THE INITIAL CREEP OF COLUMNAR-GRAINED ICE: PART I. OBSERVED BEHAVIOR

Abstract

Previously undeformed columnar-grained ice exhibits a period of increasing or constant creep rate during the transient creep stage when loaded in simple compression perpendicular to the long axis of the columns. It is shown that this behavior is associated with the formation of small-angle boundaries and internal cracks. Creep strain beyond 0.25% for first load tends to a power-law dependence on time. On reload, specimens exhibit a normal transient creep behavior and have, initially, a lower resistance to deformation than for first load. With deformation, this resistance increases so that the reload creep curves cross the first load curves at about 0.2% creep. For reload, creep strain less than about 0.025% and greater than about 0.2% appears to have a power-law dependence on time with exponent about equal to that for first load.