Constitutive model

[Aliyaghfoori]

Dear STKO

Based on field and laboratory studies, I have the following parameters: density, Poisson's ratio, porosity, cohesion, internal friction angle, and Young's modulus. Which constitutive model would you recommend for analyzing soil behavior under earthquake and blast loading conditions, specifically focusing on the plastic behavior of the soil?


Thank you for your assistance.

[STKO Team]

You should choose among the available soil constitutive models in OpenSees, based on the soil type

[Aliyaghfoori]

Thank you for your response.
The parameters obtained from the laboratory studies were quite extensive, and the soil profile included a variety of soil types such as clay, silt, coarse-grained sand, fine-grained sand, and others.
Using a normal distribution function for each layer, the mean values of the soil parameters were extracted.
Given this, is it appropriate to use the Drucker-Prager model?
Additionally, is it possible to calculate the yield stress for each layer based on the available parameters using the existing relationships?

[STKO Team]

Yes the drucker prager is a good approximation (though there are specific models for clay, sand, and silt in opensees).

[Aliyaghfoori]

Thank you for your response. I am familiar with the existing constitutive models in the software, such as PDMY, etc., but since they require a lot of input parameters and I believe calibrating each model to match the soil layers at the study site would be time-consuming, I decided to use a simpler constitutive model. Can I use the attached relationship to obtain the yield stress using cohesion and the friction angle?

[STKO Team]

Check the opensees documentation:
https://opensees.berkeley.edu/wiki/inde ... ker_Prager

Under the Notes:

The Drucker-Prager strength parameters <math> \rho </math> and <math> \sigma_Y </math> can be related to the Mohr-Coulomb friction angle, <math> \phi </math>, and cohesive intercept, <math> c </math>, by evaluating the yield surfaces in a deviatoric plane as described by Chen and Saleeb (1994). By relating the two yield surfaces in triaxial compression, the following expressions are determined

dpeq.png (8.34 KiB) Viewed 2917 times

[Aliyaghfoori]

Thanks.

Can I use the yield stress formula in both three-dimensional space and plane strain two-dimensional space?

[STKO Team]

Yes, after all a PlainStrain material in OpenSees is generally a wrapper around the 3D one.

[Aliyaghfoori]

Thanks.

[STKO Team]

You're welcome