Breakthrough Loads of Floating Ice Sheets

Abstract

For safe transportation of loads on floating ice sheets, it is important to determine the breakthrough load of an ice sheet. At present, the breakthrough load is estimated using empirical relations developed from the results of full-scale field experiments. In this paper, a theoretical formulation is presented 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. The breakthrough load is obtained 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 agreement between the theoretical estimates and the experimental breakthrough loads is good when energy dissipation due to radial deformation along circumferential cracks is ignored. The theoretical estimates of breakthrough loads are about twice the experimental loads when the radial crushing strength along circumferential cracks is assumed to be 1 MPa. Shear or punching failure due to concentrated load on a floating ice sheet is also briefly discussed.