On the transient process of contact erosion (instabilities during granular erosion)

Abstract

Internal erosion is one of the major threats for water retaining structures like embankment dams or levees. Numerous design criteria were developed in the last decades for this reason. As the main concern of the geotechnical engineer is to prevent erosion, it is not astonishing that a vast majority of the criteria are focussed on the onset or initiation of erosion, or more precise, to avoid it. However, many existing structures have already experienced the one or other event of internal erosion. Thus, it is beneficial to understand not only the initiation, but also the progression of the erosion process. This process is though still not completely understood. Among the different types of internal erosion, contact erosion is characterised by two soils (base and filter) of different grain size distributions (PSD) forming an interface to each other. The erosion process is triggered by a water flow, which can be either parallel or perpendicular to the interface. The latter configuration is sometimes referred to as filtration and is in the focus of this research. If erosion occurs, base particles are transported into the pores of the filter by a water flow, forming a mixture zone with a lower porosity and permeability. For a better understanding of the contact erosion process, the formation of this zone must be understood. My special thanks are dedicated to my main supervisor Assoc. Prof Alexander Scheuermann. Without his believe in my capabilities as a researcher I would never have come to Australia for a PhD. Giving me the freedom to develop my own ideas, he was always present if advice was needed. Without Dr Thierry Bore, I would still try to disclose some of the secrets of high frequency electromagnetic measurement techniques. It was a great luck that he joined the team of the Geotechnical Engineering Centre at UQ during my candidature resulting in a fruitful collaborative work on the Coaxial Erosion Cell. Prof. Dr.-Ing. Karl Josef Witt made the collaboration with the Bauhaus University in Weimar, Germany, possible and enabled generously the use of the laboratory equipment and erosion cell located there. This was another great luck for me and my research progress. Not to forget his counsel based on his great expertise. My third supervisor, Dr.-Ing. Andreas Bieberstein always had an advice when necessary. The realisation of the experimental setup wouldn't have been possible without the work of the faculty workshop and the performed experiments without the support of the laboratory staff of both universities. It was a pleasure to work together with these great persons. The PhD-experience would be lacking an important part without my wonderful fellow students both in Brisbane and Weimar. I will always remember the time we spent together, not to forget the coffee connection and our lunch break filled with discussions of every aspect of a PhD but much more often philosophising about all and nothing. It was great to share the nice moments and it was always a help knowing ones problems during the candidature are not uniq...