Regarding contact with particles

Hello everyone,
I am a student doing a project work, as part of my task I need to calculate traction when my sample come in contact with soil. Here the problem is particles are inserted and now there is no contact of my sample with my particles as sample is just at the surface but due to clearance between sample and particles there is no contact. Can anyone help me with this to make contact between sample and particles.
Thanks & regards.
Rohith.