292 research outputs found

    Determination of the transportable moisture limit of iron ore fines for the prevention of liquefaction in bulk carriers

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    In 2013, over 500 million metric tons of Iron Ore Fines (IOF) were transported around the world using bulk carriers. Under certain conditions IOF, while being transported, can possibly undergo liquefaction. Since 2006, there has been eight reported bulk carrier casualties possibly caused by the liquefaction of IOF. The objective of this study is to evaluate, compare and verify the limitations and relevance of the Proctor/Fagerberg, Flow Table and Penetration test methods that are used to determine the Transportable Moisture Limit (TML) of IOF. The TML is the maximum gross water content that bulk cargoes, including IOF, may contain while being transported at sea without being at risk of liquefying. A thorough literature review, along with laboratory research, was carried out to compare the TML results from the three leading test methods to determine whether they produce reliable results when testing IOF. The study concludes that the three test methods, as stated in the 2012 International Maritime Solid Bulk Cargoes Code, are unverified and therefore not appropriate for testing IOF. This is due to the variation in the results produced by the three test methods and also due to the difference in the physical properties of IOF when compared with the materials that were originally intended for testing. It is noted that the TML alone may not control the potential liquefaction of IOF and further studies, regarding the physical properties and system variables, which cause the material to liquefy, are required to determine the liquefaction potential of IOF

    Liquefaction incidents of mineral cargoes on board bulk carriers

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    Liquefaction is a frequently occurring problem taking place when transporting wet granular solid bulk cargoes on-board bulk carriers. Liquefaction of a solid bulk cargo can occur when excessive dynamic loading, induced by rough seas and vessel vibrations, is transmitted to the cargo. From 1988 to 2015, there has been 24 suspected liquefaction incidents reported, which resulted in 164 casualties and the loss of 18 vessels. The objective of this study is to investigate the collective causes of liquefaction of solid bulk cargoes on-board bulk carriers in order to make recommendations to prevent future incidents from occurring. This was achieved by analysing the seven available investigative reports relating to the incidents, focusing on the key findings and exploring the effect of excess moisture within the cargo. This study has placed significant emphasis on the importance of preventing ingress of water into the cargo during transportation, loading and storage. Recommendations have been given, based on the key findings from the reports, to reduce the potential for liquefaction incidents to occur

    A 3 dimensional simulation of the repeated load triaxial test

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    A typical flexible pavement structure consists of the surface, base, sub-base and subgrade soil. The loading traffic is transferred from the top layer with higher stiffness to the layer below with less stiffness. Under normal traffic loading, the behaviour of flexible pavement is very complex and can be predicted by using the repeated load triaxial test equipment in the laboratory. However, the nature of the repeated load triaxial testing procedure is considered time-consuming, complicated and expensive, and it is a challenge to carry out as a routine test in the laboratory. Therefore, the current paper proposes a numerical approach to simulate the repeated load triaxial test by employing the discrete element method. A sample with particle size ranging from 2.36mm to 19.0mm was constructed. Material properties, which included normal stiffness, shear stiffness, coefficient of friction, maximum dry density and particle density, were used as the input for the simulation. The sample was then subjected to a combination of deviator and confining stress and it was found that the discrete element method is able to simulate the repeated load triaxial test in the laboratory

    Moisture content limits of Iron Ore Fines to prevent liquefaction during transport: review and experimental study

