Cyclic strengthening of lake ice

Abstract

Further to systematic experiments on the flexural strength of laboratory-grown, fresh water ice loaded cyclically, this paper describes results from new experiments of the same kind on lake ice harvested in Svalbard. The experiments were conducted at −12 °C, 0.1 Hz frequency and outer-fiber stress in the range from ~ 0.1 to ~ 0.7 MPa. The results suggest that the flexural strength increases linearly with stress amplitude, similar to the behavior of laboratory-grown ice.

Behavior of Saline Ice under Cyclic Flexural Loading

“…Acoustic emission hit rate during cycling increases with an increase of stress amplitude of cycling. Flexural strength of saline ice of 3.0±0.9 ‰ salinity appears to increase linearly with increasing stress amplitude, similar to the behavior of laboratory-grown freshwater ice (Murdza et al, 2020c) and to the behavior of lake ice (Murdza et al, 2020a). The flexural strength of saline ice of 5.9±0.6 ‰ depends on the vertical location of the sample within the thickness of an ice puck; i.e., the strength of the upper layers, which have a lower brine content, was found to be as high as three times that of lower layers.…”

“…Figure 8 shows measurements obtained from saline ice of both salinities cycled at -10 º C at an outer-fiber displacement rate of 0.1 mm s -1 . For comparison, data from laboratory grown freshwater ice (Murdza et al, 2020c) of S2 character and from lake ice of the same character (Murdza et al, 2020a) are also shown. The relationship between the flexural strength, and cycled stress amplitude, , for saline ice appears to be a linear one and, within experimental scatter, to have essentially the same sensitivity to stress amplitude as freshwater ice; namely:…”

“…However, this behavior appears in conflict with the behavior of freshwater ice under cyclic loading (Cole, 1990;Gupta et al, 1998;Iliescu et al, 2017;Iliescu and Schulson, 2002;Murdza et al, 2019Murdza et al, , 2020cMurdza et al, , 2020a. In those experiments, it was discovered that the ice flexural strength increases upon repetitive loading, followed by recovery upon post-https://doi.org/10.5194/tc-2020-300 Preprint.…”

Behavior of saline ice under cyclic flexural loading

“…Acoustic emission hit rate during cycling increases with an increase in stress amplitude of cycling. Flexural strength of saline ice of 3.0 ± 0.9 ‰ salinity appears to increase linearly with increasing stress amplitude, similar to the behavior of laboratory-grown freshwater ice (Murdza et al, 2020b) and to the behavior of lake ice (Murdza et al, 2021). The flexural strength of saline ice of 5.9 ± 0.6 ‰ depends on the vertical location of the sample within the thickness of an ice puck; i.e., the strength of the upper layers, which have a lower brine content, was found to be as high as 3 times that of lower layers.…”

“…Cyclic loading may also play an important role in other scenarios. For instance, during ice-structure interactions (Jordaan, 2001;Hendrikse and Metrikine, 2016;O'Rourke et al, 2016;Jordaan et al, 2008) the structure itself, such as a lighthouse, may be weakened or damaged to a degree that depends on the strength of the ice. Other examples are runways and roads that are built by freezing water on cold oceans, rivers, and lakes and subsequently subject to cyclic loading.…”