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Feasibility of thin seam coal mining at Dorstfontein Coal Mine by Petrus C. Meyer June 2003 © University of Pretoria
Feasibility of thin seam coal mining at Dorstfontein Coal Mine by Petrus C. Meyer treatise submitted in fulfillment of a part of the requirements for the
MASTER OF SCIENCE (EARTH SCIENCE PRACTICE AND MANAGEMENT)
in the Department of Geology Faculty of Natural and Agricultural Sciences University of Pretoria Study leader: Prof. H.F.J. Theart June 2003 2
© University of Pretoria
ACKNOWLEDGEMENTS Vir my as Christenmens is dit onmoontlik om te glo dat ek aileen die vermoens gehad
het om die kursus te voltooi. Sonder die verstandelike gawes uit die hand van my
Skepper, die verfossing deur Jesus se bloed en die krag van die Heilige Gees sou dit
onmoontlik gewees het om te volhard. Dankie Here.
I would like to pay my sincere gratitude to the following people who have contributed
in one way or another to the successful completion of this degree and in the writing of
this treatise.
1. To my wife and children. The most motivation and encouragement came from my
wife and I am etemally grateful for her support over the past two and a half years.
Although the children did not understand what it was all about, they missed me as
much as I have missed them during the blockweeks and examination weeks. I will
need to find a way to make up for my absence in the evenings and over
weekends.
2. Total Coal South Africa(Pty) Ltd for allowing me this opportunity to enrich myself
with knowledge and to become a better employee. for the time off, the sponsoring
of this course and the supply of the data needed for this treatise.
3. Prof. Hennie Theart for his guidance and advice on the compilation of this
treatise.
4. Gotz Bartkowiak for the use and supply of some tables, figures as well as the
time off from work to attend the blockweeks.
5. Kierie Krugel for his mentorship and help in the mining sections
6. John Smith for all the help and advice with the financial model.
7. Mike Spengler for making available the section on the rock mechanics and proof
reading this paper.
S. Willie van Zyl for his help on the ventilation section and making available some
figures for the mining chapter.
9. Duncan Saunderson and Brian Roberts for proof reading the first draught.
3
ABSTRACT Dorstfontein Coal Mine is situated in the northern limb of the Highveld Coalfield. The
mine is currently owned by Total Coal South Africa Ltd (Pty). Mining to date has
taken place where the seam heights are in the excess of 1.5 m with an average
height of 1.9m. Some areas have been identified where the seam heights ranges
between 1.2 and 1.4m with an average
heigllt cf 1.32m. The in situ tonnage of the
thin seam areas is 7.06mil. tons.
The thin seam coal quality is very good and product yield at an ash content of 13.5%
is 95.7% and at a cut density of 1.6 the yield is 89.2% (Air dry basis).
The largest thin seam coal producer in the world is the U.S.A. followed by the
former U.S.S.R. Other countries that produced coal from thin seams are mainly
from Europe.
In the Republic of South Africa most of the thin seam coal mining was
concentrated in the KwaZulu-Natal province. Most of the larger mines are now
defunct but some small mines are still operating.
The risks involved in thin seam coal mining differ from that of thicker seam
mining. There are occupational diseases associated specifically with thin seam
coal mining. The most pronounced geological risks are changes in seam heights,
changes in coal quality, in-seam partings and unpredicted dolerite intrusions.
At Dorstfontein Mine a newly developed German Wirth Paurat thin seam
continuous miner is been tested. Some Stamler BH10 thin seam battery haulers
were introduced to the section to haul the coal from the face to the tip.
There are some advantages in mining the thin seam coal. The increase in yields,
savings in belt replacement, less handling of stone and the extension of the life of
mine are some of the major benefits.
4
For the financial evaluation it was assumed that 30% of the run of mine tons will
come from the thin seam r1IJkource. All Capex and Opex costs were allocated pro rata
at a 30% basis. The productim'r rate was based on current experience and the
assumption that this section will reach its completion at the same time as the mine
closes. The run of mine tons (RO.M.) are 3.53mil. tons which is 50% (70%
extraction, 10% mining loss, 10% geological loss) of the in situ resource of 7.06mil.
tons. For 10 years at an average daily production of 1400 tons per day, a total
RO.M. of 3,514mil. tons could be achieved, which relates to 99.55% extraction of the
in situ RO.M. tons.
Capital expenditure is minimal and many sunk costs are excluded from the model.
The main Capex item is the Wirth Paurat. The N.PV. for the project is R 27,206 mil.
at a discount rate of 15% and the corresponding I.RR is 305.2%. The distorted
I.RR is related to the small but realistic capital input.
Sensitivity analyses were performed for Operating Costs, Selling Prices (Export and
Domestic), Yield and Production. The project is the most sensitive for selling prices,
and operating costs.
5
TABLE OF CONTENTS List of tables.
P.9
List of figures.
P. 10
Introduction.
P.12
1.1.
Definitions and terms.
P.12
1.2.
The problem and its settings.
P. 14
1.3.
Hypotheses.
P.15
1.4.
Delimitations.
P. 15
1.5.
Assumptions.
P.16
1.6.
Research methodology.
P. 16
Chapter 2:
Review of related material.
P. 17
Chapter 3:
Geology of the No.2 Seam.
P.22
Introduction.
P.22
Chapter 1:
3.1.
3.1.1.
General.
P.22
3.1.2.
Topography and land usage.
P.27
3.1.3.
Mineral rights.
P.27
3.2.
Exploration.
P.29
3.3.
Stratigraphy.
P.30
3.4.
No.2 Seam and No.2 Lower Seam.
P.34
3.4.1.
Seam splitting.
P.34
3.4.2.
Seam elevation.
P.34
3.4.3.
Seam thickness.
P.34
3.4.4.
Main parting.
P. 35
3.4.5.
Seam roof.
P.41
3.4.6.
Seam floor.
P.41
3.5.
Dolerite intrusions.
P.41
3.6.
Resources and grade.
P.44
6
3.7.
3.6.1.
Summary of Resources and Grade.
P.44
3.6.2.
Thin seam resource limits.
P.46
Seam quality.
P.48
3.7.1.
General.
P.48
3.7.2.
Qualities.
P.48
3.7.3.
3.7.2.1.
Yield.
P.49
3.7.2.2.
Calorific Value.
P.49
3.7.2.3.
Volatile Matter.
P.49
3.7.2.4.
Sulphur.
P.49
3.7.2.5.
Phosphorus.
P.49
Additional Analysis.
P. 50
Previous and current mining methods.
P.51
4.1.
Introduction.
P.51
4.2.
Mining method and equipment.
P.51
Chapter 4:
4.2.1
4.3.
Chapter 5:
General.
P.51
4.2.2 Continuous Miner Section.
P. 52
4.2.3 Conventional Drill and Blast Section.
P.56
4.2.4 Stone Work Team.
P.57
Risks.
P. 58
4.3.1.
Geological.
P.58
4.3.2.
Production.
P.59
4.3.3.
Safety.
P.59
4.3.4.
Costs.
P.59
Thin seam resources.
P.61
5.1.
International.
P.61
5.2.
Republic of South Africa.
P.64
Risks associated with thin seam mining.
P. 71
6.1.
Geological.
P. 71
6.2.
Mining accidents.
P. 72
Chapter 6:
7
6.3.
Health and Safety. P. 76
6.4.
Production rate and costs.
P. 77
Current thin seam mining trial. 7.1.
Continuous Miner and Battery Haulers. P. 79
P. 79
7.2.
Ventilation. P.81
7.3.
Rock mechanics. P.83
Chapter 7:
7.3.1.
Split-seam parting tests and results.
7.3.2. Support pattern and cutting sequence.
7.4.
P.83
P.83
Advantages of thin seam coal mining.
P. 84
Economics of thin seam mining. P. 88
8.1.
Introduction. P.88
8.2.
Notes on the Financial Model. P.88
8.3.
Sensitivity analysis. P.95
8.4.
Shortcomings. P.97
Summary, conclusions and recommendations.
P.99
Chapter 8:
Chapter 9:
References.
P.104
Annexures.
P. 107
8
LIST OF TABLES Table 1.
Float fractions and qualities used in a washtable.
P. 13
Table 2.
Resources for the No.2 Thin Seam area.
P.44
Table 3.
Average washtable for the No.2 Thin Seam area.
P.45
Table 4.
Thin seam definition in various countries.
P.61
Table 5.
Thin seam output as percentage of total coal output.
P.62
Table 6.
Distribution of thin coal seams in the U.S.A.
P.63
Table 7.
Some defunct collieries in KwaZulu-Natal.
P.69
Table 8.
Active collieries in KwaZulu-Natal.
P. 70
Table 9.
N.P.v. and I.RR at different product bases.
P.92
Table 10. The N.P.v. for the product bases at different discount rates.
P.93
Table 11. Sensitivity of the N.PV. to certain parameters.
P.95
Table 12. Sensitivity of the I.RR to certain parameters.
P.96
Table 13. Cash flow.
P. 101
9
LIST OF FIGURES Fig. 3.1.
Coalfields of South Africa.
P.24
Fig. 3.2.
Coalfield Boundaries and Coal Mines of the Highveld Coalfield.
P.25
Fig. 3.3.
locality Plan and Mineral Rights.
P.26
Fig. 3.4.
Surface Topography and Borehole Plan.
P.28
Fig. 3.5.
General Stratigraphic log.
P.32
Fig. 3.6.
North-South cross-section of the Dorstfontein Deposit.
P.33
Fig. 3.7.
No.2 Seam and No.2 Seam seam-split parting.
P.36
Fig. 3.8.
Seam-Split Parting Position and Thickness.
P. 37
Fig. 3.9.
Base elevation of the No.2 Seam.
P. 38
Fig. 3.10. Total Thickness of the No.2 Seam, including Seam-Split Parting.
P.39
Fig. 3.11. Mineable Seam Thickness of the No.2 Thin Seam.
P.40
Fig. 3.12. Dolerite Positions.
P.43
Fig. 3.13. Tonnage distribution against seam heights.
P.44
Fig. 3.14. Resource limits.
P.47
Fig. 4.1.
Cutting sequence for the CM-section.
P.54
Fig. 4.2.
Ventilation layout.
P. 55
Fig. 4.3.
Cost: Volume relationship.
P.60
Fig. 5.1.
Coalfields of South Africa.
P. 66
Fig. 5.2.
Collieries in Mpumalanga.
P.67
Fig. 5.3.
Coalfields of KwaZulu-Natal.
P.68
Fig. 7.1.
Roof support: parting and coal roof.
P.86
Fig. 7.2.
Cutting sequence: 8m wide brushed belt road.
P.87
10 Fig. 8.1.
N.P.V. and I.R.R. at different product bases.
P.92
Fig. 8.2.
The N.P.v. for the product bases at different discount rates.
P.93
Fig. 8.3.
N.P.v. and I.R.R. against Yield at a 15% discount rate.
P.94
Fig.8A.
N.P.v. and I.R.R. against daily production rate at a discount
P.94
rate of 15%.
Fig. 8.5.
Spider diagram of N.P.v. changes influenced by changes in the
P.96
sensitivity parameters.
Fig. 8.6.
Spider diagram of I.R.R. changes influenced by changes in the
P.97
sensitivity parameters.
Fig. 9.1.
Cash flow.
P. 102
11 CHAPTER 1:
INTRODUCTION Dorstfontein Coal Mine is situated at the northern limb of the Highveld
Coalfield (Snyman, 1998). The close proximity of the Nebo Granite Suite
(S.A.C.S., 1980), which outcrops near the box-cut, to the No.2 Seam makes it
a very difficult mine to operate. The coal seam mimics the granite paleo­
topography and causes the seam conditions to vary extremely rapidly. Some
of the related problems are floor rolls and the sudden change in the coal seam
thickness. The mine has been in operation for four years during which time
the best parts of the ore body were exploited. The seam heights were in the
excess of 1.5 meters. In the north-western part of the mine the excessive
rolling floor prohibited production. In some areas of the mine the seam is split
into a thin (0.01 - 0.15m) upper and a thicker lower (1.2- 1.75m) seam by an
upwards coarsening sandstone parting. Currently some mining is taking place
below this seam-splitting parting where the seam height ranges between 1.5
and 1.75m. In other parts of the deposit very thin seam conditions prevail
below the parting with heights ranging between 1.2 and 1.4 meters. Hopefully
these very thin seam areas will be mined in the near future. In many countries
these heights are not be regarded as thin as the definition for thin seams is
any thickness between 0.6 and 1.0m (Clarke et a!., 1982). In this treatise a
thin seam will be regarded as a seam between 1.2 and 1.4m thick.
