Sea ice behaviour in creep/fracture regime: An experimental and theoretical study.

Title: Sea ice behaviour in creep/fracture regime: An experimental and theoretical study.
Authors: Zhan, Caizhao.
Date: 1993
Abstract: An experimental and theoretical study of sea ice behaviour is the subject of the research described in this thesis. In the laboratory, constant load experiments were performed on columnar-grained natural first year sea ice sampled in 1991 from Resolute Passage N.W.T. off Barrow strait/Lancaster Sound. Axial and lateral strains were measured, and acoustic emission data were recorded. Creep tests were carried out at ${-10}\sp\circ C,$ ${-20}\sp\circ C,$ and ${-30}\sp\circ C.$ Field tests were conducted at Resolute Bay in 1992. Two types of investigations were carried out in the field: (1) microstructural study of first year columnar grained sea ice as a function of depth, (2) borehole indentation tests on first year columnar grained sea ice with various boundary conditions. The microstructure of columnar-grained sea ice is rather complex because of the presence of the second (brine) and third (solid salt crystals) phases. A three dimensional constitutive model for the ductile behaviour of fresh water columnar grained ice was developed. The constitutive model is capable of describing the inherent anisotropy caused by the fabric, the grain size effect, the crack evolution, the effect of crack on viscous strain, and the deformation of the cracks. The model is used to predict the dependence of strength on the angle between the mean c-axis (axis of symmetry) and loading direction for oriented columnar-grained ice (classified as S3) and the anisotropic response of transversely isotropic columnar-grained (S2) ice. The model for fresh water ice was subsequently extended to sea ice to account for the effect of brine pockets on its mechanical behaviour. This constitutive model for sea ice is based on an assumed geometric pattern for the distribution of brine pockets in a single grain of sea ice. An initial defect tensor for a single grain of sea ice is defined based on the geometric pattern neglecting, for simplicity, the subgrain structures. Subsequently, the initial defect tensor for polycrystalline ice is obtained from the initial defect tensor for a single grain of sea ice and the probability distribution of c-axis. The effect of the initial defect on the response of sea ice to different types of loading is expressed by introducing two additional tensors. The constitutive equations for columnar grained sea ice are the same as those for fresh water columnar grained ice, except that an effective stress tensor is used in the sea ice constitutive equations to replace the stress tensor in the model for fresh water ice. In the last part, Sinha's creep model was generalized into 3-D and implemented into a finite element program. (Abstract shortened by UMI.)
CollectionTh├Ęses, 1910 - 2010 // Theses, 1910 - 2010
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