Geotechnical effects of polymer treatment on tailings – state of knowledge review

Reid, Donald B.; Fourie, Andries

doi:10.36487/acg_rep/1805_21_reid

Cited by 7 publications

(3 citation statements)

References 21 publications

(31 reference statements)

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“…However, it is noted that as part of their SD preparation process, Chang et al (2011) added a flocculant to the tailings to enable looser densities to be achieved. This then raises important questions about the applicability of the results to an unflocculated thickened tailings, as there is clear evidence that addition of flocculants to slurry-prepared specimens is likely to affect both mechanical properties and potentially the CSL (Mao & Fahey 1999;Reid & Fourie 2016, 2018a, 2018b. Further study of these aspects would be useful, as if flocculants can be used to achieve looser states while creating a specimen representative of in situ, this would be a major advantage for tailings laboratory testing works.…”

Section: Other Examples Of Sd In Literaturementioning

confidence: 99%

Some considerations when preparing thickened tailings for shear strength testing in the laboratory from a slurry

Reid¹,

Fanni²,

Fourie³

2021

Proceedings of the International Seminar on Paste and Thickened Tailings

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Preparation of tailings in the laboratory to simulate the likely range of densities and resulting behaviour that will occur under load in situ is challenging. A number of issues of relevance include whether effects such as subaqueous deposition can be reproduced at all in the laboratory, and the potential importance of in situ layering of segregating tailings. These issues may have (thus far, largely unquantified) effects on mechanical behaviour in ways that are difficult to predict with element tests that are usually intentionally prepared homogeneously. Thickened tailings testing is conceptually easier, as issues such as segregation and the potential for subaqueous deposition are often not relevant. Despite this relative simplicity, a number of important considerations remain. While it is trivial to pour a thickened slurry into various forms of moulds or vessels to prepare for element testing, questions remain over whether the density that is reproduced will be relevant to in situ conditions. In particular, preparation of triaxial samples from thick slurries is particularly challenging as a number of steps are required to enable such samples to be 'free-standing', with each one of these steps potentially leading to slight disturbance and thus densification of the sample. Where such densification occurs, it would result in the element test results being non-conservative. This could have important implications with respect to expectations of the contractive (and potentially liquefiable) or dilative response of the tailings in situ.To investigate these issues, a series of slurry-deposited triaxial tests was carried out using a non-segregating slurry. As test methods were refined during the program, the amount of disturbance applied to the specimen was reduced. However, comparison of the triaxial tests to slurry consolidometer tests indicated that, regardless of efforts made, the triaxial tests achieved denser states at a given amount of consolidation stress. This was found to be the case using any conceivable range of assumed geostatic stress ratio to interpret the slurry consolidometer results. This outcome is speculated to be a result of the quiescent conditions used in the preparation of a slurry consolidometer specimen, which only requires pouring and then application of vertical load, first using weights, then a load frame. The implications of the increased density seen in triaxial tests compared to the likely more realistic value seen from the slurry consolidometer are discussed. Alternative preparation methods to target this looser density range are briefly discussed.

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Section: Other Examples Of Sd In Literaturementioning

confidence: 99%

Some considerations when preparing thickened tailings for shear strength testing in the laboratory from a slurry

Reid¹,

Fanni²,

Fourie³

2021

Proceedings of the International Seminar on Paste and Thickened Tailings

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“…The stability and robustness of the IL-treated solid phase, in comparison to the polymer-treatments previously reported, is a crucial difference, since in the latter, when the treated sample is exposed to high stirring, the flocs formed by polymers are broken and the sample exhibits behavior closer to the untreated material. 51 Vacuum filtration, although still in initial development, has been used as an option for tailings disposal by several oil sands companies, 21 and hence was the third strategy we explored to separate the water from treated MFT. 100 g MFT was poured into a 250-mL beaker and mixed with different amounts of [C 8 NH 3 ][Oleate] following the mixing protocol described for centrifugation and gravity tests (i.e., using an overhead stirrer, 12 min, 500 rpm; see experimental section for details).…”

