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<p>Lacustrine soft clay is characterized by a high water content, large void ratio, low bearing capacity, and significant rheological properties, posing substantial challenges to engineering construction. The stress‒strain‒time relationship curves of lacustrine soft soil with various stress levels were obtained through a long-term uniaxial creep test. Additionally, the creep deformation characteristics of soft clay were investigated. Subsequently, the linear Newtonian dashpot in the generalized Nishihara model was replaced with a nonlinear Newtonian dashpot, thereby extending the model from one-dimensional stress space to three-dimensional stress space and establishing an improved generalized Nishihara model. Utilizing the incremental finite element method, the viscoelastic compliance matrix and the viscoplastic compliance matrix based on the Drucker-Prager (D-P) yield criterion for two-dimensional and three-dimensional elements of the improved generalized Nishihara constitutive model were constructed for numerical calculations. Afterward, a viscoelastic-plastic constitutive model program for soft soil was developed through secondary development in ADINA software. The parameters of the creep model were determined using the curve fitting method, and the model was validated through numerical simulations. The results indicate that the soft soil exhibits instantaneous deformation upon loading, followed by a significant increase in deformation over time. When the stress level is less than 50&#xa0;kPa, the creep deformation of the soil is characterized primarily by decaying creep, indicating a viscoelastic stage. Conversely, when the stress level exceeds 50&#xa0;kPa, the soil displays both decaying creep and steady creep, demonstrating plastic behavior and transitioning into a viscoplastic stage. Owing to the confining effect of the ring knife, the soft soil sample did not exhibit accelerated creep. The improved generalized Nishihara model is nonlinear, and the theoretical curves calculated from it align well with the measured creep test curves.</p>

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Creep Behavior and Constitutive Modeling of Lacustrine Soft Soil

  • 期刊论文

  • 发表日期：

    2026年1月16日

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  • Guihai Fu,
  • Ming Lv,
  • Yangqian Ou

摘要

Lacustrine soft clay is characterized by a high water content, large void ratio, low bearing capacity, and significant rheological properties, posing substantial challenges to engineering construction. The stress‒strain‒time relationship curves of lacustrine soft soil with various stress levels were obtained through a long-term uniaxial creep test. Additionally, the creep deformation characteristics of soft clay were investigated. Subsequently, the linear Newtonian dashpot in the generalized Nishihara model was replaced with a nonlinear Newtonian dashpot, thereby extending the model from one-dimensional stress space to three-dimensional stress space and establishing an improved generalized Nishihara model. Utilizing the incremental finite element method, the viscoelastic compliance matrix and the viscoplastic compliance matrix based on the Drucker-Prager (D-P) yield criterion for two-dimensional and three-dimensional elements of the improved generalized Nishihara constitutive model were constructed for numerical calculations. Afterward, a viscoelastic-plastic constitutive model program for soft soil was developed through secondary development in ADINA software. The parameters of the creep model were determined using the curve fitting method, and the model was validated through numerical simulations. The results indicate that the soft soil exhibits instantaneous deformation upon loading, followed by a significant increase in deformation over time. When the stress level is less than 50 kPa, the creep deformation of the soil is characterized primarily by decaying creep, indicating a viscoelastic stage. Conversely, when the stress level exceeds 50 kPa, the soil displays both decaying creep and steady creep, demonstrating plastic behavior and transitioning into a viscoplastic stage. Owing to the confining effect of the ring knife, the soft soil sample did not exhibit accelerated creep. The improved generalized Nishihara model is nonlinear, and the theoretical curves calculated from it align well with the measured creep test curves.