Field indentation tests were conducted on sea ice at a harbor on Lake Notoro, Hokkaido, Japan, with a model structure width of 0.6 to 6.0m, an ice thickness up to 0.5m and an indentation velocity of 0.3 to 30mm/sec. In order to conduct large scale indentation tests in the field and to observe/measure precise ice force distributions in the interface between the model structure surface and the ice sheet, new instrumentation was developed by the authors: 6m-wide (maximum) model structure, two-dimensional pressure-sensing panels (Tactile Sensor) on the surface of the model structure, 10cm-wide segmented pressure sensing model structures, servo-controlled hydraulic jack with a capacity of 100ton-force, rigid indentation structure flame, and use of a fishery harbor deckto resist large ice breaking forces.
The Japan Ocean Industries Association (JOIA) started a five-year research program, "A Study of Ice Load Acting on Offshore Structures, " (Heads of the committee :Prof. Hiroshi Saeki of Hokkaido University, Prof. Ken-ichi Hirayama of Iwate University, and Masayuki Hyodo of Yamaguchi University) in 1993 as an enterprise assigned by the Ministry of International Trade and Industry (MITI) of Japan. In order to quantify ice pressure against offshore structures, field sea ice indentation studies have been conducted by many research groups: Hokkaido University (Saeki and Ozaki, 1980, Tanaka et al., 1987), PetroCanada (Msterson et al., 1993), Ishikawajima-Harima Heavy Industry (Yanagisawa et al., 1984), Mitsubishi Heavy Industry (Kawasaki et al., 1987), and Nihon Kokan(Nakajima et a1.,1981), as summarized in Table-1. Notoro Lake and Saroma Lagoon are connected to the Sea of Okhotsk. PetroCanada conducted its tests by installing a jack inside an iceberg. The other five studies pushed model structures into floating sea ice sheets. The present study used the largest ice-structure contact area except for the study by PetroCanada.
