A Problem about collision between Softbody and rigidbody

[zjl19870808]

hello everyone! I am doing a Demo using bullet.When the rigidbody collides the softbody, it drill through the softbody.now I don't want it to drill through the softbody,so how can I set it? Of course ,it won't drill through the softbody if the rigidbody is big enough, but I don't want it to be too big, because the rigidbody in my Demo is a small wheel.
Besides, in my Demo, I want the rigidbody move gradually in a special area by pressing a special key. So the rigidbody may collides the softbody. It is just in this process, it is wanted that the rigidbody not drill through the softbody, but press the softbody and make it to be distortional.
Looking forward to your replies,Thank you very much!
Jet