Failure surface 1

[hamadadf]

I am modelling an excavation, and i am wondering which parameter should give me the failure surface (plastic zone). the closest surface to what i was looking for was the AC yield, but still not sure if that is correct. Any ideas?

 

[Cansand]

it depends on the constitutive model you are using (strain hardening , perfect plasticity... ) for example
if you are dealing with perfect plasticity model then AC yield is indication of failure occurence

 

[Cansand]

hamadadf Please read my comment I hope that we can help each other to reach an answer to this very important question as we seem in the same boat . For example, I am using Cap Plasticity
From 4.2.1 ABAQUS/Standard output variable
identifiers I quote : "For cap plasticity: PEQC provides equivalent plastic strains for all three possible yield/failure surfaces (Drucker-Prager failure surface -
PEQC1, cap surface - PEQC2, and transition surface - PEQC3) and the total volumetric inelastic strain (PEQC4). All identifiers also provide a yes/no flag (1/0 on the output database) telling whether the yield surface is currently active or not (AC YIELD: ?actively yielding?).
When PEQC is requested as output to the output database, the active yield flags for each component are named AC YIELD1, AC YIELD2, etc. and
take the value 1 or 0.
.dat: yes .fil: no .odb Field: no .odb History: yes

In this hardening model only PEQC1 indicates that failure takes place. Although, PEQC3 or PEQC2 or PEQC4 indicate that there is plastic strian , that doesnot mean failure.
The question is that I cannot get PEQC1 through Field output nor History output. I want to get the contour of PEQC1.. Any Idea please