I want to simulate load-unload cycles with the WeirdTriaxControl, but I encountered a "weird" behaviour for the unloading part. Not matter the initial conditions and parameters I set, I get a volumetric increase upon unloading, although I would expect a decrease, see the figure
I do simulate the loading - unloading with setting the stressMasks to S.lab.stressMasks=[3,7] and the goals to S.lab.goals=[-0.05,latSig]. The same happens if I do the unloading with controlling the vertical strain. In ealier simulations, three years ago when we started, I did get compressive behaviour upon unloading.
Do you have any idea what I am getting wrong?