A google returned this:
"For any holes or cracks near foundation perimeter, where it meets the cement, you can use broken up glass or steel wool mixed in with some cement to seal the opening. A rat can chew threw most anything, and wet cement is no problem. The steel wool or broken glass in the cement, when ingested, will serve to cut their intestines, cause internal bleeding and ultimate death. "
So I guess putting broken glass under there will help, but it seems you might end up with lots of dead ones rather than live ones...