here is what happened in my community when the city filled in a pool because of neglect and accidents.
They, the City, came in and stripped the pool of all obstacles sticking up above the ground, then broke up the pool decking and did dump it into the hole.
According to the person in charge, pools do indeed rise when empty. The weight and downward pressure of the water does hold the pool in place. But the dirt acts like water and is actually heavier so that problem will not exist.
The pool was filled in first with debris and concrete and junk, then sand was used to fill in the crevices. Then watering was used. Then more sandy loam was put in, more watering, then just old reg. top soil was filled in and again watering in. As yo can see, watering in is very important, it melts the dirt down and causes it to settle and stop future sink holes.
I did forget to state, they punches big holes in the bottom of the pool for drainage and to stop collection of water. this is pretty straight forward and important.
The top was hydromulched and maintained. Now, yo cannot even tell there was a pool.