After changing the model size other error is mean effective pressure is negative. Please if yu have any idea please share, thank you in advance. 

Bhim,

Did you initialize the cam clay mean effective stress by using the corresponding function? Read the constitutive models manual / Cam clay. There is also an example at the end, which shows that you need to initialize the mean effective stress by using the corresponding function.

Dear Bhim,

I am trying to model a simple multiple layer rehabilitated embankment in Flac3D and I am new to this software. In my model, I use modified cam clay model for two consecutive layers, strain hardening/softening model for the soil replacement material, and linear elastic model for the overlaying pavement. Now, any time I ran the project, I faced two errors:

1- *** Cam-clay: Bulk modulus bound must be increased for stability.

once I increase the Bulk modulus, I encounter another error:

2- *** Cam-clay: Yield envelope cannot be reached

I saw you faced this problem before. I will appreciate if you please let me know the possible reasons for these errors.

Thank you

Dear Bhim,

I don't known whether you have solved this problem, i also face the same problem when use modified cam clay model in FlAC3D. Maybe I can share some suggestions for you.

1—make sure the [ a] (zone face apply stress-xx [a] ) has the same order of magnitude with [b] ([global pre_pres =[b]])

After i modified it, it not show the error:Cam-clay: Yield envelope cannot be reached, hope it will help you.