THE BEHAVIOR OF LAKE ICE UNDER RAPIDLY INCREASINGSTATIONARY LOADS

I.A. Radial cracks on bottom of ice

A brief account of ´Deflections of an infinite plate', 1950 by Wyman is given here. Wymans expression of the maximum tensile stress, when the loading is uniform. over a circular area, has been expressed in the form of (I:4). The 'characteristic length', L, is plotted against the ice thickness, h, in fig I:2 and the 'load index', c (= P/h2 ) is plotted against the 'relative load radius', 'T'(= r/L) in fig I:3. When T = 0,6 kei' T/T: can be approximated by½(0,6159 - lnT). By inserting this expression the formula (I:4) is identical to Westergaard's formula given in 'Stresses in concrete pavements computed by theoretical analysis', Publ.Roads Vol. 7 nr 3, 1926.

I.B. Ring-cracks and break-through

This chapter gives a summary of 'The narrow free infinite wedge on an elastic foundation', 1961 by Nevel. Nevels expression of the maximum tensile stress is here given in the form of (I:8). Fig I:7 shows c_R-values for various 'T-values = 0 ,6. Nevel writes: ".... the wedge of the crack ed ice sheet will be able to carry more load than predictedby the free wedge model."

The break-through-load is here computed from formula(I:10) by B Persson. Fig I:7 shows cB-values for various "T-values. Table I:l gives numerical examples.