DN 1800 Microtunneling to Protect the River Seine
January 27, 2011
The rainwater collector and storage project that would limit the amount of overflow caused by heavy rain falls is part of the Seine River de-pollution plan and was launched by the local authority Syndicat d’Assainissement de la Boucle de Seine involving DN 1800 CC-GRP HOBAS Jacking Pipes. This was, therefore, a national premiere regarding the utilized pipeline’s size and undoubtedly represents a precedent for future trenchless undertakings with GRP.
The geological and hydrological conditions, as well as the pipeline route that includes a horizontal and a vertical curve at a 900 m radius made the project complex. Project implementation required particularly meticulous preliminary studies which were conducted by the engineering office Cabinet Merlin who was also in charge of documentation. Further studies and calculations regarding the construction works were carried out by CSM Bessac and HOBAS France.
The jacking station was built inside the 25-m-diameter storage basin. Its thrust wall, that serves to provide a reaction against which to jack, incorporated a special slab leading back to the basin wall so as to transmit the 800-ton-loads from the station to the basin’s structure.
Also the 380 m S-curved route posed a challenge to the contractor and at the same time gave HOBAS Jacking Pipes the opportunity to prove what they are made of. The 3 m pipe sections DN 1800 (De 1940), SN 64000, PN 2.5 were smoothly installed and their leak-tight flush couplings provide a tight line.
HOBAS CC-GRP Jacking Pipes have a long record of application in France and have been quality certified for trenchless projects by the CSTB (Centre Scientifique et Technique du Bâtiment). Following the market’s increased need for larger GRP pipe diameters, this certification has been extended to the full range of available HOBAS Jacking Pipes, namely to DN 250 to 3000, in October 2010.
With the successful completion of this technically audacious project and by offering sustainable high-quality products, HOBAS has once again proved its leading role in the national GRP market for trenchless applications and the successful project will certainly inspire others.
This article was supplied by HOBAS Engineering GmbH, Bois Colombes, France.