AGE HARDENING OF SNOW AT THE SOUTH POLE

The age hardening of artificially and naturally compacted snow has been investigated at the South Pole. Results show that the age-hardening process is greatly retarded at low temperatures. Artificially compacted samples of density 0.55 g/cc attained a compressive strength of less than 3.0 kg/sq cm after one year's aging at -49C. Exposure to solar radiation accelerated the age hardening. Irradiated samples attained a strength of 6.0 kg/sq cm after 100 hr, increasing to a virtual maximum of 8.0 kg/sq cm at 600 hr. Compressive strengths increased with a decrease in snow-particle size and with an increasing angularity of the particles. Below 3 m the strength of naturally compacted snow was found to increase rapidly with an increase in density. Naturally compacted snow of density 0.55 g/cc possessed considerably greater strength than any of the agehardened samples of artificially compacted snow of the same density. Thin-section studies show that age hardening can be correlated with the formation and growth of intergranular bonds, and that bond growth falls off rapidly with decreasing temperature. In view of the low strength found in both naturally and artificially compacted snow at the South Pole, 'cut-and-cover' undersnow camp construction may not prove practical at the South Pole. (Author)