Compressibility and Permeability of Sand-Silt Tailings Mixtures

2022 ◽  
Author(s):  
Jiying Fan ◽  
R. Kerry Rowe ◽  
Richard W.I. Brachman
Keyword(s):  
Hydraulic Conductivity ◽  
Void Ratio ◽  
Published Data ◽  
Internal Stability ◽  
Fines Content ◽  
Coarse Grains ◽  
Soil Skeleton ◽  
Loading Tests ◽  
Stress Dependent ◽  
Incremental Loading

Microstructure showing the involvement of the fine and coarse grains in the soil skeleton is evaluated. Incremental loading tests using a stress-dependent permeameter are conducted on the mixtures of poorly graded sand and nonplastic fines originating from tailings. The results are compared with the published data of various tailings. It is shown that increasing the fines content from 0 to 100%, the involvement of the fine and coarse components of soil skeleton can be classified into four categories: no fines involvement (<10% fines), fines partially involved (10% —35% fines), increasing cushioning effect surrounding the coarse (35% — 40% fines), and constant cushioning effect (> 40% fines). At the same consolidation stress, the void ratio, e, rapidly decreases for fines less than 30%, then almost remains constant between 30% and 50% fines, and gradually increases for fines exceeding 50%. The hydraulic conductivity, k, decreases more than 20-fold as the fines content increases from 12% to 50%, then remains constant. k is proportional to [e3/(1+e)]A and inversely proportional to S2, where A is a factor describing the effect of particle angularity and S is the specific surface. Finally, the influence of fines content on the seepage-induced internal stability is discussed.

Measurement of hydraulic conductivity in oil sand tailings slurries

1996 ◽  
Vol 33 (4) ◽  
pp. 642-653 ◽  
Author(s):  
Nagula N Suthaker ◽  
J Don Scott
Keyword(s):  
Hydraulic Conductivity ◽  
Oil Sands ◽  
Void Ratio ◽  
Large Strain ◽  
Measurement Techniques ◽  
Hydraulic Gradient ◽  
Oil Sand ◽  
Fines Content ◽  
Acid Lime ◽  
Clamping Device

Fine tails, the resulting fine waste from oil sand processing, undergoes large-strain consolidation in tailings ponds. Its consolidation behaviour must be analyzed using a large-strain consolidation theory, which requires the determination of the relationship between the void ratio and hydraulic conductivity. Conventional measurement techniques are not suitable for fine tails, and a special slurry consolidometer, with a clamping device to prevent seepage-induced consolidation, was designed to determine the hydraulic conductivity of the fine tails and nonsegregating fine tails – sand slurries. The hydraulic conductivity of slurries is not constant but decreases with time to a steady-state value. Hydraulic conductivity is also influenced by the hydraulic gradient and bitumen content. It is shown that a low hydraulic gradient, less than 0.2, is necessary to counteract the effect of the bitumen and to represent tailings pond conditions. The hydraulic conductivity of fine tails – sand mixes is controlled by the fines void ratio, hence, fines content. The hydraulic conductivity of chemically amended nonsegregating tailings can be lower than that of fine tails. However, acid–lime or acid – fly ash amended nonsegregating tailings have similar hydraulic conductivity values in terms of fines void ratio. The hydraulic conductivity of nonsegregating tailings appears to be governed by fines content and by the nature of the fines aggregation caused by the chemical additive. Key words: tailings, slurries, hydraulic conductivity, slurry consolidometer, nonsegregating tailings, oil sands.

