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HUESKER “Incomat® System”
– victory from start to finish for the double culvert ND 1400

During the second six months of 2009 the water procurement company WGE – Wassergewinnung Essen GmbH – was able to implement its double culvert ND 1400 to transport drinking water and soil filtrate to the drinking water purification plant in the area where it crosses the river Ruhr between the districts of Essen-Horst and Überruhr which is part of Essen’s drinking water network system. The innovation with this particular building is the concrete casing which was made on the basis of the industrial woven synthetic material “Incomat® Standard 20.120” manufactured by HUESKER Synthetic. Geosynthetics specialists from Gescher developed a tailor-made “jacket” which surrounds the pipes and is designed in a double layer filled with concrete to form a 21.5 cm thick concrete shell to protect the pipes. The “Incomat® System” is an economical and time-saving alternative when compared with the type of construction used in Germany until now.

With an overall length of 92 m the dimensions of the double culvert ND 1400 used for the Ruhr crossing are quite impressive. A total of 54 m in the horizontal area of the river bed was coated with concrete using Incomat® bringing the total weight of the culvert to 600 tonnes, including an additional conduit ND 1200 positioned at the centre for cables (without concrete casing).
The western pipe ND 1400 conveys soil filtrate to Überruhr to the new drinking water purification plant of the water procurement company Wassergewinnung Essen GmbH while the eastern pipe returns the water to “Essen-Horst” pump station in drinking water quality. From here, the water is then fed back into the piping system.

All aspects of the application of the concrete sheathing “Incomat® System”, type Incomat® Standard 20.120, were intensively designed, tested, manufactured and implemented as planned, on the one hand, with regard to adjusting the casing to fit the pipe shape and, on the other hand, with regard to the concrete filling and stability of the casing.      
           
Incomat® – the ideal solution: “tailor-made” to fit the pipe
In order to achieve a feasible solution, double-walled, sleeve-like Incomat® elements 5 m in length were manufactured for the two 54 m long pipe sections which were to be protected and given uplift retention in the river. Eleven elements installed alongside one another provided cladding for a straight pipe section, at the end of which shorter elements were connected for the bends.

Woven material, specially manufactured by HUESKER to fulfil the specific requirements (even thickness of the concrete casing and close contact to the pipe wall), was used for the protective elements. This woven material was designed and produced especially for this project. The double-layer concrete casing made of woven material is held together with synthetic bands, the constant length of which determines the thickness of Incomat® Standard. Diagonal bands, which served as additional reinforcement, were used for this project. After the elements had been cast in concrete the necessary concrete thickness of 21.5 cm was attained, thus guaranteeing the required weight for the uplift retention.

By means of the specially designed arrangement of zip fasteners the casing could be attached to the pipes without any difficulty and continuously charged with concrete. According to specifications nonwoven material was used as padding to prevent the cathode protection of the steel pipes from becoming damaged by the concrete casing.
In the past, similar pipe casing with Incomat® has already been used on pipes with smaller diameters for “Gaz de France”. However, due to the size of the Ruhr culvert, emphasis was placed on achieving a safe solution during the planning phase with regard to the Incomat® System and the concrete quality. A few weeks before starting construction two test runs and sampling took place on the company grounds of the construction company KLAUS STEWERING GmbH & Co.KG, Borken in Germany, in order to optimize the concrete casting work and the composition of the concrete.

“Let the concrete flow” – report from the building site
All work on the pipes was performed in a dry dock. The Incomat® elements were installed step by step once the pipes had been pressure-tested. Beginning with the east pipe and working alternately, every second position was fitted with the Incomat® casing. When concrete was pumped into the Incomat® elements according to schedule, temperatures were around 30° Celsius. A “Putzmeister” mobile double reciprocating pump delivered concrete alternately via two filler necks.

Using the same procedure the west pipe was also fitted with the Incomat® concrete casing. Insertion of the Incomat® elements for the bends then took place after concrete charging without any difficulty.     

After about two weeks, at the beginning of September 2009, a trial lift was performed in the flooded dry dock without any problems. The big day came at last on 5th September 2009. Using building cranes and a specially built buoyancy pontoon the double culvert ND 1400 was floated out and sunk into the Ruhr.

The “Incomat® System” makes the grade of the ND 1400
The challenge that began for design engineers and technicians ended with a “victory from start to finish” for everyone involved. For the first time, a double culvert ND 1400 was protected with a concrete shell made of Incomat® Standard (20.120) and secured against uplift. Despite the particularly complex requirements which had to be fulfilled, the intensive preparation, material quality and specialized production performed by the HUESKER Synthetic team in producing the Incomat® casing were worth the effort.

The careful preparation, professional implementation and good teamwork performed by the consortium of building contractors KLAUS STEWERING from Borken, Germany, and the pipeline construction company from Münster, Gerhard Rode Rohrleitungsbau, resulted in a remarkable “600 tonne product” which is already highly respected among experts.

The building owners, Wassergewinnung Essen, can be pleased with their choice of the HUESKER “Incomat® System” – an application of culvert protection used for the first time in Germany. Furthermore, they can also be sure that not only a great deal of time was invested but also high-quality, cost-effective and culvert-protecting construction techniques were implemented.