ABSTRACT
Due to the high damage potential that a possible flood event has for the densely populated areas along the 26 km-long International Stream of the alpine Rhine, the discharge capacity needs to be expanded from the current 3100 m³/s (100-year flood) to 4300 m3/s (300-year flood), in line with the requirements of the Swiss-Austrian project RHESI Flood Control for the Rhine Valley. In this context, a new Rhine Bridge connecting the Austrian towns of Hard and Fussach was designed to replace the old structure, which is no longer able to ensure the primary framework conditions for neither flood protection nor the increasing volume of traffic. The extremely unfavourable subsoil conditions, consisting of shallow, very soft to soft plastic lacustrine clay deposits, required a deep foundation solution for the substructure (abutments and piers). Due to the high flood risk, the construction of the substructure could only be carried out during a period of low water discharge (winter), resulting in a very tight construction schedule (winter half-year 2020/2021). For the deep foundation of the substructure, several options were evaluated. Finally, a solution consisting of pile grillages, executed with ductile cast-iron driven piles (320 mm of diameter), was adopted for the project. The fast, safe and simple execution of the piles allowed for the successful erection of the substructure within the limited available time frame. The completion of this construction stage was critical for the further phases. After a construction time of only 28 months, the Rhine Bridge Hard- Fussach was officially opened for traffic on November 18, 2022. The following technical paper presents an overview of the adopted deep foundation solution, covering the design and execution of the piled foundation.
