Piecewise-Linear Formulation of Coupled Large-Strain Consolidation and Unsaturated Flow. II: Testing and Performance

Qi, Suitao; Simms, Paul; Vanapalli, Sai K.; Soleimani, Sahar

doi:10.1061/(asce)gt.1943-5606.0001658

Cited by 21 publications

(11 citation statements)

References 11 publications

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“…One can visualise the constitutive surfaces as an extension of conventional saturated virgin compression and unload-reload lines into a 3D surface for dependency on suction (Figure 4). Details of the theory and operation of the UNSATCON code are given in the other sources (Qi et al 2016a(Qi et al , 2016b(Qi et al , 2017Qi 2017). The hypothetical analyses for both tailings types are for an imaginary mine in a northern Canadian climate.…”

Section:  -mentioning

confidence: 99%

“…The large strain consolidation algorithm is modified from the piecewise linear approach of Fox and Bereles (1997) for unsaturated conditions, as described in Qi et al (2016a). The model has been validated using field data from oil sands tailings (Qi et al 2016b), through simulation of a multilayer drying box experiment of Daliri et al (2016) for hard rock tailings, and from Rozina et al (2015) for oil sands tailings -these simulations are reported in Qi et al (2016c) and Qi (2017).…”

Section: Introductionmentioning

confidence: 99%

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Analysis of dewatering and desaturation of generic field deposition scenarios for thickened tailings

Qi¹,

Simms²

2018

Proceedings of the 21st International Seminar on Paste and Thickened Tailings

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Models that compute dewatering using accurate coupling of evaporation, unsaturated flow and large strain consolidation may have utility in providing guidance to optimise deposition of thickened tailings. A recently developed research model, UNSATCON, is used to analyse some typical field deposition profiles for both hard rock and oil sands fine tailings deposits. Model parameters are selected from previous studies on hard rock and oil sands tailings. Some validation with select field data is presented. Exploratory analysis reveals a number of interesting findings. For hard rock tailings, where self-weight consolidation after lift placement occurs relatively quickly due to high hydraulic conductivity of the tailings, maximisation of density can be achieved for a wide range of lift thickness and rates of rise even with relatively low rates of evaporation. For desaturation and risk of oxidation, lift thickness and deposition timing become more important. For oil sands tailings, the timing of deposition and lift thickness are more important for maximising density due to the much lower hydraulic conductivity and, therefore, the longer time of self-weight consolidation.

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Section:  -mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Analysis of dewatering and desaturation of generic field deposition scenarios for thickened tailings

Qi¹,

Simms²

2018

Proceedings of the 21st International Seminar on Paste and Thickened Tailings

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“…For example, Soleimani et al (2014) and Qi et al (2017) reported column tests (0·15 m diameter) on the same kind of polymer-amended MFTs as used in this study: no influence of cracks on A E was discernible from that scale of test.…”

Section: Utility Of Large-scale Testingmentioning

confidence: 99%

Cracking, salinity and evaporation in mesoscale experiments on three types of tailings

