Ice shell construction in Hokkaido of Japan during 1980–2012.

This paper summarizes research and development of an ice shell construction carried out in inland Hokkaido of Japan from 1980 to 2012.The ice shell is made of thin-walled curved ice plate and constructed according to the following method. (1) Building up a three-dimensional formwork by inflating a two-dimensional membrane bag covered with ropes anchored to the snow-ice foundation ring. (2) Covering the formwork with a thin saturated snow layer of less than 1 cm thickness by blowing milled snow with a rotary snow blower and spraying water with an adjustable nozzle, and letting it freeze naturally at temperatures below −10°C. (3) Repeating (2) until shell thickness reaches to the design thickness, then removing the bag and ropes for reuse. A number of ice shells were constructed as temporary winter structures while improving the construction technique through the repeated construction experiences. Based on the field experiments of 10–30 m ice domes (" X m ice dome" means the ice dome constructed by using X m diameter of circular membrane bag in the formwork before inflation) which measured the deflection and temperature under long term period after the completion and further observed the behavior of the collapse, it was recognized that understanding the creep behavior is extremely important for evaluating the structural safety of the ice shell. [ABSTRACT FROM AUTHOR]