Revisiting the Sanderson pressure–area curve: Defining parameters that influence ice pressure

There is a strong perception in the ice mechanics community that during ice–structure interaction, the ice pressure always decreases as the area of contact increases. This understanding is often based on the pressure–area plot published by Sanderson (1988), which combines a large number of data sources and ice interaction situations on a single plot and shows a definite decrease in pressure with increasing area. This paper examines the data sources in the Sanderson plot as well as some more recent data, and discusses the definitions of global, local, spatial and process pressure–area. It is found that the pressure over a defined local geometric area or over the full global ice contact area can either show no dependence on area or a decrease with increasing area, depending on the interaction scenario. Factors other than area are examined to determine their influence on pressure including the loading rate, aspect ratio, ice failure mode, and ice properties. It is shown that in many cases, these factors are more important than the area in predicting ice pressure. The theory of Palmer et al. (2009) provides a reasonable explanation for some of the observed trends in pressure–area behavior. Examples from field data are provided to illustrate the application of pressure–area relationships for offshore structures in icy waters.