Determination of Consolidation Parameters by Selfweight Consolidation Test in Centrifuge

Takada, Nobuyasu; Mikasa, Masato

doi:10.1520/stp34634s

Cited by 16 publications

(6 citation statements)

References 4 publications

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“…The permeability results obtained by means of constant head tests in the slurry consolidometer, and as estimated through initial settling rate (Takada & Mikasa 1986) in the undrained settling test are presented in Figure 4. The proposed permeability -void ratio relationship fit to the results, which is used in consolidation modelling (see below), is included.…”

Section: Figure 3 Density Resultsmentioning

confidence: 99%

“…A batch of tailings at 25% solids were treated with polymer as described above, and immediately poured into a 1 L graduated cylinder and a slurry consolidometer column (Sheeran & Krizek 1971). The depth of material vs. time was monitored in the 1 L graduated cylinder to establish initial settling rate, and hence initial permeability (Takada & Mikasa 1986), and an estimate of settled dry density.…”

Section: Settling and Slurry Consolidometermentioning

confidence: 99%

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Stability of a proposed steepened beach

Reid¹,

Boshoff²

2015

Proceedings of the 18th International Seminar on Paste and Thickened Tailings

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Existing topography at an operational lateritic nickel facility is such that if the tailings beach slope could be increased to 1-2% for approximately one year, significant costs related to wall building could be deferred. As additional thickening capacity would require significant capital expenditure, polymer treatment technologies have instead been investigated. As part of the trial process for polymer treatment, the stability of the potential steepened beach was assessed. While beach slopes of the range targeted here would, for many materials, be unlikely to produce an unstable landform, lateritic nickel tailings develop very low dry densities, consolidate slowly, and contain hypersaline pore fluid. This combination results in a lower resistance to slope instability, all else being equal. Further, polymer treatment technologies, while providing benefits through rapid dewatering and beach slope development, have been shown to result in an increased brittleness for some materials. Laboratory characterisation of the polymer treated material was first undertaken, by means of (i) monotonic, cyclic and post-cyclic simple shear testing, to assess the potential for strength loss of the material, (ii) laboratory-scale shear vane testing, to estimate residual shear strength, and, (iii) settling and consolidation tests, to provide input to consolidation modelling. A consolidation model of the proposed steepened beach was then developed. Outputs from this model were used as the basis for infinite slope stability analyses on a variety of scenarios. It was found that over the one year planned deposition period, beach slopes of 1.5% or less are likely to result in a satisfactory factor of safety (FS) for the steepened beach. 2 Previous relevant studies 2.1 Steepened beach stability A number of previous studies have been undertaken to assess the expected stability of proposed unconstrained tailings beaches, most of which were developed from thickened tailings deposition. Each of

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Section: Figure 3 Density Resultsmentioning

confidence: 99%

Section: Settling and Slurry Consolidometermentioning

confidence: 99%

Stability of a proposed steepened beach

Reid¹,

Boshoff²

2015

Proceedings of the 18th International Seminar on Paste and Thickened Tailings

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“…Settling tests results show that lime has a short-term negative impact on both density and permeability, reducing dry density by 13% and also reducing inferred permeability (Table 3). *Inferred from initial settling rate using method proposed by Takada and Mikasa (1986) Subsequent consolidation testing to simulate longer term conditions in the cell however indicated that there is no significant difference between the two samples when loading is applied, with void ratios, coefficients of consolidation and permeability tests giving similar results to each other (Figures 9-11). For each of these soil properties, the variation seen between the two samples are within the likely range of accuracy for consolidation testing.…”

Section: Effect Of Lime On Tailings Consolidationmentioning

confidence: 97%

Tailings co-disposal case study – art or science?

Beveridge¹,

Mutz²,

Reid³

2015

Proceedings of the 18th International Seminar on Paste and Thickened Tailings

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Murray Zircon Pty Ltd operates the Mindarie Mineral Sands Project in South Australia comprising a mine and concentrator plant. The program for environmental protection and rehabilitation (PEPR) approved by the South Australia Department of Manufacturing, Innovation, Trade, Resources and Energy (DMITRE) requires diligent management of the tailings deposition and overall mine rehabilitation processes. The mining licence was granted based on a maximum permitted operational footprint of the open area of the mine. Mining at Mindarie follows the 'moving-hole' concept whereby topsoil and overburden is removed, ore is mined, tailings are deposited in the mined-out space and are then capped by overburden. The moving hole must advance at approximately 10 m per day. Consequently, it is imperative that dewatering, consolidation and stabilisation of deposited tailings happens quickly. Tailings are treated using a high molecular weight polymer which rapidly releases clean water for reuse in the concentrator plant. The polymer binds the coarse and fine particles together to create a non-segregating deposit and accelerates the consolidation rate. Polymer dosing regimes for the tailings have historically relied on a visual interpretation of the material entering the tailings cells to determine the optimum dose; however, it is the consolidation rate and associated strength gain that determines when overburden replacement can begin. To provide an improved assessment of the impacts of dosage on consolidation, geotechnical testing was undertaken on material treated with different polymer levels. A recent development for the Mindarie mine is to adjust the natural acidic pH of tailings to a slightly alkaline level using lime. This was done in order to overcome a throughput bottleneck in the slimes thickener and reduce polymer dosing levels in the slimes thickener and tailings applications. The impact of lime addition on polymer dosing, together with the effect of lime on tailings consolidation properties is also investigated.

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“…Time dependent behaviour was monitored through use of a strobe light to observe settlement of the material over time. In estimating permeability, they made use of a formula developed by Takada and Mikasa (1986). This expression provided an indication of initial permeability based on the approximately linear initial settling rate.…”

Section: Previous Related Workmentioning

confidence: 99%

“…Derivation of the full time-dependent behaviour from the settlement or pore pressure response of samples in a centrifuge of the kind described here is not possible using conventional analytical methods. McDermott and King (1998) recognised this, and limited their permeability interpretation to the initial settling rate method of Takada and Mikasa (1986), relevant to the initial void ratio of the sample. This provided excellent estimates of permeability.…”

Section: Permeability -Effective Stress Interpretationmentioning

confidence: 99%

Accelerated consolidation of soft clays and mine tailings using a desktop centrifuge

Reid

Fourie

Watson³

2012

Proceedings of the 15th International Seminar on Paste and Thickened Tailings

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Many mine tailings streams contain appreciable quantities of clay minerals, examples including mineral sands fines, diamond and coal tailings. Tests to determine appropriate consolidation properties for these materials, as well as natural clays, are usually very time-consuming and the availability of equipment (such as a Rowe Cell) can sometimes be a limiting factor. This paper describes the development and testing of a modified desktop centrifuge that should eventually allow the determination of a full suite of consolidation material parameters within two days for soils of very low permeability and stiffness. The results of a series of consolidation tests using the desktop centrifuge are presented. The void ratio-effective stress profile is developed from these tests based on centrifuge theory and direct moisture content measurement. Development of a numerical model of the system to allow estimates of the permeability-effective stress profile of tested slurries is currently underway. Encouraging results have been obtained, indicating the ability of this method to provide reasonable results in the time frame outlined. Suggestions for further developments related to this procedure planned at The University of Western Australia (UWA) are outlined.

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Determination of Consolidation Parameters by Selfweight Consolidation Test in Centrifuge

Cited by 16 publications

References 4 publications

Stability of a proposed steepened beach

Stability of a proposed steepened beach

Tailings co-disposal case study – art or science?

Accelerated consolidation of soft clays and mine tailings using a desktop centrifuge

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