These thin seam areas were previously regarded as not mineable and omitted
from reserves. These areas contain very high-grade coal and have the
potential of adding another 6 years to the life of the mine. The aim of the study
is to determine whether these areas can be mined economically and
profitable.
1.1
Definitions and terms
Box-cut:
A decline ramp intersecting the strata at an angle of ± 7° and
ending in the mineable coal seam.
Thin seam:
A seam with a thickness between 1.2 and 1.4m.
12 Parting:
A competent layer of sandstone or siltstone in the coal seam
and sometimes separating different seams.
Pre-Karoo:
All rocks older than Karoo age, that is older than ±320 Ma.
Proximate analysis: The most basic analysis for a coal sample and done on
an air dried basis: Moisture content, Ash content, Volatile
matter, Fixed Carbon content (Karr, 1978 and Meyers, 1981).
Raw coal: Not beneficiated, as mined.
R.O.M.:
Run of mine, the material coming out of the mine.
± 50 -60%
of in situ reserve.
Seam:
The coal horizon.
Strong roof:
The horizon above the coal that forms a roof with strength in
the access of 60 MPa. It normally consists of a fine to
medium grained sandstone.
Wash fraction: The relative density or densities (R.D.) at which coal is
beneficiated. Listed in a washtable (Table 1). Can be any
R.D. between 1.0 and 2.7.
Table 1. Float fractions and qualities used in a washtable
Washtable:
The quantitative values of each coal quality analyzed for, at a
specific R.D., listed in table form (Table 1).
Weak roof:
any horizons that will break up or part during normal mining
activities.
Yield:
The resultant tonnage when 1 ton of coal is washed at a
specific R.D., expressed as a percentage. For this study all
13 yields quoted are theoretical yields i.e. no plant efficiency or
other losses were factored into the yield.
1.2 The problem and its settings
The areas of the thin seam coal resources are normally associated with
the seam-split parting. This parting divides the coal into a very thin upper
coal and a lower thicker coal. It is this lower coal that is of economic
importance and needs to be extracted. The following problems exist:
a.} The parting left to form the roof creates dangerous roof conditions and
reduces the mining heights to between 1,2 and 1,4 m. If the parting is
extracted, the heights increase but the yields of the thin seam coal
drop to uneconomical proportions. Stowing the parting underground is
an option but stone handling is costly and can cause injury.
b.) It is clear that the continuous miner (eM) mining method is the most
efficient to extract thin seam coal.
Drill and blast methods need
reasonable heights and space and currently the equipment on the
mine is too high for the thin seam areas. Drill and blasting below the
parting causes it to break and separate which defeats the whole object
of excluding the sandstone from the R.O.M. The eM operation would
probably be more effective but the eM can not cut hard stone.
c.) Production rate. There is a production cutoff where the cost of the
tonnage mined exceeds the revenue received for the product. What is
the minimum tonnage that can be produced economically from thin
seam areas?
d.) Yield cutoff. Hand-in-hand with production rates goes the yield of the
extracted material.
If the yield is to low, the production must be
increased to make up for the lost product coal.
The parting must
remain up to increase the yield. What is the cutoff yield and how is it
affected by inclusion of the parting?
e.) Health and Safety. What are the safety implications if the parting is
kept up? How will personnel and machinery be able to work safely in
14 the thin seam area? What are the new health and safety risks when
mining thin seam coal?
f.) Costs. How much will it cost to undertake thin seam mining? New thin
seam equipment will be introduced and tested below the parting.
What is the break-even point in production rate and costs?
1.3 Hypothesis
Current thick seam mining operations in similar conditions as thin seam
areas indicate that the theoretical yield falls from 85% to 65% when the
parting is included. This means that for every hundred tons mined, only
65 tons can be sold but the company still has to pay for hundred tons
mined. It is more economical to mine as much "clean" coal as possible.
The feeling is that in the thin seam areas the parting will have to stay up
and form the roof to increase the yields and to make this an economical
area. This mining method creates numerous problems regarding health
and safety and will lead to a decline in the production rate. The risks
have to be quantified and weighed up against the necessity to mine
these thin seam areas. In the end the decision to go ahead with thin
seam mining will be based on economical as well as health and safety
issues. It is postulated that mining the thin seam coal will be expensive
but profitable. The working conditions will change and workers will have
to become comfortable with their new working environment
1.4 Delimitations
1.4.1 Only thin seam areas have been assessed and evaluated.
1.4.2 The mine will be in operation for at least the next ten years.
1.4.3 This is not a complete feasibility study and only focuses on one
aspect of the geology namely the thin seam resource.
1.4.4 The current borehole spacing is 1 hole I 300m and all the
geological conditions have been modeled based on this spacing.
1.4.5 Very little information exists about other thin seam operations.
15 1.5
Assumptions
1.5.1 It is assumed that the entire infrastructure exists on the mine
surface and underground. This will just be an additional section at
the mine.
1.5.2 This study assumes that the geology has been well defined and
this is no attempt to revise the geological section of the feasibility
report of Dorstfontein Mine. The geological insert merely acts as
background for the reader with additional information about the thin
seam added, as gathered through the lifetime of the mine.
1.5.3 The study intends to change the long-term planning and
scheduling of the mine as it adds additional information and
creates the possibility of extending the life of the mine.
1.5.4 This study assumes that the current policy of I.C.S.A., to use
contractors for mining and to outsource all activities, will not
change in the future.
1.6 Research methodology
1.6.1 Current history of Dorstfontein mine. The past and current mining
problems and geological conditions will be reviewed.
1.6.2 Use of borehole information. Borehole core was used to study and
analyze the parting strengths and properties. The information
gathered from these reports and the analyses from coal sampling
were used in this study.
1.6.3 Geological model simulations. Use was made of the geological
data supplied by I.C.S.A. head office. The Minescape/Stratmodel
software was used to model coal qualities and seam heights.
1.6.4 The same software was used to determine the in-situ thin seam
coal resource.
1.6.5 The data gathered and analyzed was used to come to a
conclusion regarding the feasibility of extracting coal from thin
seam areas.
16 CHAPrER2:
REVIEW OF RELArED MArERIAL.
Very little information exists about thin seam coal mining. Contrary to this there
exist great volumes regarding coal mining and coal as a rock. These publications
are not relevant to the problem of thin seam mining, its methodology, products
and cost. The only relevant publication found is that of Clarke et ai, (1982): Thin
Seam Coal Mining Technology. Another very interesting but old book by Smyth:
Coal & Coal Mining was published in 1886. This book makes very interesting
reading about the mining methods, problems and history of the old British
collieries.
In the book of W. W. Smyth he refers to the startling observation made in 1860
that the British coal output had doubled in 20 years, from 65 million tons to 134.6
million tons per annum. The big concern of the day was the new technology of
using explosives to liberate coal at the face, which led to many fatalities and
injuries due to "blow-out" shots. One of the biggest concerns of the time was
underground explosions caused by gases and poor ventilation. It seems that the
greatest danger was the extinction of the miner's cap lamp flame during an
explosion leaving the underground workers without light. This resulted in many
miners being lost underground in the dark, as they could not find their way out.
This seems to be one of the earliest health and safety problems due to bad
lighting or no lights at all.
The relevant issues at the time (1885), which still hold for today's drill and blast
mining and of which some can be applied to continuous miner operations, are the
following: i.) adopting such methods that will produce the least dust, ii.) the
removal of such dust and prevention of it being carried down the downcast
ventilation system, iii.) watering where practical the places in which dust
accumulates and the sprinkling of common salt or other deliquescent material,
iv.) the avoidance of common concussions accompanied by much flame as
caused by "blown-out" shots and the careful examination for gas and clearing of
dust from the place where a shot is to be fired.
17 Smyth (1886) also describes the very primitive ways that were employed in the
1800s to liberate coal. The first procedure was to "hole" the coal by cutting a
groove two to three feet deep in the lowest part of the coal with a pick. For this
holing at the bottom of the seam the collier laid on his side and in an apparently
constrained attitude swung the pick almost horizontally. Some coal seams had
the advantage of being able to be holed in the middle, depending on the position
of the in-seam partings. The sides were cut vertically. called shearing. to form a
short block of coal that needed to be collapsed. The final breaking down or
"collapsing" of the seam was done by applying taper wedges a few feet apart and
driving them with heavy hammers. In some cases where the coal was more
resistant to collapsing. use was made of gunpowder. Later developments made
use of hand drills to drill holes into the coal seam and charged with gunpowder.
This method led to many injuries as proper tamping of holes did not exist and
gunpowder easily pre-ignites. It is also rendered useless when wet and
waterproof packaging did not exist at the time.
Bord and pillar mining layouts were the most common but longwall-mining did
exist. leaving nothing but goaf or gob behind. Support was installed by means of
timber props to uphold the overlying strata and in many cases where the heaviest
roof pressure was expected they used nogs and chocks instead of props. Coal
was removed from the face by dragging sledges. loaded with coal. along the
floor. In some of the more primitive mines the coal was loaded into baskets and
carried by woman bearers. The Germans were the first people to introduce
underground rails. The problems encountered with underground rails were their
frequent sinuosity and unevenness, confined space and the tendency to disturb
roof and floor. Special designed wagons were used to transport the coal up an
incline shaft. The various trolleys and tubs were either pulled by Shetland ponies
or pushed by boys. It is mentioned that where very thin seams were worked the
cost of carting the coal becomes very onerous (Smyth, 1886). In thin seams the
tubs or wagons must necessarily be low and the wheels small so that the total
weight is low in order for the onsetler and banksmen to easily pull or push the
trolley up the mostly incline shafts.
18 During the 1800's the fatality in British coal mines were between nine hundred
(900) and one thousand two hundred (1,200) people per year. The most common
cause of deaths and accidents were falls of roof, methane explosions due to poor
ventilation, shaft accidents and holing into old workings where methane and other
gases have accumulated as well as inrushes of water which were lying under
pressure in the old areas. The most feared substance and cause of fatalities in
the mines was so called firedamp better known today as methane.
A very interesting book and one used very extensively in this study is one on thin
seam coal mining technology and by Clarke et al. (1982). This is the only book
dealing exclusively with thin seam mining methods as most other publications
and books deal with coal and mining methods in general. It can also be
concluded that thin seam coal mining has become unfavourable due to its low
production rate and high cost and that the focus is more on high output (economy
of scales) from thicker coal seams. Clarke et a!. (1982) highlights the
occurrences of accidents in thin seams, various extraction methods and
equipment, health and safety issues, mine design and layout, costs and thin
seam resources, from mainly U.S.A based mines. This book was published in
1982 and covers mainly the mining in the 1960's and 1970s when coal prices
were high and costs exuberant. The mines sold low ash coal (12-16%) for $28.0
but mined that coal at $34.0-$40.0 per ton. They were and still are heavily
subsidized and many tax incentives were introduced to keep these mines open
so that small communities could survive.
Many lessons can be learned from the American thin seam collieries regarding
their mining methods, health and safety issues and mining costs. Real issues and
factual data was used from operating collieries within the U.S.A and compared to
other collieries in the former U.S.S.R., Colombia, Great Britain, and other
European countries. Many of the issues raised in this publication can be directly
implemented and applied to the Dorstfontein scenario. The risks involved are
pertinent to our current mining as well as to the proposed thin seam mining
19 areas. As very few mines are currently mining thin seam coal in the R.S.A.,
lessons must be learned from the past and be applied at Dorstfontein.
In Chapter 3 (Clarke et al., 1982) a comparison is made between the accident
analysis of thick seam and thin seam mining. The various kinds of accidents
mentioned are relevant to the current mining a Dorstfontein and will be used as
risks for the thin seam mining. Chapter 12 deals with productivity and the factors
affecting productivity. Although many of the statistics and data goes back to the
1960s and 1970s, it can be assumed that because of the mining conditions and
productivity with modern-day machines will not be dissimilar from those eras.
