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Acid mine drainage prediction techniques and geochemical modelling: case study on gold tailing dams, West Rand, Witwatersrand basin area, South AfricaWu, Changhong January 2021 (has links)
Doctor Scientiae / Acid Mine Drainage (AMD) is identified as one of the contributors to
environmental hazard in the gold mining region of South Africa, as caused by the
mining operational activities performed by mining industries in South Africa. This
effect motivates the development of AMD prediction techniques application and
geochemistry modelling using gold tailing dams located in West Rand area,
Witwatersrand Basin as a case study. Control strategies are devised to assess,
understand and measure the acidic potential generation of waste materials in
ensuring the right method required to analyse risks caused by AMD to environment.
The method encompasses mineralogical and geochemical analysis of 93 samples
collected, AMD prediction, test modification and geochemical modelling. This
method was appropriately applied to understand the basic mechanisms involved in
controlling acid generation, assessing prediction procedure and selecting the right
prediction tools.
Study objectives are attained by performing a series of experimental lab tests on the
samples collected from the two major tailing dams (Mogale and Gold One_1
tailings). Results derived from the lab experiments (XRD and SEM-EDS) show
presence of mineral phases characterised with the surface feature of samples, and
unknown substances of samples were identified. Geochemical characterisation was
performed by XRF and ICP-MS to determine the major oxides elements and trace
elements, respectively. Leco test generate total sulphur and total carbon. Multistatistical
analysis is used to interpret the data derived from geochemical
characterisation process to explicate the metal and trace elements distribution and
occurrence. Initial samples were screened and categorised based on paste pH and
EC using kinetic tests to determine acid-forming and neutralising minerals in
samples and static tests to determine acid generation potential in samples.
Net Acid Producing (NAPP) was mathematically calculated from Acid Neutralising
Capacity (ANC), Maximum Potential Acidity (MPA) and total Sulphur. Results obtained from the Paste pH demonstrate that samples collected from 1 meter
downward the holes to 10 meters, with a few meters samples in hole T003 at Gold
One_1 are non-acidic while the remaining tailing samples are acidic. ANC/MPA
ratio was applied to assess the risk of acid generation from mine waste materials.
Graphical illustrations of the Acid Base Account (ABA) are plotted to demonstrate
the net acidic generation potential trends of samples, which were classified into
non-acid forming, potential acid forming and uncertain categories. Results
integration between ANC, Single Addition Net Acid Generation (NAG) test and
NAPP were used to classify acid generation potential of the samples. Leachate
collected from leaching column test were analysed for pH, EC and chemical
element by ICP-MS. The leaching column test used to analyse samples (T004) and
(T001) collected from the two major tailings was set up for a 4-month experiment.
Study findings present environmental assessment report on the two investigated
gold tailing dams in Witwatersrand Basin area. Other findings are improved
understanding of the application and limitations of various existing AMD prediction
methods for assessment of gold mine waste and conceptual geochemical modelling
developed to test appropriate methodology for AMD potential at a given gold mine
site.
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[en] BEHAVIOUR OF AN EXPERIMENTAL LANDFILL OVER A GOLD TAILINGS DEPOSIT PARACATU MINING CO / [pt] COMPORTAMENTO DE UM ATERRO EXPERIMENTAL SOBRE UM DEPÓSITO DE REJEITOS DE OURO: MINERAÇÃO PARACATUGERMAN LUIS GONZALES MAMANI 05 September 2013 (has links)
[pt] Em projetos de barragens de rejeitos de mineração, normalmente existe uma
grande preocupação relacionada aos aspectos construtivos e de segurança, em
função do processo de lançamento de material sobre depósitos fofos de rejeitos
saturados. Os maiores desafios consistem na avaliação da resistência e da
deformabilidade do material de fundação, na possibilidade de ocorrência de
liquefação, e no desenvolvimento e velocidade de dissipação das poropressões.
Neste contexto, a Rio Paracatu Mineração (RPM) construiu um aterro
experimental instrumentado em grande escala,com material de empréstimo
siltoarenoso sobre o depósito de rejeito na Mina do Ouro. Este aterro
experimental foi projetado e construído com 10,0 m de altura, talude frontal de
1,5H:1,0V e um talude suave com uma berma de estabilização de 4,0 m de altura
no talude oposto. A fundação do aterro foi instrumentada com piezômetros
elétricos de corda vibrante, inclinômetros e placas de recalque. Além da
instrumentação de campo, há uma base de dados de ensaios de laboratório
realizados nas universidades de Viçosa (UFV), São Carlos (USP/SC) e PUC-Rio.
