Federal motorway A6 Mannheim-Heilbronn case study


Courtesy of NAUE GmbH & Co.KG

Stable RiStWag -construction guidelines for roadways in water preservation areas

Included in the A6 federal motorway construction project lot Mannheim – Heilbronn/Weinsberg, AS Bad Rappenau – AS Neckarsulm is the widening of km 631+640 and km 641+060 to six lanes.

This section is runs through a water preservation zone, type IIIa, protected under RiStWag. Because of this, a sealing system conformant with the standard cross-section specified by RiStWag 2002 is projected to prevent environmental impacts on bodies of water as a result of the construction or operation of the widened autobahn.

The sealing layer for the cut slope and the retaining wall was provided with about 10,000sqm of Bentofix BFG 5000. Bentofix is a geosynthetic clay liner consisting of three layers: a cover nonwoven, a natural sodium bentonite powder sealing layer, and a carrier woven. These three layers are needlepunched together creating a high internal shear resistance, allowing Bentofix to be installed evven on steep slopes. This geosynthetic clay liner (GCL) is placed on the slope at a (vertically measured) depth of 0.8 m. It extends outward as far as 1 m beyond the roadway surfaces outer edge. Once laid, it is then covered with topsoil. The slope stability, with an angle of approx. 33 degree (1.5(H):1(V)), is reinforced with 6,000sqm of Secugrid 60/60 Q6 geogrid, over Bentofix . Secugrid is a geogrid of oriented, monolithic flat straps with vibratory welded joints that is used for soil reinforcement. At the side edges drainage pipes are installed, all surrounded with warre gravel. To ensure filterstability with the surrounding soil these are wrapped with 14.000sqmof Secutex nonwoven geotextiles.

The contractor Weiss, headquartered in Satteldorf, started the construction project in the fall of 2003. The local regulator for this project is the Autobahnbetriebsamt Heilbronn [autobahn operating authority, Heilbronn], the consultant was Ingenieurbüro Bung, Heidelberg [engineering office Bung, in Heidelberg].

Year of construction: 2003
City / Country: Mannheim/Heilbronn, Germany
Installed products:
Bentofix BFG 5000 10.000sqm
Secugrid 60/60 Q6 6.000sqm
Secutex 151 GRK 3 14.000sqm

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