EXPERIMENTS ON FREEZE-BONDING BETWEEN ICE BLOCKS IN FLOATING ICE RUBBLE

ABSTRACT. Series of experiments were conducted with the aim of determining the influences following factors on freeze-bonding between contacting ice blocks in floating ice rubble: pressure normal to the contact plane, period and area of contact, and salinity of the water in which freeze-bonding occurred. Freeze-bonding between ice blocks air was also investigated. The experiments were conducted with water air temperatures of about O·C and pressures, between ice blocks, up to 4 kPa. This range of normal pressures may occur hydrostatically between ice blocks in layers of floating ice rubble up to about 10 m thick, or in 2-3 m thick layers which are in a passive Rankine state of pressure. The experiments show that stronger freeze-bonds develop between ice blocks in distilled water, water, and water from the Iowa than develop between ice blocks contacting in air at O· C. However, stronger freeze-bonds developed in air at O· C than developed ice blocks in O·saline (NaCI) solutions salinities in excess of 12.5% by weight. The strength of freeze-bonding increased linearly with contact period for ice blocks in distilled, tap, and river waters, but did not increase with contact period for ice blocks contacting in saline solutions or in air. The results of the experiments are useful contributions to explanations of the shear-strength behavior of a layer of floating ice rubble. For example, thicker layers of ice rubble show greater cohesive behavior, normal pressures and thus freeze­bond strengths increase layer thickness. RESUME. Experimentations sur l'agregation par regel entre dans la blocaille de glace [lollan/e. Des series d'experiences ont ete menees dans le but de determiner I'influence des suivants sur I'agregation par regel entre les blocs en contact dans la blocaille de la glace f1ottante: pression normale sur le plan de contact, dUflle et surface de contact et salinite de I'eau dans laquelle se produit collage par rege!. L'agregation par regel entre les blocs dans I'air a aussie ete examinee. Les experiences ont eu lieu avec des temperatures de I'eau et I'air voisines de O·C et des pressions normales entre blocs, superieures a 4 kPa. Ce domaine de pressions normales pe ut exister entre les disposes en couches dans la blocaille de glace sur des hauteurs de 10 m d'epaisseur ou sur des de 2 a m qui se trouvent en etat de pression de Rankine. Ces experiences montrent collage par regel se developpe plus intensement entre blocs places dans de I'eau distillee, de I'eau du robinet, et de I'eau INTRODUCTION Laboratory studies (e.g. by Uzuner (1974), Tatinclaux and Cheng (1978), and more recently by Hellman (1984)) show the shear strength and deformation behavior of a relatively (block size being small compared to layer thickness) layer of floating ice may be described using a Mohr--coulomb relationship involving a for apparent cohesion. Additionally, these studies show that la Iowa River, qu'il ne se developpe entre blocs en contact dans I'air a O· C. Cependant. une agnlgation se develo