Snow pillow overloading by slope induced creep

A snow pillow in southeastern British Columbia has been subject to overloading since it was installed in the summer of 1979. It had been installed in a sheltered meadow below a resource road where the ground slope was about 17 to 23%. Other pillows are installed in sloping sites, where overloading has not been observed, so creep loading was not anticipated. After a number of other possibilities had been rejected, the pillow was subjected to field testing when the snowpack was near its seasonal maximum. The test program involved trenching to isolate the pillow from the uphill slope and monitoring the pillow response. Extensive core sampling on and around the pillow, prior to the tests, were conducted to check snowpack uniformity and ice layers. By the time the uphill trench was completed, the pillow overload had all but disappeared. The results were sufficiently impressive to induce a relocation to a new site in August, 1983. The site and test results are described and illustrated.