Evaluation and validation of phenomena culminating in cargoes of iron ore fines shifting during marine transportation
Creators: name: Munro, Michael
Publisher: name: RMIT University
Year: 2024
Subjects: classificationCode: 400502
subject: Civil geotechnical engineering
classificationCode: 400506
subject: Earthquake engineering
classificationCode: 400512
subject: Transport engineering

description: In 2011, legislation that governs the safe transportation of solid bulk cargoes, known as the International Maritime Solid Bulk Cargoes Code (IMSBC Code), became mandatory under the SOLAS Convention. Included in this legislation are test methods used to determine a safe moisture content that certain solid bulk cargoes can contain, during transportation, if they have been deemed potentially liquefiable.<br><br>Liquefaction of a cargo solid bulk cargo during transportation can result in the cargo shifting and altering the buoyancy of the transporting vessel. Depending on the mass of cargo that shifts, it may result in the vessel listing or capsizing. Between 1988 and 2016, 23 incidents were reported where liquefaction of a solid bulk cargo was suspected. These incidents resulted in 138 casualties and the loss of 17 vessels.<br><br>Due to the mandatory implementation of the IMSBC Code and the occurrences of incidents where liquefaction of iron ore fines was suspected during transportation, industries and research institutions were required to consider the adequacy of the current methods and/or amend or introduce a suitable method for testing the cargo. The outcome of this work was the introduction of a new test method specifically designed for the testing of iron ore fines. The test, known as the Modified Proctor/Fagerberg Test (MPFT), was first introduced in 2013 and its use was made mandatory from January 2017.<br><br>As previously stated, the MPFT was designed to determine a moisture content under which a cargo of iron ore fines was considered unable to liquefy and therefore safe for marine transportation. During preliminary testing and investigations, questions arose surrounding the; validity of the test, methodology behind its creation, and whether liquefaction was indeed the correct phenomenon that was occurring, which resulted in cargoes of iron ore fines shifting during marine transportation.<br><br>The objective of this research was to investigate, at a fundamental level, the possible phenomena that may be responsible for cargoes of iron ore fines shifting, in the holds of bulk carriers, during marine transportation. In this study, both practical and theoretical analysis were employed to visualize as well as objectively quantify, both the cause and type of phenomena that may be possible. To fully understand and reproduce the possible phenomena, standard test methods were used, in combination with unique and novel methods, designed and developed during this study. Summarizing the information that was gathered and produced during this research resulted in conclusions regarding the validity of implementing the MPFT that is used to protect against liquefaction during marine transportation.<br><br>It was concluded that there are multiple phenomena that can result in a cargo of iron ore fines shifting in the hold of a bulk carrier during marine transportation, with a sensitive dependence on initial conditions. Although liquefaction was the primary phenomenon suspected, this study concludes that liquefaction of the cargo, as a whole, is unlikely. There are two likely phenomena that both masquerade as full cargo liquefaction. The first phenomenon is identified as liquefaction, although not liquefaction of the cargo as a whole as speculated. It was shown that moisture migration can occur towards the surface of the cargo transporting fine particles creating areas of material with a greater potential to liquefy.<br><br>This research also identified incremental collapse as another possible phenomenon that may occur resulting in a cargo of iron ore fines shifting. Unlike partial liquefaction as described above, this phenomenon is most likely to occur to an untrimmed cargo. Incremental collapse may ultimately result in a shear plane developing resulting in the cargo abruptly shearing, such as occurs during a slope failure. These phenomena can be linked to the behaviour of the cargoes and vessels described during the suspected liquefaction incidents investigated during this research.<br><br>It was also concluded that the principal theory used to design and develop the MPFT is not one that is widely accepted in geotechnical engineering and soil mechanics to determine the liquefaction potential or cyclic behaviour of soils. It was identified that the moisture-holding ability of iron ore fines is a major influence in the likelihood of partial liquefaction occurring. Preventing moisture migration will likely prevent the possibility of partial liquefaction.<br><br>During this research, the Transportable Moisture Limit (TML), the parameter determined using the MPFT, was consistently equal to or higher than the moisture contents measured where migration of moisture and fine particles were recorded. This indicated that if a cargo of iron ore fines is loaded onto a bulk carrier, at the TML, moisture migration may occur resulting in areas within the cargo with a high potential to liquefy.<br><br>The results from this study are based on the results from the testing of limited specimens of iron ore fines. The comments and conclusions made within this thesis relate to the assumption that iron ore fines, as a cargo, have a constantly changing and significantly wide range of physical properties, from location to location, which has also been shown to be the case. The majority of the results from this research are presented in eight international journals, which are included in chapters within this thesis. Additional results that have not yet been published are currently being prepared or reviewed for publication.<br><br>In this day and age, the loss of human life is unacceptable under any circumstance and must be avoided at all costs. Incidents occurring during the transportation of iron ore fines and other similar solid bulk cargoes can and must be avoided to protect the safety of maritime personnel, the environment, and prevent the needless loss of resources and assets. Hopefully, this research will not only improve safety at sea but may be built upon in the future and used for the analysis of other solid bulk cargoes where the occurrence of such phenomenon is still prevalent, such as nickel ore and/or bauxite.