Horizontal Snow Pressures
Horizontal Snow Pressures
(OP)
Are there any horizontal snow pressures that build up from deep layers of mountain snow? In all of our research, we have not found any mention of horizontal snow pressures.
I understand that a heated space will melt the snow back from the face of the wall, leaving an air space and no horizontal pressure. What about the case where the space is not heated?
I understand that a heated space will melt the snow back from the face of the wall, leaving an air space and no horizontal pressure. What about the case where the space is not heated?






RE: Horizontal Snow Pressures
Interesting question. On the one hand, when I think of snow, there is that fluffy moldable white stuff of our childhood where we built snow forts with vertical walls, on the other hand with additional moisture or pressure does this condition change? Here is what Bernhard Muessen, an expert in snow thermo-mechanics has to say on the subject. Glean what you will.
"The exploration and exploitation of polar regions requires the ability to work in and with the firn layer, which is the topmost layer of the continental ice sheet. A firn layer consists of meteoric snow which changes by metamorphosis from original snow flakes to a stable firn body. As the firn is compressed by subsequent layers of snow, a porous granular material evolves with density that is increasing with depth. This leads to polycrystalline ice in the bottom layers. The porous structure of the firn gives rise to volumetric viscous behaviour. Its granular build-up leads to an increase of volume under shearing conditions (dilatation). Furthermore, firn exists at high homologous temperatures, thus it shows creep behaviour.
A material law for snow and firn is proposed, which accounts for these characteristic features of the material. Following the approach by von Mises, it is based on the assumption of an elastic and a viscous potential. The dilatation is described by the third invariant of the stress tensor to model a strain orthogonal to the shearing direction. Creep experiments are used to evaluate the material parameters."
So....it appears that poisson's ratio may be in evidence for polar snow regions such as these, but for practical purposes I'd guess that lateral creep may not be present or not sufficiently large under normal seasonal conditions to warrant building design consideration in the lower US.
Hope this helps.
PE in NE
RE: Horizontal Snow Pressures
I would think it is minimal unless there are layers of ice/sleet involved.
RE: Horizontal Snow Pressures
RE: Horizontal Snow Pressures
Good observation. Goes to show that a single train of thought is not ususally conclusive.
I was only thinking about lateral pressures due to a precipitation event. As you mentioned, stored potential energy due to a mass of snow falling from a loader would certainly demonstrate viscous behavior immediately upon being deposited, but would it also exhibit any creep effects after in its final position without being subject to further surcharge loading?
PE in NE
RE: Horizontal Snow Pressures
RE: Horizontal Snow Pressures
RE: Horizontal Snow Pressures