Todos estes dados permitem a caracterização do material do rejeito, além da
determinação de parâmetros de resistência, deformabilidade, permeabilidade e
adensamento. O objetivo desta Tese é contribuir para uma melhor compreensão
do comportamento de barragens de rejeitos de mineração com base nas evidências
laboratoriais e na retroanálise do comportamento do aterro experimental de larga
escala. Para tanto, foi realizada a simulação numérica do processo construtivo do
aterro experimental, buscando-se o modelo constitutivo e os parâmetros mais
adequados para a representação do comportamento de solos granulares saturados.
As análises numéricas foram executadas com o programa computacional Plaxis V11, de elementos finitos. Uma vez reproduzido o comportamento do aterro
experimental, procedeu-se à previsão dos recalques e deslocamentos horizontais
da barragem de ouro da Rio Paracatu Mineração. Os resultados mostraram que o
modelo Hardening Soil permitiu a reprodução do comportamento do aterro
experimental durante as etapas construtivas. A boa seleção de parâmetros, com
base em um extenso programa experimental, permitiu a previsão do
comportamento da barragem principal. / [en] In projects of mining tailings dams, there is usually a big concern and
constructive aspects related to security, according to the release process of
material on saturated tailings deposits cute. The biggest challenges consist in
evaluating the strength and deformability of the foundation material, the
possibility of liquefaction and speed the development and dissipation of
poropressures. In this context, the Rio Paracatu Mineração (RPM) built an
instrumented experimental landfill on a large scale, with sandy silty material loan
on the deposit of waste in the Gold Mine. This experimental landfill was designed
and constructed with 10.0 m height, front slope of 1.5 H: 1.0 V and a gentle slope
with a stabilizing berm of 4.0 m high on the slope opposite. The foundation of the
embankment was instrumented with vibrating string electric piezometers,
inclinometers and settlement plates. Besides the instrumentation field, there is a
database of laboratory tests conducted at the Universities of Viçosa (UFV), San
Carlos (USP / SC) and PUC-Rio. All these data allow the characterization of
tailings material, besides the determination of parameters of resistance,
deformability, permeability and density. The goal of this dissertation is to
contribute to a better understanding of the behavior of mining tailings dams based
on laboratory evidence and backcalculation behavior of large-scale experimental
landfill. Therefore, we performed a numerical simulation of the construction
process of the experimental landfill, seeking the constitutive model and
parameters best suited to represent the behavior of granular soils saturated. The
numerical analyzes were performed with the computer program Plaxis V11, finite
elements. Once reproduced the experimental behavior of the landfill, proceeded to
the prediction of settlements and horizontal displacements of the dam the Rio
Paracatu gold mining. The results showed that the model Hardening Soil allowed
playback behavior of the experimental landfill during the construction stages. A good selection of parameters based on an extensive experimental program allowed
the prediction of the behavior of the main dam.
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The relationship between void ratio and shear wave velocity of gold tailingsChang, Hsin-Pei Nicol 07 June 2005 (has links)
South Africa, as one of the world’s largest gold producing countries, also generates large amounts of tailings. These tailings are disposed in tailings dams, which pose great threat to the environment in the case of failure, in particular, liquefaction. In order to evaluate the potential of liquefaction, the void ratio of the tailings is required and is often impossible to obtain. Seismic methods allow an indirect method to estimate void ratio of in situ deposits of which tailings are examples of. Currently, the use of seismic methods to estimate void ratio of tailings rely on shear wave velocity – void ratio relationships derived for sands. It is thus uncertain whether this relationship holds for gold tailings, which is classified as a sandy silt or silt. The measurement of shear wave velocity of tailings is done in the laboratory using a triaxial apparatus modified to accommodate bender element. Shear wave velocities are measured using wide square pulses and continuous sinusoidal waves. The results show that there is a near linear relationship between void ratio and shear wave velocity normalized against effective stress. The position of this relationship lies below the previously published results for sands. Shear wave velocity of gold tailings is more sensitive to changes in effective stress than changes in void ratio or over-consolidation ratio. Furthermore, using phase sensitive detection of continuous waves, we can conclude that shear wave velocity of gold tailings is also frequency dependent. / Dissertation (MEng)--University of Pretoria, 2006. / Civil Engineering / MEng / Unrestricted
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Geochemical monitoring of soil pollution from the MWS-5 gold tailings facility on the Farm Stilfontein / Angelique DaniellDaniell, Angelique January 2015 (has links)
The rehabilitation and restoration of degraded landscapes adjacent to gold tailings disposal facilities (TDFs) that have suffered loss of efficiency through anthropogenic forces has become a primary concern to environmental sciences and management in recent decades. Due to the lack of environmental legislation and enforcement thereof, minimal surface rehabilitation took place on the Mine Waste Solutions (MWS) No. 5 TDF prior to 1992, a commonplace occurrence in South Africa at the time.
