Taller walls backfilled with heavier soil risk failure unless correct design methods are followed.
Poured concrete retaining wall height.
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.
They are generally economical up to 10 feet in height for cast concrete structures.
Recommendations there are some basic rules of thumb for foundation wall thickness and these are outlined in many modern building codes.
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.