SFB "Offshore-Megastructures" (Second Funding Period)

Description:

To study the behavior of soil under cyclic loading at the element level, further tests using the direct shear device acquired during the first funding period are planned for the second funding period. The goal is to describe the effects of preconditioning in the form of preloading or preshearing on the cyclic response of the soil sample under drained and undrained loading. The results of the planned several hundred tests will then be transformed into a contour plot and serve as a basis for numerical calculations in AP3.

To study and describe the behavior of soil under cyclic loading at the system level, a new model setup for experimental investigations was planned and completed by IGtH during the first funding period. The investigations in the first funding period were conducted on a model of a gravity-based foundation under drained and partially drained conditions. In the current funding period, the focus is instead on investigations of a monopile model foundation, also under monotonic and cyclic loading, which can be implemented with simple, minor adjustments to the existing model setup. In this context, in addition to the overall deformation of the monopile (settlement and rotation), the pore water pressures and their accumulation over time are of particular interest (Figure 1).

With the investigations at the element and system levels, the prediction of the behavior of various foundation structures can be validated and further developed using the explicit numerical model (EPPE) developed by IGtH. One goal is the development of a generic methodology for predicting the load-bearing and operational behavior of foundations subjected to intensive cyclic loading.

In close collaboration with subproject A04, experiments with a monopile model (D ~ 60 cm) are also planned in the large wave flume (GWK+). The behavior of the pile under wave loading, as well as under additional cyclic horizontal loading applied via a test cylinder, is to be measured, with a particular focus on the magnitude of pore water pressures in the sand bed. Furthermore, the effects of scour and scour protection layers on the pile’s load-bearing behavior will be investigated. These experiments provide an excellent complement to the experimental investigations planned on a significantly smaller scale in AP 2 and can be used to validate the explicit and implicit numerical simulation models of AP 3.