Adopting the CEL finite element method to systematically simulate the penetration process of rectangular spudcan foundations under typical offshore wind geological conditions. Based on simulation results, the extent of plastically strained soil around the foundation is quantified, soil softening zones are identified, and corresponding strength reduction factors are calculated. Subsequently, small-strain finite element model incorporating these softening parameters are developed to calculate directional stiffness reduction coefficient η. Comparative analyses with non-softening reference models reveal the substantial influence of soil strength degradation on foundation stiffness. A comprehensive parametric study further evaluates the sensitivity of stiffness characteristics to two critical geotechnical parameters： the normalized shear stiffness ratio Gmax/su and the critical shear strain at failure γfp. Results demonstrate that：1） Soil softening effects varies with different directional in-situ stiffness components, but the extent cannot be neglected; 2） Stiffness reduction coefficients exhibits consistent decreasing trend with increasing level of loading;3） Stiffness increases with higher Gmax/su, but decrease with larger γfp.

offshore wind power  /  numerical simulation  /  stiffness matrix  /  spudcan foundation  /  installation effect  /  NGI-ADP constitutive model