Introduction  In order to facilitate the design optimisation of foundation for offshore wind turbines, it is necessary to promote application of advanced geotechnical constitutive models that are theoretically sound and capable of modelling realistic soil behaviours in real engineering scenarios.

  Method  Firstly, the theoretical framework of the Unified Hardening model (UH model), an advanced constitutive model, was introduced. Then, further modifications oriented to requirements in real engineering applications were presented. Finally, the modified model was applied to the pile-soil analysis of large-diameter monopoles, and the results were analyzed at the macroscopic and element level to verify its effectiveness and practicability.

  Result  The UH_G0 model obtained through modification and verification is applicable to addressing issues in real engineering practices. The parameter "initial void ratio" in the original UH model is replaced by "overconsolidation ratio". By incorporating the Andersen empirical formula, the shear modulus is decoupled from the constitutive parameter κ, significantly improving the initial shear stiffness of the original UH model, and thus allowing the UH model to be applicable to the deformation (stiffness) sensitive boundary value problems.

  Conclusion  As an advanced constitutive model with a well-defined theoretical framework and physically meaningful parameters, the UH model demonstrates high potential for practical engineering applications. The two modifications tailored to engineering design requirements are necessary, which improve the convenience in application of the UH model to address boundary value problems and the accuracy in calculating initial stiffness, respectively. The modified UH_G0 model is proven to be effective and practical for solving practical engineering problems in the process of finite element simulation.