Development of a rotational shear penetrometer for assessing snowpack stability.

Abstract

This Master of Engineering thesis describes the development of a portable, multiple-sensor instrument to provide rapid, quantitative snow stability information over the area of an avalanche start zone. Using a modified geomechanics shear vane an extensive fieldwork programme was carried out with the primary objective of correlating the shear vane against traditional measures of snow shear strength. Numerous shear vane configurations were investigated during the course of this research and their relative effectiveness in predicting snow slope stability was determined. A prototype shear penetrometer was then developed based on the findings of this study and incorporated sensors to measure snowpack penetration force, temperature and shear strength. Use of a miniature signal transmitter contained within the instrument probe enabled data to be transmitted to a receiver unit and laptop computer at the snow surface. A test rig was also developed, applying the mechanical force required to drive the instrument probe down into the snowpack. The design of this test rig provides the instrument probe with a rotational motion in an axis perpendicular to snowpack layering and a translational motion along this axis with rotational and translational speeds able to be varied independently. The shear penetrometer was developed to a level where all three system components (the instrument probe, laptop/receiver unit and the test rig) were operational to a degree that field testing could be carried out. Work is to continue within the University of Canterbury on the development of the operator interface, field testing of the prototype instrument and development of new sensor modules.