Hello,
I have a problem in my simulation with Plaxis FEM 2D.
I have modelled a pile that passed 8 m from a soil layer and then embedded around 50 cm in a bedrock layer in a “Axisymmetric” Model. I modelled the soil layer in Mohr Coulomb and modelled the rock layer in Hoek-Brown. I want to mode the Bearing capacity of the pile on bedrock. Therefore, I performed the “Displacement” method with increasing around 1 mm in each step to understand what is the final bearing capacity of the pile on bedrock. This is like Pile test simulation.
I After modelling and analysing I understand there is a problem in results. Referring the picture, I expect that in a load test simulation and pile testing or any foundation testing simulation, the graph be like “Picture 01” output results. This means that after reaching the peak resistance of the soil, the graph continue which shows that by applying more deformation, the pressure will be constant or even reduced depending on the soil type.
But, in my simulation I understand there is a problem, because as I applied the “Displacement” method to reach the bearing capacity, always my graphs in the final reached a kink (jerk) and then the analysis finished the same of “Picture 02”. This is even routine in my simulation in soil layer bearing capacity that always my graphs are finished in just a jerk and does not continue anymore. I want the graph continue and show me that after more deformation the pressure will be stayed constant to understand this is the real bearing capacity of the layer. I could trust this kind of graph stopped with a jerk to show the bearing capacity.
I think there should be something wrong in my simulation or data and setting, because for example, as I showed in previous “Picture 01” the graph was achieved from a FLAC FDM results which showed clearly the bearing capacity pressure stayed constant after applying more deformation. At the 1st I thought maybe this is a local failure (Punching failure), but I understand this procedure of jerk stops without continuing the deformation in a constant pressure is always the same for all my modelling even in soil layer.
I my simulation I created:
“Initial Phase” with K0 calculations
“Pile Installation” Phase to activate the Pile and interface
“Pile Testing” Phases in Plastic phases which includes the “Displacement” increment in each phases
In the “Pile Testing” Phases I perform with the default setting of the plaxis FEM menu and receive these kind of results. In the following, in the failed phase I applied the changing as “Max load fraction per step to 0.1”, “Max number iteration to 100”, active “Use line search”, and the bearing capacity mostly increased but again in a kink (jerk) at the final without continuing.
I also attach “Picture 04” which shows my failure points as “Plastic points” and “Incremental Deviatoric Strain” in failure, but anyway this kind of jerk (kink) in my graphs that are stopped and does not continue is the same in all my foundation bearing capacity simulation even in soil layer.
Could someone please guide me what is the problem and how should I solve my perform to achieve a trustable, clear and good results in my foundation testing simulation?
Thanks for all your support and guidance,
I would sincerely appreciate it if you could provide a quicker response.
Amir
