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Cyclic Behavior of China Laizhou Bay Submarine Mucky Clay at an Offshore Wind Turbine Site
Bo Han, Xinran Yu, Jinyong Guo, Ben He and Song Dai

Large-diameter monopile foundation has been used for more than 75% of offshore wind turbines, and foundation stability is the guarantee of complete wind-turbine structural safety. However, reliable safety design and analysis of large-diameter monopile foundation under complex wave loadings requires a clear understanding for the cyclic behavior of submarine geotechnical materials. This paper concentrates on the experimental investigation of the mechanical behavior of a submarine clay at Laizhou Bay, China. Cyclic triaxial tests are carried out to reveal the cyclic characteristics of submarine mucky soft clay. The experiments analyze the cyclic stress-strain and stress path behavior, revealing the cyclic mobility behavior under different Cyclic Stress Ratio (CSR) and buried depth levels. Further research investigates the insight mechanical behavior by concentrating on the development law of cumulative strain, pore pressure and modulus attenuation behavior. Based on the experimental results, critical CSR values are proposed against buried depth, considered as the failure-triggering threshold loading boundary. This provides helpful reference for the dynamic stability evaluation and design for monopile foundations under cyclic wave loadings.

Keyword: Submarine clay, triaxial tests, cyclic soil behavior, cyclic mobility, cyclic stress ratio