This is absolutely neato for our giant rock mechanics experiment (without instruments). You can see from the curve on the bottom that they will slowly 'walk' the form along and pour the floor (invert). This gives a nice firm bottom for the tunnel, and forms a base for the rest of the lining. Obviously, they are very happy, and aren't worried about the extra support needed for all that overbreak.
I am really interested in how they will support this extra concrete filling the overbreak. Will they just pour, and trust to the sidewalls and invert to take the load? Will they put in extra rock bolts to act as hangers? How much stress are they going to put in the sidewalls, which directly relates to how much margin they will leave for rock squeeze. Personally, I don't think the lining is going to last that long, but that's just me talking. :)
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