I used two concentric, 24-segment circles. The radial elements simply connect corresponding endpoints.
I drew a short horizontal line at ground level, moved a copy to the height of the disk, then made an array by filling the distance between the bottom and top lines with 9 copies using the /9 operator. Then I just raised the nine radial faces to the heights of the lines in the array using inferencing.
The spacing around the curve was determined by the circle segmentation. The height of each step was transferred from the array.
After the geometry is constructed, clean up the inside of the ramp/foundation from the bottom.
-Gully