They are generally economical up to 10 feet in height for cast concrete structures.
Poured concrete retaining wall height.
Taller walls backfilled with heavier soil risk failure unless correct design methods are followed.
Poured concrete foundation walls that are less than 8 feet tall and have soil outside that is 6 or 7 feet deep against the wall can often be 8 inches thick and function quite well.
In general the top of the stem of any cast concrete retaining wall should not be less than 12 inches for the proper placement of concrete.
Gravity poured concrete retaining walls gravity retaining walls depend on their own weight and any soil resting on the concrete in resisting lateral earth forces.
Backfilling with a clay soil instead of sand can increase the load by double or more while going from an 8 foot to a 10 foot wall just a 25 height increase adds 50 to the lateral pressure.