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Pipeline Cover

Project information

Project name

EVN Netz GmbH – “West 4” western trunk
gas pipeline - encasement of inverted syphons


Tulln, AT


EVN Netz GmbH Maria Enzersdorf


Consortium comprising Leyrer + Graf Bau
GmbH and Nacap Rohrleitungsbau GmbH

Construction time

April - June 2011

Project details

Project description and challenge

For the development of EVN Netz GmbH’s “West 4” western trunk gas pipeline between Auersthal / Gänserndorf and Langenschönbichl / Tulln, a consortium comprising Leyrer + Graf Bau GmbH and Nacap Rohrleitungsbau GmbH was contracted to build an approx. 60 km long pipeline section. The route includes a series of inverted syphons by means of which the (DN 800) pipeline crosses under the many intervening waterbodies and watercourses. To protect the pipeline against mechanical damage and buoyancy or uplift, the inverted syphons were encased in concrete.


The solution adopted to install the concrete encasement made use of concrete mattress system – in preference to the originally specified ballasting method by means of shuttered in-situ concrete. The concrete mattresses comprise two high-strength woven layers connected by synthetic spacer ties. The mattress thickness is determined by the length of these spacers. The mattress elements were filled with selfcompacting concrete (SCC) of class C 25/30 (minimum 28-day cylinder strength ≥ 30 N/mm2) to DIN 1045-2 (EN 206-1) so as to create a monolithic body of concrete within the textile formwork.