Many U.S.A. thin seam mines produced 20 000 tons per month per section from
24 inch (0.6m) high seams.
In the conclusions it is quoted that there is a
correlation between seam thickness and labour productivity. There are also
countries where thin seam mines are very productive due to good geological
conditions such as competent and strong roofs and flat seams.
Chapter 13 (Clarke et aI., 1982) deals with costs and although costs in the 1960s
and 1970s cannot be compared to today's cost, one can come to a conclusion
about the exorbitant costs of thin seam mining. It is interesting however that the
selling price of high quality coal in dollar terms in 1977 is the same as today but
decreased in terms of inflation adjusted figures. The main reason for this is that
the highest quality coal occurs in thin seams and is well sought after because of
the low sulphur and ash content. This is the same quality coal produced at
Dorstfontein Mine. Chapter 14 covers the health and safety environment and
gives a very good inSight into conditions that could be expected when entering
the thin seam areas. Up to now at Dorstfontein seam heights (all above 1.5m)
comparable to that mined in the U.S.A (between 0.6 and 0.75m) have not been
encountered. In Chapter 15 the authors deal with the various mining systems and
methods and give one inSight into the various methods employed in thin seam
coal winning. Chapter 19 discusses the output and productivity of various mining
methods. At Dorstfontein the mining methods are fixed, in the sense that bord
and pillar layout applies, continuous miner machines are being used and that the
20 necessary equipment for thin seam extraction has already been bought or current
equipment adapted. Chapter 20 deals with the costs involved in thin seam
mining. It appears that labour cost forms the greatest component in the U.S.A.
but in the R.S.A. the possibility exists that the capital costs will form the greatest
component due to the volatile exchange rate. The financial sensitivities involved
in thin seam mining and their effect on production and cost are discussed in
Chapter 22. Extracts from this publication have been used to design the financial
model. assess the risks and the sensitivities. It provides a general background on
the various thin seam mining methods used in the U.S.A. and other parts of the
world.
Very little information exists in the R.S.A. about previous mining of thin seams in
KwaZulu-Natal. Spurr et al. (1986) published a few papers on the general
geology of the Vryheid and Utrecht coalfields. its qualities and tonnages. Most of
the mining problems. production rates and costs are kept in in-house reports and
are not available to the public.
Jacobs (1989) identified the relationship between geological conditions and
mining problems at Ermelo Mines. but the problems of the thin seam areas here
differ distinctly from Dorstfontein as they encountered bad roof conditions. which
do not occur at Dorstfontein as frequently as they did at Ermelo Mines.
This document would therefore appear to be one of the few documenting the
potential mining of thin seam coal resources in South Africa. This is a radical
opinion since thin seam coal mining has become unfavourable due to its high
costs and low production rates. It is the opinion of the author however, that this
view will change as thick coal seam resources are being depleted and the need
for additional coal resources will necessitates the reinvestigation of thin seam
deposits. The findings relevant to the Dorstfontein deposit may have far reaching
consequences in other mining areas as it may result in substantial increases in
available resourcess.
21
I
Ib0J..')..U~S
b\v.J9 UUW ~/1
CHAPTER 3:
3.1
GEOLOGY OF THE NO.2 THIN SEAM.
Introduction
Extracts from a 1999 AngloVaal Minerals geological report by Stewardson and
Saunderson have been used for this chapter. A few amendments have been
made based on additional information that has become available from recent
drilling programmes. Underground mapping and recording of mining problems
have added to this information, which has been reconciled with the borehole
data.
The term "reserve" used in this study complies with the SAMREC code
(SAMREC, 2000) as this thin seam area has been included in the approved
Environmental Management Programme Report (EMPR) and the mining
permission area. The necessary extraction rates are known, the market exists
and all the other elements of the definition have been met. The thin seam was
not regarded as mineable due to practical reasons like the non-existence of
modem high productive equipment.
3.1.1 General
Dorstfontein Coal Mine falls within the Highveld Coalfield and is
situated 4 km east of the town of Kriel and 25 km northwest of Bethal.
(Fig. 3.1) Adjacent collieries include the defunct Ingwe operated
Transvaal Navigation Colliery (TNC) , the current Xstrata Mines of
Arthur Taylor Colliery (ATC) and Arthur Taylor Colliery Open Cast Mine
(ATCOM) which are 15 km to the north, the Anglo Coal operated Kriel
Mine and Eyesizwe operated Matla Colliery, about 10 km west
(Snyman, 1998 and Baker, 1999). Only Matla and Kriel Collieries are
also in the Highveld Coalfield while the other neighbours fall inside the
Witbank Coalfield. Other mines in the Highveld Coalfield (Fig. 3.2.) are
the SASOL owned Secunda Collieries (Brandspruit, Twistdraai,
Syferfontein and Bosjesspruit) at Secunda, the Anglo Coal owned New
22 Denmark Colliery near Standerton and the Total Exploration SA owned
Forzando Colliery near Hendrina (Jordaan, 1986 and Barker, 1999).
Various studies were conducted to determine the local and regional
stratigraphy as well as the depositional environment of the Highveld
Coalfield (Winter et at, 1987). The area studied by Winter et al. in 1987
was seen as part of the Highveld Coalfield at the time but is currently
viewed as the western part of the Witbank Coalfield (Snyman, 1998).
The seam correlations and depositional environment are similar to the
Highveld Coalfield and may still be used for research. Other
researchers have done some work in various parts of the Highveld
Coalfield since 1928 and include names like Wybergh, W.J. in 1928,
Venter, F.A in 1934. Stanistreet, LG. et al. in 1980, Smith, D.AM. in
1970, Cadle, AB. and Hobday, D.R. in 1977 (Jordaan, 1986).
T.C.S.A owns all the coal rights over the farms Dorstfontein 71 IS,
Welstand 551S.
Fentonia 541S and Boschkrans 531S (Fig. 3.3)
(Stewardson and Saunderson. 1999). Mining is currently taking place
on the farm Dorstfontein 711S where a high-grade coal, suitable for
export and metallurgical applications, is extracted.
The study only
deals with the very thin seam coal area (heights between 1.2 and
1.4m) at Dorstfontein 711S. which was until recently been regarded as
un-mineable and thus exduded from reserves.
23 3.1.2 Topography and land usage
The topography is gently undulating (Fig. 3.4) with a few small
tributaries of the Steenkoolspruit draining the property. The previous
farmer or owner constructed a few farm dams on the property. The
T.C.S.A. owned surface is currently being rented out to farmers who
use it for maize cultivation and grazing.
The property is sparsely
populated by a few farm workers staying in workers huts (Stewardson
and Saunderson, 1999). The use of bord and pillar mining methods
and the properly designed pillars, prevent surface subsidence.
In
terms of sustainable development objectives, the surface should be
retumed to its original use for agriculture as minimal negative impacts
on the surface was done by mining.
3.1.3 Mineral Rights
T.C.S.A. owns all of the mineral rights in the mining lease area
(Stewardson and Saunderson, 1999). These rights were acquired by
AngloVaal Minerals in the 1980s and 1990s and transferred to
T.C.S.A. with the selling of Dorstfontein in 1999.
rights owners are:
•
Anglo Coal Pic and
•
Mr. N.E. Hirschowitz
27 Adjacent mineral
3.2
Exploration
Since the early 1960's up to 1999 a total of 174 holes were drilled in the then
Dorstfontein resource area of which 19 holes were angled holes to confirm
dolerite dyke positions (Fig. 3.4) (Stewardson and Saunderson, 1999).
Subsequently another 64 holes were drilled in the reserve area since mining
started in 1999.
Anglo American Corporation carned out the earliest exploration in the mid­
1960s. Between 1974 and 1975, South Cape Exploration (pty) Ltd drilled 47
holes on Dorstfontein. A further 43 holes were drilled by Sun Mining and
Prospecting during the period 1975 to 1978 (Stewardson and Saunderson,
1999). These holes had limited washability data for the No. 2 Seam as only
the No. 4 Seam was prospected for (see Stratigraphical Log, Fig. 3.5). In
some cases only proximate analysis were performed on raw coal from the No.
2 Seam. All of the prospecting companies cancelled their optioning
agreements and prospecting rights as the No.4 Seam is of inferior quality and
regarded as uneconomical. Options were taken out by AngloVaal Minerals
when they considered the No. 2 Seam as mineable. This company drilled
another 60 boreholes between 1980 and 1982 with a further 105 holes
between 1996 and 1998. All AngloVaal Minerals' boreholes and subsequent
I.C.S.A. holes were analyzed at 10 density fractions to get a better
understanding of the washability of the coal.
In 1995 a helicopter-bome high resolution aeromagnetic survey was
conducted to define magnetic dykes (Stewardson and Saunderson, 1999).
Some anomalies were confirmed by drilling angled holes and by ground
magnetometry.
In 1997 a helicopter-borne EM survey was carried out to
define some non-magnetic dykes.
Anomalies were identified and angled
boreholes drilled which confirmed some of these anomalies to be dolerite
dykes (Stewardson and Saunderson, 1999). Most of the major dolerite dykes
in the mining area were correctly predicted and very few surprises were
encountered during mining. Only a few thin dolerite dykes/stringers were
29 intersected during mining and a few situations the positions of the major dykes
were out by not more than 25 meters.
3.3
Stratigraphy
The Pre-Karoo basement rocks consist of granite of the Nebo Granite
Suite of the Bushveld Complex and in a few places Transvaal shales and
sandstones (SACS, 1980). The granite outcrops close to the box-cut
position and defines the northem mining reserve boundary.
The
basement is overlain unconformably by diamictites and associated· glacial
sediments of Dwyka age (Winter et aI., 1987). These in turn are
conformably overlain by sediments of the Vryheid Formation that
comprise of a series of stacked upwards-coarsening sequences of
siltstone and sandstone. Each sequence is capped by a coal seam (Fig.
3.5).
Five major seams are present and numbered from the base upwards as
Seams No. 1 to 5 (Snyman, 1998 and De Jager, 1976). Thickness and
distribution of the seams were controlled by paleotopography as well as
pre- and syndepositional events (Winter et aI., 1987). The best developed
and most extensive seam is the No. 4 Seam which reaches maximum
thicknesses of up to seven meters. Unfortunately this coal has a very low
yield for export products and the calorific value and volatile matter of the
seam renders it only suitable for use as steam coal. Currently an
oversupply of this type of coal exists but there is always the possibility that
some market might become available in the future. The No. 5 Seam is
developed only in the topographically elevated areas and the negative
experience of other No. 5 Seam producers discourages any mining of this
seam. The No. 1 Seam is only locally developed in a small palaeo-valley
in the northeast of the mining reserve. It is of inferior quality and
uneconomical. The NO.3 Seam is very localized and thin and occurs only
in a few places in the deposit. Currently the No. 2 Seam is the only
30 economic viable seam in the deposit and a detailed description is to follow
(Fig. 3.6).
Late Jurassic time dolerite intrusions, which coincided with the Gondwana
breakup, have resulted in some areas of burnt and or devolatilised coal
(Jordaan, 1986). The migration of dolerite sills to different stratigraphical
levels had resulted in seam displacement but had only a limited effect on
the No. 2 Seam reserve area. The eastern mining reserve boundary has
been defined using such a migrating sill as reserve limit (Stewardson and
Saunderson, 1999).
31 1575
1575
1550
1550
1525
1525
1500
SA
1500
-­
'--­
SA
1475
1470
1475
1470
2902300N
2903000
2903500
2904000
2904500
2905000
2905500 2905750N
-29000E
1591
-29000E
1591
DF198
o
Of137
1575
DSi
1550
1550
1525
1525
1500
1500
~------'-1475
1460
2902600N
Fig. 3.6.
1575
2903000
i»,________ --- --- --­ -­ _­
____
----­
2903500
North-South CIOSHeCtion of the~tfontein Deposit (after Bartkowiak; 2001).
2904000
2904500
2905500
2905000
"
1460
1475
2905800N
3.4 No.2 Seam and No.2 Lower Seam
The palaeo-basement geometry determined the geometry and thickness of the
No.2 Seam (Fig. 3.6 and 3.7). The rate at which the surface subsided during
peat accumulation controlled the thickness and character of the coal. Height
variations can be attributed to pre- and syndepositional geological events
(Stewardson and Saunderson, 1999).
