Laboratory-scale mixed-mode I/II fracture tests on columnar saline ice

Abstract

Laboratory-scale experiments on mixed-mode I/II (including pure modes I and II) fracture of non-oriented columnar saline ice were performed. In the experiments, obliquely notched, three-point bending specimens were used, with the load applied in the direction perpendicular to the columnar grains. Tests were performed on dry isothermal (−10 °C) specimens and specimens floating in water and having a temperature gradient (mean temperature: −2.5 °C). The fracture loads and crack initiation angles were analyzed. The apparent mode I, mode II and mixed-mode fracture toughness and the flexural strength of the floating and relatively warm specimens were only about thirty percent of those of the dry and cold specimens. The results showed that the T-stress significantly influenced the mixed-mode I/II fracture of ice; good agreement was found between the experimental results and those predicted using the generalized maximum tangential stress criterion. Both trans- and inter-granular crack growth were observed, regardless of the specimen type or mode of loading.