The general equation provided by the Principle of Natural Proportionality (PNP) for the evolution of the settlement of embankments is applied to the experimental data of the Kansai International Airport (KIA) built in an artificial island 5 km from Osaka in Japan. The general equations provided by the PNP have been proven to describe the mechanical behaviour of geomaterials: solids, liquids and gases. They have been applied to rocks, concrete and granular and fine soils. The application of this general equation to the settlement data of a friction–piled box foundation in Mexico City clay is also included.