Section: Selection Of Ilmentioning

confidence: 99%

Design of ionic liquids for dewatering stable solid/liquid complex slurries

et al. 2021

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Exploitation of mineable oil sands in Canada has thus far produced over 50 km 2 of tailings in ponds where the fine solids remain suspended for years, even decades. These ponds represent a major liability and environmental burden for operating companies, with their dewatering critical to their remediation. In this work, we used the chemistry of the tailing pond constituents to design an ionic liquid (IL) for dewatering the mature fine tailings (MFT), taking advantage of the ability to introduce unique and different functionalities into each ion of the IL. We chose a class of protic ILs whose ions will interact with the solids while rejecting water. As an example, octylammonium oleate can be used to remove more than 70% of the water from MFT. The nature of the ILs makes their use amenable to a variety of large-scale separation techniques allowing engineering versatility in the design of the final process.

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“…Owing to the increased application of forms of PT, studies to characterise the effects PT may have on post-deposition geotechnical behaviour of the treated slurry have been undertaken. Broadly, these studies have indicated the following effects of PT: lower consolidated densities at a given vertical effective stress and higher permeability at a given density (Jeeravipoolvarn et al 2009;Yao 2012;Manzotti et al 2014;Beveridge et al 2015;Gholami & Simms 2015;Reid & Boshoff 2015;Riley et al 2015;Znidarcic et al 2015;Reid & Fourie 2016, 2018aAbdulnabi et al 2022), higher undrained shear strengths at a given density (Jeeravipoolvarn et al 2009;Yao 2012;Beier et al 2013;Manzotti et al 2014;Cooling & Beveridge 2015;Gholami & Simms 2015;Reid & Fourie 2016Abdulnabi et al 2022) and higher CSL elevation (Reid & Fourie 2016), and various contrasting outcomes when examining the effects of PT on brittleness in undrained monotonic or post-cyclic shearing (Beier et al 2013;Gholami & Simms 2015;Reid & Fourie 2017) and drastically different penetrometer responses (Reid and Fourie 2018a), with a summary of recent studies provided by Reid and Fourie (2018b).…”

Section: Introductionmentioning

confidence: 99%

Large strain shearing behaviour of untreated and polymer treated clayey silt slurry specimens

Reid¹,

Tiwari²,

Fourie³

2023

Paste 2023: 25th International Conference on Paste, Thickened and Filtered Tailings

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Polymer treatment (PT) of tailings has been observed experimentally and in physical models, resulting, in some cases, in changes to geotechnical properties including: (i) higher hydraulic conductivity, (ii) lower density at a particular vertical effective stress, (iii) a change to the critical state line (CSL), and (iv) different penetrometer response when at the same in situ state. The different CSLs observed could be theorised to converge at sufficiently high strain once the PT fabric had broken down through shearing. However, the available penetrometer test results in controlled centrifuge experiments do not support the suggestion of converging CSLs, with drastically different cone penetration test (CPT) resistance seen in PT clayey silt of importance as the CPT represents a large strain measure. To further investigate PT effects on shearing, a series of multi-stage direct simple shear and constant volume ring shear tests was carried out to investigate the large strain response of untreated (UT) and PT specimens. The tests showed consistently higher, or similar, large strain strengths from PT specimens despite their lower consolidated densities. This result is generally consistent with previous observations of an increase to CSL elevation from PT.

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Geotechnical effects of polymer treatment on tailings – state of knowledge review

Cited by 7 publications

References 21 publications

Some considerations when preparing thickened tailings for shear strength testing in the laboratory from a slurry

Some considerations when preparing thickened tailings for shear strength testing in the laboratory from a slurry

Design of ionic liquids for dewatering stable solid/liquid complex slurries

Large strain shearing behaviour of untreated and polymer treated clayey silt slurry specimens

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