed space with water and then the pipelines were examined for possible defects. Zach, said: “After a positive conclusion of the


examination, the tunnel was filled with a concrete suspension and sealed permanently.” The concrete-sealed arrangement is “maintenance-


free”, he added. The company has invested about Euro10 million (US$11 million) in the project.


Below:


The AGRULINE pipes made of PE 100-RC in dimensions OD 560 mm ensure the drinking water supply on both banks of the Danube


PHOTO CREDIT: AGRU Bottom:


The carriage, made of steel and wood, enabled the pipelines to be pulled in PHOTO CREDIT: EVN


Left:


AGRULINE pipes used on utility company EVN’s under Danube tunnel link PHOTO CREDIT: AGRU


Spring 2023 | 25


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