In 2000, MWS intervened and committed to the rehabilitation of the entire site with profits generated by the reprocessing (extraction of residual gold and uranium) of certain TDFs. However, the adjacent grazing land north of the MWS No. 5 TDF had already been subjected to pollution from the TDF which resulted in a pollution plume on the land.
Although it has been inactive since April 2011, the pollution plume can be seen from the north-eastern corner of MWS No. 5 TDF, with a north-eastern/south-western direction on the farm Stilfontein. During dry periods, significant amounts of sulphate salts accumulate on the soil surface on the farm Stilfontein over a distance of at least 3.5 km from the TDF. The presence of sulphate salts in association with gold TDFs is highly common but not particularly common, in the chert-poor dolomites of the Oaktree Formation itself, in which the presence of sulphate salts is a rarity.
The primary concern of this study was to determine both the quantitative and extent of the pollution observed on the farm Stilfontein over a period of 30 months via monthly monitoring of the different soil geochemical assessments across twelve fixed points, and quarterly interval assessments of three transect lines. In addition, the study was also concerned with the identification of potential linear structure anomalies associated with the pollution plume and weathered zones (fractures, joints and cavities) in the Oaktree Formation dolomites. These zones may be associated with, or may result in, the pollution extending over the area despite a topography as well as geological dip and strike that is adverse.
These features and weathered zones create pathways for groundwater to flow and it was anticipated that, if present, these anomalies and weathered zones may be primary contributing factors to the pollution plume forming in a north-easterly direction and extending over the farm Stilfontein. The MWS No. 5 TDF has a hydraulic pressure head of approximately 40 m; the elevations of the north-eastern corner of the TDF and fixed point (FP) 8 (the farthest FP from the TDF) are 1368 m and 1360 m respectively, falling in close range of each other. It is anticipated that as the TDF material dries, the phreatic water level inside the TDF will lower; causing the pressure exerted by the hydraulic head of the TDF to lower over time, which will eventually end the pollution process on the soil.
This study discusses the results of a holistic approach towards the evaluation of soil, vegetation and water pollution by utilizing soil quality parameters and indicators, geohydrology, geophysical surveys, Landscape Function Analysis (LFA) and other means of vegetation assessments.
Salt accumulation on the soil surface was common in specific areas from 2010 – 2012. X ray diffraction (XRD) analyses confirmed that the salts originated from the No. 5 TDF due to the similarity in mineralogy.
The pH values from the start of the 30-month monitoring period remained neutral to slightly alkaline due to the neutralising effect of the dolomitic bedrock. The electrical conductivity (EC) values of the soil decreased significantly from 2010 to 2014; during dry seasons since 2012, no sulphate salts accumulated on the soil surface. Joints, fractures and cavities were found within the bedrock dolomites which created pathways for the polluted TDF water and groundwater to flow towards the study area.
