Hello,
I am using CODE_BRIGHT to model bentonite desiccation due to thermal gradients. I have used Nonlinear Elasticity (ICL=4, ITYCL=1) which gives reasonable results. However, I have convergence difficulties with high thermal gradients if P6, tension term to avoid tractions, is smaller than 0.2MPa. Can you please tell me how does P6 ("tens") work? Is it a reflection of soil tensile strength? And where can I find more information about it?
Best regards,
Ali Ghavam-Nasiri
Nonlinear Elasticity (ICL=4, ITYCL=1)
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Ali Ghavam-Nasiri
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code_bright
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Re: Nonlinear Elasticity (ICL=4, ITYCL=1)
Hi!
In ICL=4, ITYCL=1, "tens" is a term that has the purpose of avoiding tractions, because the formula used does not work with positive (traction) values of mean effective stress, so that way you make sure to keep the mean effective stress in the compression zone. I guess you have numerical problems because of the reason explained above. In ITYCL=2 "tens" is not considered since GiD only allows 10 parameters (P1,...,P10) per row and every parameter is already taken, but a Kmin=10 MPa have been set for ITYCL=2 to avoid this problem.
Regards,
Alfonso
In ICL=4, ITYCL=1, "tens" is a term that has the purpose of avoiding tractions, because the formula used does not work with positive (traction) values of mean effective stress, so that way you make sure to keep the mean effective stress in the compression zone. I guess you have numerical problems because of the reason explained above. In ITYCL=2 "tens" is not considered since GiD only allows 10 parameters (P1,...,P10) per row and every parameter is already taken, but a Kmin=10 MPa have been set for ITYCL=2 to avoid this problem.
Regards,
Alfonso
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Ali Ghavam-Nasiri
- Posts: 2
- Joined: Tue Aug 18, 2015 6:16 am
Re: Nonlinear Elasticity (ICL=4, ITYCL=1)
Dear Alfonso,
Thanks for your answer. It is very helpful. The convergence difficulties are also because I am modelling high thermal gradients under low overburden stress and net mean stress in the layers close to the surface tends to zero (and tension) quickly. As you explained, the formula doesn't work with negative (tensile) stresses.
Kindest regards,
Ali Ghavam-Nasiri
Thanks for your answer. It is very helpful. The convergence difficulties are also because I am modelling high thermal gradients under low overburden stress and net mean stress in the layers close to the surface tends to zero (and tension) quickly. As you explained, the formula doesn't work with negative (tensile) stresses.
Kindest regards,
Ali Ghavam-Nasiri
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Melia_Hawaii
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Re: Nonlinear Elasticity (ICL=4, ITYCL=1)
Aloha,
I am not familiar with the viscoplastic parameters for viscosity and the power of the stress function (N). Can you please comment on the sensitivity of the parameters, their implications on the model behavior, typical values for water and elastic silt applications, and tests to determine their magnitudes? I am using Code_Bright to model atmospheric effects on slope stability of a homogeneous residual elastic silt.
I would also like to mention that there is a difference between the suggested k1, k2, k3, and k4 parameters for the BBM model (pg VIb.21) and Cam Clay model (pg. VIb.23 of the manual), which is understandable. However, the suggested example parameters for the use of the BBM model in the Appendix (pg VIb.36) suggest the use of the Cam Clay model rather than the BBM model. Which should we use?
Finally, the example parameters for P1 and P2 (pg VIb.36) are not in the same format as in the current software (version 5_4) or in the description of the parameters on page VIb.23. Please edit.
Thank you,
Melia
I am not familiar with the viscoplastic parameters for viscosity and the power of the stress function (N). Can you please comment on the sensitivity of the parameters, their implications on the model behavior, typical values for water and elastic silt applications, and tests to determine their magnitudes? I am using Code_Bright to model atmospheric effects on slope stability of a homogeneous residual elastic silt.
I would also like to mention that there is a difference between the suggested k1, k2, k3, and k4 parameters for the BBM model (pg VIb.21) and Cam Clay model (pg. VIb.23 of the manual), which is understandable. However, the suggested example parameters for the use of the BBM model in the Appendix (pg VIb.36) suggest the use of the Cam Clay model rather than the BBM model. Which should we use?
Finally, the example parameters for P1 and P2 (pg VIb.36) are not in the same format as in the current software (version 5_4) or in the description of the parameters on page VIb.23. Please edit.
Thank you,
Melia