Undrained monotonie triaxial loading behaviors of a type of iron ore fines

Concerning the static liquefaction properties of an industrial cargo, i.e., iron ore fines (IOF), undrained monotonie behaviors of a type of IOF are revealed through conducting triaxial compression tests. It is found that IOF exhibit some similar behaviors as those of common sandy soils, while some very unusual behaviors are also observed. All IOF specimens with compaction degree of 84%-95% and confining pressure of 50-200 kPa exhibit dilative behavior from the beginning of axial loading until the deviator stresses reach their peaks ([q.sub.pk]). Then the dilative behavior transforms to a contractive behavior, and the contractive behavior continues until reaching the residual stress without observation of phase transformation and quasi steady state. These behaviors are not usually observed for common sandy soils based on extensive previous works. More studies may be necessary as these unusual behaviors imply that flow failure, similar to the undrained monotonic behavior of very loose sand, may be triggered regardless of the density of IOF. In addition, this study also establishes the relationships of IOF between its initial conditions, peak stress conditions, and residual conditions by employing classical knowledges developed for sandy soils. Key words: iron ore fines, undrained triaxial test, static liquefaction, steady state, collapse surface. En ce qui concerne les proprietes de liquefaction statique d'une marchandise industrielle, les fins minerais de fer (<< IOF >>), les comportements monotones non draines d'un type d'IOF sont reveles par des essais de compression triaxiale. Il est constate que les IOF presentent des comportements similaires a ceux des sols sableux communs, alors que certains comportements tres inhabituels sont egalement observes. Tous les specimens IOF avec un degre de compaction de 84-95 % et une pression de confinement de 50-200 kPa presentent un comportement dilatatif depuis le debut du chargement axial jusqu'a ce que les contraintes de deviateur atteignent leurs maximums ([q.sub.pk]). Le comportement dilatatif se transforme ensuite en comportement contractif, et le comportement de contraction continue jusqu'a atteindre la contrainte residuelle sans observation de transformation de phase et d'etat quasi d'equilibre. Ces comportements ne sont generalement pas observes pour les sols sablonneux communs sur la base d'importants travaux anterieurs. D'autres recherches peuvent etre necessaires, car ces comportements inhabituels impliquent que la defaillance de l'ecoulement, similaire au comportement monotone non draine du sable tres lache, peut etre declenchee independamment de la densite de l'IOF. En outre, cette recherche etablit egalement les relations de l'IOF entre ses conditions initiales, les conditions de contrainte maximale et les conditions residuelles en utilisant les connaissances classiques developpees pour les sols sableux. Mots-cles : fins minerais de fer, essai triaxial non draine, liquefaction statique, etat d'equilibre, surface d'effondrement.
Introduction Iron ore fines (IOF) are transported as a type of bulk cargo for the iron-making industry. Together with some other cargoes, such as nickel ore and sinter feed bauxite, [...]