New method to determine proper strain rate for constant rate-of-strain consolidation tests

2012 ◽  
Vol 49 (1) ◽  
pp. 18-26 ◽  
Author(s):  
A. Tolga Ozer ◽  
Evert C. Lawton ◽  
Steven F. Bartlett
Keyword(s):  
Strain Rate ◽  
Linear Equation ◽  
Pore Pressure ◽  
Void Ratio ◽  
Semiempirical Method ◽  
The Other ◽  
Initial Void Ratio ◽  
Constant Rate ◽  
Loading Tests ◽  
Incremental Loading

The development of a new semiempirical method to predict the proper strain rate for constant rate-of-strain (CRS) consolidation tests is described herein. The validity of the proposed method is analyzed using experimental results from CRS and incremental loading tests on four types of soil: Lake Bonneville clay, Massena clay, kaolinite, and montmorillonite. It is found that the maximum allowable strain rate depends on the initial void ratio of the soil and thus is related to the compressibility of the soil. The effect of the strain rate on the distribution of the pore pressure within the sample is investigated by comparing values of effective vertical stress calculated using a linear equation published by Wissa et al. in 1971 with values of effective stress at the base of the specimen determined from measured values of pore pressure. Overall, the proposed method predicts the maximum allowable strain rate very well for three of the four soils and moderately well for the other soil.

Predicting the saturated hydraulic conductivity of sand and gravel using effective diameter and void ratio

2004 ◽  
Vol 41 (5) ◽  
pp. 787-795 ◽  
Author(s):  
Robert P Chapuis
Keyword(s):  
Hydraulic Conductivity ◽  
Void Ratio ◽  
Saturated Hydraulic Conductivity ◽  
Effective Diameter ◽  
Predictive Capacity ◽  
K Value ◽  
Maximum Value ◽  
New Equation ◽  
Silty Soils ◽  
Sand And Gravel

This paper assesses methods to predict the saturated hydraulic conductivity, k, of clean sand and gravel. Currently, in engineering, the most widely used predictive methods are those of Hazen and the Naval Facilities Engineering Command (NAVFAC). This paper shows how the Hazen equation, which is valid only for loose packing when the porosity, n, is close to its maximum value, can be extended to any value of n the soil can take when its maximum value of n is known. The resulting extended Hazen equation is compared with the single equation that summarizes the NAVFAC chart. The predictive capacity of the two equations is assessed using published laboratory data for homogenized sand and gravel specimens, with an effective diameter d10 between 0.13 and 1.98 mm and a void ratio e between 0.4 and 1.5. A new equation is proposed, based on a best fit equation in a graph of the logarithm of measured k versus the logarithm of d102e3/(1 + e). The distribution curves of the differences “log(measured k) – log(predicted k)” have mean values of –0.07, –0.21, and 0.00 for the extended Hazen, NAVFAC, and new equations, respectively, with standard deviations of 0.23, 0.36, and 0.10, respectively. Using the values of d10 and e, the new equation predicts a k value usually between 0.5 and 2.0 times the measured k value for the considered data. It is shown that the predictive capacity of this new equation may be extended to natural nonplastic silty soils, but not to crushed soils or plastic silty soils. The paper discusses several factors affecting the inaccuracy of predictions and laboratory test results.Key words: permeability, sand, prediction, porosity, gradation curve.

A relation of hydraulic conductivity — void ratio for soils based on Kozeny-Carman equation

2016 ◽  
Vol 213 ◽  
pp. 89-97 ◽  
Author(s):  
Xingwei Ren ◽  
Yang Zhao ◽  
Qinglu Deng ◽  
Jianyu Kang ◽  
Dexian Li ◽  
...  
Keyword(s):  
Hydraulic Conductivity ◽  
Void Ratio

Hydraulic conductivity of bentonite-sand mixtures

2000 ◽  
Vol 37 (2) ◽  
pp. 406-413 ◽  
Author(s):  
P V Sivapullaiah ◽  
A Sridharan ◽  
V K Stalin
Keyword(s):  
Hydraulic Conductivity ◽  
Water Retention ◽  
Void Ratio ◽  
Clay Content ◽  
Liquid Limit ◽  
Natural Soils ◽  
Waste Containment ◽  
Clay Liner

