Hi Itascans,
I am in abit of a fix, i am simulating an open pit excavation. The issue is i am facing very high deformation values than expected when the model is cycling to equilibrium. I have all the set in boundary condtions, material properties all seem realistic and stress initialization seems okay. But i still dont know why the model is outputting high values, can any Itascan suggest what can be done to tackle and understand the causes?. Thank you.
Which constitutive model are you using, and what are its properties? It seems there are some locally unstable zones due to gravity.
You could try running “model solve elastic” to see if the situation improves.
If the model surface is obtained by excavation, try slower excavation.
Another possibility is that, given these properties, geometry, and slopes, the locally unstable zones may be physically realistic. This could further indicate that the properties are not accurate or appropriate. Try adjusting properties or change to elastic model for these zones.
Hi Cheng,
I employed an Elastoplastic model governed by the Mohr Coulomb failure envelope. Sent you fish code of the modelling.
I received your files, but they are incomplete. I cannot run the datafile because it requires several geometry files that are not available to me.
However, after a quick review of your datafile, I would not recommend using the command “zone initialize-stresses” in this model. This command is best suited for level ground with lateral confinement. Since your model has a mountain-like surface, I suggest removing this command and using “model solve elastic” instead to determine the in-situ stresses.
It is possible that some isolated, locally exploding points may still occur. This is acceptable as long as the global average unbalanced force ratio stabilizes to an appropriate value (avoid using other criteria). Afterward, you can reset the displacements to zero for subsequent modeling stages.
On the contrary, I would argue that is exactly what zone initialize-stresses should be used for, since (at least according to the manual) it calculates the appropriate stress for each zone according to the densities of the zones above it and should therefore give reasonable stresses especially for uneven ground surfaces.
In all likelihood in in this case there is a mismatch between the initialized stresses and the applied boundary conditions or the applied parameters simply are not able to withstand even the initialized stress. Is this using a built-in constitutive model or something self-written?
Thank you @cheng …will run it with that command.
Yeah its a native Flac3D constitutive model.
