Forces of a skier on snowpack?

[0g]

It seems like if you could make a freebody diagram of the forces a skier puts on the snowpack, figuring out how it is split up between shear and compression you could devise a tests and a weighting system of some sort to give you a better idea of the snow's stability. Has anybody done this?? It seems really obvious and simple. I don't know if it would actually work or not but I'd just like to know the split in forces I guess. I really am not in the right mindset to do physics right now though

[KoKopeLLi]

Wow, someone just got out of a physics class. You just gave me a headache with your run-on sentenceness

[0g]

run-on sentenceness

lol

[Toby]

Wow, someone just got out of a physics class.

Engimaneering, methinks.

0g, what about the different loads depending on the skiers' actions? E.g. if you were straightlining it's be pure compression. If you were laying down trenches, more shear than compression.

[0g]

It wouldn't be pure compression though, unless you were on a flat slope. It would be super easy to figure it out, it is something like the

sin(slope angle)9.8(skiers weight)

might be cosine though?? I just graduated this summer and already my brain is mush. Then you would also need to figure in velocity and acceleration I think.

[summit]

But what about varying snow consistency through the depths and varying skier weighting depending on their speed, maneuver, balance, skis, weight, weight distribution, etc etc etc etc etc... dynamic vs static forces etc

[0g]

Yeah there would be a lot to it I guess, seems like you could get a pretty good approximation though??

[0g]

I really didn't mean for it to be that complicated though, just thought that knowing how much of a skiers force is shear and how much is in compression would help in knowing the overall strength of the snowpack. For example if it took X newtons of force to cause a shear failure, it would be nice to know how much of the skiers overall force is typically directed in the shear direction so you could determine if human triggered failure is likely. I know this is really simple and probably wouldnt help all that much, but I was just thinking this afternoon.

[summit]

hmmm email ian mccammon

[mrkristofo]

From Bruce Jamieson's dissertation at the U of Calgary (11/95), Avalanche Prediction for Persistant Snow Slabs



There's a good 255 pages on this very thing.

[0g]

Cool!

I knew it was out there...

[0g]

Hey you dont have a link to that paper do you??

I tried google, but cant find the actual paper. Will try one other place real quick....

[mrkristofo]

Negative, only a hard copy.

[OldSchool1080s]

...guess this is why my ass dropped out of Mechanical Engineering... damn statics and dynamics classes kicked my ass...as in i walked out of multiple midterms feeling as if i had been molested by a barbed wire condom... all those FBDs for nothin...

[pechelman]

i think its important to notice the caption on that figure as well as summit's post.

that picture only relates to static skier loads, and really, how important is that?

[wannabe]

Not to beat this too much but along with all of summit's variables you then must look at what type of equipment are they on i.e. (alpine, snow board,or tele) then are they a smooth skier or bouncing around.

Some of these variables have been looked at when doing rutshblock test, even broken down to what kind of tele binding are they on.

Sorry I know you were looking for a simple equation but snow dynamics are anything but simple.

[iskibc]

This thread needs a visit from Ogre


Just kidding. Interesting stuff. Would be difficult to measure mostly due to the varying density of the snow from spot to spot.

[eirikainersharp]

One thing to remember is that snow packs fail locally under skiers often - the necessary condition for stability is whether the failure propigates and it seems based on the latest research that this is an internal property of the snow pack.

[Fatty]

It seems really obvious and simple. I don't know if it would actually work or not ...

What good is simplicity if it doesn't give the right answer?

you could probably generate a fairly complete model in a computer, but I don't see it being much use 'in the field'

[PNWbrit]

I wish someone would invent the Rutschblock Test.

Really are the current range of tests the problem or is it just that people don't do them or more likely don't pay attention to more obvious warning signs let alone the results any number of tests would provide?

[eirikainersharp]

I wish someone would invent the Rutschblock Test.

Really are the current range of tests the problem or is it just that people don't do them or more likely don't pay attention to more obvious warning signs let alone the results any number of tests would provide?

what he said.

[mrkristofo]

Really are the current range of tests the problem or is it just that people don't do them or more likely don't pay attention to more obvious warning signs let alone the results any number of tests would provide?

Its because skiers are selectively ignorant, egotistical, self-gratifying risk takers that often ski the line, not the aspect. You could have the most complex x-ray vision, terrain mapping, layer cohesion calculating system in the world available to the masses for free, and people would still die in slides because "it looked like it was gonna be siiiiiiiiiiiiiiiiiiiick."

If you read the accident reports in archives such as Snowy Torrents, you'll see general commonalities in line exactly with what you just said.

Now I'll get off my soapbox and return to making stupid ego-driven decisions.