in order to prevent this from happening rock bolts must be inserted into the upper part of the face of the tunnel and radially around the shaft
per evitare che ci� accada � necessario prevedere un intervento di chiodatura sia sul fondo della galleria superiore che radialmente al contorno del pozzo.

identifying the extent of the plastic ring of ground around the excavation.
individuando l�estensione della fascia plastica al contorno di scavo.

This ring of ground, is ground that has been loosened and has become "plastic" (not elastic), which means that it won't hold its shape, if you breathe on it, it might just fall on top of you.