The simultaneous determination of air permeability and gas diffusion through ice layers in the field

摘要

A coupled air permeameter-gas chamber has been used to measure both the air permeability and diffusion coefficient of an inert gas through natural ice layers. The apparatus was designed to take sequential measurements of both these parameters for the same sample without any intermediate manipulation of the specimen. In avoiding manipulation, errors related to the structural variations between different replicates are eliminated. The apparatus is portable, allowing measurements to be made directly at the study site. The permeability is directly measured in situ by the air permeameter while gas samples used in the diffusion experiments are collected and subsequently analysed at the laboratory. The validation of the apparatus was accomplished by comparing theoretical values for the permeability of beds of spherical beads with known dimensions. Measured permeability values, for different ice samples vary from 0.005 x 10~(-10) to 12.9 x 10~(-10) m~2. Mean diffusion coefficients ranged from 0.013 to 0.028 cm~2 s~(-1). These values are situated in the range for those found between hard packed snow and loose compacted soil.