It was also established that there were no adverse effects on the natural vegetation, other than encroachment by Seriphium plumosum which affected the grazing quality (overgrazed sites) of the area. It was therefore concluded that after the TDF became dormant in April 2011, the pollution plume in this area is decreasing in magnitude and severity due the lowering of the phreatic water level inside the TDF to significantly lower levels. Consequently, the decrease of the hydraulic pressure head of the TDF as well as rainwater infiltration and high percolation due to the presence of fractures, joints and cavities in the dolomites resulted in the leaching of the sulphate salts to a significant extent. It was also concluded that while there were no apparent adverse effects of the pollution on the functionality of the land, additional monitoring and maintenance would be required for at least the next five years in order to ensure the continuance of current conditions. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2015
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Geochemical monitoring of soil pollution from the MWS-5 gold tailings facility on the Farm Stilfontein / Angelique DaniellDaniell, Angelique January 2015 (has links)
The rehabilitation and restoration of degraded landscapes adjacent to gold tailings disposal facilities (TDFs) that have suffered loss of efficiency through anthropogenic forces has become a primary concern to environmental sciences and management in recent decades. Due to the lack of environmental legislation and enforcement thereof, minimal surface rehabilitation took place on the Mine Waste Solutions (MWS) No. 5 TDF prior to 1992, a commonplace occurrence in South Africa at the time.
In 2000, MWS intervened and committed to the rehabilitation of the entire site with profits generated by the reprocessing (extraction of residual gold and uranium) of certain TDFs. However, the adjacent grazing land north of the MWS No. 5 TDF had already been subjected to pollution from the TDF which resulted in a pollution plume on the land.
Although it has been inactive since April 2011, the pollution plume can be seen from the north-eastern corner of MWS No. 5 TDF, with a north-eastern/south-western direction on the farm Stilfontein. During dry periods, significant amounts of sulphate salts accumulate on the soil surface on the farm Stilfontein over a distance of at least 3.5 km from the TDF. The presence of sulphate salts in association with gold TDFs is highly common but not particularly common, in the chert-poor dolomites of the Oaktree Formation itself, in which the presence of sulphate salts is a rarity.
The primary concern of this study was to determine both the quantitative and extent of the pollution observed on the farm Stilfontein over a period of 30 months via monthly monitoring of the different soil geochemical assessments across twelve fixed points, and quarterly interval assessments of three transect lines. In addition, the study was also concerned with the identification of potential linear structure anomalies associated with the pollution plume and weathered zones (fractures, joints and cavities) in the Oaktree Formation dolomites. These zones may be associated with, or may result in, the pollution extending over the area despite a topography as well as geological dip and strike that is adverse.
These features and weathered zones create pathways for groundwater to flow and it was anticipated that, if present, these anomalies and weathered zones may be primary contributing factors to the pollution plume forming in a north-easterly direction and extending over the farm Stilfontein. The MWS No. 5 TDF has a hydraulic pressure head of approximately 40 m; the elevations of the north-eastern corner of the TDF and fixed point (FP) 8 (the farthest FP from the TDF) are 1368 m and 1360 m respectively, falling in close range of each other. It is anticipated that as the TDF material dries, the phreatic water level inside the TDF will lower; causing the pressure exerted by the hydraulic head of the TDF to lower over time, which will eventually end the pollution process on the soil.
This study discusses the results of a holistic approach towards the evaluation of soil, vegetation and water pollution by utilizing soil quality parameters and indicators, geohydrology, geophysical surveys, Landscape Function Analysis (LFA) and other means of vegetation assessments.
Salt accumulation on the soil surface was common in specific areas from 2010 – 2012. X ray diffraction (XRD) analyses confirmed that the salts originated from the No. 5 TDF due to the similarity in mineralogy.
The pH values from the start of the 30-month monitoring period remained neutral to slightly alkaline due to the neutralising effect of the dolomitic bedrock. The electrical conductivity (EC) values of the soil decreased significantly from 2010 to 2014; during dry seasons since 2012, no sulphate salts accumulated on the soil surface. Joints, fractures and cavities were found within the bedrock dolomites which created pathways for the polluted TDF water and groundwater to flow towards the study area.
It was also established that there were no adverse effects on the natural vegetation, other than encroachment by Seriphium plumosum which affected the grazing quality (overgrazed sites) of the area. It was therefore concluded that after the TDF became dormant in April 2011, the pollution plume in this area is decreasing in magnitude and severity due the lowering of the phreatic water level inside the TDF to significantly lower levels. Consequently, the decrease of the hydraulic pressure head of the TDF as well as rainwater infiltration and high percolation due to the presence of fractures, joints and cavities in the dolomites resulted in the leaching of the sulphate salts to a significant extent. It was also concluded that while there were no apparent adverse effects of the pollution on the functionality of the land, additional monitoring and maintenance would be required for at least the next five years in order to ensure the continuance of current conditions. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2015
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