| Glorious Catenary Avalanches |
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| Written by Ryan Hunt | |||
| Wednesday, 16 February 2005 06:16 | |||
We got busy with The big arches on Friday and Saturday. The design is pictured here and involved a 40 foot long major vault and two intersecting vaults that will open to the south. On Friday we finished the form and then moved it into place and started dumping snow onto it with the Bobcat.  It required some additional packing to break up the chuncks and fill int he gaps, but it worked ok till the Bobcat ran out of reach. Saturday was a beautiful, sunny, warm day. Pete brought his Bobcat and snow blower attachment. We used that to finish making the first arch. As the form was lowered, everything worked beautifully.  We stood under the arch and admired it. The space inside it felt very nice.  Then we moved the form over and tried it again. That piece went up smoothly, too. The snow went through the snow blower very well and with a few experiments with different guides and tools we learned to get the snow into the right area. At this point is where things started to get frustrating on this 50 degree and sunny day. As we lowered the form, the snow slid off the north side of the form with a sickening sound. After that we rebuilt the north side and let it set while we went to lunch. After lunch we tried it again and it failed again with another frustrating catenary avalanche. After that, the original part of the arch that was still standing was cracked and looking worn. When we tried to slide the form back under that section to repair it, it also collapsed. At this point in the afternoon, we decided to try again and build the arch a full 24 inches thick with the results pictured below.  What we learned from these experiments is that at 50 degrees, the nice dense wet snow didn't want to carry the 3 PSI at the bottom of the arch. The snow from the Ice Hotel in Sweden was tested at approximately 80 PSI, but htat was after it had set in cold temperatures. So, we'll try again this week after we do some studies of load bearing capacities of snow blown snow at different temperatures and different packing techniques. And then I'll keep you posted.
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