The model refuses to converge.

[Harrie7]

Greetings,
I'm a newbie in this soil modelling business; have modelled a 'tank' full of soil. But once I input the *Mohr Coulomb model by inputting the friction angle and dilation, the model refuses to converge. the cohesion of the material is 4.4kPa. But I don't know the cohesion yield stress and absolute plastic strain. how can I input them? Please help me.
Thank in advance.
With regards

 

[FEA way]

I would look for research papers with such material data for your kind of soil. It's pretty much the only way apart from performing physical tests.