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Quantitative aspects of mining induced seismicity in a part of the Welkom GoldfieldFerreira, Ricardo Isidro Loureiro January 1997 (has links)
A dissertation submitted to the Faculty of Science, University of the
Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of
Master of Scieuce in Geophysics . / Rockbursts continue to be one of the more high profile and problematic worker
hazards in the South African gold mining industry. Recent advances in the technology
of seismic monitoring systems and seismic data analysis and interpretation methods
hold considerable promise towards improving the success rate of rockburst control
measures. This study tests different methods for the evaluation of the response of
geological structures to mining induced stress changes.
A small part of Western Holdings Gold Mine in the Welkom goldfield -- the Postma
Area -- offers a challenge because of its geological complexity, accessibility and high
incidence of seismicity. The sensitivity of the local network to ground motions in this
area of interest and the expected spatial location accuracy is established and deemed
adequate for a detailed investigation of seismic activity. The local mining geometry,
geology and methods of mining are discussed. The fractured state of the rock mass
observed in situ, close to the stope faces, is in agreement with the results of numerical
elastic modelling and the high stresses inferred seismically. Almost immediately after
the incidence of a large event (ML 3.7) which occurred close to one end of a dyke, an
increased rate of seismic activity became apparent at another part of the same dyke,
some 250 m to the east. A change in the state of seismic stress, before and after the
large event, points to a transfer of stress along this geological discontinuity.
A quantitative analysis of recorded seismicity indicates spatial and temporal variations
in the state of stress and strain throughout the rock mass surrounding Mining
excavations. The elastic stress modelling performed routinely by rock mechanics
engineers in the deep gold mines is, by itself, incapable of catering for the rheological
nature of the rock mass, but taken together with independent seismic evaluations of a
fault orthogonal to a highly stressed dyke it is shown that both methods are mutually
complementary and can enhance the assessment of the seismic instability of the
structures. A back-analysis is conducted on ten large seismic events (ML> 2.5) to
identify precursors. These show that the timely recognition of high gradients in
physical seismic parameters pertaining to strain rate and stress in time and space
immediately prior to major seismic events is a real and practical possibility, as such
constituting an early warning mechanism. The fore-warning of a large event is best
served by an analysis of seismicity over the short term (weeks or days) through
time-history variations and/or contouring of various seismic parameters, although
long-term seismic responses (months or weeks) characterise specific patterns and
trends which are useful in the forecast. / AC2018
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The wasted years: a history of mine waste rehabilitation methodology in the South African mining industry from its origins to 1991Reichardt, Markus 01 August 2013 (has links)
A thesis submitted to the School of Animal, Plant and Environmental Sciences (APES), University of the Witwatersrand, Johannesburg, South Africa in fulfilment of the academic requirements for the degree of
Doctor of Philosophy
Johannesburg, February 2013 / Decades after the commencement of modern mining in the 1870s, the South African mining industry addressed the impacts associated with its mine waste deposits. In this, it followed the pattern its international peers had set. This study aims at chronicling, for the first time, the mining industry’s efforts to develop scientifically sound and replicable methods of mine waste rehabilitation. Mindful of the limitations in accessing official and public written sources for such an applied science, the study seeks to take a broader approach: It considers factors beyond pure experimental results (of which only patchy records exist), and considers the socio-economic context or the role of certain personalities, in an effort to understand the evolution of the applied technology between the 1930s until the passage of the Minerals Act in 1991. The bulk of this mine waste rehabilitation work during this period was done by the Chamber of Mines of South Africa and its members, the gold and (later) coal miners. The focus will therefore be on these sectors, although other mining sectors such as platinum will be covered when relevant.
