Dynamic strain response of lake and sea ice to moving loads

Abstract The results from two experiments to measure the strains due to a vehicle moving over ice are discussed in the context of theoretical work derived from existing solutions in the literature. The experiments took place on two very different types of ice; the lake ice of Femund in Norway, and sea ice near Scott Base in the Antarctic. In both cases, strain was measured directly by means of strainmeters developed specifically for use on ice. The existence of a critical velocity at which the strain is resonant is discussed, and using values derived from the data, a dispersion equation for free waves is solved in the super-critical domain to provide wavelength estimates. At subcritical speeds a moving static load calculation provides the equivalent theory. The experimental results for lake ice and sea ice are similar, although some differences do exist. The magnification factor of the critical strain over static strain is, for example, larger for lake ice (2.25) than for sea ice (1.45). A critical velocity of 15.2 ms−1 was observed for lake ice, for sea ice the value was 19.6 ms−1; both are associated with the minimum phase velocity of free wave propagation.