3.4.1
Seam splitting
The single coal seam in the north is split into an upper and lower seam in the
south by a persistent sandstone parting (Fig. 3.7 & 3.8). The parting is
positioned towards the top of the seam and ranges from 0.0 to 0.75m in
thickness. The No.2 Upper Seam is thin (0.01 to 0.35m thick) and only the No.
2 Lower Seam forms an economic unit. In the No.2 Thin Seam area the parting
is thick and as only 0.3m is enough to form a safe beam, this parting will form a
proper roof for the lower, mineable part of the No. 2 Seam (Spengler, pers.
comm., 2002).
3.4.2 Seam Elevation
The elevation of the base of the No. 2 Thin Seam ranges from the 1511 to
1518m AMSL (Fig. 3.9). The seam topography reflects the Pre-Karoo relief with
the seam dipping gently from east to west towards a north-south trending
paleovalley. The overall regional dip of the seam is from north to south, that is
from the granite outcrop towards the depositional basin. In the study area the
coal seam is flat with a barely noticeable dip towards the south.
3.4.3 Seam Thickness
The total thickness of the No.2 Seam, including the parting, is illustrated in
Fig. 3.10. The central area of maximum thickness reflects the zone of maximum
parting thickness. In the study area the seam thickness below the parting
ranges from 1.2 to 1.4m (Fig. 3.11).
In the area where the seam splitting occurs, the No. 2 Upper Seam is
developed and ranges in thickness from 0.01 to 0.35m. There is no correlation
34 between the No. 2 Upper Seam thickness and the underlying parting thickness.
The clean, well-sorted sandstone that overlies the No. 2 Upper Seam has
generally a thin, silty zone at its base. This suggests disturbance of the peat
surface during transgression. The absence of rip-up clasts indicates little or no
erosion of the seam (Stewardson and Saunderson, 1999).
3.4.4 Main Parting
The parting thickness ranges from 0.0 to 0.75m with its maximum thickness in
an east-west linear zone (Fig. 3.8). The parting consists of an upwards­
coarsening sequence grading from lenticular-laminated siltstone through
interlaminated sandstone-siltstone to cross-laminated sandstone at the top.
The lithology and geometry suggested a crevasse splay deposit, which
emanated from a channel system in the east of the reserve area (Stewardson
and Saunderson, 1999).
Mechanical strength tests were done on core from the 2002-drilling programme
(Spengler, 2002). The results indicated that the parting is competent and will
not collapse during mining and that it will form a safe beam jf bolted with full
column resin roofbolts. The only provision is that the mining method below the
parting should not be the conventional drill and blast methods but preferably
mechanical continuous mining methods.
Mechanical mining methods cause
the least disturbance and possible separation of the laminated strata, which
could result in the beam thinning to dangerous proportions. In Chapter 7 there
is a detailed discussion on the testing of the parting and instructed support
pattern.
35 3.4.5 Seam Roof
The purpose of this study is to determine the result and affect if the seam-split
parting forms the roof in the study area. However, it would be necessary to do
roof stripping (parting) in the belt road and main travel roads to increase heights
for the people and vehicles to move. The stripping, normally done to a height of
1.8m, will expose the overlying fine grained, homogeneous, clean and well­
sorted sandstone unit, which currently forms the roof. This unit is mostly
unbedded and lack silty laminae. Occasional occurrences of bioturbation and
cross trough bedding are developed.
These occurrences do not have any
negative effects on overall rock strength (Stewardson and Saunderson, 1999).
All roof rock (parting) will be mined as a second cut and be stowed
underground to prevent contamination of the mined coal.
3.4.6 Seam Floor
Competent, medium grained sandstone underlies the seam. The sandstone
floor forms the final depositional stage of a prograding delta platform upon
which the coal seam developed (Stewardson and Saunderson, 1999). In
currently mined areas and old workings, the floor is still competent and did not
scale or break-up during vehicle movements. It is expected to behave the same
in the thin seam areas.
3.5 Dolerite Intrusions
MagnetiC and non-magnetic dykes as well as magnetic dolerite sills occur (Fig.
3.12). These were detected using both geophysical surveys and borehole
intersections (Stewardson and Saunderson, 1999). In the study area and the
current reserve, dolerite sills do not underlie the mineable seam. In the east of
the current reserve a dolerite sill cuts vertically across the strata to outcrop on
surface. It underlies the No. 2 Seam in the east, displaces the seam upwards
the same distance as the dolerite thickness and thus renders the coal
inaccessible and unmineable due to this discontinuity. This position of the sill
41 transgression was used to define the eastern boundary of the current mineable
reserve.
In the south of the study area a major magnetic dyke was identified using an
aeromagnetic survey. It trends more or less east - west and is near vertical.
Mining through this dyke has proved its thickness to be 2.8m at the locality it
was intersected.
In the western part of the study area, 3 dykes occur. Mining confirmed their
positions during a southern development towards higher seam areas, the so
called South Main area. All of these dykes were relatively thin ( < 2 m thick)
and had no serious effect on the coal seam. It is concluded that these dykes
should not pose any serious problem for mining the thin seam area.
42 To conclude: the thin seam resource consists of 7.06 mil. tons in-situ coal of the
same quality as the current mining reserve. By factoring in an extraction rate of
70% and a geological and mining loss of 10% each, the recoverable (run of
mine) tons comes to 3.56 mil. tons. By applying the product yield at a 13.5%
ash content (yield = 95.7%) the product tons are 3.41 mil. tons and by applying
the yield at RO=1.6 (yield = 89.2%), the product tons are 3.18 mil. tons.
3.6.2 Thin seam resource limits
The main study area is defined by the 1.2 to 1.4 m seam height contour line
(Fig. 3.14).
A mined-out area forms the northem boundary, while a sill
transgression line defines the eastem boundary. There will no other restrictions
placed on defining the resource area.
46 3.7
Seam Quality
3.7.1
General
For the geological study of 1999, coal quality values were quoted as at
RD.=1.6 on an air-dried basis (Stewardson and Saunderson, 1999). At this
wash fraction the mine was viable and the coal could be economically
exploited. The quality parameters normally quoted are: Yield, Calorific Value
(CV), Ash %, Moisture Content %, Volatile Matter % (Vols), Fixed Carbon %
(FC), Sulphur % (S) and Phosphorous % (P). In practice it has been found that
it is more practical to wash the coal to achieve 13.5% ash content (Air dry). The
market also readily accepted this quality as little change was brought upon the
volatile matter and calorific value. Therefore all current qualities are quoted as
for an ash content of 13.5%. In the study area the ash content is 11.6% at a
RD. = 1.6. The direct effect of an increase in ash content is an increase in
yield.
Therefore, in the study area the average yield of 89.2% at RD. = 1.6
has gone up by 6.5 percentage points to 95.7% at an ash content of 13.5%.
This relates to an increase of approximately 2100 tons per month more of
saleable coal from the thin seam area alone.
3.7.2 Qualities
Coal and Mineral Technologies, a subsidiary of the SASS, did all resent
analysis according to the ISO 1928 standards (The South African Coal
Processing Society, 2002). Various other laboratories were used in the
past but most of them have dosed. Analysis from some of the older
borehole data could be used but many of the older holes did not intersect
the No. 2 Seam. Since AngloVaal Minerals drilled a 500m grid and
loC.S.A dosed the grid to 250m, enough borehole information exists to
confidently predict the coal qualities and tonnage for the thin seam area.
48 Some of the more important qualities for the thin seam coal are briefly
discussed. For Fixed Carbon and Moisture Content, see the details
tabulated in Table 4.
3.7.2.1 Yield
The theoretical yield for the thin seam area is 95.7% at an ash
content of 13.5% (RD.
=1.99) and 89.2% at a R.D. =1.6 (air
dry).
3.7.2.2 Calorific Value
The CV in the study area is 28.31 MJ/kg at a R.D.
=1.6 and
27.21 MJ/kg at an ash content of 13.5% (air dry).
3.7.2.3 Volatile Matter
The volatile matter at RD.
=1.6 is 26.52% and 26.15% at an
ash value of 13.5% (air dry), showing very little difference
between the two products.
3.7.2.4 Sulphur
It was initially perceived that Dorstfontein had a sulphur problem
but the markets steadily accepted slightly higher sulphur values
so that the mine is currently meeting all the product
specifications. Most of the resource area has an average
sulphur content of 0.42% at the RD.
=1.6 float fraction. At an
ash of 13.5% the average sulphur content is 0.79% and in
some mining blocks it can go as high as 1.25% because of the
free pyrite occupying the deats.
Because of this, the current
beneficiation practice to wash to an ash content of 13.5% will
not be suitable to produce low sulphur coal. The wash density
will have to be reduced to a suitable fraction of between 1.6 and
1.8 to make a low ash and low sulphur product.
3.7.2.5 Phosphorus
The phosphorus content of the entire deposit is below 0.010%.
This low value makes the Dorstfontein coal well sought after as
a product used in the metallurgical industry.
49 3.7.3 Additional8nalysis
No additional analyses were done on core from boreholes in the study
area. It is recommended that the following additional analysis be done
for future market requirements (The South African Coal Processing
Society, 2002):
•
Ultimate Analysis: • Full Ash Analysis:
Carbon, Hydrogen, Nitrogen, and Oxygen.
Si02, Al20 3, Fe203. Ti02• CaO, K20, S03.
P205, MgO, Na20.
•
Ash Fusion Temperatures.
•
Hardgrove Grindability and Abrasiveness
•
Forms of Silica.
•
Forms of Sulphur.
•
Swell and Coking Properties.
It should therefore be concluded that based on the continuity of the No. 2 Seam and
the consistency of the seam quality, that a product meeting the market specifications
could be produced from the No.2 Seam thin area.
50 PREVIOUS AND CURRENT MINING METHODS.
CHAPTER 4:
4.1
Introduction
a.) Numerous coal-winning methods have been used on the mine
during its four years of existence. The current methods must be
judged on the economic factors and their advantages and
disadvantages.
b.) During the history of the mine, rapid variations in seam heights
were encountered. These were attributed to the irregular nature
of the roof and floor. It has been proved that conditions improve
as mining proceeds southwards. The roof conditions generally
vary according to the mineable portion of the seam selected.
Currently the whole seam is mined and the roof conditions have
proved to be very good. Isolated instances of roof slumping have
occurred, which in turn led to difficult mining conditions in those
specific areas.
c.)
Some areas have a mudstone roof but even this kind of roof has
proved to be competent and the coal mineable.
d.)
4.2
The floor is generally very competent sandstone.
Mining method and equipment
4.2.1 General
The bord and pillar mining layout will be maintained because of its
reliability, flexibility, low capital cost, low working costs and large skills
source availability (Woodruff, 1966). Increasing mechanization has
resulted in an increasing production in the amount of the fine coal
fractions, which attract Significantly lower prices. The introduction of the
continuous miner in some areas has decreased the amount of the
higher valued coarser fractions. From the start a combination of two
conventional drill and blast sections and one continuous miner with a
continuous haulage were used. The haulage system was abandoned 1
year ago due to numerous breakages and expensive repairs and its
51 inflexibility in problem areas. It was replaced with 3 Stamler thin seam
battery haulers. A revolving stone crew undertakes the development of
dykes and does the roof brushing to 1.8m in thinner seam areas.
When the need arose a contractor was employed to catch up with the
roof brushing and in some cases install additional roofbolts.
4.2.2 Continuous Miner Section
From early days on the trend in bord and pillar mining was towards
continuous miners (Woodruff, 1966). More recently there has been an
increasing trend in the industry to replace the traditional shuttle cars,
battery cars and scoops by continuous haulage systems. The opposite
took place at Dorstfontein Coal Mine where shuttle cars are preferred
for their flexibility and low running costs.
In the CM-section the continuous miner cuts between 7 and 11
roadways, depending on the preferred layout at the time (Fig. 4.1, 4.2).
Pillar and bord widths are 6.8m, giving a coal extraction in the region of
70 to 75%. In Figure 4.1 it is illustrated that the CM cuts a split of 6.8m
wide to the right of the travel road (marked 1) and while resin bolts are
installed in this split the CM cuts a straight (marked 2) and another split
(marked 3) of 6.8m wide. During the support of these last two cuts, the
CM moves back into the right side of the panel and cuts numbers 4
and 5. Since it is illegal to work under unsupported roof, the CM has to
wait while cut 4 is supported before moving to cut number 6 and 7. The
whole cycle is repeated and the installation time of the support
determines the cutting time of the CM.