Following decades of ad hoc experimentation, concern about impending legal pollution control requirements in the 1950s spurred key gold industry players to get ahead of the curve to head off further regulation. Their individual efforts, primarily aimed at dust suppression, were quickly combined into an industry initiative located within the Chamber of Mines. This initiative became known as the Vegetation Unit. Well resourced and managed by a dynamic leader with horticultural training – William Cook – the Unit conducted large-scale and diverse experiments between 1959 and 1963 to come up with a planting and soil amelioration methodology. The initial results of this work were almost immediately published in an effort to publicise the industry’s efforts, although Cook cautioned that this was not a mature methodology and that continued research was required. The Chamber of Mines, however, was trying to head off pending air quality legislation and in 1964/65, the organisation publicly proclaimed the methodology as mature and ready for widespread application. With this decision, the Unit’s focus shifted to widespread application while its ability to advance the methodology scientifically effectively collapsed in the 1960s and early 1970s.
In addition to this shift of focus and resources to application rather than continued refinement, the Unit was constrained by non-technical and non-scientific factors: Key among them was the industry’s implicit belief, and hope, that a walk-away solution had been found. The Unit’s manager Cook stood alone in driving its application and refinement for most of his time in that position. In his day-to-day work, he lacked an industry peer with whom to discuss rehabilitation results and he compounded this isolation through limited interaction with academia until very late in his career. This isolation was amplified by the lack of relevant technical knowledge among the company representatives on the committee tasked with the oversight of the Vegetation Unit: As engineers, all of them lacked not only technical understanding of the botanical and ecological challenge, some even questioned the legitimacy of the Unit’s existence into the 1980s. In addition, the concentration of all rehabilitation efforts in this single entity structurally curtailed the individual mining companies’ interest in the advancement of the methodology, creating a further bottleneck. Indeed, as late as 1973, the key metallurgy handbook covered mine waste rehabilitation only for information purposes, specifically stating that this was the responsibility of the Chamber’s Vegetation Unit alone.
To some extent, the presence of a champion within the Chamber – H. Claussen – obscured some of these challenges until the early 1970s. Indeed, the Unit had acquired additional scientific capacity by this stage, which gave it the ability to renew its research and to advance its methodology. That it failed to do so was mainly due to three factors coinciding: the retirement of its internal champion Claussen, a lack of succession planning for Cook, which left the Unit on ‘auto-pilot’ when he retired, and a rising gold price, which turned industry attention away from rehabilitation towards re-treatment of gold dumps.
During this period of transition in the mid 1970s, the Chamber’s approach was thus somewhat half-hearted and vulnerable to alternative, potentially cheaper, rehabilitation proposals such as physical surface sealing advanced by Cook’s eventual successor – Fred Cartwright. Though not grounded in any science, Cartwright’s proposal gained ascendance due to his forceful personality as well as the industry’s desire for an alternative to the seemingly open-ended costs associated with the existing rehabilitation methodology. During this time, the Chamber’s structures singularly failed to protect the industry’s long-term interests: The oversight committee for the Vegetation Unit, remained largely staffed by somewhat disinterested engineers, and relied heavily on a single individual to manage the Unit. Not only did the oversight committee passively acquiesce to Cartwright’s virtual destruction of the Unit’s grassing capacity, it also allowed him to stake the Chamber’s reputation with the regulator by championing an unproven technology for about five years. Only Cartwright’s eventual failure to gain regulator approval for his – still un-proven – technique led to a reluctant abandonment by the Chamber in the early 1980s.
Cartwright’s departure in 1983 left the Unit (and the industry) without the capacity to address mine waste rehabilitation, at a time when emerging environmental concerns were gaining importance in social and political spheres in South Africa and across the world. The Unit sought, unsuccessfully, to build alliances with nascent rehabilitation practitioners from the University of Potchefstroom. It furthermore failed to build mechanisms for sharing technical rehabilitation knowledge with fellow southern African or international mining chambers, leading to further stagnation of its method. At the same time, up-and-coming South African competitors such as the University of Potchefstroom seized the opportunity to enter the mine waste rehabilitation field as commercial players during the mid 1980s, at a time when the Unit had been reduced to grassing dumps for a single customer, the Department of Minerals and Energy Affairs (DMEA).
