A fascinating and beautifully photographed video of this work, by Croatian caver Boris Watz, won an award in this year's NSS Video Salon. You can check out a copy from the NSS library for showing at grotto meetings, etc.: Bridge in Tunnel, Boris Watz 23:02 minutes
Frank Binney (Video salon judge this year with Alex Sproul and Lee Stevens) On 8/19/10 11:32 AM, "Mixon Bill" <bmixon...@austin.rr.com> wrote: > An article in the latest issue of Acta Carsologica > (http://carsologica.zrc-sazu.si/downloads/391/5garasic.pdf > ) contains a description of the most extreme measures I've ever read > about taken to stabilize a cave roof--other than, of course, just > filling the whole thing with grout. Boring of a road tunnel > encountered a large cave room, in which a 58-meter-long bridge was > built for the road to cross the room. The ceiling of the room was > judged unsafe, as the overburden was "only" about 40 meters. So the > entire ceiling of the room was tied to the surface with hundreds of > pretensioned steel cables on a 2-meter grid. On the surface, the > cables are anchored to a grid of concrete beams 1 meter high and 0.5 > meters thick. The cables are attached to "geotechnical anchors" that > aren't really described, but that appears to mean that they are > cemented throughout their lengths in holes 150 mm (6 inches) in > diameter. -- Mixon > ---------------------------------------- > Home is that place where, when you have to go there, they have to take > you in. > ---------------------------------------- > You may "reply" to the address this message > came from, but for long-term use, save: > Personal: bmi...@alumni.uchicago.edu > AMCS: edi...@amcs-pubs.org or sa...@amcs-pubs.org > > > --------------------------------------------------------------------- > Visit our website: http://texascavers.com > To unsubscribe, e-mail: texascavers-unsubscr...@texascavers.com > For additional commands, e-mail: texascavers-h...@texascavers.com > > --------------------------------------------------------------------- Visit our website: http://texascavers.com To unsubscribe, e-mail: texascavers-unsubscr...@texascavers.com For additional commands, e-mail: texascavers-h...@texascavers.com
