The total weight of the pool is effectively meaningless. The load per square inch = weight of water at that depth. Thus the pressure at the top of the pool is effectively zero. At the bottom it's around .42psi/foot * 3feet = 1.3psi which is not all that bad. Anyway, I suspect the load is actually less than the average basement wall which often holds back 6 feet or more of soil.
Now, I'm not a structural engineer. However, if at the bottom of the pool you can crush/shear/buckle/etc concrete, you should also be able to crush/shear/buckle/etc six-year-old-girl, right? I'm betting the bending and tension load resistance of 6 year old girls are decidedly suboptimal for residential construction.
I see photographic evidence of six year old girl, decidedly uncrushed.
Concrete carries essentially no bending or tension loads. I'm amazed it's stood up to this amount of additional pressure.