An ice-specific phase-field fracture model for predicting brittle and ductile failure

The material behaviour of ice is complex: At short time scales it behaves as a brittle solid in extension, or a plastic material under compression/shear, whereas at longer time scales the visco-elastic behaviour dominates in all deformation modes. Furthermore, as the temperature of ice is close to its melting point, material properties are strongly impacted by small temperature changes (e.g. those induced via plastic dissipation). All these phenomena are also interlinked with fracture propagation: At lower confining pressure cracks form in a purely brittle manner as a response to sudden stress changes, whereas viscous creep will prevent cracks from forming during slower loading. Instead, at higher pressures (e.g. near the base of ice sheets), cracks develop based on the energy dissipated by plastic work.

Here, a modelling framework able to capture these different regimes will be presented, using the phase-field fracture paradigm to allow for complex fracture patterns. Application will be shown to both small-scale tri-axial compression tests, demonstrating the accuracy of the model and its ability to replicate experimental observations, as well as large-scale cliff failure to showcase the impact of using this material model on predictions of ice-cliff failure.