Figure 4.2 illustrates the ventilation layout of the CM section.
Ventilation is very important for a healthy working environment and
even more important in thin seam mining were only small volumes of
air can pass through the restricted and narrow workings. The intake air
moves in on the right side of the section and ventilates the coal face,
52 removes all the methane and dust and returns on the left side of the
panel. Some leakage does occur since the temporary scoop brattices
or curtains, installed to direct the air. are not airtight and sealed
properly. Some of these temporary curtains are removed to allow the
haulers to move from the face to the tip.
These curtains are later
replaced by brick walls as the section moves forward.
The section is equipped with the following:
1 x Joy 12HM15 Continuous miner with a 1.12 meter drum.
-
3 x Thin seam Stamler BH1 0 Battery Haulers (1 m high).
1 x Self-propelled thin seam roofbolter.
1 x Battery scoop.
1 x Feeder-Breaker.
1 x Mobile 750 t<NA transformer.
1 x Mobile switch trailer with flameproof gate end boxes.
1 x Portable jet fan.
The manpower is:
1x Miner.
1x CM operator and assistant.
1 x Cable handlers.
3 x Hauler drivers.
1 x Roofbolter operator and assistant.
2 x Feeder-Breaker operators.
7 x General labourers.
The total number of persons per shift is 16.
53 4.2.3 Conventional Drill and Blast Section
The flexibility of the conventional drill and blast sections in negotiating
geological obstacles together with the improved creation of the
financially attractive coarser fraction product, is still important factors in
the use of this method of mining. Unfortunately this method only works
effectively for seam heights above 1,6m as production rates decrease
exponentially with the reduction of heights. In the current thin seam
area the parting is included in the mining to provide the necessary
height for this section. The yield decrease is significant by including this
parting.
In this section an amount of 11 roadways are been mined with pillars
width 6.8m and bords 6.8m, giving an extraction in the region of 70 to
75%.This section is equipped with the following:
1 x Coal loader. 1 x Roofbolter. 1 x Feeder- Breaker. 1 x Coal Cutter. -
2 x Joy Shuttle Cars. -
2 x Electric Coal Drills. 1 x Mobile 750 twA transformer. The manpower is: 1 x Miner 2 x Electric Coal Drill operators and 2 x assistants. 2 x Drill assistants Oackhammer). 1 x Coal Cutter operator and assistant. 1 x Coal Loader operator and assistant. 2 x Shuttle Cars drivers. 1 x Feeder-Breaker operator. 1 x Roofbolter operator and assistant. 56 5 x General labourers. The total number of persons per shift is 21. 4.2.4 Stone Work Team
The mine has a dedicated stonework team, whose duties include:
a.) Mining through dykes exposed by coal winning.
b.) Brushing and supporting of the roof to 1.8m heights in roadways
and belt roads.
c.)
Brushing and supporting of the roof designated for ventilation and
mine infrastructure e.g. air crossings.
d.) Installation of superior and additional support in areas where poor
roof conditions prevail.
The stonework team is operating on a single shift but can be changed
to a double shift when conditions dictate. Additional contractors were
introduced to help with specialized support and to assist where
additional support was required.
The stonework team is equipped with the following:
1x Self propeller roofbolter
1x Mobile 500 cpm compressor
3x Pneumatic drills uackhammer) and air legs
1x Mobile switch trailer with flame proof gate end boxes
1x Mobile 500 kVA transformer
1x Portable explosives magazine
The manpower is: 1x Miner 2x Drill operators uackhammer) 2x Drill assistants uackhammer) 2x General labourers The total number of persons per shift is 7.
57 All external waste mined, such as roof rock, dyke material and burnt
coal is stowed underground in such a manner so as to minimize the
risk of spontaneous combustion.
4.3
Risks.
4.3.1
Geological.
a.) In-seam partings. These partings result in a drop of yield and
cause materials handling problems, which in tum adds to the cost
of maintenance on equipment and conveyor belts.
b.) Roof slumping and compaction structures. Sudden changes in
roof heights lead to difficult mining conditions. This so-called
"pinching" of seam heights creates difficult working conditions for
hauler- and shuttle car operators.
c.)
Unexpected laminations in the roof. Thin laminations of silty
material in the roof lead to dangerous conditions as delamination of
the roof can result in rock falls, which can cause injury and
fatalities.
d.) Changes in coal quality. The drop in product yield directly results
in an increase in production costs. Unexpected quality changes
might result in dissatisfied customers, which can result in the
cancellation of contracts. The highest risk in this category is the
possibility of high sulphur values.
e.) Floor rolls. These occurrences are as unpredictable as their
extent is limited. Floor rolls caused dangerous conditions during
machine movements. The continuous miner had difficulty moving
over these rolls as the length of this machine caused the rear end
to "hang up" on the roof as the front-end traverse down the slope of
a roll.
t.) Dykes. Dolerite intrusions normally cause a section to come to a
halt as the roads need to be developed through the dyke by the
stone crew. Dykes result in burned or devolatilised coal, which can
not be sold. Dykes form gas traps for methane and often have bad
roof conditions associated with them.
58 4.3.2 Production.
Many of the production problems encountered at Dorstfontein mine
were associated with geological features. Unexpected thin seam
conditions (1.5m and thinner) resulted in a sudden halt of production in
many sections. For a continuous miner section a serious geological
thread is the appearance of an in-seam parting. Production losses may
be as much as 50% when these features occur in the CM-section. For
the conventional sections the most deleterious conditions are sudden
drops in seam height due
to roof slumping. The fixed set of mining
equipment in a conventional section makes it almost impossible to
negotiate this kind of problem. Production losses may be as much as
70% of normal production as roof stripping needs to be done for the
haulers to move around. A loss of production means less product coal
to sell which results in a loss of income. Production losses also mean
an increased unit cost, as the fixed cost component remains constant.
4.3.3 Safety.
Many of the geological risks may result in a serious injury or fatality.
Currently Dorstfontein mine has a very good safety record with almost
2000 fatality free shifts (will be achieved June 2003) and a lost time
injury frequency rate (LTIFR) below 2. This has only been achieved by
the continuous awareness of the workers of the difficult mining
conditions encountered so far. Another factor contributing to the good
safety record is the fact that during most of the mine's life it has been
prodUCing in the higher seam areas (1.5 - 2.5m). The occasional,
unpredicted and localized geological problems were negotiated in a
safe and efficient manner. The largest part of the remaining reserve will
be in similar or even better conditions. The risks, which may possibly
result in injury or fatality, have been identified and are well managed by
a dedicated management team and workforce.
4.3.4 Costs.
High costs are a fact of mining but sudden increases in working cost is
a huge risk for a small operation. Unexpected changes in geological
59 CHAPTER 5:
5.1.
THIN SEAM RESOURCES. International.
They are only 3 main areas in the world where significant quantities of
thin seam coal are mined namely the U.S.A, Europe and the former
U.S.S.R. (Clarke et aI., 1982). Of these the former U.S.S.R. produced
more than 75 percent of all thin seam coal worldwide and that mainly
from the Ukraine. In Europe the mining techniques have been developed
for deep mining conditions while in the U.S.A shallower and flatter
seams have allowed for room and pillar methods.
The largest producers of thin seam coal are the former U.S.S.R. and the
U.S.A Other countries produce smaller tonnages but still have significant
output. Countries like Spain, the U.K.,
Czechosl~akia,
Poland and
Colombia produced significant quantities of coal from thin seams. In the
late 1980s and during the 1990s most of the U.K. mines were closed
principally because of economic reasons following decreases in state
subsidy. Some of the old mines like Trimdon Colliery (1840 - 1925)
worked seams with heights of 3 feet 8 inches (1.11 m) at depths of 195m
using drill and blast methods. Very small tonnages are still produced in
the U.K. and this country has become a net importer of coal.
Table 4.
Thin seam definition in various countries (Clarke et at,
1982).
m
in
0.60
24
Germany
0.70
28
U.K.
0.91
COUNTRY
Belgium, U.S.A
I
36
•
France, Poland, Ukraine,
1.00
39
I Former U.S.S.R.
1.20
48
I Bulgaria
1.30
51
I
i
I
I
Czechoslovakia
61 I
I
Table 5.
Thin seam output as percentage of total coal output (Clarke
et al., 1982)
% OF RESERVES
COUNTRY
...........................
Spain
70.0
Colombia
50.0
Former U. S. S. R.
47.6
I--------­
Belgium
38.4
Czechoslovakia
30.0
U.S.A.
10.8
France
7.8
U.K.
7.0
Poland
2.0
Germany
_--_.....
1.1
I
Since thin seam mining has become unfavourable due to its low
production
rate
and
output,
these
figures
could
have
changed
subsequently, as some countries have closed their thin seam mines.
Countries like France, Belgium and Germany produced significant
tonnages from thin seams in the 1960s but have ceased production from
these mines. In Annexure 1 the various thin seam reserves are described.
No information about thin seam mining in China could be obtained. It is not
even known if they do mine thin seams, as information coming from that
country is either non-existent or not translated. It is well known that China has
almost tripled its coal production and has become one of the major coal
producing countries.
In Australia collieries are focused on high output from 30m seams and consist
mainly of opencast mines.
Some information about Australian thin seam
62 Other states with potential thin seam mines do exist and their potential
was investigated in more recent times. In Annexure 1 it can be seen that
West Virginia has introduced a tax reduction and new tax formula for thin
seam mines. Other states have made similar proposals to their
legislators in order to keep thin seam mining and their communities alive
and to promote the opening of new thin seam mines.
5.2. Republic of South Africa. (See fig. 5.1)
In the South African scenario most of the thin seam coal mining took place
in the KwaZulu-Natal Coalfields. Some thin seam mining of the No. 5
Seam took place in the Highveld and Witbank Coalfields for example the
old Blesbok, Landau, Springbok and Greenside collieries. The NO.5 seam
does not fit our definition of the thin seam as the average thickness of this
seam in the Highveld and Witbank regions is 1.8m (Jordaan, 1986). Even
today some successful mining of the NO.5 Seam (1.5 - 1.8m thick) is
taking place at Bank Colliery and with variable success at Matla Coal Mine
(1.8m thick).
The two largest collieries in the Eastern Transvaal Coalfield (Greenfields,
1986), namely Usutu and Ermelo Mines, were closed due to adverse
geological conditions. These two mines occasionally mined thin seams
although their focus was not exclusively thin seam mining (Jacobs, 1989).
At Ermelo Mines some roof brushing had to be done when 1.2 m seam
thicknesses were intersected. As this mine was not equipped and focused
on thin seam mining, this development was mainly done to work through
thin seam areas to access thicker seams beyond. Similar conditions
prevail at the currently operating Spitzkop and Strathrae collieries (Fig.
5.2) (Greenshields, 1986). Carolina Coal Company produces (drill and
blast method) 11,000 ton per month from the 1.0m thick C-Seam and
16,000 tons per month from the 1.45m thick B-Seam. Eastside Colliery
has similar seam heights but only produce from an open pit (Mr. J.
Ackerman - Owner/operator, 2003, Pers. comm.)
64 It !s therefore safe to say that a very small amount of coal is produced
from thin seam mining in the Highveld, Witbank and Eastern Transvaal
Coalfields.
Exclusive thin seam mines were those operating in the KwaZulu-Natal
Coalfields. Many of these mines are now defunct with only a handful still
producing low tonnages for strategic purposes. In the past most of these
mines supplied anthracite and coking coal to the then fully operational
Newcastle steelworks of ISCOR and the export anthracite market. As ISCOR
has closed down and scaled down many of their operations it directly affected
the production of the thin seam collieries in the KwaZulu- Natal Coalfields. A
downturn in the international anthracite market as well as the introduction of
new metallurgical processes, such as direct reduction and briquetting in the
steel industry, has obviated the need for coking coal. Small output from these
collieries would not make them economically viable for the inland market only.
Most of them were kept open for strategic reasons and heavily subsidized by
a captured market (the then government-owned ISCOR).
