BREAKTHROUGH LOADS OF FLOATING ICE SHEETS

In cold regions, ice covers on rivers and lakes are often used as roads and airfields. Determination of the breakthrough load of an ice sheet is important for the safe transportation of loads across those ice covers. Currently, the breakthrough load is estimated using empirical relations developed from the results of full-scale field tests. This paper presents a theoretical formulation to derive an expression for the breakthrough load using plastic limit analysis. The velocity field in the vicinity of a distributed load is assumed, and the stresses induced in the columnar ice are assumed to be the biaxial strength, which depends on the strain rate derived from assumed velocity field. By equating the rate of work done by the load to the rate of energy dissipation during compression of ice caused by radial and circumferential wedging of ice during deformation, the breakthrough load is determined. Theoretical estimates and the experimental breakthrough loads are in good agreement when energy dissipation due to radial deformation along circumferential cracks is ignored. When the radial crushing strength along circumferential cracks is assumed to be 1 MPa, the theoretical estimates of breakthrough loads are about twice the experimental loads. Shear or punching failure due to concentrated load on a floating ice sheet is addressed briefly.

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