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  • 1.
    Bhanbhro, Riaz
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Knutsson, Roger
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Rodriguez, Juan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Edeskär, Tommy
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Knutsson, Sven
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Basic description of tailings from Aitik focusing on mechanical behavior2013In: International Journal of Emerging Technology and Advanced Engineering, ISSN 2250-2459, E-ISSN 2250-2459, Vol. 3, no 12, p. 65-69Article in journal (Refereed)
    Abstract [en]

    Tailings are artificial granular materials that behave different as compared to natural soil of equal grain sizes. Tailings particle sizes, shapes, gradation and mechanical behavior may influence the performance of tailings dams. Hence it is essential to understand the tailings materials in depth. This article describes present studies being carried out on Aitik tailings. Basic tailings characteristics including specific gravity, phase relationships, particle sizes, particle shapes and direct shear behavior are presented in this article. The results showed that particles size decreases along depth from surface for collected sample locations. The angularity of the particles increases as the grain size decreases. Vertical height reduction was observed during shearing of samples by direct shear tests.

  • 2.
    Bhanbhro, Riaz
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Rodriguez, Juan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Edeskär, Tommy
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Knutsson, Sven
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Evaluation Of Primary And Secondary Deformations and Particle Breakage of Tailings2015In: From Fundamentals to Applications in Geotechnics: Proceedings of the 15th Pan-American Conference on Soil Mechanics and Geotechnical Engineering, 15–18 November 2015, Buenos Aires, Argentina / [ed] Diego Manzanal; Alejo O. Sfriso, IOS Press, 2015, p. 2481-2488Conference paper (Refereed)
    Abstract [en]

    Tailings are the waste product of mining which is left over after extraction of materials of interest. Tailings material may possess different material properties depending upon type of ore and method of concentration. Sometimes the tailings material itself is used in construction of tailings dams and tailings dams are constructed to withstand for long times. A tailing dam can be exposed to settlements due to incremental load as these dams are raised in stages. Increasing load with time may also lead to particle breakage. This article presents the results from oedometer tests conducted on tailings materials. The study includes the stress-deformation behavior and particle breakage of tailings material of different gradations upon application of incremental loads in oedometer tests. The samples were collected from different sections of tailings dam from Sweden. Remolded samples were manufactured in laboratory as four batches of particle sizes i.e. 1-0.5 mm, 0.5-0.25mm, 0.25-0.125mm and 0.125-0.063mm. The results are analyzed from tested samples at different stress levels and compared with different particle sizes. The breakage of particles of each batch is analyzed by sieving the specimens after oedometer tests. The results are evaluated in terms of primary and secondary deformations. The primary and secondary deformations are also compared with different particle sized specimens.

  • 3.
    Rodriguez, Juan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Importance of the particle shape on mechanical properties of soil materials2013Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Particle shape of soil aggregates is known to influence several engineering properties; such as the internal friction angle, the permeability, etc. Even if this is known, there has been only minor progress in explaining the processes behind its performance and has only partly implemented in practical geotechnical analysis. Previously shape classification of aggregates has mainly been performed by ocular inspection and e.g. by sequential sieving. In geotechnical analysis has been a lack of an objective and rational methodology to classify shape properties by quantitative measures. The image analysis, as quantitative methodology, is tested and it is investigated how the results are affected by resolution, magnification level and type of shape describing quantity. Tailings as a part of granular materials need to be stored safely in facilities and for a long time perspective a good knowledge of current and future materials properties is needed. Tailings are site specific and not well investigated compare to natural geological materials. There also is a need of prognosis tools for long term behavior. Based on laboratory test tailings from Aitik mine has been investigated through triaxial test and particle shape (using two dimensions image analysis).The overview has shown that there is no agreement on the usage of the descriptors and is not clear which descriptor is the best. The resolution in the processed image needs to be considered since it influences descriptors such as e.g. the perimeter. Recent development in image analysis processing has opened up for classification of particles by shape. The interpreted results show that image analysis is a promising methodology for particle shape classification. Results are affected by the image acquisition procedure, the image processing, and the choice of quantity, there is a need to establish a methodology to ensure the objectivity in the particle shape classification. A comparison between laboratory shear strength tests of the analysed tailings material and previously published empirical relationships between shape and friction angle indicates that the minimum quantity value have the shortest difference between obtained data and expected results.

