depth 1

[gholam1]

At what depth would a tunnel/shaft colapse if say their were no cracks and was solid rock? (a 25 meter diamiter shaft/tunnel)

 

[Kivi]

please seek professional advice on this. look up Mining Engineering or Geotechnical Engineering on the web.

 

[RobPE]

A very simple approximation would be to compare the uniaxial compressive strength of the rock to the normal stress (gamma * h). As the normal stress approaches the uniax strength, rock burst potential and roof failure are more likely.

This of course excludes several other very important factors including the extent of fracturing, which is typically the most critical factor in the stability of underground excavations, horizontal stress magnitude, orientation of tunnel relative to principal stress directions, groundwater, and ground support.