I have a problem with a particle system and my sphere objects deep half way through my collision object, the screenshot is here:
If you have already have activated the Collision option on your surface, you will have to adjust the Particle Dampening value. Based on the size of the balls, you would want them to bounce and settle on the surface. If you want to keep the balls embeded into the surface on impact, just don't change anything. But activating the Collision option on the surface the particles are falling to would be your best bet.
I found that the problem is just with the sphere shape and box shapes are good for collision so i tried a subdivision box instead of icosphere but issue is still exists, so spheres have this problem and solid boxes are o.k. then i appreciate any solution for spheres. it seems like a bug.