Using its status as a part of the Chamber of Mines, the Unit gradually regained its position of prominence through the development of industry guidelines for rehabilitation. Yet, it would never again occupy a position of pre-eminence in practical fieldwork, as industry players, academic capacities and commercial players entered the field in the mid-1980s in response to a growing environmental movement worldwide. When the passage of the Minerals Act in 1991 formally enshrined not merely rehabilitation but environmentally responsible mine closure in law, the Unit had been reduced to a prominent but no longer dominant player in this sector. This lack of pre-eminence ultimately caused the Unit to be among the first Chamber entities to be privatised when the Chamber began to restructure. This ended its role as a central driver of applied rehabilitation techniques for the South African mining sector once and for all. As this privatisation coincided with the broader opening up of South Africa’s society and economy after the unbanning of the ANC, there would never again be an entity (commercial or otherwise) that would dominate the rehabilitation sector as the Chamber’s Vegetation Unit had done in its day.
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Polygraph: a palimpsest pigment factory: a colour plant as a recording device for the sedimented scars on Johannesburg's mining landscapeVally, Sumayya 29 April 2015 (has links)
The mining that gave rise
to Johannesburg as a city
has left in its wake pieces
of geologically disturbed,
disused, and unusable
land. These leftover
fragments of landscape
carry with them, not
only memory of the city’s
foundations, but scars of
the mining processes that
now render them unusable
- Not only do these vaguescapes
have potential for
the memory within them to
be unearthed, but they
are highly polluted, and
seek to be reimagined as
productive city spaces.
The chosen site, an
abandoned piece of mineland
with a concealed old
mine shaft; on the edge of
a highway on the fringe of
the CBD, is simultaneously
highly visible to the
city, but forgotten to
it. Its positioning is
unique in that it allows
for the potential for
the extraction of the
mine pollutants and site
remediation to become a highly visible process.
Understanding and
uncovering layers and
traces of the site as means
of understanding what is
possible on this highly
polluted landscape became
an important architectural
and design generator. The
architecture consolidates
and reimagines the
fragments of ruin, both
physical and ephemeral,
contained on the site,
and curates the users
experience through these
forgotten traces. Its
programme - a colour plant,
which extracts useful
metallic colour pigments
from the contaminated
earth, becomes a visceral
reminder of these past
traces ;and a recording
device for the current
consequences of past
mining activity.
The approach is an almost
critical speculation. The
age of the picturesque
landscape is no more.
Our effects on the land have depleted the earth and
diseased its rhythms. But
these unstable consequences
hold possibilities that
can be engaged with
imaginatively; rather than
merely re-mediated. How can
architecture engage with
this instability?
The project accepts the
presence of rising acid
mine water; and imagines
a new reality emerging
from it. The project is a
comment on our own epoch;
one where waste, toxicity
and radiation are so
rife, that they are now a
quiet, sinister backdrop
to our world. More than
an apocalyptic future,
this project deals with a
dystopian present.
The precarious site
conditions pose questions
for an architecture
which can engage with
the instability, and not
merely withstand it. The
architectural concern is to
render visible and intensify
a consciousness of these traces, to investigate a
palimpsest infrastructure.
Colour, like architecture is
a link between the conscious
and the subconscious. It
is a mediator between
the realms. It holds
possibilities for suggesting
and molding atmospheres and
perceptions.
The architecture negotiates
all the realms, concerned
with past, present and
future.
It consolidates and makes
apparent the traces but it
is also developed with an
awareness that it becomes
part of these traces.
It is an intervention
which aims to heighten an
awareness of the presence
of the past in the life of
the city;
and also as palimpsest
infrastructure; as a
recording device for the
geological happenings of
the earth.
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A pre-feasibility study of the Kloof Eastern Boundary Area project, Kloof Gold MineGhoussias, Konstandinos January 2003 (has links)
Thesis ((M.Sc.) Engin))--University of the Witwatersrand, Faculty of Engineering & the Built Environment, School of Mining Engineering, 2003. / The ore reserves of the Kloof Sub Vertical Shaft operations are coming to
an end and as such, the Eastern Boundary Area mining operations, which
will extract the Ventersdorp Contact Reef ("VCR"), must be commissioned
to replace the diminishing reserves. Although feasibility studies have been
carried out on the eastern portion of the Kloof Gold Mine lease area, none
have been undertaken to investigate the potential benefits of including the
new mineral rights recently acquired from JCI. This project report is a prefeasibility
study into the potential value to Kloof of accessing and
extracting the resources of the Eastern Boundary Area.
