Flexural and compressive strength of the landfast sea ice in the Prydz Bay, East Antarctic

Abstract

Abstract. A total of 25 flexural and 55 uniaxial compressive strength tests were conducted in laboratory using landfast sea ice samples collected in the Prydz Bay. Three-point bending tests were performed at ice temperatures of −12 to −3 ∘C with force applied vertically to original ice surface, and compressive strength tests were performed at −3 ∘C with a strain-rate level of 10−6–10−2 s−1 in the directions vertical and horizontal to ice surface. Judging from crystal structure, the ice samples were divided into congelation ice, snow ice, and a mixture of the two. The results of congelation ice showed that the flexural strength had a decreasing trend depending on porosity rather than brine volume, based on which a mathematical equation was established to estimate flexural strength. Both flexural strength and effective modulus of elasticity increased with increasing platelet spacing. The uniaxial compressive strength increased and decreased with strain rate below and above the critical regime, respectively, which is 8.0 × 10−4–1.5 × 10−3 s−1 for vertically loaded samples and 2.0 × 10−3–3.0 × 10−3 s−1 for horizontally loaded samples. A drop-off in compressive strength was shown with increasing sea ice porosity. Consequently, a model was developed to depict the combined effects of porosity and strain rate on compressive strength in both ductile and brittle regimes. The mechanical strength of mixed ice was lower than congelation ice, and that of snow ice was much weaker. To provide a safe guide for the transportation of goods on landfast sea ice in the Prydz Bay, the bearing capacity of the ice cover is estimated with the lower and upper envelopes of flexural strength and effective elastic modulus, respectively, which turned out to be a function of sea ice porosity.

Experimental study on flexural strength and effective elastic modulus of granular ice in the Bohai Sea, China

“…Therefore, the gas volume should be considered when analyzing the physical factors affecting its mechanical properties, especially for laboratory small-scale ice specimens tested at relatively high ambient temperatures. However, rare studies have quantitatively examined porosity's influence on sea ice flexural strength (Wang et al, 2022). Figure 8B shows the results of flexural strength σ f versus the square root of porosity obtained in this study.…”

“…The simple beam tests include three-point and fourpoint bending tests performed in the field or a laboratory, often with small sizes (Ji et al, 2011). Full-scale in-situ tests can provide the actual mechanical properties of the whole natural ice sheets in practical applications, but they are usually highly time-and labor-consuming (Aly et al, 2019;Wang et al, 2022). Small-scale laboratory tests are easier to conduct with accurate testing machines and flexible settings of test conditions (Cox and Weeks, 1986).…”

“…Given brine and gas in sea ice cannot bear loads, the mechanical properties of sea ice should depend more on the total porosity (i.e., brine volume plus gas volume) than the brine volume, especially for the warm ice that gas within sea ice may occupy more volume than brine (Timco and Weeks, 2010;Frantz et al, 2019;Wang et al, 2020). However, rare studies quantitated the effects of porosity on flexural strength and effective elastic modulus of sea ice (Wang et al, 2022).…”

The porosity effect on the mechanical properties of summer sea ice in the Arctic

“…3b). Detailed description 150 on the machine can be found in Wang et al (2022). The machine is equipped with a force sensor of 100 kN capacity and ±0.5 % accuracy as well as a displacement sensor with ±2 μm accuracy.…”

“…The sea ice porosity has been adopted to estimate sea ice strain modulus in the engineering standards of ISO19906 (2010), which, however, is replaced by sea ice brine volume fraction in the latest version standard of ISO 19906 (2019). Recent experiments conducted by Wang et al (2022) showed that both brine volume fraction and porosity had no statistically significant effect on sea ice strain modulus. Sea ice substructure is much more important, and the strain modulus increased with increasing platelet spacing.…”