ISCOR found
alternative sources for coking coal, Groottegeluk at Ellisras and Tsikondeni
near Mussina, and could therefore close down not their Natal mines.
65 Table 7. Some defunct collieries in KwaZulu-Natal (Spurr et al., 1986)
Colliery
•
I
Coalfield
I
Date closed
i
?
i
1966
Balgray
Utrecht
Boemendal Consolidated
Utrecht
Constantia Coal Mine
Vryheid
?
Dumbe
Utrecht
1938
Dumbe
Utrecht
1975
Elandsberg Anthracite
Enyati
i
Vryheid
,
I
!
i
I
1971
Hlobane
Vryheid
Kilbarchan
K1iprivier
Kempslust
Utrecht
?
Long ridge
Utrecht
Mid 1990s
Makateeskop
Utrecht
?
Mooihoek
Utrecht
Mooiklip
Vryheid
Pivaan
Utrecht
I
1979
I
Vryheid Coronation
• ryheid
Late 1980s
!
Vryheid Coke
.ryheid
Vryheid Export
i
i
Vryheid
Weltevreden Anth racite
Vryheid
!,
!
1966
t
I
I
I
I
I
Late 1980s
1990s
1966
I
I
I
?
I
I
?
?
?
The above listed mines are not necessarily exclusive thin seam mines but most were
a combination of thin and thick seams extracted simultaneously. Spurr et at., (1986)
and Bell and Spurr, (1986) listed many other mines of which many were not
exclusively thin seam mines. At Newcastle, in the K1iprivier Coalfield, the main seam
mined was the Upper Seam. The Middle Seam is the thin seam, 0.94m thick, but was
not always mined. The main coal produced from this area was anthracite and
currently some small operators still reclaim dumps and mine small pits e.g. AfriOre at
Springlake.
69 Active collieries in KwaZulu-Natal (Pinheiro, 1999)
Table 8.
Coalfield
I
CBR Mining
Kliprivier
I
Duiker Heritage
Vryh.. . ':
Duiker Nyembe
Vryheid
Durban Navigation
Kliprivier
..
KliprlVler
Colliery
I Springlake
I Umgala
Utrecht
>---'~'~.-.c-------
• Welgedacht
Utrecht
Zululand Anthracite
Somkele
There are currently only 2 operating mines in the Vryheid area but in its prime this
area had a huge output of coking coal and anthracite for the export market. In the
whole KwaZulu-Natal Coalfield there are still some substantial thin seam
resources left but no market exists for these costly to mine thin seams. The total
indicated resource for all coal types in all the coal seams in the KwaZulu-Natal
coalfields is 3,035 Mt in situ of which unknown proportions are thin seams (Barker,
1999).
70 CHAPTER 6:
RISKS ASSOCIATED WITH THIN SEAM MINING. At Dorstfontein Mine all of the mining has taken place in seam heights exceeding
1.5m. The risks and associated mining problems identified during the life of the mine
were discussed in Chapter 4 and differ from that identified by Clarke et al. (1982) for
very thin seam mining. This chapter discusses the risks as well as the health and
safety issues associated with thin seam mining (at Dorstfontein below 1.4m heights).
Although some of these risks may be more applicable to hand-got coaling, they may
not be omitted as although continuous miners replaced the pick and shovel, people
still work and move around in these thin seam CM-sections.
6.1.
Geological.
a.) Seam heights. One of the greatest risks in thin seam coal mining is
unexpected decreases in the already thin seam height. These
changes are unpredictable and may be attributed to various factors
for example floor rolls and slumping structures in the roof. These
kind of geological features could bring a section to a standstill.
b.) Quality changes. In Chapter 3 it is apparent that the coal quality
and product yield of the thin seam areas could be extremely
good. Unexpected changes in product yield may increase costs,
and might terminate this difficult way of mining. The sulphur
content is one of the most important quality parameters that
must be monitored carefully. Coal analysis has showed that in
some areas the sulphur tends to be high due to free pyrite in the
coal seam.
An increase in the sulphur content, outside the
product specifications, would create a problem on the marketing
side.
c.) In-seam partings. Throughout all the exploration programmes
there were few in-seam partings intersected. This does not
exclude the possibility that extra thin shale bands and flood
sheets may occur. This will reduce the yields and create
problems fqr continuous miner production.
71 d.) Change of parting lithology. The seam-split parting will form the
roof of the thin seam section and exploration has shown that
this parting has an upwards-coarsening sequence with a lower
section of interlaminated sandstone and siltstone. This parting
can be supported, as tests have shown, as long as it stays
upwards coarsening. Changes in the laminations of this parting
may render it a dangerous roof and create production- and yield
problems.
e.) Water. Excessive discharge of water from either the coal seam,
overlying roof strata or dyke developments would create
problems for people working in such conditions. The thin seam
does not allow ease of movement and in the event of excess
water people would get wet which will lead to health problems.
Excess water would also enter machinery and motors and result
in breakdowns. Slippery working conditions would lead to
injuries.
f.) Unpredicted dykes. Most of the dykes in the thin seam area
have been predicted and some of them were intersected during
the South Main development. In the unlikely event that some
unpredicted dykes do occur it will create a serious problem for
production and could result in adverse roof conditions. Some
dykes discharge a great amount of water, which could lead to
mining problems and health and safety issues.
6.2. Mining Accidents.
An accident has been defined as "any unplanned exchange of energy
which degrades the system in which it occurs". The effect of an accident
on mine personnel is the most noticeable and the recording of such
injuries provides the bulk of the statistical information on accidents. In
most countries this wider concept of an accident is reflected in mining
legislation that demands more records and reporting of certain
dangerous occurrences that mayor may not cause personal injury. The
72 major factor in determining whether an accident is recorded and
reported is the nature of the injury sustained. That is the effect in terms
of disability and the time the injury prevented the person from working
(Clarke et aI., 1982).
In the United States a relatively low number of incidents were reported
in thin seam coal mining. There was no significant variation of the
frequency of fatalities between thick and thin seam mining. The average
rate for accidents was higher for thin seams than for medium to thick
seams. The frequency rate of disabling injuries was approximately 100
times higher than the fatality rate. It was found that the accident rate
was significantly higher in the thin seams than in the thicker or medium
seam mines. The increase in the level of hazards may be explained by
the decrease in lighting and comfort in thin seam working conditions. In
the case of injuries from falls of roof, it was suggested that it was more
difficult to avoid an imminent fall in the more cramped conditions of the
thin seam. Another possible explanation was the lack of protective cabs
and canopies on thin seam face equipment (Clarke et aI., 1982).
In contrast to the disabling accidents, the reverse trend was apparent
for non-disabling accidents. The frequency rate of non-disabling
accidents was lower for thin seam than for thicker seam mines. This can
be explained by the fact that thin seam coal accidents are likely to be
more serious when they occur since it is harder to get away from or to
correct a potential accident situation owing to the confined space. It was
found from analysis of sub categories of fall of roof that higher
proportions of accidents in thin seams occur during installation of timber
or other support, than in thicker seams. The difficulty of installing
roofbolts was identified and the protrusion of such support resulted in
obstructed travel ways, which could lead to head and back injuries
during machine movement (Clarke et aI., 1982).
73 It was found that at mines with low accident rates the morale of the
people was good, the geological conditions in terms of strong roofs and
floors were good and that increased mechanization has led to fewer
injuries. The most common single injury on the thin seam mines was
that of a sprained back (Clarke et aI., 1982).
In the British collieries there was a steady decrease of the accident level
as miners became more safety conscious. The fatality rates have
decreased from 4 per 1000 men to 0.25 per 1000 men. The most
common injuries were from falls of roof and machinery and haulage
movement. The fall of roof rates for the thin seam in the U.K. mines are
much higher than for all other mines. This may be attributed to the lack
of mobility in the thin seam sections and the support tended to be of a
lighter construction to maximize available traveling and working space.
A relatively small proportion of accidents from machinery and haulage
movement occurs at the face. Most accidents in this category appear in
the load-out and out-bye areas. The rate in all haulage and transport
accidents is higher for thin seam mines than for thicker seams. In the
U.K. mines accidents of this nature contributes to over one third of all
serious accidents (Clarke et aI., 1982).
In the U.K. mines serious accidents from the use of hand tools in thin
seam areas are rare. Stumbling and falling accidents account for the
highest number of total accidents in a single category. This high rate is
reflected in the serious accident category and shows a higher rate for
thin seam than for thicker seam. The rate for serious accidents resulting
from slip or falls is much higher for thin seams than for all other mines
(Clarke et al., 1982).
In the former U.S.S.R. few statistics exist about their thin seam mining
operations. It is noted however that augering operations in the thin
seam mines have had no accidents. The conclusion can be drawn that
74 remote operation was much safer than any other mining method. No
certain conclusions can be made about any of the former U.S.S.R.
mining operations (Clarke et aI., 1982).
In the Republic of South African most of the thin seam coal mining was
done in Kwa-Zulu Natal. The accident rate in the thicker seam levels is
lower than in the thin seam levels, except where the No. 5 (not a thin
seam) seam has been worked in the old Transvaal province (now
Mpumalanga). Accidents from roof falls were more common in these
operations due to the weaker mudstone roofs. Haulage and transport
accident frequencies were also high due to the use of track equipment
and tubs in thin seam mines (Clarke et al., 1982).
In Colombia most of the coal production is from thin seam mines. The
collection of accident statistics is not reliable as there is no legal
obligation to report and record accidents. The reportedly high accident
rate in this country can be attributed to the lack of controls and
standards and not so much to thin seam conditions (Clarke et aI., 1982).
To conclude: the U.S.A. experience indicates that the accident
frequency rate per million man-hours of exposure in thin seams is
higher than in medium or thick seam mines. If the accident frequency
rate is calculated on the basis of accidents per million tons mined, the
thin seam rates are substantially higher than that for medium or thick
seams due to the lower productivity in thin seams. In the U.S.A. the
occurrence of hazards, involving mobile machinery in thin seams, are
partly due to the difficulty of working by means of bord and pillar
methods which involves frequent moving of large items of machinery in
confined spaces. The difficulty in supporting the roof is another
contributory factor. The U.K. and the former U.S.S.R. trials with remote
mining systems have indicated that men may be removed from the face
with the expected improvement in safety.
75 6.3.
Health and Safety.
Hazards that result in physical injuries are easier to identify than those
that affect the health of workers. The reason for this is that the injury
normally occurs as a result of some violent event and the object that
cause the accident is directly identified. The detrimental effect on health
takes place over a period of time and until some loss or impairment of
body function has occurred, the employee may not be aware that the
process is taking place. The more obvious hazard to health is that
affecting the respiratory system, named pneumoconiosis. In thin seams
another health problem is beat diseases, which are caused by working
and traveling in unnatural positions. Beat diseases are more common in
ultra thin seams where miners work on their knees and elbows. These
diseases are described as sores, abscesses and swellings due to
constant beating of limbs against the roof and floor. Correctly fitting and
comfortable knee and elbow pads are important (Clarke et aI., 1982).
This condition is less likely to develop where remote control equipment
is used and the operator sits while working, but may be common
amongst the roof support crew and cable handlers.
Other environmentally related health problems are those associated
with working in close contact with water and oil, the danger to eyes from
particles picked up by high air velocities, noise and poor illumination
(Clarke et al., 1982).
Hazards to respiratory health in coal mining come mainly from inhalation
of respirable dust particles. In general the relationship between health
and dust apply to all seam conditions. The problem may be more acute
in thin seams owing to higher velocities of air needed to supply the right
velocities to the coalface. In the U.S.A. some thin seam mines required
dilution of methane and the only way to get enough volume for the
dilution was to increase the velocity. High velocities may produce a
76 counter effect by causing dust pickup. Velocities above 2 mls cause
appreciable pickup of dry dust but, when the dust is wet, velocities of
above 4 mls can be tolerated. Particle size also affects the pickup of
dust. Items of equipment in roadways can cause restrictions in cross
sectional areas and result in funneling of air with a resultant increase
velocity at the restricted point. In the vicinity of any cutting machine at
the coalface, the area is reduced causing funneling of the air with an
increase in velocity at that point. It is particularly important in thin seam
coal mining that adequate dust suppression equipment be used (Clarke
eta/.,1982).
