Deflection of a floating sea ice sheet induced by a moving load

A large number of time-deflection curves was obtained from a field experiment carried out on the sea ice sheet at Lake Saroma, Hokkaido, Japan, using a Skidoo snowmobile as a moving load with the test speed changed from 0 to 14.2 m/s. The thickness of the ice sheet was 0.17–0.18 m, the ice temperature was ?2.5 to ?4°C at the surface, and the water depth was 6.8 m beneath the ice sheet. The experimental results indicated the existence of a critical speed u_c and its value was estimated to be 5.8 m/s. At speed above it two ice waves were generated, one ahead of and the other behind the vehicle. A variation of wavelength with vehicle speed was expressed by a modified dispersion relation for the flexural ice wave in a floating ice sheet. The ice deflection pattern was classified into five stages. At u_c the depression around the vehicle was maximal in depth and minimal in width. The center of the depression began to lag behind the vehicle even at fairly low speeds below u_c.