Epoxy Creep

[Thor]

I just read a news story some of you may have also seen about a phenomenon known as "epoxy creep."

According to the Yahoo News story, epoxy creep is "the tendency of some epoxies to slowly give way under constant pressure." It was apparently a contributing factor in the death in the Big Dig tunnel in Boston where ceiling panels fell and crushed a woman.

Does anyone have any facts or opinion as to whether or not this should be considered over time when using glued-in bolts? Of course, all bolts should be checked before using.

[Ralph E. Powers]

Does anyone have any facts or opinion as to whether or not this should be considered over time when using glued-in bolts? Of course, all bolts should be checked before using.

Bolts used for climbing/rappelling/caving should all be placed where the shear force is going to be on the bolt and the rock and not in such a way that the bolt can be pulled straight out. The hangers are put perpendicular to the rock face and the pull is at a right angle to the rock/bolt. Never straight out. The epoxy helps keep the bolt in the hole drilled and acts as an additional bond to the rock along with the expansion collar.
I've seen bolts drilled into mines and seen the ones placed in ceilings and such. Of course over time they're going to fail, mines are never supposed to be permanent fixtures anyway and if they're for the long term usually the bolts are inspected on a regular basis and replaced where needed. Abandoned mines are dangerous for this lack of inspection/replacement. So of course over time (even as short as 10-15 years) an epoxied bolt placed straight up into the ceiling or at such an angle where the forces of the rock are pushing against it ... yeah they're going to fail.

[cavedoc]

I read the story. It's pretty interesting. The panel that fell weighed 12,000 pounds. Not sure if that was spread over the 20 bolts that was mentioned or if it was fewer. Seems like the problem though is constant traction at high levels. Glue-ins put into a wall should be no problem at all. IIRC glue-ins are the prefered way to bolt a ceiling. But in the cave context they'll only be weighted for a few moments at a time. Doesn't sound like epoxy creep is going to be an issue for us at all.

[Wormster]

OH NO, not this old chestnut again.

Sorry folks but there's been a bit of paranoia over this on Mendip* over the last few months..............I'm not going into details I prefer to spare you that...

Suffice to say that instead of pull testing bolts (something like 6KN for 10 mins on an axial pull = Pass) its all down to individual caver's visual inspection.

*see here for more details:

http://ukcaving.com/board/index.php/topic,3947.0.html

and:

http://ukcaving.com/board/index.php/topic,3697.0.html

There's more out there but I'm too tired of the whole situation to post any further links.................

Good luck in resolving any bolting issues that you have though.