stilt - A post which raises a structure above ground or water level.

ground beam - A horizontal heavy timber or reinforced concrete beam at or near ground level for distributing a load which it supports

groundsil, ground beam, ground plate, mudsill, sole plate - In a framed structure, the sill which is nearest the ground or on the ground; used to distribute concentrated loads.
[Dict. of Architecture and Construction]

sablière - longue pièce porteuse, en partie basse d'un ouvrage ...
[Dicobat]

Nothing to do with sand or gravel pits.