The Strength of Ice Strength is define as the maximum stress that a material can take before it fails. This value depends on a variety of factors: Type of Failure Mode of Failure Other Influences bending/flexure brittle flaws in the ice crushing/compression dutile test technique shear      Bending/Flexure: This stress is the maximum stress that an ice sheet can withstand if subjected to a load that will cause it to bend or ride up on an object. The fibers int he outer layer are subjected to tension while the fibers in the inner layer are subjected to compression. Tension cracks eventually penetrate into the deeper layers and cause the ice to fail. Examples of this are certain shapes of bridge piers that cause the ice to ride up instead of colliding with it head on. Or ice ride-up events on the northern sea coast of Alaska where strom events push the fast ice onto the beach for up to 1/2 mile and break the sheets once the allowable stress is exeeded. Crushing/Compression: The compressive strength of ice is at its maximum right before failure by a load that acts normal to the ice surface. This ice property for freshwater ice depends on the crystal size, the strain rate, and the ice temperature as described by Michel. For sea ice the porosity plays an important role since air and brine entrappments cannot support any load. The tensile strength of ice is smaller then the compressive strength by a factor of 3 to 5.   An additional important point for engineering purposes is the bearing capacities of an ice flow which can be calculated from the buyoancy or approximated by taking the square of the ice thickness times a constant. For further explanations see the "Ice Engineering" Manual.