[CIG-SHORT] Pylith Drucker-Prager Plasticity Problem

[Jianbo Zhu]

To whom it may concern,

I am a postdoc at Caltech with Professors Ares Rosakis and Nadia Lapusta. I am using Pylith to compute the plasticity during fault rupture. But I met a problem after running Pylith.

The example is a very simple 2D horizontal fault rupture. The material properties are density 2700, vs 3000, vp 5291.5, friction angle 20 degree, cohesion 1 MPa, dilatation angle 1 degree, which are the same as those in Pylith "tests" files. After running pylith by command "pylith tri3.cfg tri3_100m_gradient.cfg", an error occurred as:

"RuntimeError: Infeasible stress state - cannot project back to yield surface.
  alphaYield:       0.148583
  alphaFlow:        0.00675674
  beta:             3.67479e-05
  trialMeanStress:  0
  stressInvar2:     0
  yieldFunction:    -3.67479e-05
  feasibleFunction: -3.67479e-05"

I need the computation results urgently. Would you please tell me the reason for this error and how to solve it? Thank a lot!

Attached is the zip file for my example. 

Best regards!

Yours sincerely,

Jianbo Zhu
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