THE FOUNDATIONS OF THE RHINE BRIDGE FUSSACH-HARD (AUSTRIA)-Paper

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The Fussach–Hard Rhine Bridge in Austria was replaced to accommodate growing traffic and support the RHESI flood-control project, which aims to increase the Alpine Rhine’s capacity from 3,100 to 4,300 m³/s. The new 255.6 m steel-composite bridge opened to traffic in November 2022.<br /><br />Foundation design was challenging because very soft, compressible lacustrine clays extend to at least 50 m below ground. Conventional end-bearing piles were therefore unsuitable, and shallow foundations could not provide adequate support. After evaluating alternatives, the project adopted pile grillages of vertical and inclined, grouted ductile iron piles. The inclined piles helped resist horizontal forces, while the broad grillage distributed loads and controlled settlement.<br /><br />The 320 mm-diameter piles were driven using hydraulic percussion equipment, with grout pumped through the pile and out through a conical shoe to form a bond zone around the shaft. Load testing informed the design: a 25 m test pile had a characteristic compression and tension capacity of 750 kN, while the service load was approximately 300 kN per pile.<br /><br />Flood risk restricted construction of the bridge substructure to the low-water winter period of 2020–2021, creating a demanding schedule. The piling system’s adaptable equipment and rapid installation enabled the foundation work to be completed on time. Approximately 36,260 m of ductile iron piles were installed for the bridge and related structures. The substructure was completed by April 2021, and the bridge opened after 28 months of construction.<br /><br />The authors conclude that grouted ductile iron piles offered a suitable, cost-effective solution under difficult ground, weather, scheduling, and pandemic-related supply conditions.

Keywords

Fussach-Hard Rhine Bridge

Austria

RHESI flood-control project

Alpine Rhine

steel-composite bridge

soft lacustrine clays

grouted ductile iron piles

pile grillage

foundation design

bridge construction