The rescue team trying to reach the trapped Beaconsfield miners is about to begin perhaps the most dangerous phase yet.
Workers are about one and a half metres directly below the miners, and are now blasting through, despite fears of triggering a rock fall.
Australian Workers Union Secretary Bill Shorten says the team must first go through solid rock then through loose rubble known as "fill".
He says they have not decided yet how exactly to approach their task.
"The challenge of the waste rubble and this fill is not that it is hard, although it will have a certain degree of strength, but that if it is dislodged you don't want to have an effect where the sides of where the rock is being dislodged from - the other sides around it are rubble and fill - collapsing in to where the hole is."
He says; "If you're coming up you take out the dirt, all of a sudden the sides start collapsing into you."