Effect of saturation on liquefaction resistance of iron ore fines and two sandy soils

Over the past several years, the International Maritime Organization (IMO) has become increasingly concerned about the liquefaction of unsaturated solid bulk cargo (e.g. iron ore fines) during maritime transportation. This concern has arisen due to several accidents including the capsizing of vessels. In addition, although the resistance against liquefaction of ordinary unsaturated soils is higher than for saturated soils, possible key parameters governing the liquefaction resistance of unsaturated soils (R_L,unsat) have not yet been clearly identified. Therefore, in this study, undrained cyclic loading tests of saturated and unsaturated iron ore fines and two sandy soils were conducted using a triaxial apparatus to reveal the liquefaction behavior of iron ore fines and to find the key parameters governing R_L,unsat. Through comparisons, it was found that the liquefaction behavior of iron ore fines is similar to that of sandy soils. The degree of saturation and potential volumetric strain, which have been proposed as the governing parameters of R_L,unsat, were examined based on experimental data obtained in this study and by other researchers. It was shown that neither of the two parameters correlate with the liquefaction resistance ratio (LRR), a ratio of R_L,unsat to the liquefaction resistance of the saturated soils (R_L,sat) with a unique relationship, especially when considering soils with considerable fines content. Following the concept of potential volumetric strain, which considers the compressibility of pore air in the unsaturated soils, volumetric expansion due to the reduction in confining pressure during cyclic loading is further considered, and a new index, the volumetric strain ratio (R_v) is proposed in this study. According to the experimental data obtained in this study, R_v exhibits a much better correlation with LRR than the two former parameters.