This project report shows, using DCF analysis, that the Eastern Boundary
Area has potential to economically generate the additional reserves that will
be required to supplement Kloof s diminishing Three Shaft reserves. An
NPV and IRR are calculated for the project, the results of which support the
commissioning of further investigative work in order to obtain a better
understanding of the orebody and to generate results that are more accurate. Despite its popularity, traditional DCF analysis has fundamental
shortcomings, as do the commonly associated measures of NPV and IRR.
This project report identifies and reviews these shortfalls and comments on
methods to overcome these as far as practically possible.
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New models for borehole valuation of new mining operations and routine valuation of ore reserve blocksAssibey-Bonsu, Winfred January 2016 (has links)
This thesis proposes some new valuation models and procedures for
global and local ore reserve estimation.
To obtain efficient grade and tonnage estimates for global borehole
valuations of new gold mining properties, the appropriate spatial and
distributional models for the mineralisation are absolutely essential. [Abbreviated Abstract. Open document to view full version] / GR 2016
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Modelling of low temperature oxidation of coal dumps.Kaitano, Rufaro January 1998 (has links)
A dissertation submitted to the Faculty of Engineering,
University of the Witwatersrand, Johannesburg, for the
Degree of Master of Science. / storage and waste dumps from coal mining tend to
spontaneously combust. This is mainly as a result of the
oxidation process which is accelerated by the
availability of oxygen and the exothermic nature of the
oxidation process. In cases of poor ventilation the heat
accumulation within the bed is thought to lead to the
spontaneous combustion of coal.
The work in this dissertation aims to investigate the
change in oxygen concentration in a bed of coal and also
measure the rate of oxidation (oxygen absorption) in a
closed reactor under isothermal conditions. Drying rate
of coal under nitrogen was also looked into.
An analysis of the oxygen concentration profile in a
three metre 20 cm ID plastic column filled up with coal
has been carried out. As the coal ages (becomes oxidised)
its reactivity towards oxygen decreases and changes in
the oxygen concentration profile are noticed.
Experiments have been carried out up to 8 months and from
the results obtained, a simple pseudo-steady-state model
has been developed to describe the diffusion of oxygen
into a reacting coal bed. The findings could prove useful
in trying to find a solution to coal and waste dump fire
control.
The second experiment is a simple isothermal oxygen
absorption experiment in which the rate of absorption of
oxygen on a given coal sample is measured at different
initial concentrations of oxygen. The initial
concentration of oxygen is varied over a fairly wide
range in order to determine the dependence of the rate of
oxidation on the oxygen concentration. The rate- limiting
step in low temperature oxidation of coal is found to be
the absorption of oxygen.
Moisture also plays a role in coal oxidation. Drying
experiments were also carried out so as to quantify and
investigate the rate of loss of moisture. Models have
been developed which try to explain the mechanisms
involved in the drying process. The modelling suggest
that the bound water model is more appropriate to the
type of behaviour exhibited during the drying process / Andrew Chakane 2018
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Modelling of low temperature oxidation of coal dumps.Kaitano, Rufaro. January 1998 (has links)
A dissertation submitted to the Faculty of Engineering,
University of the Witwatersrand, Johannesburg, for the
Degree of Master of Science. / Storage and waste dumps from coal mining tend to
spontaneously combust. This is mainly as a result of the
oxidation process which is accelerated by the
availability of oxygen and the exothermic nature of the
oxidation process. In cases of poor ventilation the heat
accumulation within the bed is thought to lead to the
spontaneous combustion of coal.
The work in this dissertation aims to investigate the
change in oxygen concentration in a bed of coal and also
measure the rate of oxidation (oxygen absorption) in a
closed reactor under isothermal conditions. Drying rate
of coal under nitrogen was also looked into.