The use of bentonite alone or amended with natural soils for construction of liners for water-retention and waste-containment facilities is very common. The importance of bentonite content in reducing the hydraulic conductivity of liners is well recognised. The study illustrates the role of the size of the coarser fraction in controlling the hydraulic conductivity of the clay liner. It has been shown that at low bentonite contents the hydraulic conductivity of the liner varies depending on the size of the coarser fraction apart from clay content. At a given clay content, the hydraulic conductivity increases with an increase in the size of the coarser fraction. But when the clay content is more than that which can be accommodated within the voids of the coarser fractions, the hydraulic conductivity is controlled primarily by clay content alone. Four different methods of predicting hydraulic conductivity of the liners are presented. Using two constants, related to the liquid limit, the hydraulic conductivity can be predicted at any void ratio.Key words: clays, hydraulic conductivity, liquid limit, liners, void ratio.

Physical characteristics of sands amended with fly ash

Soil Research ◽  
1983 ◽  
Vol 21 (2) ◽  
pp. 147 ◽  
Author(s):  
DJ Campbell ◽  
WE Fox ◽  
RL Aitken ◽  
LC Bell
Keyword(s):  
Fly Ash ◽  
Hydraulic Conductivity ◽  
Binary Mixtures ◽  
Void Ratio ◽  
Coarse Sand ◽  
Power Station ◽  
Sand Fraction ◽  
Water Capacity ◽  
Available Water ◽  
Available Water Capacity

Fly ash from a coal-fired power station was incorporated with each of a 'fine' (0.2-0.5 mm) and 'coarse' (1.4-2.0 mm) sand fraction to give mixtures containing 0, 10, 20, 30, 40, 50, 75 and 100% fly ash by weight. The addition of 10% by weight of ash increased the available water capacity by factors of 7.2 (1.0-7.2% by weight) and 13.5 (0.4-5.4% by weight) for the 'fine' and 'coarse' sands respectively. Subsequent additional 10% increments of ash increased the capacity by smaller amounts. The saturated hydraulic conductivity of the sands decreased markedly with ash addition. The changes in available water capacity and hydraulic conductivity were associated with an increase in capillary pores at the expense of non-capillary pores. Addition of fly ash to both sand fractions resulted in a bilinear relationship between void ratio (volume voids/volume solids) and fly ash percentage in the mixes which was closely related to that theoretically predicted for binary mixtures. The measured void ratios of the mixes exhibited minimum values at 36% and 20% ash by volume for the 'fine' and 'coarse' sand mixes respectively, which compared with the theoretical void ratios for these mixes of 27% and 23% respectively.

scholarly journals One-dimensional large-strain thaw consolidation using nonlinear effective stress – void ratio – hydraulic conductivity relationships

2018 ◽  
Vol 55 (3) ◽  
pp. 414-426 ◽  
Author(s):  
Simon Dumais ◽  
Jean-Marie Konrad
Keyword(s):  
Heat Transfer ◽  
Hydraulic Conductivity ◽  
Effective Stress ◽  
Void Ratio ◽  
Moving Boundary ◽  
Initial Conditions ◽  
Large Strain ◽  
One Dimensional ◽  
Consolidation Theory ◽  
Thaw Consolidation

A one-dimensional model for the consolidation of thawing soils is formulated in terms of large-strain consolidation and heat-transfer equations. The model integrates heat transfer due to conduction, phase change, and advection. The hydromechanical behaviour is modelled by large-strain consolidation theory. The equations are coupled in a moving boundary scheme developed in Lagrangian coordinates. Finite strains are allowed and nonlinear effective stress – void ratio – hydraulic conductivity relationships are proposed to characterize the thawing soil properties. Initial conditions and boundary conditions are presented with special consideration for the moving boundary condition at the thaw front developed in terms of large-strain consolidation. The proposed model is applied and compared with small-strain thaw consolidation theory in a theoretical working example of a thawing fine-grained soil sample. The modelling results are presented in terms of temperature, thaw penetration, settlements, void ratio, and excess pore-water pressures.

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