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    Iron ore is without doubt one of the most essential commodities of our time. With this, the growing demand from countries, such as China and Japan for iron ore produced in countries, such as Australia and Brazil, is only increasing. Iron Ore Fines (IOF) are a product of iron ore, commonly having a particle size less than 6.3mm, which is transported around the world in bulk carriers. Since the holds of bulk carriers are not designed to carry liquid, if liquefaction of IOF or other minerals occurs, it can cause the vessel carrying the cargo to list or even capsize. Since 2006, there have been at least eight reported bulk carrier incidents possibly caused by the iron ore cargo shifting. Currently, the only available parameter used to prevent this from occurring is the Transportable Moisture Limit (TML). The TML is the maximum gross water content that certain mineral cargoes may contain, while being loaded in bulk carriers, without being at risk of liquefying during transportation. The first half of this paper presents a review of the three test methods stated in the 2013 International Maritime Solid Bulk Cargoes Code (IMSBC Code) and the recently introduced Modified Proctor/Fagerberg test (MPFT). Along with the aforementioned tests, also reviewed are recent developments and advancements made in the field. The second half of this paper presents a comparison of the results of our experimental study with two of the three 2013 IMSBC Code tests along with the MPFT. This study shows that the three test methods which are currently used to determine the TML of minerals are not appropriate for testing of IOF and that the Modified Proctor/Fagerberg test produces a value higher than all the other test methods when used to determine the TML of IOF

    Development of a new dynamic lightweight penetrometer for the determination of mechanical properties of fine-grained soils

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    Dynamic cone penetrometer is mainly used as an in situ device and laboratory application, in a mould, has rarely been reported due to the confining effect. In this study, a dynamic lightweight cone penetrometer that can be used in a CBR (California bearing ratio) mould in the laboratory as well as in the field, with similar results, was developed. The results show that the influence of the mould confinement can be eliminated when the hammer mass is 2.25 kg. A strong correlation was found between CBR values and the new dynamic lightweight penetrometer index, for six fine-grained soil samples, with different moisture contents, used in this study

    Moisture content limit of iron ore fines for the prevention on liquefication in bulk carriers

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    In 2013, over 500 million tonnes of Iron Ore Fines (IOF) were transported around the world using bulk carriers, more than any other unrefined mineral. Since the holds of bulk carriers have not been designed to carry liquid, if liquefaction of IOF or other minerals occur it can cause the vessel carrying the cargo to list or even capsize. Since 2006, there have been at least eight reported bulk carrier incidents possibly caused by the iron ore cargo shifting. Currently, the only available parameter used to prevent this from occurring is the Transportable Moisture Limit (TML). The TML is the maximum gross water content that certain mineral cargoes may contain, while being loaded in bulk carriers, without being at risk of liquefying during transportation. The objective of this study is to compare the three test methods stated in the 2013 International Maritime Solid Bulk Cargoes Code (IMSBC Code), which are used to determine the TML of IOF. They are the Proctor/Fagerberg, Flow Table and Penetration test methods. The study also covers recent developments and advancements made in the field, which includes the Modified Proctor/Fagerberg test along with goethite content provisions, which are included in the 2013 draft individual schedule for IOF, and to be amended in the 2015 IMSBC Code. This study shows that the three test methods, stated in the 2013 IMSBC Code, which are used to determine the TML of minerals, are not appropriate for testing of IOF and that recent developments, such as the Modified Proctor/Fagerberg test along with goethite content provisions, permits IOF to be transported at higher moisture contents than if one of the previous three test methods were used

    A review of the newly developed method used to prevent liquefaction of iron ore fines on board bulk carriers.

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    Liquefaction is a commonly occurring problem affecting solid bulk cargoes on board bulk carriers. If liquefaction of a solid bulk cargo occurs on board a bulk carrier it can result in the vessel listing or capsizing resulting in the loss of human life and industry assets. Recent incidents involving bulk carriers transporting iron ore fines has initiated research into, and implementation of, a new test method used to determine a safe moisture content at which it can be transported without being at risk of liquefying. The new test method, known as the Modified Proctor/Fagerberg Test, is to be amended in the International Maritime Solid Bulk Cargoes Code in 2015 and entered into force in 2017. The objective of this paper is to provide a review regarding the development of the Modified Proctor/Fagerberg Test developed by the Iron Ore Technical Working Group. The review focusses on the key findings from five publicly available reports released in 2013
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