Wellenbelastung und Stabilitat hydraulisch gebundener Deckwerke

Many sea dikes along the coast of the North Sea are protected against wave loading and currents by riprap revetments that are grouted with mortar. The mortar bonds the individual stones of the top layer, thereby forming a coherent structure that is able to withstand normal forces and shear forces as well as momentums, thus leading to a planar load distribution. While this kind of revetment has been built for decades, its design is yet solely based on empirical knowledge. On the one hand, the current design practice of mortar-grouted riprap revetments may therefore potentially lead to an uneconomic design exceeding the load and safety criterion for a particular site. On the other hand, it is also possible that the current design practice will lead to a weaker revetment than is required for the load and safety criterion for a particular site. Therefore, the objective of the project "Wave Toad and Stability of Mortar-Grouted Riprap Revetments" is to derive a scientific basis for the design of mortar-grouted riprap revetments. In order to describe the structural integrity of mortar-grouted riprap revetments, the results of an assessment of the condition of revetments in the field and a literature research are used to describe mechanisms leading to damage of the revetments. For the mechanism "crack development in the top layer" a structural model is set up in order to describe the load and resistance in the limit state. The hydraulic load due to wave action was measured duringfull-scale model tests in the Targe Wave Flume in Hannover, Germany. The resistance and structural parameters were determined using mechanical and fracture mechanical tests with the individual components as well as with the compound material of mortar and stone. Furthermore, pull-out tests to determine the force for debonding of an individual stone were carried out in the field and under laboratory conditions. The models for the structural stability of mortar-grouted riprap revetments presented in this study describe the processes relevant for designing a mortar-grouted riprap revetment, namely "crack development in the top layer" and "debonding of an individual stone". For the functional dimensioning, the wave run-up height was determined and reduction coefficients for the EurOtop wave run-up formula have been established.