Parallel channels' fracturing mechanism during ice management operations. Part I: Theory

Abstract

It is frequently observed that long cracks in sea-ice tend to form between parallel channels during ice management operations. The long cracks that develop play an important role in reducing the size of the managed ice floes, which is one of the main goals in an ice management operation. However, the fracture mechanism behind these long cracks remains unclear. To address this issue, a comprehensive study is reported here in two associated papers.In the current paper (i.e., Paper I), an edge-crack theoretical model is proposed to elucidate the parallel channels' fracture mechanism. The proposed theoretical model is partially based on theories regarding ship -level ice interactions and partially based on previous studies on the general ice fracturing mechanism. The edge-crack theoretical model is extensively examined using a separately developed numerical scheme based on the eXtended Finite Element Method (XFEM), which allows for the existence of a singularity field and displacement jump within conventional Finite Elements (i.e.., FEM). The numerical scheme is benchmarked against known asymptotic analytical solutions and field experiments. Afterwards, with the developed numerical scheme, through fitting numerical simulation results in terms of the edge crack's Stress Intensity Factors (SIFs) and a relevant asymptotical analysis, we managed to derive a group of closed-form formulae with wide application ranges. For the current engineering problem, this set of formulae quantifies the maximum parallel channel spacing max h , beyond which the observed parallel channels' fracturing events cease to occur. Moreover, the same numerical scheme is utilised to study parallel channels' fracturing paths. Based on the XFEM-based crack path simulations, a second group of formulae and a numerical recipe were obtained to characterise a simplified crack path. This set of equations enables us to quantify the maximum floe size MCD L that can be generated between two parallel channels and its corresponding floe size ratio. In the sequel paper (i.e., Paper II), these equations are validated by a series of well-controlled field experiments undertaken during the Oden Arctic Technology Research Cruise of 2015 (OATRC2015).

Strain response and energy dissipation of floating saline ice under cyclic compressive stress

“…Moreover, the specimens harvested from floating ice sheets lose brine once removed from the sheet; warm ice in particular can lose a significant amount of brine, which could significantly alter the mechanical properties in subsequent experiments. In addition, some remaining brine (for example, in capillary brine channels) must freeze during the storage process of dry specimens; this may as well lead to some difference in the macroscopic mechanical behavior (for example, in elastic modulus) of dry and floating specimens (Marchenko and Lishman, 2017;Eicken, 1992;Jones et al, 2012;Gough et al, 2012). The methodology developed in the present effort avoids such problems and is expected to produce more realistic mechanical behavior, particularly when interest centers on behavior at relatively warm temperatures where brine drainage is extensive.…”

Simulator for Arctic Marine Structures (SAMS)

“…Moreover, the current version of SAMS adopts an analytical framework that supplements the NDEM method with analytical closed-form solutions to simulate the fracture of sea ice. This methodology was first presented by Lubbad and Løset (2011) to model the bending failure of ice. Later, the method was expanded with a number of closed-form solutions that cover other failure modes such as splitting and radial cracking of ice.…”

An overview of the Oden Arctic Technology Research Cruise 2015 (OATRC2015) and numerical simulations performed with SAMS driven by data collected during the cruise

“…Crack orientation and occurrence frequency were quantified versus different channel spacing to reveal the relationship between the parallel channel spacing and the size of the generated ice floes during an IM operation (Lu et al, 2016b). Lu et al (2018a) presented a theoretical model for parallel channels' fracturing mechanism during ice management operations, and Lu et al (2018b) used full-scale data from OATRC2015 to validate that model.…”

“…These equations are derived by Lu et al (2018a), and they take into account the crack's kink behaviour. .…”

“…In regard to the validation of SAMS, the OATRC2015 expedition provides ample cases and data sets to validate each module separately and collectively. For example, within this special issue, Tsarau et al (2018) utilised the OATRC2015 data to validate the developed propeller wash model within the hydrodynamic module, and Lu et al (2018a;2018b) developed and validated analytical formulas to account for the kinking behaviour of long splitting cracks, and these analytical formulae became a further enrichment to the existing fracture module. The following text, on the other hand, focus on the overall validation of SAMS using OATRC2015 full-scale data.…”