Sinkhole destructible physics?

I am currently trying to create a sinkhole effect where the ground begins to crumble and fall with gravity. I have tried to create 2 perfectly fitted geometries, one that is the part of the ground I want to crumble away, and one that is the surrounding ground that remains. I used the APEX plugin to fracture the inside ground geometry, but it explodes rather than falls crumbles and falls. Is this the best workflow for this effect or can someone who has been there and done that, suggest a better way. I would like the ground to crumble away when triggered by the approaching player.