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Title: Structural control of vertical variation of the strength of sea and salt ice
Authors: Weeks, W. F.
Assur, A.
Keywords: Sea ice
Ice crystals
Ice crystal growth
Ice structure
Ice properties
Ice mechanics
Ice strength
Mathematical analysis
Mathematical models
Publisher: Cold Regions Research and Engineering Laboratory (U.S.)
Engineer Research and Development Center (U.S.)
Series/Report no.: Research report (Cold Regions Research and Engineering Laboratory (U.S.)) ; 113.
Description: Research Report
Summary: The vertical variation in the strength of sea ice was studied by using data from NaCl ice which shows a structural similarity to sea ice and has straightforward phase relations. Nested horizontal thin sections were prepared at seven different levels below the surface of the test NaCl ice sheet and the plate spacing and the distance between centers of adjacent brine layers measured parallel to the c-crystallographic axis were determined. The measurements show that the plate spacing is a linear function of the sixth root of the distance below the upper ice surface (z). Available values of the same parameter for natural sea ice are in good agreement with this relation. Equations giving the dependence of the ring-tensile strength of the ice on z are developed. The specific equation depends upon which model is assumed for the variation of brine pocket dimensions with changes in the brine volume. A significant decrease in the volume of brine necessary to cause the ice to have zero strength with increasing distance below the upper ice surface was found as predicted. A new least squares estimate (0.112 mm) of the minimum width of a continuous brine layer before it splits to produce separate brine pockets was obtained which is 60% greater than previous values. It is demonstrated that in NaCl ice sheets the systematic increase in the plate width with depth produces significant changes in the ring-tensile strength of the ice. Field tests previously performed indicate that similar relations hold for sea ice.
Rights: Approved for public release; distribution is unlimited.
Appears in Collections:Research Report

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