THE INITIAL CREEP OF COLUMNAR-GRAINED ICE: PART II. ANALYSIS

Observations on the initial creep behavior of columnar-grained ice are analyzed by assuming that the creep strain at a given time has a power-law dependence on the applied constant compressive stress. The exponent for the stress was time-dependent during transient creep. For first load it started at a low value, increased to a maximum of about 2.23 approximately 75 minutes after the application of the load, and decreased thereafter. For reload it started at a high value and decreased continuously to a constant value of 1.46 by 100 minutes after the application of the load. Creep rates at a given time, calculated from the observed power-law dependence of the creep strain on stress, also had a power-law dependence on stress for time greater than about 25 minutes after the application of the load. The observations are shown to be in agreement with observations by Krausz (1963) on the deflection rate of ice beams and by Steine-mann (1954) and Glen (1958) on the stress-dependence of the minimum creep rate during secondary creep. The observations indicate that the creep rate during secondary creep varies approximately as t−0.5.