I had read a post of brianlu who had a similar issue as mine. I had put in a deck 16'x20'. Ground is hard clay as I live in an area north of Toronto Canada. We began construction when the clay was moist and used 24" sono tubes as we were going to stone the columns to a total height of 12'. We ran into lots of moisture as the sky opened up when we poured. We had back filled prior so after the pour I was not sure if we ended up with smooth side. Sure enough, the first winter we saw some heave in half the posts. This summer, I dug down to the base of the posts, over 48" and found that there was some rough edges. On the concrete that was fairly smooth we ground and on the bad ones, we boxed an re-poured, first putting gravel and some 2" SM at the bottom of the boxes. Figured the SM would help if frost every got that far down which it never does. This winter we saw two posts push. These were the ones that were fully boxed and re-poured. The only thing I can figure is that the clay soil is such that it literally grabs around the concrete and heave with huge pressure. These two post see lots of water come by them. Clay does not have good drainage. I was thinking of digging down around these columns and back filling with gravel. In doing this my concern is that water will just flow to the bottom. I was thinking of putting weeping hose (with or without sock?)about 1/4 of the way down to at least grab the water and take it away. Anyone have any suggestions?