How wide is the sole of a three-meter-high rubble retaining wall to bear?

The bottom of the three-meter-high rubble retaining wall is 60 cm before being stressed. According to relevant public information, the top width is about 60 cm, the slope is about 1: 0.25, and the bottom width is about 1.35 when it is 3 meters high (it can be reduced if the fill can be fully compacted in layers and waterproof measures are taken), and the masonry (masonry) is very large, so it may be uneconomical to use bricks, so stone is the first choice.