the floating bodies. Thus, the influence of ice on the floating bodies differs according to the angle of tilt of the side walls of the floating bodies and their color.
From this information, we used the following four kinds of floating bodies in the study.
・Floating body A: white rectangular parallelepiped, in stalled 2 m from the quay wall.
・Floating body B: white floating body with an angle of tilt, installed 10 m from the quay wall.
・Floating body C: white rectangular parallelepiped, in stalled 10 m from the quay wall.
・Floating body D: black rectangular parallelepiped, in stalled 10 m from the quay wall.
The horizontal and vertical displacement of these floating bodies in the frozen port and their freezing condition were examined to find the suitable conditions to install a floating body in frozen sea areas, including its distance from the quay wall, the angle of its draft and its color. Figure 1 shows the plane location of each floating body and its mooring method.
3. Experimental results
3. 1 Results of the observations of the freezing condition
Table 1 shows the summary of freezing conditions. The No. 4 basin for small craft was almost completely frozen on February 5, 1996, but the later warm weather increased unfrozen areas and the pancake ice from February 13 to 19 in 1996. Then the cold weather again made the basin completely frozen from February 22,1996.
All the floating bodies were adfrozen to ice floes on February 8, 1996, but on February 13, 1996, the floating body A was completely adfrozen to the floes, the floating bodies B and C were partially adfrozen to the floes, and the floating body D was not adfrozen, being affected by the warm weather. After February 16,1996, the floating bodies A, B and C were completely adfrozen, and only the floating body D was partially adfrozen. After March 7, 1996, the ice started to thaw due to the warm weather, and pancake ice was in contact with the floating bodies. The floating bodies partially adfrozen to the ice floes, had their unfrozen sides on the east and the south of the body receiving sunshine.
3. 2 Results of the observations of the floating bodies
(1)Vertical displacement of the floating bodies
Figure 2 shows the vertical displacement in the direction of X changing with time for the whole experimental period. The direction of X is defined as the direction of the shorter side of the floating body (east-west), and the direction of Y is the direction of its longer side (north-south).
The vertical displacement in the direction of X was the difference between two average values, each of which was derived from the values at two corners on the same vertical line at right angles to the axis of X. When the displacement was positive, the east side of the floating body was high and the west side was low. The average value shown in the figure was the average of the values obtained from thirty-three observations. The largest displacement of the average displacement in the direction of X was 3.7 cm for floating body B, and the smallest was 2.0 cm for floating body D. But the differences in the results between the four cases were small.
Figure 3 shows the vertical displacement in the direction of Y changing with time. When the displacement was positive, the south side of the floating body was high and the north side was low. The largest displacement of the average displacement in the direction of Y was 10.2 cm for floating body A, and the smallest was 0.9 cm for floating body C.
Figure 1 Plane location of each floating body and its mooring method
