Soil Liquefaction around Offshore Pile Foundations: Scale Model Investigations: Fid-Bau Portal

Soil Liquefaction around Offshore Pile Foundations: Scale Model Investigations

Kluge, Katharina

The present research work investigates the pore pressure in the soil around cyclically loaded offshore pile structures in order to gain first experience on the probability of occurrence of soil liquefaction. The influence of the deflection of the structure and its loading frequency on the pore pressure is analysed by means of experimental and numerical investigations. In the first part of the present work, offshore wind energy structures are presented and the phenomenon of soil liquefaction, its consequences, the criterion for the initiation of liquefaction and the inducing factors are discussed. Since the wave-induced movement of structures is only poorly examined until now, the research focuses on the sodefined deflection-induced liquefaction. The second part focuses on the description and analysis of the experimental test series carried out within this research. Those test series represent the first investigations of their kind and are regarded as first step towards the ambitious aim to assess the risk of soil liquefaction around offshore pile foundations. The central part of this work covers a detailed analysis of the measurement data obtained in approximately 40 test series at four measurement levels. Soil liquefaction is observed in most of the tests series. It is shown that the pore pressure strongly depends on the deflection of the structure and on the loading frequency, but also on the depth under ground surface and on the horizontal distance from the test pile. The last part of the thesis covers the numerical simulation of the test series with the finite-difference program FLAC. It is shown that the deflection-induced pore pressure accumulation can be simulated and that it is in good agreement with the results of the test series. The results of this research work supply important information on the behaviour of pore pressure near cyclically loaded pile structures and provide a sound basis for the estimation of the susceptibility of the soil to liquefaction.