Simms

SoleimaniSahar

MizaniShabnam

et al. 2019

Environmental Geotechnics

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Evaporation is a phenomenon useful in assisting in the dewatering and stabilisation of various mineral wastes. This paper summarises findings on the influence of cracking and salinity on evaporation in mesoscale (1·0 m by 0·7 m in plan) deposition experiments on three different mineral slurries: thickened gold tailings, thickened oil sands tailings and oil sands tailings modified by in-line polymer flocculation. Each tailings exhibited substantially different evaporation related phenomena. In the two finer-grained oil sands tailings, crack development correlated with apparent actual evaporation rates larger than the potential rate, which ceased once crack volume stopped increasing. Total suction at the surface was dominated by osmotic suction in the thickened oil sands tailings, whereas total suction was largely matric in the other two tailings. In the gold tailings, no strong signal from cracks on evaporation could be detected. The gold tailings exhibited 'declining stage I' evaporation, which has been recently described from idealised drying experiments on sands. The relatively unique behaviour of each tailings type with respect to evaporation highlights the importance of considering larger scale effects when assessing tailing dewatering by evaporation. NotationA E actual evaporation (mm/d) A EV air entry value (kPa) a soil-dependent parameter in the soil surface resistance equation C a specific heat of air (MJ/(kg°C)) D xx percent (%) of particles less than XX microns in size G flux of heat into the soil away from the soil surface (MJ/(m 2 d))L L liquid limit (%) P E potential evaporation (mm/d) P L plastic limit (%) R universal gas content R E relative evaporation R H relative humidity R Ha relative humidity of the air above the evaporating surface R n net short and long wave radiation (MJ/(m 2 d)) r a density of air (kg/m 3 )r s , r a soil surface and aerodynamic resistance factors S L shrinkage limit (%) T temperature (K) v s , v a vapour pressures at the soil surface and in the air (kPa) W molecular weight of water (kg/mol) w geotechnical gravimetric water content (%) g psychometric constant (kPa/°C) D slope of vapour pressure-temperature relationship (kPa/°C) q ref reference volumetric water content at an arbitrary depth used to calculate soil surface resistance factor q top actual water content at the same depth as the reference volumetric water content L latent heat of evaporation (MJ/kg) y total suction (kPa) IntroductionDrying tailings to increase density and strength is often used to assist stabilisation and reclamation of tailings impoundments. The aluminium industry relies heavily on evaporation to stabilise 'red muds' (Doucet and Paradis, 2010), while thickened tailings deposition in a variety of climates takes advantage of evaporation to reduce tailings volumes (Simms, 2016). Certain tailings management methods in the Canadian oil sands industry, such as Suncor's tailings reduction operations (Caldwell et al., 2014) and Shell's atmospheric fine drying technologies , use evaporation to reduce tai...

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“…Various academic research projects (Jeeravipoolvarn et al 2010;Qi et al 2017b;Rozina et al 2015;Soleimani et al 2014) and field trials (Dunmola et al 2014) have indicated that flocculated FFT consolidation behaviour is superior to that of raw FFT, at least up to some critical stress level. It is well understood and established that geotechnical engineering problems, such as high-volume change deposits (consolidation), stability of earthfill structures, and reclamation of tailings impoundments can best be analysed using fundamental principles of soil mechanics for both saturated and unsaturated soils.…”

Section: Introductionmentioning

confidence: 99%

“…It is well understood and established that geotechnical engineering problems, such as high-volume change deposits (consolidation), stability of earthfill structures, and reclamation of tailings impoundments can best be analysed using fundamental principles of soil mechanics for both saturated and unsaturated soils. For example, unsaturated flow behaviour has been used to predict the dewaterability of thin and/or multilayer tailings deposits of high-density hard rock tailings as well as evaporation and drainage of tailings (Fisseha et al 2010;Qi et al 2016Qi et al , 2017aQi et al , 2017bSalfate et al 2010;Simms et al 2007Simms et al , 2010Simms et al , 2017. Large-strain consolidation properties and shear strength development for treated FFT was investigated under stress-controlled conditions (Fisseha et al 2017).…”

Section: Introductionmentioning

confidence: 99%

Assessment of self-weight consolidation of flocculated fluid fine tailings under various environmental conditions

Fisseha¹,

Wilson²,

Simms³

2018

Proceedings of the 21st International Seminar on Paste and Thickened Tailings

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Self-weight consolidation properties of polymer-flocculated fluid fine tailings (FFT) have been investigated in a laboratory using a meso-scale column apparatus with dimensions of 300 mm (diameter) by 1.8 m (height). Four meso-scale columns were used to carry out self-weight consolidation of flocculated FFT with flocculant dosages of 650 g/L (one column) and 850 g/L (three columns). The laboratory investigation attempts to mimic setups of the meso-scale consolidation columns under various environmental considerations such as with no evaporation (one column of 850 g/L dosage), with evaporation only (one column of 650 g/L and one column of 850 g/L dosage), and with evaporation and decantation (one column of 850 g/L dosage). The laboratory investigation enables the characterisation of self-weight consolidation of flocculated FFT, using the relationship between the total settlement of deposited tailings versus measured excess pore water pressure dissipation and expected hydrostatic line for various flocculant dosages and environmental considerations. The measured data will be used to assess and verify the self-weight consolidation properties with respect to the principles of soil mechanics.

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Piecewise-Linear Formulation of Coupled Large-Strain Consolidation and Unsaturated Flow. II: Testing and Performance

Cited by 21 publications

References 11 publications

Analysis of dewatering and desaturation of generic field deposition scenarios for thickened tailings

Analysis of dewatering and desaturation of generic field deposition scenarios for thickened tailings

Cracking, salinity and evaporation in mesoscale experiments on three types of tailings

Assessment of self-weight consolidation of flocculated fluid fine tailings under various environmental conditions

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