I woke this a.m. to hear that they are planning to use explosives for last bit of the tunnel,  There is an alternative method to fracture rock without explosives. 

Fill the holes (already drilled) with either slacked lime or burnt lime, I forget which . Then add water.  The mixture expands generating huge forces which fractures the rock.  This has been commonly used in the past for controlled quarrying of blocks of stone. 

You may be in a better position than I to forward this suggestion.  It may be too late.  It may have been considered.  But on the other hand it may not and be a more safe way of reaching the chaps,
Sincerely
Chris Malcolm

I’m sure a similar expansion method had been tried using Expandex (?) and failed, hence the experimentation with and eventual precision use of some form of gun-powder like substance. No longer an issue however as horizontal work finished and now on vertical phase apparently.

On another bit of news, dear Les Rochester has been at it again. Where did young Les spring from? He certainly seems dedicated to making a name for himself.