how much weight can a weak layer take before it collapses?

very light precip for about an hour today that fell a total of 0.5cm. other wise cloudy.

today was staff training for us and part of it was to gather snow observations and chase the reactivity of the surface hoar hidden below a rain crust down about 10-15cm in the Norns Range. We dug 2 pits (one at 2000m NE aspect and the other at 2240m on an E aspect) and both had the same very easy sudden collapse results. When we isolated the columns with the snow saw, the surface hoar layer did a sudden collapse of the weak layer. The question is, how much weight can this weak layer take before failing? We will be keeping an eye out on this possible developing problem as we get more snow and weight on top of it.