Creep tests on Antarctic Glacier ice

Abstract

THE strain rate of polycrystalline ice is known to depend on the applied stress, the temperature and the orientation of crystals in the specimen. From laboratory creep tests on randomly oriented ice, Glen1 derived the simple flow law Equation presented where ε is the strain rate, σ is the stress, and k is constant for a given temperature. Other workers have confirmed the validity of this relationship for the stress range 2-15 bars. From observed minimum strain-rates Glen1 deduced n=3.17; but he considered that a value of 4.2 derived from analysed quasi-viscous creep-rates was a more correct one for randomly oriented ice. Some observations on glacier tunnel deformation tend to confirm Glen's higher value for the exponent 2, whilst the closure of a bore-hole in the Greenland ice-cap gave an exponent of 3.773. Other laboratory tests on glacier and commercial ice of high density gave figures ranging from 2.42 to 3.53 with a mean of 2.964. Weertman's dislocation climb theory calls for a dependence on stress to the power 4.5. Below a stress of 1 bar the flow mechanism is different and there is an approximation to viscous behaviour, with an exponent of about 1.5 applying. © 1959 Nature Publishing Group.