Experimental studies on ice shells in Asahikawa

Ice shell construction in Hokkaido of Japan during 1980–2012

“…The ice shells can be constructed by the following method which is technically simple, mechanically reasonable and economical. 6,7 (1) Building up a three-dimensional formwork by inflating a two-dimensional membrane bag covered with reticular ropes anchored to the snow-ice foundation. (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.…”

“…25 Based on the recognition that understanding the creep behavior is extremely important for evaluating the structural safety of the ice shell, the deflection, and temperature of the 10-30 m ice domes were measured under long term period after the construction experiment and further the structural behavior of the collapse was carefully observed. 7,[26][27][28] According to the experimental results, the deflection-time curve is approximated by connecting two lines as the elastic deflection is quite small compared to the creep deflection; the first line showing the stationary stage where the deflection has a linear function of time, and the second showing the accelerating stage where the deflection rate increases with time up to the collapse, as shown in Figure 14. The possible causes of the transition from the steady stage to the acceleration stage are: 1.…”

“…The outside air temperature fluctuated widely in the range of 5°C to −25°C, while the ice temperature fluctuates stably from 0 to −7°C, according to the field experiments of the 10–30 m ice domes. 7,25,27,28 As the ice in this temperature range creeps easily, the structural safety against creep is very important subject to be understood. Figure 13 shows relationship between stress and strain-rate for uniaxial creep test on a polycrystalline ice at −7°C.…”

“…And then, the author started the research and development of the ice shell construction towards the realization of a large ice shell spanning 20–30 m in inland Hokkaido with sufficient snow and low temperature. 7…”