In thick and medium seam collieries, water on the floor is merely a
problem that should be dealt with. In thin seams however the problem is
more severe when miners become sodden from crawling and sitting on
wet "floors. The use of hydraulic fluids in equipment and machinery
causes skin diseases such as dermatitis. Spillage must be kept to a
minimum and protective gloves must be worn at all times. Complaints
such as colds, influenza and rheumatism may develop where the
ventilating air is cold and the wet miners move in and out of this cold air
(Clarke et a/., 1982).
The amount of noise in thin seam working conditions is much more
pronounced than in larger working spaces. It is therefore imperative that all
workers wear hearing protection at all times. The advantages of remote
control operations are obvious as in the case of noise as the operator is
physically removed from the source of this noise (Clarke et a/. , 1982).
6.4. Production rate and costs.
In thin seam mining a greater area of ground has to be mined in order to
extract an equivalent tonnage to that from thicker seams. Many of the
tasks that have to be performed in underground mines are related to
linear advance and so for a given output they must be carried out more
77 frequently in thin seam mining. Extensions of rail track, conveyor belts,
water- and power lines can reduce the productivity in thin seam
sections. Other tasks such as sweeping and stone dusting needs to be
done and are directly related to area extracted and not tonnage mined.
These factors reduce productivity in thin seam mining. In the late 1960s
many mines still operated at 10 tons per manshift. This production
output has increased with the introduction of longwall mining methods
and bigger and more powerful continuous miners. The greatest risk to
the production rate is the lack of availability of mining equipment,
adverse geological conditions, high equipment maintenance and
downtime on the transport systems (Clarke et aI., 1982).
The direct result of a low productivity is the escalation of cost. Although
the fixed costs cannot be changed. its component in the Rand I ton cost
of the RO.M. tons, will increase. With the high output this component
becomes less pronounced in the Rand I ton costs of the RO.M. tons
e.g. if the fixed component equal R 200 000.00 per month and the
section produces 20,000 tons per month, the RO.M. fixed cost is
R 10.00 I ton. If the section only produces 10,000 tons for that month,
the RO.M. fixed costs will be R 20.00 I ton. Likewise the variable cost
will be influenced by additional maintenance and repair costs during
adverse mining conditions. It is common for collieries to have a high
fixed cost and relatively small proportion of variable cost. This feature of
a mine makes it imperative that output targets are achieved. Nearly all
the profits come from marginal tonnage i.e. tonnage mined over and
above the base tonnage.
Another risk factor that seriously affects the cost of thin seam mining is
the yield. By either cutting the floor or the roof the yield from the thin
seam sections would be reduced which in turn would increase the costs.
Therefore it is imperative that mining horizons being maintained to
produce is much coal as possible and exclude contaminants.
78 CHAPTER 7:
7.1.
CURRENT THIN SEAM MINING TRIAL. Continuous Miner and Battery Haulers.
In 2002 the German company Maschinen- und Bohrgerate Fabrik GmbH
designed a thin seam continuous miner that is capable of cutting as low as
1.0m. It is called the Wirth Paurat H4.30. (For specifications see Annexure 3).
The main purpose of this design was to directly compete with the American
company, Joy Mining Machinery (a subsidiary of Joy Global Inc. Company),
which has a huge market share in the U.S.A coal mining industry and in the
RS.A and who also specializes in thin seam mining equipment (pers.
comm.). T.C.S.A management heard about the new development and
enquired about the possibility to test this machine at Dorstfontein Mine and
compare it to the current Joy 12HM15 on the mine. It was agreed to, with the
arrangement that Dorstfontein uses and tests the machine for 1 year at a fixed
rent after which T.C.S.A has the option to buy the machine at a reduced
price. The Wirth arrived at the mine in middle December 2002 and moved into
a section where the seam height is 1.6m. For the coal haulage there are 2
Stamler BH10 thin seam battery haulers (For specifications see Annexure 4).
The Wirth is equipped with a DebbexlKennametal double rotating drum,
which has been designed to be able to cut thin stone bands. The
configuration of the cutterhead is such that a fair amount of the large coal
fraction is produced and the fine fractions kept to a minimum.
Initially there were problems with the power supply and software of the
Wirth as this machine was built and assembled in Germany and needed to
be adapted for South African conditions. A few minor design errors also
needed to be corrected on mine to suit our specific conditions. Once the
Wirth was in operations it was clear that this machine is well constructed
and built and should easily cut in-seam partings and even be able to pull
down the seam-split parting in areas where roof brushing is necessary.
Presently the parting is being blasted down by drilling holes into the upper
coal seam as there exist the potential to damage the machine.
Further
problems needed to be sorted out during the following few months in order
to achieve full production. During March 2003 the standing time became
less and availability started to increase. The increased availability has led
to another problem regarding the availability of the Stamler BH 10 thin
seam battery haulers. The Wirth machine cuts too fast for the 2 battery
haulers and has to wait before it can discharge more coal from its bin. It
became apparent that there is a need for another thin seam battery hauler.
The installation of roofbolts to support the parting is quick and no delay
times have been experienced during their installation.
The Wirth has a cutting range between 1,0 and 2.8 m but will spent most of
the trial time cutting between 1.5 and 1.6m. The maximum allowed cutting
depth is 12m, for safety reasons, after which the parting needs to be
supported before the machine can cut that heading again. Roof brushing is
currently been done only in the combined travel and belt road, while full
support of the parting is done in al\ the other roads. The planned production
rate is 1250 tons per day for the first year after which production will be
increased to 1500 tons per day for six years and then again reduced to 1250
tons per day for the last three years. This gives an average production rate of
1400 tons per day for ten years. The lower production rate in the first year is to
allow time for all the problems with the new machine to be solved while the
lower production in the last three years is to allow lower productivity in the very
low seam areas.
The current labour complement is as follows:
1 x Miner
1 x Continuous miner operator
1 x Continuous miner assistant
-
2 x Hauler drivers
1 x Feeder-breaker overseer
80 1 x Roofbolter operator
1 x Roofbolter assistant -
4 x General labourers A total of 12 persons per shift. 7.2. Ventilation
The primary consideration when determining the ventilation requirements for
thin seam mining is the provision of healthy, safe and comfortable working
environment. Sufficient fresh air must be supplied to the workings to keep the
concentration of methane in the general body within the legal limits which
prescribes an concentration in the air below 1,4% per volume, reduce dust
concentration to at least 1,0 mg/m 3 and maintain air velocities of not less than
1,Om/s along the last through road in the section. As shown in Chapter 6
equipment in roadways can cause dust pick-up and chOking of the airflow to
the face (Clarke et aI., 1982).
Methane emission tests are done on a regular basis by taking core samples
from a production face at the mine. Some of the results are tabled below.
Gas Content (mj/ton)
Emission rate (liters/tons/min)
I
0.95
34.3
I
Normally a thin seam does not emit large quantities of methane (small volume
of coal) but caution should be taken near dykes and where dolerite sills over1ie
coal seams to form a cap that prevent degassing of the strata during
secondary coalification. This is not the case at Dorstfontein Mine and methane
gas should not be a risk in the thin seam areas. The maximum allowable
concentration of methane in the general body of the air in any place where
people are required to work or travel is 1,4% by volume. If a limit of 0,1% is
used to determine the dilution volume of air, then a safe volume of air of at
81 least 15m 3/s will be required to ensure that the methane content of the return
air volume does not exceed this 0,1%.
Calculation (Van Zyl, 2001, pers. comm.):
• m3/ton/min = 34.3 liters I ton I min + 1000 => 0.0343 m3 1ton I min
3
• The CM cuts 22 tons I min => 22 x 0.0343 = 0.7546 m I min of gas
released during cutting.
• To get to the ventilation needed:
0.7546
m3 1 min + 60 =0.01257667 m3 1sec gas released.
• The dilution needed is 0.1%:
3
0.01257667 m /sec+ 0.1%
=12.577 m3/sec
To be safe, use 15 m3/sec
The air volume necessary to ensure healthy and safe working conditions will
be more than that required to dilute the methane. The ventilating air will be
distributed to at least the last two through roads from the faces at a minimum
velocity of 1,0 m/s. This will require a quantity of air calculated as follows:
Average seam height:
1,3m
Bord width: 6,8m
Section air quantity
=
last through road area x velocity
=
(6,8 x 1,3) m2 x 1,Om/s
=
8.8 m3/s
By allowing 40% for leakage (Van Zyl, 2001, pers. comm.) and adding 15
m3/sec for dilution, the volume must be increased to at least 27 m3/s.
A
conservative figure of 30m 3/s for the Wirth-section will be sufficient which is
not much less than the 35 m3/s currently supplied to the sections on the mine.
The current practice of erecting brick stoppings between pillars to separate the
intake and return air roadways will be maintained.
3
A jet fan capable of
handling an air volume of 4m /s will be used to positively ventilate the
82 advancing face in the Wirth-section. Directional water sprays in association
with a dust scrubber are currently been used on the Wirth. So far it has
effectively controlled the dust liberated during cutting operations.
The dust
scrubber installed on the Wirth currently handles an air volume of 7m3/s.
In order to achieve a last through road velocity of 1.0 m/s the total amount of
air to the section should not be less than 30 m3/s. The current ventilation fan
on the mine is capable of supplying this additional air to an extra underground
section. To channel the air to the new working area, some additional
aircrossings will have to be constructed at a current cost of R 15,000 each,
which have been catered for in the financial evaluation.
7.3.
Rock mechanics.
7.3.1. Split-seam parting tests and results.
Detailed evaluations of the seam-split parting were done by Mike Spengler,
the practicing rock engineer on the mine. These tests involved impact splitter
as well as compressive strength tests. A detailed report is attached as
Annexure 6. From these tests it was clear that the parting is strong and
competent enough to form a safe beam to undermine. Due to safety reasons
and to uphold the safety record of the mine, it was decided to construct a
double safe beam by suspending the parting and upper coal from the proper
roof using 1.5m full column resin bolts as well as clamping the layers together
to for a strong beam (Spengler, 2002).
7.3.2. Support pattern and cutting sequence.
For the support pattern and cutting sequence that will be introduced in the
thin seam areas, see Fig. 7.1 and 7.2. The generally accepted safety factor
for coal mines is 1.6 where the probability of pillar failure is only 0.998468
(Van der Merwe and Madden, 2002). For shallow to medium depth mines
with a very competent roof is general practice to design the bord widths to
seven meters while six meters is used in mines with poor roof conditions.
With this knowledge and working to a safety factor of 1.6, the pillar widths
83 can be calculated using Salamon's Formula (Van der Merwe and Madden,
2002, p. 51). At Dorstfontein the centers (from the middle of the pillar to the
middle of the bord) is 13.5m at a safety factor of 1.6.
7.4.
Advantages of thin seam coal mining.
It is human nature to follow the easiest way to reach a goal. So why would
companies pursue thin seam coal mining and why would Dorstfontein specifically
pursue the thin seam resource? There are many reasons and some of it has
been dealt with in other chapters of this treatise. The current mining trial at
Dorstfontein Mine has confirmed what has been suspected for a very long time.
The following reasons make it worth pursuing the thin seam coal beneath the
seam split parting:
a.)
During the mmmg trial with the Wirth machine, the yields increased
significantly by 8 percentage pOints from about 72% to about 80% within a
matter of a few days of mining below the parting. In this, one of the most
important objectives of this exercise were met namely to improve the yield
by undermining the seam-split parting.
b.)
There is less standing time due to discharge shoot- and crusher
blockages caused by the seam-split parting breaking up in huge lumps
and fouling up the coal chain to the plant.
c.)
One big advantage is the saving in belt replacements and maintenance.
When the seam-split parting gets dumped on to the main belt gOing out of
the mine, holes are punctured into the belt due to the weight and shape of
the stone. This has been reduced, as there is less stone coming from this
section.
d.)
In order to increase yields and prevent damage to the belts the section
crew picked some of the stone by hand to be stowed underground.
Fortunately no injuries occurred during the handling of the stone, but a
chance existed that an accident could have occurred. This kind of injury is
now less likely as the current handling of stone underground, has been
reduced.
84 e.) The biggest and most important advantage is the extension in the life of
the mine and the longer utilization of existing facilities. Further more there
is the extraction of the whole No.2 Seam reserve and the additional
revenue coming from this thin seam resource.
