Theoretical Development of Forces on Cylindrical Ice Booms

Abstract

This paper presents generic equations and analyses of a cylindrical pontoon boom's capacity to retain ice. The presentation arises out of actual booms deployed on the St. Lawrence River downstream of Montreal but are valid for any cylindrical ice boom deployment. The boom's retention capacity not only relates to the pontoon's dimensions but also directly relates to the ice sheet's characteristics including thickness and strength. The role of friction and the geometry of the ice at the interface of the pontoon also determine the behavior of the structure and the associated line loads that develop. The analyses of environmental load show that the traditional theory of ice, acting as an aggregate, cannot explain observed values. Instead, this paper suggests that the ice upstream of a boom is a relatively coherent sheet. The internal strength of the ice sheet is compared to the environmental forces and the boom's capacity. These analyses improve understanding of the observations of the St. Lawrence booms made over the last 30 years.