On the influence of loading frequency on the pore-water dissipation behavior during cyclic consolidation of soft soils

The growing demand for renewable and ecologically sensitive energy sources enhances the installation of more and more offshore windcraft plants. In the focus of the present study stands the analysis of stress evolution under foundations for offshore windcraft plants on soft soils, where time-dependent consolidation processes due to the cyclic wind and wave loading are highly non-linear and therefore require a distinct analysis of the overlying mechanisms. As wind and wave loading are non-homogeneous loadings with varying frequencies and amplitudes one of the key questions and objective of the present study is to analyze, whether the time-dependent dissipation behavior of excess pore-water pressures during the consolidation process is dependent on the loading frequency. This study is carried out on the basis of experimental tests on Kaolin clay under haversine cyclic loading using a newly designed oedometer device. A comparison of the test results to an analytical solution for a one-dimensional, linear-elastic Terzaghi consolidation model is drawn. It reveals, that the two approaches (experimental testing and analytical model) show similiar results for the pore-water pressure dissipation during the cyclic consolidation process from a qualitative point of view, while some effects appearing in the experimental testing cannot be reproduced by the simplified analytical consolidation model.