Zur Verbesserung des ökologischen Zustandes an Binnenwasserstraßen sind in den nächsten Jahren umfangreiche Uferumgestaltungen vorgesehen. Naturnahe Ufersicherungen unter Verwendung von Pflanzen sollen dort, wo es möglich ist, die bisherigen Steinschüttungen ersetzen, um wieder mehr Lebensräume für Pflanzen und Tiere sowie mehr Strukturvielfalt zu schaffen. Mit diesen technisch‐biologischen Ufersicherungen gibt es an Wasserstraßen mit der heutigen Schifffahrtsbelastung noch relativ wenig Erfahrungen. Auf der Grundlage von verschiedenen Forschungsergebnissen und Erkenntnissen aus einem groß angelegten Naturversuch am Rhein bei Worms wurde unter Einbeziehung der Erfahrungen an kleineren Fließgewässern ohne Schifffahrt ein erstes Bemessungskonzept für die Ingenieurpraxis der Wasserstraßen‐ und Schifffahrtsverwaltung erarbeitet und in eine Software integriert. Damit können jetzt neben Schüttsteindeckwerken auch Ufersicherungen mit Pflanzen dimensioniert werden. Die Besonderheiten der lebenden Baustoffe, die hydraulischen Einwirkungen, die zu untersuchenden geotechnischen Versagensmechanismen und die einzelnen Dimensionierungsschritte werden im Folgenden vorgestellt.
The hole erosion test (HET) was developed to simulate piping erosion and to study the erosion parameters of cohesive soils. The erosion rate in the HET is evaluated by the enlargement of a pre-performed hole in the axis of the specimen with time. The hole diameter during the test is estimated using the pipe flow theory with an assumption that the friction factor varies linearly with time. To investigate this assumption, measurements of the hole diameter during the test are needed. So far, there have been no measurements of the hole diameter during the HET and the hole diameter is measured only at the end of the test after cutting the specimen. In this study, a novel approach to measure the hole diameter at different time steps during the HET using micro-computed X-ray tomography (µCT) is presented. Combining the HET and µCT data, the assumption regarding the friction factor was investigated. Moreover, a linear relation between the flow rate and the hole diameter was found in the range of the tested diameters. This relation was confirmed with HETs using non-erodible PVC specimens with different hole diameters. Accordingly, a new method to interpret the HET for high plastic clay was proposed, in which the hole diameter is calculated based on the flow rate, given that the initial and the final hole diameters are known. A comparison between the analysis of the HET using the proposed and the previous analysis methods is presented.
This paper focuses on the experiences and benefits of using the Finite Element Method (FEM) in order to describe soil-structure interaction behavior taking the example of two successfully completed lock repair projects. lt turned out that the influences and interactions of the repair works on the existing lock, in particularly the deformation of the lock, earth pressures acting on the lock and structural forces in different lock sections, could only be determined in a realistic way by calculations with the FEM. Based on the calculation results, limit values for the monitoring system, which is necessary to check the system behavior and to verify the calculation assumptions during the repair works, were defined. An additional focus is on the relevance of small-strain stiffness in the analyses. For this purpose, an extension of the Hardening Soil model (HS-model) that accounts for a higher stiffness at small strains was used.
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