68 research outputs found
Dewatering of Mine Tailings Slurries Using Superabsorbent Polymers (SAPs) Reclaimed from Industrial Reject of Baby Diapers: A Preliminary Study
Traditional deposition of tailings slurry in a tailings storage facility (TSF) can create risks of dike failure. In order to minimize these risks and slurry spillage, the surface deposition technique of densified tailings (DT) through dewatering of the slurry has emerged. The DT technique has the potential to maximize water reuse, improve the shear strength of surface tailings, and reduce the ecological footprint of TSF. The consistency of DT covers a continuum ranging from thickened state, to paste state, to dry state. Despite its efficiency and economic feasibility, DT densification using thickeners sometimes proves unable to achieve the design target solids mass concentration (Cw%). Hence, the use of superabsorbent polymers (SAPs) seems to represent a promising alternative, owing to their higher water absorbent capacity. In this paper, superabsorbent polymers (SAPs) reclaimed from industrial reject of baby diapers (Na-polyacrylates) are explored as a promising alternative to mine tailings slurries dewatering. To this end, laboratory-scale dewatering tests have been performed using two grades of Na-polyacrylate SAPs (grade 1 SAP = SAG-A06P coarse-grained, and grade 2 = SAG-M01P-100 medium-grained) for the tailings slurries densification. A higher water absorbency (or swelling capacity) was observed using the coarser SAPs (SAG-A06P) compared to the finer SAPs (SAG-M01P-100). The preliminary results showed that a SAP volume dosage in the range 10–13 kg of SAP/m3 of slurry allowed achieving a final solids mass concentration (Cw%_final) ≥ 70%, despite the occurrence of gel-blocking phenomenon
Oxygen diffusion and consumption in unsaturated cover materials
Résumé: Dans plusieurs problèmes de géotechnique environnementale, les ingénieurs doivent analyser des
situations d’écoulement simultané d’eau et de
gaz. C’est typiquement le cas lorsque des
couvertures en sol sont conçues pour des sites
d’entreposage de rejets. Étant placés bien au-
dessus de la surface phréatique, les matériaux de
recouvrement sont non saturés, et ils peuvent
permettre à des composés gazeux (tels que l'air et
le méthane) d’entrer ou de s’échapper du site.
Comme c’est le cas avec l’eau, le flux de gaz doit habituellement être contrôlé par le
recouvrement. Une application particulière à cet
Ă©gard concerne les couvertures construites pour
limiter le flux d’oxygène vers les résidus miniers sulfureux, qui peuvent générer un lixiviat acide.
Dans cet article, les auteurs présentent une a
pproche pour évaluer ce flux et les paramètres de
contrĂ´le, incluant le coeffi
cient de diffusion effectif
D
e
et le coefficient du taux de réaction (ou de
consommation)
K
r
. Un procédé expérimental pour la mesure simultanée de ces deux paramètres
en laboratoire est décrit, et une procédure d’in
terprétation avec quelques résultats d'essais sont
présentés. Des solutions analytiques sont de
plus dĂ©veloppĂ©es pour calculer le flux d’oxygène Ă
travers des systèmes de recouvrement. Ces solu
tions sont comparées aux résultats obtenus d'un
traitement numérique des lois de Fick modifiées
. Diverses applications spécifiques de la méthode
de conception des barrières à l'oxygène sont présentées et discutées. ---------- Abstract: In many environmental geotechnique problems, engineers must analyse situations where water
and gas can move simultaneously. Such is typica
lly the case when soil covers are designed for
waste disposal sites. Being located well a
bove the phreatic surface, cover materials are
unsaturated and may allow gaseous compounds (such
as air and methane) to
flow in or out from
the disposal facilities. As is the case for water, the flow of gas must usually be controlled by the
cover. A particular application in that rega
rd relates to covers built to limit oxygen flux to
reactive sulphidic tailings, which can be the source of an acidic leachate. In this paper, the
authors present an approach to evaluate the oxygen flux with the controlling parameters,
including the effective diffusion coefficient
D
e
and the reaction (consumption) rate coefficient
K
r
.
An experimental procedure to determine these
two parameters simultaneously during laboratory
experiments is described, and sample results
are presented with the proposed interpretation.
Analytical solutions are further developed to
calculate oxygen flux through cover materials. The
proposed solutions are compared to calculation
results ensuing from a numerical treatment of
modified Fick’s laws. A vari
ety of specific applications of the method for designing oxygen
barriers are also presented and discussed
Predicting the Unsaturated Hydraulic Conductivity of Granular Soils From Basic Geotechnical Properties Using the Modified Kovacs (Mk) Model and Statistical Models
Apport des mesures en continu des teneurs en eau et des succions à la compréhension du fonctionnement hydrogéologique d'une couverture avec effet de barrière capillaire
Oxygen consumption test to evaluate the diffusive flux into reactive tailings: Interpretation and numerical assessment
Mine Backfilling in the Permafrost, Part II: Effect of Declining Curing Temperature on the Short-Term Unconfined Compressive Strength of Cemented Paste Backfills
When cemented paste backfill (CPB) is used to fill underground stopes opened in permafrost, depending on the distance from the permafrost wall, the curing temperature within the CPB matrix decreases progressively over time until equilibrium with the permafrost is reached (after several years). In this study, the influence of declining curing temperature (above freezing temperature) on the evolution of the unconfined compressive strength (UCS) of CPB over 28 days’ curing is investigated. CPB mixtures were prepared with a high early (HE) cement and a blend of 80% slag and 20% General Use cement (S-GU) at 5% and 3% contents and cured at room temperature in a humidity chamber and under decreasing temperatures in a temperature-controlled chamber. Results indicate that UCS is higher for CPB cured at room temperature than under declining temperatures. UCS increases progressively from the stope wall toward the inside of the CPB mass. Under declines in curing temperature, HE cement provides better short-term compressive strength than does S-GU binder. In addition, the gradual decline in temperature does not appear to affect the fact that the higher the binder proportion, the greater the strength development. Therefore, UCS is higher for samples prepared with 5% than 3% HE cement. Findings are discussed in terms of practical applications
Discussion on "Effects of different drying rates on shrinkage characteristics of a residual soil and soil mixtures" by Henry Krisdani, Harianto Rahardjo, Eng-Choon Leong [Engineering Geology 102 (2008) 31-37]
Measurement and Prediction of the Oxygen Diffusion Coefficient in Unsaturated Media, With Applications to Soil Covers
Modification of the predictive MK model to integrate hysteries of the water retention curve
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