Wing crack models of the brittle compressive failure of ice

Abstract

This paper presents possible models for brittle compressive failure of ice based on the formation and growth of wing cracks. The limitations of each model are discussed, along with the implications of the model's respective functionality. Those results which are available in the literature are discussed in the light of the models. It is shown that none of the existing models describes the available data completely. Recent attempts to describe brittle failure in ice have concentrated on the Wing Crack model put forward by Ashby and Hallam, proposing that failure arises from the stable propagation of such wing cracks. However, at least two other possibilities must be considered. One is that wing cracks may indeed cause failure, but by an unstable propagation mechanism. The second is that rather than wing cracks causing the failure, the initiation of new cracks into the aggregate may give rise to a catastrophic reduction in stress. Given the failure of any of the models to provide good fits to the available data under the three test conditions, and their incorrect functionality for at least one of those test conditions, it is concluded that a model of the brittle compressive failure of ice that is based on wing cracks is inherently incorrect. New models or descriptions of the failure process must be found.