Abstract: As the core issue of soil mechanics in the 21st century, the structure of undisturbed soil has been widely concerned. In particular, the mechanical behavior of structural damage in soft clay will pose a non-negligible impact on the foundation in offshore engineering. This paper takes the structural characteristics of the undisturbed submarine soil as the research object, and derives the numerical implementation format of the SANICLAY model considering the structure of the clay. Based on the analysis of the triaxial test results of the undisturbed marine clay, it is found that the marine soils have significant structural damage mechanical behaviors which means soil strength would reduce under static deviatoric stress. Through the Substepping Explicit Integral Algorithm method, the multi-yield surface soil constitutive model which can accurately reflect the structure damage of the marine soil is established. The evolutions of plastic potential surface and yield surface of soil under different consolidation conditions and shear conditions are studied. It is revealed that consolidation can reduce the degree of structural damage of the marine soil. Also, the occurrence of structural damage of the marine soil in the shearing process mechanism is illustrated. A series of analyses of the static bearing capacity of the bucket foundation that can consider the influence of the structured soil is carried out. The influence of the soil structure on the failure mode of the bucket foundation is analyzed. Through the parametric analysis of the structural damage factor, the change of the peak bearing capacity and the residual bearing capacity are studied; the concept of residual attenuation ratio is proposed to describe the residual bearing capacity of the foundation after the soil structure is completely lost. The relationship between residual attenuation ratio and the structural damage factor is established.

Key words: marine soils, structured soil, constitutive model, bucket foundation, bearing capacity of foundation