Drystone walls as gravity retaining walls
If a dry stone wall must be able to bear a certain load (traffic load, building etc), the load-bearing capacity of the dry stone wall must be calculated by an engineer.Dry stone retaining walls designed by the engineer are constructed as gravity walls. This means that the weight of the built stone body counteracts the forces from earth pressure and superimposed load.
Normally, a gravity wall has a trapezoidal cross-section.
If a retaining wall is designed by the engineer as a gravity wall, the calculated trapezoidal cross-section must be "solidly" filled in consistent masonry quality. In the trapezoidal cross-section, there is therefore no backing, but only stones that have a similar degree of dressing as in the wall face. These stones are laid in bond. Only behind the trapezoidal cross-section does the backing of lesser quality stones begin. The illustration below shows (A) a traditional dry-stone wall with a facing shell and backing and (B) a trapezoidal cross-section filled with masonry of consistent quality.