Abstract :
Existing failure criteria for the bearing capacity of floating ice sheets predict the load for
the occurrence of the first radial crack or a circumferential crack, when the maximum stress obtained
from an elastic analysis in the ice equals the tensile strength. From full-scale and small-scale tests.
the ultimate load to cause complete penetration of a floating ice sheet is much higher than that to
cause the first radial crack. This can be attributed to wedging action during deformation of a radially
cracked ice sheet. We present three approaches taken to determine the ice penetration force : (1)
plastic limit analysis, (2) small-scale experiments, and (3) full-scale measurements in the field.
Small-scale experiments were conducted with freshwater ice in the basin at the laboratory to
understand the wedging action during the vertical loading of floating ice sheets. Results of the
following series of experiments are presented : (a) beams with fixed ends, (b) paired cantilever beams
arranged free-end to free-end and loaded together, (c) beams with an apparatus inserted between
the free ends of paired cantilever beams to measure the in-plane force during vertical loading, and
(d) vertical downward loading of floating ice sheets with fixed and free boundaries. Analysis of the
data from the beam tests reveals that the wedging action results in the development of wedging
pressure in the top or bottom third of the ice thickness, and this results in a resisting moment that
counters the deformation of a cracked ice sheet. An ice sheet attached to the basin wall inhibits the
propagation of radial cracks because of the wedging action, whereas an ice sheet free at the edges
from the surrounding ice sheet fails by the propagation of radial cracks all the way to the ice sheet’s
free boundary. The difference between the two breakthrough loads of the free and the fixed ice
sheets can be attributed to wedging action. The results of the beam tests are used in the results of
plastic limit analysis to predict the breakthrough loads of floating ice sheets, which are in agreement
with loads measured during full-scale and small-scale experiments. 0 1998 Elsevier Science Ltd.
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