| dc.description.abstract | In recent years, the government of Taiwan has encouraged the construction of green energy and wind farms. Offshore wind turbine technology is at an early stage in Taiwan. At the foundation, offshore wind turbines have some differences compared to other countries, it must take into account earthquakes and liquefaction capacity. In this thesis, the topic of riprap improves the impact of liquefaction on the foundation of the structure.
This study focuses on the foundation of the offshore wind turbine at different depths of the liquefaction layer and uses different sizes of riprap range. Using a laminar box in a gravity field eighty times to prepare experiments. The relative density 50% above the soil layer is used to simulate the liquefied layer and the relative density 90% is used to simulate the bearing layer. Then, the gravel is placed around the pile to simulate the riprap on the seabed.
Based on the model test results, the following conclusions are made:
1. In 1Hz Hanning wave of 20m and 30m liquefaction layer, com-pared to the acceleration of the upper turbine without riprap, the one with riprap is obviously increased.
2. In 1Hz Hanning wave, when the riprap area is larger, the bending moment of the liquefaction layer will be larger.
3. In 1Hz Hanning wave, the acceleration of upper turbine and the bending moment maximum of pile are highly relevant. For ex-ample, when the acceleration of upper turbine is larger, the bending moment will also be larger. As a result, when the upper turbine needs to resist larger acceleration, the capacity of bending moment maximum for the pile should be increased.
4. In 1Hz Hanning wave, excess pore water pressure ratio of the experiment with riprap is larger than the one without riprap. At the deep liquefaction layer, excess pore water pressure ratio around the pile is larger than in the free-field.
5. In the experiment of 20m and 30m liquefaction layer, the residual displacement caused by tower of the condition with Riprap will be larger than the one without Riprap.
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