An analysis of the oxygen concentration profile in a
three metre 20 cm ID plastic column filled up with coal
has been carried out. As the coal ages (becomes oxidised)
its reactivity towards oxygen decreases and changes in
the oxygen concentration profile are noticed.
Experiments have been carried out up to 8 months and from
the results obtained, a simple pseudo-steady-state model
has been developed to describe the diffusion of oxygen
into a reacting coal bed. The findings could prove useful
in trying to find a solution to coal and waste dump fire control.
The second experiment is a simple isothermal oxygen
absorption experiment in which the rate of absorption of
oxygen on a given coal sample is measured at different
initial concentrations of oxygen. The initial
concentration of oxygen is varied over a fairly wide
range in order to determine the dependence of the rate of
oxidation on the oxygen concentration. The rate- limiting
step in low temperature oxidation of coal is found to be
the absorption of oxygen.
Moisture also plays a role in coal oxidation. Drying
experiments were also carried out so as to quantify and
investigate the rate of loss of moisture. Models have
been developed which try to explain tile mechanisms
involved in the drying process. The modelling suggest
that the bound water model is more appropriate to the
type of behaviour exhibited during the drying process. / Andrew Chakane 2018
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The geology of the Lily Syncline and portion of the Eureka Syncline between Sheba Siding and Louw's Creek Station, Barberton Mountain LandAnhaeusser, C R (Carl Robert) 16 September 2014 (has links)
No description available.
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Rib Cutting Resue Stoping, improvement on stoping rates and reduction in waste dilution compared with other known resue stoping methods on a Free State gold mineScholtz, Alwyn January 2018 (has links)
Mining of the Basal Reef at Jeanette Mine, is typically complicated due to an overlaying Khaki Shale (shale) that has unfavourable rock engineering properties. Shale has always been either left underground or mined as part of the orebody. The first approach can only be applied in areas where the quartzite beam (directly above the Basal Reef and below the shale) is of sufficient thickness to support the shale in the hanging wall. This method is known as undercutting. Alternatively, open stoping can be applied in areas where the shale and the Basal Reef is extracted concurrently and sent to the mill as diluted ore.
Alternatively, a resue stoping method can be considered in areas where undercutting cannot be done, due to a thin quartzite middling. Resue stoping involves stowing or packing of the shale into the mined-out area and is not included as part of the hoisted rock. In the past, resue stoping was done by hand packing, which is unsuitable for a modern mine. As such, two mechanised resue stoping methods can be considered, namely; Longhole Resue Stoping and Rib Cutting Resue Stoping.
Rib Cutting Resue Stoping utilises a continuous miner (“CM”) to remove the shale in a first pass, extract the reef during a second pass and backfilling the mined-out rib with shale. The use of a CM will significantly improve the extraction/mining rate, sidewall stability, backfill placement, dilution and overall safety.
Longhole Resue Stoping utilises strike drives from where longholes are drilled into the shale and the reef in an up-dip direction moving on retreat. The shale is blasted with sufficient force into the mined-out area behind it, compacting it. The reef will be loaded by Load Haul Dumper (“LHD”) or dozer.
It was determined that Rib Cutting Resue Stoping is more effective than Longhole Resue Stoping due to a higher extraction rate, lower dilution, reef loss reduction and improved shale sidewall stability. The operating angles and equipment height limits the application to only 51% of the available reef at Jeanette mine with favourable dip and thickness. Longhole Stoping can navigate hard rock, shale and increased dip angles; it can be applied to 91% of the available ore deposit.
Longhole Resue Stoping and Rib Cutting Resue Stoping should both be considered as suitable stoping methods for Jeanette. / Thesis is submitted in partial fulfilment for the degree of Master of Science in Engineering to the Faculty of Engineering and the Built Environment, School of Mining Engineering, 2018 / XL2019
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Understanding operation Chikorokoza Chapera : the political ecology of 'formalising' Zimbabwe's gold and diamond mining sectors, 2006-2012Spiegel, Samuel Jason January 2014 (has links)
No description available.
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