How can gravel pads help protect permafrost beneath buildings and roads?

Gravel pads are used in permafrost engineering as a passive method to protect the ground's thermal equilibrium and maintain a stable foundation for structures.12

To effectively prevent the underlying permafrost from thawing, a gravel fill must be sufficiently thick to contain the entire amplitude of seasonal temperature variations. By restricting the annual cycle of freezing and thawing to the fill itself and the compacted active layer, the pad prevents summer warming from penetrating deep enough to melt the permafrost.1

If a gravel pad is too thin, it can act as a heat conductor and inadvertently accelerate thawing. Furthermore, while this technique is feasible in the Arctic, it becomes impractical in warmer subarctic regions due to the massive volume of fill required. Protecting permafrost is particularly challenging beneath heated buildings, where thawing can occur more rapidly than under roads or airfields.1