I just came across some problems with the implementation of the “Sand Hypoplasticity Model” in Plaxis. I wanted to to perform a simulation of an oedometer test on a material for which i know the hypoplastic parameters using the soilt test tool in plaxis. While for the triaxial test every thing seems to work out quite well, i can’t manage to get proper results for the oedometer test. The strange thing is, during the test i get vertical strains with no change of the vertical stresses. It just shows a straight line within the epsilon1-sigma1-diagram. I have tried to check it with different sets of hypoplastic parameters (different materials) but still i get equal results. Is there any specific input i have to enter to make the oedometric test in Plaxis work in combination with the Sand Hypoplasticity Model. When using for example simple elasto-plastic contitutive models, its no problem to perform the oedometer test. What could be the problem?
Regards Manuel Winkler
Hi Manuel, this is due to step size. In the model, a cutoff is implemented such that if in the step the state would reach inallowed state due to linearisation during integration, variables are not updated. Please rerun your oedometer test with smaller step size, or use some of the element test drivers available at SoilModels, and it should be OK. Regards David
Thank you very much for your fast and very helpful response.