Geotechnical properties of a type of iron ore fines

Accidents and life loss caused serious concern on the liquefaction problem of some solid bulk cargoes such as iron ore fines during transportation at sea. To understand the liquefaction property of a type of iron ore fines, a series of tests, e.g. SEM observation, monotonic loading triaxial test, cyclic loading triaxial test etc. were conducted. Test results show that this unusual material possesses some special properties, for instance, much higher specific gravity G_s (average G_s=4.444) as compared to common materials in geotechnical engineering. SEM observation unveils that the tested iron ore fines has a multi-layer, micro-porous structure which may affect its water retention ability under unsaturated states. The result from the undrained monotonic loading test indicates an angle of internal friction of 45.6° according to the Mohr-Coulomb failure criterion. Interestingly, the peak strength and the residual strength were achieved at values of axial strain of approximately 2.5% and 13%, respectively, regardless of confining pressure among three undrained monotonic loading tests. The undrained response of tested iron ore fines to cyclic loading shows similar characteristics as those of common sands and the liquefaction resistance of this material defined based on the relationship between cyclic stress ratio (CSR) and number of cycle is not significantly affected by change of confining pressure.