Abstract

Failure processes in ice play a crucial role in limiting loads transmitted to platforms and vessels during ice-structure interactions. Coupling between ice failure processes and structural response has also been identified as a key mechanism contributing to the excitation of dynamic response in offshore structures subjected to ice loads. At the same, significant knowledge gaps remain regarding the conditions under which such coupling events can occur in nature. To help address some of these knowledge gaps and to advance understanding of the mechanics of ice-structure interaction, recent laboratory tests have been carried out on ice specimens under confined conditions (e.g. ice specimens molded into a cylindrical confining ring). Preliminary results from these confined ice specimen experiments are presented and compared with results from previous tests carried out on unconfined ice specimens (e.g. indentation of a conical ice specimen with a spherical indenter). A discussion of the effect of confinement on observed ice failure processes, the relative importance of fracture and damage during these interactions and on the magnitudes of measured loads is provided. A discussion of observed dynamic aspects of ice crushing behavior for confined and unconfined conditions is also presented.

Introduction

In Arctic environments, it has been widely observed that during ice-structure interactions, the nature of ice failure processes have a significant influence on the magnitude and dynamic character of loads transmitted to the structure. Factors such as boundary conditions and scale are well known to influence failure (e.g. Sanderson, 1988; ISO19906, 2010), but certain aspects of the underpinning mechanics are still not fully understood. While it is generally understood that confined boundary conditions tend to suppress fractures (e.g. Ashby and Hallam, 1986; Frost, 2001; Schulson, 1990, 2001) and promote damage-type failure mechanisms associated with microstructural changes and softening of the ice (e.g. Melanson et al., 1999), increasing scale increases the probability of fracture occurring (e.g. Taylor, 2010; Taylor and Jordaan, 2015).

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