I am using Hypoplasticity model with explicit asymptotic boundary surface proposed by Prof. Masin in 2014. In this model, parameter ‘nu’ controls initial stiffness in CU test. But when I was applying this model to simulate CU test on normal consolidated soil, I couldn’t match with the experiment even I am using 0.001 as ‘nu’ value (see attached picture). Parametric study on ‘nu’ shows it does have influence on initial stiffness but smaller value of ‘nu’ than 0.001 would have almost the same curve as 0.001 one, it seems like this is the highest stiffness I can have.

The soil I am using is a mixture of sand (40%) and clay (60%), does this composition make stiffness in experiment high while the model is only for clay use? Another parameter in this model, alpha_f, controls stiffness degradation rate so I think changing it won’t help with my problem. Does anyone encountered a similar problem, or any suggestion will be appreciated.

Thank you!




1 Comment
  1. Shen Wang Author
    Shen Wang 3 years ago

    I found taking ‘nu’ as negative value leading to higher stiffness, which matches my experiment results. However, I am not sure if ‘nu’ has a clear physical meaning and whether it can be negative or not.

    If ‘r’ parameter is taken as smaller than 0.1 in Prof. Masin’s 2005 model, according to the relationship between ‘r’ and ‘nu’, ‘nu’ can be calculated as a negative value.

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