  • 4.
    Rodriguez, Juan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Particle shape quantities and influence on geotechnical properties: a review2012Report (Other academic)
    Abstract [en]

    It has been shown in the early 20th century that particle shape has an influence on geotechnical properties. Even if this is known, there has been only minor progress in explaining the processes behind its performance and has only partly implemented in practical geotechnical analysis.This literature review covers different methods and techniques used to determine the geometrical shape of the particles as well as reported effects of shape on granular material behaviour. Particle shape could be classifying in three categories; sphericity - the overall particle shape and similitude with a sphere, roundness - the description of the particle’s corners and roughness - the surface texture of the particle. The categories are scale dependent and the major scale is to sphericity while the minor belongs to roughness.Empirical relations and standards had been developed to relate soil properties, e.g. internal friction angle, minimum and maximum void ratio, density, permeability, strain, with the particle shape. The use of the relations and standards enhance the bulk material performance e.g. asphalt mixtures and rail road ballast.The overview has shown that there is no agreement on the usage of the descriptors and is not clear which descriptor is the best. One problem has been in a large scale classify shape properties. Image analysis seems according to the review to be a promising tool, it has many advantages. But the resolution in the processed image needs to be considered since it influence descriptors such as e.g. the perimeter.

  • 5.
    Rodriguez, Juan
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Bhanbhro, Riaz
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Edeskär, Tommy
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Knutsson, Sven
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Effect of vertical load on tailings particles2016In: Journal of Earth Sciences and Geotechnical Engineering, ISSN 1792-9040, E-ISSN 1792-9660, Vol. 6, no 2, p. 115-129Article in journal (Refereed)
    Abstract [en]

    Tailing dams could store hundreds, thousands or millions of cubic meters of tailings result of the mining extractive industry. Mechanical behavior of this man-made soil should be known in order to maintain a safe storage. Dykes rise up to form the dams and they are buildup with the same tailing material especially in the upstream method using the coarse part. The study uses oedometer classical test to determine the load effect over tailing coarse particles. Tailings are site specific and so its characteristics. It is necessary to understand the tailings degradations to achieve safe impounds. The study comprises four samples of one range-size tailing particles (e.g. 1-0.5, 0.5-0.25, 0.25-0.125, 0.125-0.063mm) subject to vertical load in traditional oedometers. Vertical load effects are measured using two dimensional image analysis and sieving. Results show that 0.063mm sample is the only one that has change in shape with low breakage (<1%) while the rest of the sizes have no shape change but high breakage is present especially in fraction 0.5mm. Settlements also are more pronounced in coarse fractions 0.5 and 0.25mm.

  • 6.
    Rodriguez, Juan
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Bhanbhro, Riaz
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Edeskär, Tommy
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Knutsson, Sven
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Shear Strength in Uniformed Sized Tailing ParticlesIn: International Journal of Geotechnical Engineering, ISSN 1938-6362, E-ISSN 1939-7879Article in journal (Refereed)
    Abstract [en]

    Mining industry provides mineral to the modern society. Minerals are indispensable raw materials for commodities. A by-product of the mineral extraction is the mine waste also called tailings. Tailings are safety storage in tailing dams. Tailings dams troughs the history had had incidents and failures. Economic, environmental and social consequences of a tailing dam failure could be devastating. Soil strength is given by the consolidation, particle shape, stresses path, water content, hydraulic conductivity among other factors. Change on these factors produces changes in the soil strength. The development of economical and fast tests could improve the safety of the tailings deposits. Drained direct shear tests using uniformed graded tailing particles were performed. Three different size ranges 0.25, 0.125 and 0.063mm were used. Effect of particle size on shear strength and the effect of shearing on the tailing particles were studied. Normal consolidation pressure, void ratio, particle size and particle shape were monitored properties. Strength of the tailings was related with the monitored properties to suggest four empirical relations, two of them base in the morphology of the particle and two bases in the angularity. Results have shown that particle elongation diminishes the tailings strength but the angularity increases the strength. Particle size results are ambiguous and seem to be more related with the shape descriptor.

  • 7.
    Rodriguez, Juan
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Edeskär, Tommy
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Knutsson, Sven
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Mechanical weathering effect on tailing particles2016In: Proceedings of Nordic Conference on Soil Mechanics and Geotechnical NGM: Reykjavik, Iceland 25th – 28th of May 2016, 2016Conference paper (Refereed)
    Abstract [en]

    Over the last century the tailing volume generation has grown dramatically due to the mineral demand. Nowadays the mining industry is producing every year millions of tons of tailings. The storage of the tailings has become a challenge due to the increased storage capacity demanded. Physical risk associated to the tailings dams is the stability itself since tailing dams are considered a walk-away solution. Physical changes as breakage and shape occur to the tailing particles affecting the stability of the fills by reduced strength properties. In order to understand the reduction and shape changes of tailing particles degradation test by milling attrition (erosion) and image analysis was conducted. Uniform fractions 1-0.5, 0.5-025, 0.25-0.125 and 0.125-0.063mm were used.Results have shown that attrition agents e.g. ball attrition can increase the physical erosion but also change the shape of the particles compared with autogenous attrition. However particles shape has become more regular (less elongated) and rounded in coarse fractions 1-0.5 and 0.5-0.25mm while smaller fractions 0.25-0.125 and 0.125-0.063mm seems to have opposite behavior. Comparison with previous milling studies show consistent differences probably due to the breakage of the particles was the objective. In perspective if tailings become more rounded the strength could be compromised. More studies are needed to verify this.

