[Erasmus]

First of all, the length of the bolt should not make any difference as far as i can tell.

Maybe it had to do with the depth to which it would be anchored.

[mamelukesabre]

If what you say is true, then the anchors would be like old fashioned lag bolts. that would be that last thing I would choose to hang these panels.


Here's my assumptions...admittedly based on ignorance of this tunnel:

The panels are apparently falling on people. This leads me to believe the panels are purely architectural in nature and contribute nothing in terms of the structural integrity of the tunnel itself...otherwise we would be reading of a tunnel collapse and people sealed off and trapped and running out of air...etc.


Without a schematic, I'm going to simplify everything and imagine these concrete panels are like a bigger version of drywall on your ceiling. Lets say they are 8" thick and supported at or near the corners by bolts. I would probably have specified brackets of some kind protruding from the back of the panel to be bolted to a steel framework of some kind above the panels. Actually, I would have preferred welded connections of some kind...but bolts it is, for whatever reason. If the bolts were in fact some kind of lag-like bolt...then length is indeed a serious factor...unless they are screwing into the side of a steel tube or I-beam or something. Then the thickness of the steel they are screwing into becomes the determining factor...not the length of the bolt. Also, if the bolts are machine type threaded into nuts on the otherside of a tube or plate then you need to consider the washer adequacy.