Determining ball size in PFC for UCS and triaxial test

My result from experiment and numerical are matching. so can I understand that ball size which I have selected is corrected.

Also my model is consist of clumps and balls. I am uploading the image and may I know the model are correct and contact is generated.

I am not sure if this answers your questions but to find the size of balls or clumps you can use the FISH intrinsics - ball.radius() or ball.vol(); clump.pebble.radius() or clump.vol

@ShivamPandey If you are asking whether the selected size is correct, you can use the same grain size as your laboratory specimen. If the lab grain size is very small and affects computation time, you can start with a specific size and gradually reduce it. Observe when you achieve convergence in the macroscopic response of the model. This will help you select the optimum ball size for the simulation. I hope this helps.