  • 8.
    Rodriguez, Juan
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Edeskär, Tommy
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Knutsson, Sven
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Particle shape quantities and measurement techniques: a review2013In: The Electronic journal of geotechnical engineering, ISSN 1089-3032, E-ISSN 1089-3032, Vol. 18/A, p. 169-198Article in journal (Refereed)
    Abstract [en]

    It has been shown in the early 20th century that particle shape has an influence on geotechnical properties. Even if this is known, there has been only minor progress in explaining the processes behind its performance and has only partly implemented in practical geotechnical analysis. This literature review covers different methods and techniques used to determine the geometrical shape of the particles. Particle shape could be classifying in three categories; sphericity - the overall particle shape and similitude with a sphere, roundness - the description of the particle’s corners and roughness - the surface texture of the particle. Thecategories are scale dependent and the major scale is to sphericity while the minor belongs to roughness. The overview has shown that there is no agreement on the usage of the descriptors and is not clear which descriptor is the best. One problem has been in a large scale classify shape properties. Image analysis seems according to the review to be a promising tool, it has advantages as low time consumption or repeatability. But the resolution in the processed image needs to be considered since it influences descriptors such as e.g. the perimeter. Shape definitions and its potential role in soil mechanics are discussed.

  • 9.
    Rodriguez, Juan
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Johansson, Jens
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Edeskär, Tommy
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Particle shape determination by two-dimensional image analysis in geotechnical engineering2012In: Proceedings of Nordic Conference on Soil Mechanics and Geotechnical NGM, Copenhagen: Danish Geotechnical Society , 2012, p. 207-218Conference paper (Refereed)
    Abstract [en]

    Particle shape of soil aggregates is known to influence several engineering properties; such as the internal friction angle, the permeability etc. Previously shape classification of aggregates has mainly been performed by ocular inspection and e.g. by sequential sieving. In geotechnical analysis has been a lack of an objective and rational methodology to classify shape properties by quantitative measures.Recent development in image analysis processing has opened up for classification of particles by shape. In this study 2D-image analysis has been adapted to classify particle shape for coarse grained materials. This study covers a review of soil classification methods for particle shape and geometrical shape descriptors. The image analysis methodology is tested and it is investigated how the results are affected by resolution, magnification level and type of shape describing quantity. Evaluation is carried out on as well idealized geometries as on soil samples. The interpreted results show that image analysis is a promising methodology for particle shape classification. But since the results are affected by the image acquisition procedure, the image processing, and the choice of quantity, there is a need to establish a methodology to ensure the objectivity in the particle shape classification.

  • 10.
    Rodriguez, Juan M.
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Edeskär, Tommy
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
    Case of study on particle shape and friction angle on tailings2013In: Journal of Advanced Science and Engineering Research, ISSN 2231-8844, Vol. 3, no 4, p. 373-387Article in journal (Refereed)
    Abstract [en]

    Tailings are crushed and milled materials result of the mining production. Tailings need to be stored in facilities, usually tailings dams, for a long time period for mainly safety and environmental protection. In order to design tailings dams in a long term perspective not only current material properties is needed but also future changes of these properties due to e.g. weathering. On a particle level the weathering will result in shape changes and decomposition. By studying the changes in shape a prognosis of changes in properties of a tailings deposit may be established.Tailings are site specific material and are not well investigated compared to natural geological materials such as soil. Tailings materials size ranges generaly from sand to silt and the particle shape by genesis or production processes. Based on laboratory tests tailings from the Aitik mine has been investigated through triaxial tests and particle shape quantification by two dimensions image analysis. The shape descriptors Aspect Ratio, Circularity, Roundness and Solidity are used in this study. These shape descriptors are evaluated based on how well these describes talings materials. The evaluated shape descriptors are used in previous published empirical relations between shape and friction angle. As reference are friction angles evaluated by triaxial tests on the material used.The results show that the particle shape is affected by the size of the aggregates. Aggregates in small fractions are more elongated and less rounded, i. e. more angular, compared to larger. Furthermore, the Aspect Ratio and Circularity seems to be the most situable quantities to describe the tailings behaviour in relation with the empirical model. The accuracy in predicting the friction angle of the tailings by previously published relations based on uniformly graded sand material are low. But the systematic underestimation of the friction angle indicates that it would be possible to establish such empirical relations based on tailings material.

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