Background I joined a power company in the hydro division and I am currently working in the planning department. I have a bachelor's degree in mechanical engineering & unfortunately most of the things I am facing everyday are related to civil engineering, lots & lots of construction terms & all.(I spend most of the time reading IS codes for concrete & other civil stuff) Important topic I had a discussion with a colleague(a civil engineer) about tunnel stability with respect to its depth. If the rock mass properties are exactly same & the tunnel dimensions are also same, he says that a tunnel which has lesser vertical cover will be much more safe than one with more vertical cover, because it has to support lesser mass(rock mass between the roof of tunnel & the natural surface land). I have a different take on this, I think the lower tunnel will be much more safer because a lot less tensile stress occurs at the roof of tunnel(I dunno much of soil(or rock) mechanics though). Safer tunnel => at lesser risk of caving in with same magnitude of lining. Question to civil engineers: Which explanation is correct? To Mods: shift it to general engineering if you think so, I thought otherwise.