There is now a better way to do Interparticle Collisions, pouring liquids, rubble, etc...
Use nParticles.
Check this tutorial by Duncan Brimsmead, one of the developers of Maya Fluids & the Nucleus system etc.

https://area.autodesk.com/blogs/dunca...ith_nparticles

It is essentially for fluid-like sims, but it can be altered for your needs easily