The proposed approach (stacking irregular rocks) is much more labor and probably time intensive, one of the reasons it’s not done any more. Another is the diff

The proposed approach (stacking irregular rocks) is much more labor and probably time intensive, one of the reasons it’s not done any more. Another is the difficulty of estimating the load bearing strength when you don’t have predictable uniformity in the structure. And transporting irregular large rocks is less efficient than gravel. The good news is these problems can be solved down the road! On the labor side, I imagine robots can be used to do the stacking and transporting. Probably 20 years down the road but definitely within the realm of serious possibility. As for the strength, you can watch and assay each large rock as you place it, and use some test + statistical methods to estimate structural integrity (the current model of pouring slurry into a wooden form is just a simplified version of this anyway, one that can be computed with a slide rule). As a bonus the result could be stronger due to its amorphous structure.