Shear modulus degradation of China Laizhou Bay mucky clay under cyclic loading at an offshore wind turbine site

The stability of offshore wind turbine (OWT) foundation under long-term cyclic loading is critical to its normal operation, and the dynamic characteristics of submarine clay are the fundamental references to the design and construction of OWT foundations. Due to the insufficient investigation in the dynamic characteristics of the submarine mucky clay, this paper concentrates on the shear modulus stiffness degradation of submarine mucky clay under cyclic loadings at a China Laizhou Bay offshore wind turbine site. A series of cyclic triaxial tests under different stress paths are carried out to investigate the shear modulus degradation of the mucky clay. The experiments analyze the cyclic stress–strain and stress path behavior, identifying two distinct development modes of submarine clay under different cyclic stress ratios (CSR), i.e., the stable mode under low CSR and destroy mode under high CSR. Further research investigates the development law of shear modulus degradation behavior under different CSR and confining pressures. More critically, the stiffness degradation models of submarine clay stable and destroy mode are put forwarded, respectively, based on the inapplicability of traditional stiffness degradation model. The experiments and discussion provide a helpful reference for the design and stability evaluation for OWT foundations under long-term cyclic loading.