Towards reliability-based bank revetment design : investigation of limit states and parameter uncertainty

To ensure safety and ease of navigation and to protect the adjacent terrain, sloped banks at inland waterways are commonly secured by bank protections, which safeguard slopes against erosion, e.g. caused by hydraulic loading from shipping and, if applicable, natural currents. Bank protection, which serve as superimposed load, reduce the risk of local slope sliding failure and liquefaction resulting from ship-induced rapid lowering of the water level. In order to promote inland shipping as a sustainable transport mode, it is required to provide a sustainable waterway infrastructure, which, for instance, allows for a broad navigability of larger or more powerful vessels. As a result of high design standards which bank protections had and still have to meet, to date, the expansion of a waterway is required to allow for the passage of larger vessels, which, in turn, resulted in large construction and ecological costs. However, under increasing economic and ecological pressures, an increased utilisation of the existing infrastructure, possibly with a reduction of standards, attracts growing attention. Current deterministic design approaches eschew any information on risks and lack a systematic basis for evaluating the degree of conservativeness inherent to design. They account for uncertainties arising from the definition of characteristic values of actions and material parameters as well as from the design model itself by conservative design assumptions and empirical knowledge. However, the development of a sustainable design and maintenance strategy involves meaningful key figures about the performance of a structure over lifetime, considering site-specific design conditions and with respect to risks associated with failure.Using the example of loose armour stone revetments at German inland waterways, this thesis examines how probabilistic methods can be applied to revetment design. It is assumed that a reliability-based approach provides comparable key figures such as the reliability index or the probability of failure, which allow for a systematic evaluation of the degree of conservativeness inherent to design. Moreover, it is assumed that updated recommendations for the choice of characteristic values, the consideration of their probability of occurrence as well as the clarification of limit states will allow for a project-specific design that accounts for local traffic and safety requirements. Conservative design assumptions can be replaced by site-specific knowledge. By means of expert interviews, the most significant causes of damage and damage types as well as current maintenance procedures are explored. Sensitivity analyses are performed to identify significant input parameters. Reliability analyses assist in investigating the most significant parameter uncertainties inherent to actions and material parameters. Within the scope of this thesis, statistical uncertainty is investigated by an extended bootstrapping approach; model factors are determined to account for transformation uncertainty, and a random field approach is used to quantify the effects of spatial variability of soil properties on revetment design. As for the practitioner, the effect of parameter uncertainty on the resulting armour stone size and armour layer thickness is studied. Based on the findings of this thesis, a probabilistic design concept for bank revetments is drafted and supplementary recommendations regarding selected aspects of such a probabilistic design concept are outlined

Statistische Analysen der Scherfestigkeit, Index- und Kompressibilitätseigenschaften glazilimnischer Sedimente in Norddeutschland

Der Tagungsband "Vorträge der Fachsektionstage Geotechnik - Interdisziplinäres Forum 2023, Congress Centrum Würzburg, 12. - 13. September 2023" erscheint im Open Access und ist hier kostenfrei abrufbar: https://www.dggt.de/index.php?option=com_content&view=article&id=397%3Atagungsband-fstg&catid=45%3Apublikationen&Itemid=6