The optimal design of the retaining walls built by the Incas in their agricultural terraces

Abstract The stability of the retaining walls built by the Incas was analyzed using images obtained from Google Street View and Google Earth Pro combined with a simple mechanical model. The study was conducted using ten retaining walls from the Lower Agricultural Sector of Machu Picchu, Peru, which were analyzed under drained and saturated conditions. The analysis revealed that the Inca retaining walls are both functional and highly optimized, exhibiting a safety factor that is remarkably close to those recommended in modern geotechnical design standards. This is mainly due to two factors: (1) the mechanical role played by the large blocks, many of which weigh several tons; and (2) the excellent drainage conditions in both the inner structure and the wall face.