Ice Fracture

Abstract

AbstractThis paper presents an overview of ice fracture at engineering scales. Although ice fractures are ubiquitous in the Arctic and it spans a wide range of scales, e.g., from geophysical to engineering scales, fracture mechanics is not always adopted to describe ice fractures. This is largely due to that a fracture mechanics – based framework is lacking regarding Arctic offshore structural design; and characterising the ice fracture by the strength theory is often simpler and more conservative. Limiting our ice fracture studies at the engineering scale (i.e., Arctic offshore structural design and Arctic marine operation), a fracture mechanics—based framework is proposed in this paper to describe the two most typical ice failure modes (i.e., out-of-plane bending and in-plane splitting) during ice and sloping structure interactions. In this regard, two numerical methods (i.e., a hybrid approach and a purely analytical fracture-based approach) are introduced and related simulation examples and validations are presented in this paper. While characterising the splitting failure mode, a review on the strength theory—based approach and Linear Elastic Fracture Mechanic (LEFM)—based approach is conducted. This reveals the size effect in ice fracture and the introduction of the fictitious crack model (or cohesive zone model, CZM) to characterise the fracture of sea ice from geophysical scale down to grain scale. Because of the following two reasons: (1) most of the calculation methods in the fracture mechanics—based framework requires the fracture toughness of sea ice as an important input; and (2) based on the CZM, we see vividly a size effect in the fracture of sea ice and it deviates from the LEFM scaling at the laboratory scale, we carried out three field ice fracture experiments campaigns in a consecutive of three years (i.e., 2016–2018). Albeit only preliminary unprocessed results are available, we observed the importance of including the creep behaviour of sea ice in deriving the fracture properties of sea ice. This was also highlighted in previous studies through the development of the so-called Viscoelastic Fictitious Crack Model (VFCM). In addition, based on the most recent theoretical development in the CZM, we reviewed our field tests’ set-ups; and we also presente some initial results in relation to the loading rate effect.KeywordsIce fractureIce–structure interactionArctic marine operationAnalytical fractureSize effect