Fracture and Creep of Warm and Floating Columnar Freshwater Ice Under Different Loading Scenarios Under Laboratory Conditions

Abstract

Investigating the mechanics of freshwater ice fracture is crucial for ensuring safe activities in lakes and rivers. Climate change is bringing warmer conditions and making the ice warmer. Accordingly, the necessity to study and model warm ice is increasing. The properties and behavior of the ice may be fundamentally different when it is warm, very close in temperature to zero degrees, than cold. While cold ice has been mainly studied in the literature, this paper reviews a study case of warm freshwater ice (>-0.5oC) and provides a strong evidence that warm ice may behave differently than the cold ice typically tested in laboratories or nature. Large-scale fracture experiments, using edge-cracked rectangular plates loaded at the crack mouth, were conducted in the Ice Tank of Aalto University. The plates covered a size range of 1:39, the largest for ice tested under laboratory conditions, with three plate sizes: 0.5m x 1m, 3m x 6m and 19.5m x 36m. The monotonic loading rates applied led to test durations from fewer than 2 seconds to more than 1000 seconds, with some experiments tested under creep/cyclic-recovery loading. Under the monotonic loading, size and rate effects were interrelated as rate dependent size effects and size dependent rate effects. Under the creep/cyclic-recovery conditions, the way the ice deformed did not fit our conventional understanding, and the ice response was interestingly elastic-viscoplastic with no significant viscoelasticity.