The German Federal Waterways and Shipping Administration (WSV) maintains about 7235 km of waterways whose shores are mainly secured by loose or grouted armor stones. To enable the WSV to make optimal use of its resources, taking into account boundary conditions such as economic efficiency and nature protection requirements, an extension of the current German design concept towards maintenance is required. In this paper a "classical" reliability analysis is conducted to investigate the probability of armor stone displacements along German inland waterways. Subsequently, it is proposed to use the obtained probabilities of armor stone displacement in Markov chain simulations to relate the former to the number of ship passages and time. Eventually, this may allow estimating maintenance intervals in regard to actual traffic density. The methodology is illustrated with traffic observations along four artificial inland waterways in Germany. The results are discussed in relation to the consequences for embankment maintenance and applicability in practice.
Geometrically closed filters are usually applied for marine structures, because they are designed neglecting the hydraulic load and geometrically open filters cannot be reliably designed so far. There are still gaps in the knowledge concerning hydro-geotechnical processes under the influence of oscillatory flow and combined oscillatory with unidirectional flow. The focus of this work is on the contact erosion at the interface between base and overlying filter under vertical oscillatory flow. Therefore, laboratory experiments on the stability of granular filters were performed. The objectives are (i) a better understanding of hydro-geotechnical processes, (ii) the description of hydraulic gradient, pore pressure and (iii) the development of prediction formulae for the hydraulic stability of granular filter under wave loads. Preliminary results show that geometrically closed filters are not stable under oscillatory flow and the hydraulic load cannot be neglected for a reliable filter design.
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