Learn how to identify a potential weak layer: Perform A Shovel Shear
Shovel Shear
Shovel shears can identify potential weak layers; they can
not quantify snow stability. Shovel shears can be done on a flat or on an angled slope.
First, dig a hole or pit in the snow. The vertical wall of the pit should be straight up and down, and smooth. Make a mark on the uphill portion of one corner of your pit with your shovel blade. This will mark the boundaries of your column, which should be roughly 30 cm by 30 cm or 12 inches square (A). Next, cut both sides using a snow saw or your ski, all the way to the floor of the pit making sure that the cuts are straight (B). The back of the column should only be cut as deep as your shovel blade is long, so note the length of your shovel relative to your saw (C) and then cut the back (D). Perpendicularly insert your shovel in the back cut of the column and pull gently and evenly forward being careful not to lever your shovel handle (E). Examine the shear layer where the block failed (F).
|
The force applied to the shovel that causes a weak layer to shear from the layers surrounding it can be rated as follows:
VERY EASY if the layer shears when you are cutting the column or inserting the shovel
EASY if the layer shears when you are pulling forward gently on the shovel
MODERATE if more force is applied before shear failure
HARD if the shovel has to be levered or pulled hard for shear failure to occur.
Repeat the process for lower layers.
|
THE SHOVEL SHEAR ONLY HELPS IDENTIFY WEAK LAYERS...IT IS NOT INTENDED TO QUANTIFY SNOW STABILITY!!
TO TEST THE STRENGTH OF BONDING BETWEEN LAYERS YOU MUST PERFORM A STABILITY TEST SUCH AS A COMPRESSION TEST OR RUTSCHBLOCK.
Next Section: Compression Test »