As shown in the above, vertical ice forces in flooding conditions are smaller than ordinary ice forces. Accordingly, to reduce the vertical ice forces acting on pile structures, the following methods can be used,
1) To intentionally cause flooding conditions
2) To use materials whose adfreeze bond strength is small for the surfaces of pile structures
3) To prevent adfreezing between a pile structure and an ice floe
The details of each method are as follows,
(1) Intentionally causing flooding conditions
1) Insert a heat resource into a structure and heat vertically from high water level to the lowest part of the ice thickness at low water level, making at least one hole on the adfreezing surface between the structure and the ice floe.
2) Set an air valve on the sea bottom very close to the structure and make at least one hole on the adfreezing surface between the structure and the ice floe.
(2) Using materials whose adfreeze bond strength is small for the surfaces of pile structures
1) If the pile structure is steel, apply paint with a small adfreeze bond strength, such as INERTA 160 and ZEBRON.
2) If the pile structure is concrete, minimize the surface roughness by surface treatment.
(3) Preventing adfreezing between a pile structure and an ice floe
1) Prevent adfreezing between the structure and the ice floe by covering the structure with a heat resource.
2) Prevent adfreezing between the structure and the ice floe by setting an air valve around the structure.
6. Conclusions
The main results from this study are,
1) From the theoretical solution of deflection in flooding conditions, the calculation method of vertical ice forces was determined when an ice floe adfreezes to a structure and when an ice floe does not.
2) Comparing the vertical ice forces when flooding exists and when flooding does not exist, Pf/Pn is always 1 or under. The relationship between Pf/Pn and ice thickness is proportional to each other, and the relationship between the change in water level and the pile radius is inversely proportional to each other.
3) From these results, in order to design structures, it is safer to estimate the external force when flooding does not occur. However, it is possible to economize by reducing the vertical ice forces with the following methods,
･intentionally causing flooding conditions,
･using materials whose adfreeze bond strength is small for the surface of a pile structure,
･preventing adfreezing between pile structure and ice floe.
References
1) A. D. Kerr: "Ice Forces on Structures due to a Change of the Water Level", IAHR, Proceeding of Third
International Symposium on Ice Problems, Hanover 1975
2) F. T. Christensen: "Interaction Between Floating Ice Sheets and Vertical Structures due to Water Level
Fluctuations", Technical University of Denmark, Series Paper No. 38, Lyngby 1986
3) N. Nakazawa, M. Yamada, K. Hamanaka and H. Changes in Water Level", Proceeding of Cold Region
Technology Conference, 1985
4) T. Terashima, N. Nakazawa, S. Kioka, Y. Watanabe and H. Saeki: "Vertical Ice Forces on Pile Structures and Its Design Method", Proceeding of Civil Engineering in the Ocean Vol. 11, 1995
