Portuguese to English Tech/Engineering Mining & Minerals / Gems working of a mine

In a brief caption describing a historical model (late nineteenth century) showing the workings of a mine:

"O método de exploração consistia em desmontes por degraus direitos e/ou invertidos, procedendo-se ao enchimento com material estéril, ao nível inferior (enchimento aos “pés”) e, suportados neste nível inferior, acedia-se e explorava-se as zonas superiores do jazigo (desmonte do “teto”)."

could this be 'stage filling' or 'back filling'? I can't find any conclusive answers via internet research, and the term doesn't seem very common in PT. It's a translation for a museum, and mining is not my normal area, so all help is much appreciated.

Many thanks