Figure 7: Relationship between the duration of the impact force and the momentum
Figure 8: The relationship between the maximum impact ice force and the impulse
Figure 9: Relationship between the maximum impact ice force and the momentum
Figure 10: Relationship between the dimensionless maximum impact ice force and the momentum
Also, the collision was found to have taken place at a high speed. Figure 7 shows the relationship between the duration of the impact force (td) and the momentum of the ice plate (M). When the momentum was great. the duration of the impact force was almost constant at between 5 msec and 10 msec, which is similar to Figure 3.
Figure 8 shows the relationship between the maximum impact force (Fmax) and the impulse (I). The maximum impact force tended to increase with an increase in the impulse. When observing the relationship between the maximum impact force (Fmax) and the momentum (M), the maximum impact force also increases with an increase in the momentum (Figure 9). Here, we found the dimensionless maximum impact force by dividing the Fmax by the product of the contact area of the ice plate (bh (b: width of the ice plate, h: thickness of the ice plate)) and the average value of the unconfined compressive strength of ice (σ c). Figure 10 shows the relationship between the dimensionless maximum impact force and the momentum (M); the dimensionless maximum impact force increased with an increase in the momentum, but the values generally did not exceed 1, when the ice plates with half an area in contact are excluded. Some values are above 1, which is reasonable when the dispersion of the unconfined compressive strength is considered. That is, the unconfined compressive strength was from 19.6 kgf/cm to 29.2 kgf/cm2 (Figure 2), and using mean values gives the vertical axis a value of I in Figure 10. Consequently, the dimensionless maximum impact force can exist between 0.8 and 1.2 when considering the range of the confined compressive strength. The broken lines in Figure 10 show this range. The ice plates with half the area in contact have larger values; a detailed explanation for this has not been given.
A field test in a river by Neill5) showed that when ice floes with average ice thickness of 38 cm, 46
