Characteristics of Field-scale High Pressure Zones during Non-simultaneous Failure of Thin First-year Sea Ice

For temperate ice regions, the guidance provided by current design codes regarding ice load estimation for thin ice is unclear, particularly for local pressure estimation. During the non-simultaneous failure of ice under compression, spalling fracture localizes contact into high pressure zones (hpzs), through which the majority of loads are transmitted. Much of our present understanding of hpzs comes from inferences made from the analysis of pressure panel data collected during medium-scale field tests or full-scale measurements on ships or structures. During medium-scale field indentation tests conducted by the Japan Ocean Industries Association (JOIA) from 1996-2000, tactile pressure sensors were also deployed. The JOIA dataset provide detailed information about pressure distributions at a sufficiently high resolution so as to allow for the identification and tracking of individual hpzs throughout an interaction. Given their importance in the transmission of loads during an ice-structure interaction, understanding the birth, evolution and death of individual hpzs is seen as being an important direction both for guiding fundamental studies of ice mechanics and also for guiding the development of new ice load models. Recent analysis of these tactile sensor data has led to the development of an empirical hpz-based model which can be applied to model local and global pressures for thin ice conditions (Taylor and Richard, 2014). From this analysis, new insights into the nature of hpzs for thin first year sea ice during non-simultaneous failure have resulted. In the present paper, an overview is provided of analysis techniques used to extract information about individual hpzs from the tactile sensor dataset, as well as the characteristics of these hpzs. Aspects discussed include spatial and temporal characteristics of high pressure zones, as well as pressure and geometric attributes. While observations of the shape of spatial distributions and total contact area covered by hpzs are consistent with previous observations (line-type distributions with total contact area on the order of 10% of the nominal interaction area), these results indicate that individual hpzs are smaller and more densely distributed than indicated by previous analyses based solely on pressure panel data. The implications of this finding in terms of scale effects and ice load modeling are discussed.