85 CHAPTERS:
8.1. ECONOMICS OF THIN SEAM COAL MINING.
Introduction.
It is a known fact that thin seam mining can be very expensive, both in
monetary value and in human life. The main decision to pursue thin coal
seams is made on both strategic and financial factors. In modem society and
with legislated protection the human cost will outweigh economic factors.
With modem technology and the speed of modem day transport, strategic
reasons do not play such a big role as in the early to middle decades of the
previous century. Countries have become less dependent on coal and with
open market economies and the "global village" concept any grade of coal
can be sourced and delivered in very short periods of time. It seems that
financial evaluations dictate decision making but risks (human lives) can
terminate these same decisions. The use of computer constructed financial
models makes it easy to calculate a Net Present Value (N.P.v.) and Internal
Rate of Return (I.R.R.) for a specific project. It also has the added benefit
that sensitivity parameters can be built in which can be changed to see the
effect on the N.P.v.
8.2. Notes on the Financial Model.
It has been assumed that the thin seam area will be mined concurrently
will the other sections and will be fully extracted by the time the mine
closes. This exercise must not be regarded as a stand-alone evaluation for
a new mine. The thin seam area will supply additional coal to the current
operation and markets and may in future replace some of the current
sections as these tail down towards the end of the mine's life.
In the construction of the thin seam financial model a few assumptions were made. The following were regarded as sunk cost: a.)
Cost of lease or rights to the mine. b.)
Cost of exploration and evaluation. c.)
Cost of establishing the surface infrastructure. 88 d.)
Cost of establishing and developing the underground facilities. The
thin seam resource forms the northern boundaries of the current
southern mineable reserve, called South Main (see fig. 3.14). All
current and future mining in this area will be done up to where the
seam thins down to below 1.5m. Extending these mining panels into
the thin seam resource should not cost additional money and may
not
need
any
development through
barren
grounds.
Some
development had taken place to reach South Main (called the "Neck
Development" after the thin and narrow area that needed to be
I
developed, see Fig. 3.14) and an established main conveyor belt,
ventilation road and travel road were established to connect South
Main with the northern part of the reserve.
e.)
Cost of the washing plant.
f.)
Some costs already incurred and accounted for during previous
mining to develop the South Main Area, for instance the 2 thin seam
battery haulers, roof bolters and belting infrastructure.
g.)
All yields quoted are theoretical yields but in the financial model a
plant factor has been used in order to get to a practical yield. All
financial calculations are based on the practical yield.
The financial model was constructed for a ten year period of thin seam
mining. This period coincides with the closing of the mine in the year 2013
and the introduction of the thin seam must be done sooner than later as
only one operating section on the mine will not be feasible. An extraction
rate of 70%, geological loss of 10% and a mining loss of 10% were
factored in to reduce the 7,06mil. in situ tons to 3,56 mil. R.O.M. tons. The
production rate was calculated by using current knowledge gained from
current mining with the Joy 12HM15 and the Wirth trial. Zwaigin's method
of production rate calculations (Class notes, 2002) is inappropriate for this
exercise as his formula provides for a multiple section mining operation.
USing his formula (tons/annum
= 390
89 x (in situ tons)O.5 ) will yield a
tonnage of 4100 tons per day, which is about three times more than
practical for a single thin seam section.
The first year's production rate will be at 1,250 tons per day RO.M. which
is 50% of the current Joy production in a 1.8 to 2.0m thick seam. This
tonnage should add up to 313,750 tons per year. The production rate will
increase to 1,500 RO.M. tons per day, or 376,500 tons per year, for six
years. This increase is due to the learning experience during the first year
of production. The production will fall back to 1,250 RO.M. tons per day
for the last three years due to the very low area to be mined at the end of
the mine's life. These production rates will result in the extraction of
99.55% of the potential RO.M. thin seam resource.
The main capital equipment is the full cost of the Wirth machine at
R 15,000,000 while provision was made for an additional Stamler hauler in
year 2004 at a current cost of R 4,000,000. Financing of this equipment
has come from the operating profits of the mine and has been budgeted
for in the preceding year. All other capital and operational expenditure
from the year 2003 onwards were allocated pro-rata to the thin seam
section at a rate of 30%. This was done on the assumption that eventually
30% of ROM production will come from this section.
The overhauling of the Wirth will be done every four years while money is
allowed for continuous repairs and overhauling of the other machines
(haulers and roofbolters) throughout the life of the project. This should see
the equipment through till the end of the life of mine as this kind of mining
machinery practically have an unlimited life and only become redundant
when new technology replaces them.
Provision was made for additional support of the parting. Extraordinary
support was provided for under Capex while normal support falls under the
contractor's rates. The current contractor, LTA Grinaker, will charge 10%
90
above his normal rate for working in thin seam areas. This additional cost
was factored in under Operational Costs and includes the additional labour
cost for thin seam mining.
No additional costs were allocated for roof brushing. The combined belt
and travel road will be one intersection, 8 m wide, and is the only road that
will be brushed to a height of 2.0m. The only additional roof brushing will
be done in the very low areas of 1.2 m, where the total seam height is in
the order of 1.7 m. The brushing will mainly entail the pulling down of the
parting and upper seam and in a few instances the blasting into the proper
sandstone roof above the No.2 upper Seam.
The discount rate of 15% was chosen based on T.C.S.A. policy. This rate
is based on country risk and market related risks used by the foreign
mother company (TOTAL) to evaluate projects in South Africa. Escalations
are factored into the financial model (Annexure 10) only as from year 2004
as all costs and increases for 2003 are fixed for the rest of the year. The
inflation rate is based on government guidelines to keep inflation between
3 and 6% per annum. The maximum figure is used. The P.P.I. (production
price index) used is 5%, based on current figures of 5.4% (Finansies en
Tegniek, 9 April 2003, p. 62). The capital escalates at 10% based on the
annual devaluation of the Rand against the U.S. Dollar and worldwide
inflation of about 2% per year. Inland selling price increases at inflation
rate (6%) while the average dollar-selling price for the past 5 years is used
for the export sales (US$ 27.77). All other operational costs escalate at
6% per annum.
The yield used in the model is that of the current practice at Dorstfontein to
beneficiate to an ash content of 13.5%. At this yield value (95.7%) the
N.P.V. is R 27,206 mil. at a discount rate of 15% while the I.R.R. is
305.2% compared to the company's hurdle rate of 15%. The equivalent
values at a R.D. =1.6 cutting point is R 15,180 mil. and 120.7% (See
91 From Fig. 8.4 it can be seen that the N.P.v. an I.R.R. follow similar trends to that of
the yield. It is imperative that the production be kept above 1100 tons per day to
make this thin seam economical. Many factors influence production in thin seam
mines and these adverse conditions will need constant monitoring and management.
8.3. Sensitivity analysis.
Sensitivity analyses were done for the N.P.v. and the I.R.R. at the 13.5%
ash content yield and at a discount rate of 15% for the N.P.v.
The following parameters were used to construct a spider diagram (Fig. 8.5)
for the sensitivities:
a.)
Operating Costs b.)
Selling Price (Export) c.)
Selling Price (Domestic) d.)
Yield e.)
Production f.)
Capital Expenditure Table 11. Sensitivity of the N.P.V. to certain parameters.
Parameter
Variation
erating Costs
•30% to -40% I Selling Price (Export)
i -40% to 30% elling Price (Domestic) -40% to 30% • Id
-40% to 0% I -40% to 30% I
30% to-40%
o
1
95 Another shortcoming is the escalations that should be built in over a period of
time. Few would have predicted that inflation would be 13% in 2002 when it
was around 6% in 2001. Who knows what inflation will be in 2008?
Unknown global events will have or can have a huge effect on profitability of
an operation. Incidents such as terrorist attacks (U.S.A. bombings), changing
governments and legislation can impact heavily on the profitability of an
operation.
Another shortcoming is the unpredictability of market requirements. Overseas
clients can change specifications on coal, which might negatively affect the
coal price. Changes in environmental legislation in the European Community
can negatively affect the perception of coal.
Another unpredictable factor is the production rate in the future. There may be
a sudden increase in demand from customers, which could positively affect
the profitability but negatively affected the life of mine. The opposite is true as
a decreasing demand for coal can negatively affect the profitability, as
operating costs per R.O.M. ton (R/t) will increase as production decreases.
These outside influences are unknown and unpredictable and cannot be
accounted for in the discount rate and financial model.
98 CHAPTER 9:
SUMMARY, CONCLUSIONS AND RECOMMENDATIONS.
Dorstfontein Coal Mine has some 7.0S mil. tons of bituminous coal in a thin seam
resource with heights varying from 1.2 to 1.4 m. The geological setting of this
colliery makes it is a more difficult mine to operate and result in many mining
problems. Some mining related problems in the past four years were due to
geological features encountered during mining. Experience gained from the past
mining can be employed in the thin seam resource area. The big advantage at
Dorstfontein is the high quality of the coal. High yields, low sulphur, low
phosphorous and low ash values make it a well sought after product. The
proposed product from the thin seam resource is a coal with an ash value of
13.5% at a theoretical yield of 95.7%. An alternative product is achieved at a
relative density cut of 1.S, which gives a yield of 89.2% and an ash content of
11.25%. Initially this was the product specification until the market started to
accept slightly higher sulphur and ash values.
In the south of the Dorstfontein Mine reserve, a persistent seam splitting parting
exists varying in thickness from 0.1 to 0.75m. The upper coal seam is very thin
(0.1 to 0.35m) and is uneconomical while the lower seam varies from 1.0 to
1.75m in thickness. In the study area the lower seam ranges from 1.2 to 1.4m in
thickness and forms the lower economic unit. During extraction of the lower seam
the seam-split parting will form the roof. The purpose of this study was to:
a.)
determine the possibility of mining the thin seam resource,
b.)
study the possible risks,
c.)
review and comment on other thin seam coal mining,
d.)
to determine the economic value of the thin seam deposit and
e.)
quantify the resource in the category 1.2 to 1.4m seam thickness.
The extraction of thin seam coal occurs throughout the world. The definition of
thin seams varies from country to country and some countries regarded the cut­
off seam height at 24 inches (O.SOm) while some European countries regard the
cut-off as 1.0m. The largest thin seam coal producers are the U.S.A. and the
99 Ukraine. Many countries in Europe produced coal from thin seams. Thin seam
coal mining became unfavourable due to its low production rate and very high
cost of mining. Only a few strategic mines were kept open and heavily subsidized
by governments in order to keep them in production for the higher quality coal
they produced and to prevent small villages becoming ghost towns due to
unemployment. In the U.S.A. many small thin seam collieries exist around West
Virginia and the other southern states. Production from these mines is very low
and tax incentives were introduced to keep them operating and to act as an
incentive for new mines.
In South Africa most thin seam mining took place in KwaZulu-Natal. The most
common product was anthracite produced for the steel industry and the export
market. Most of the Natal mines are now defunct and only a few small-scale
operators are mining under very difficult conditions. The largest operating colliery
in KwaZulu-Natal is the Zululand Anthracite Colliery, owned by the Ingwe Pic
group. Current production at the mine is 60 000 tons per month.
Most of the literature used in this study comes from old publications since many
of the worldwide thin seam collieries were mined in the 1900s and started to tail
off in the 1970s to 1980s. A publication by Clarke et al. (1982), Thin Seam Coal
Mining Technology, was very helpful in order to determine the risks of thin seam
coal mining, health and safety problems and to get an overview of worldwide thin
seam mines in the 1970s. In the R.S.A. a few publications on the defunct
KwaZulu-Natal collieries was helpful in order to determine the coal fields mined,
defunct collieries and current operations.
The advent of the mechanized continuous miner technology has changed the
economic parameters pertaining the mining of thinner seams and especially
within the range of 1.2 to 1.4m as considered here. This combined with the
dwindling high quality thick seam resources may be seen as the principal reason
for the current investigation.
100 One continuous miner section and two drill and blast sections undertake the
current mining at Dorstfontein. Most of the mining took place at seam heights in
excess of 1.5m. Various mining methods were looked at to extract the thin seam
but the most cost effective and productive current technology is the continuous
miner method. Currently a thin seam mining trial with an imported German­
designed continuous miner (the Wirth Paurat) is taking place. Numerous
problems were encountered during the first few months of the trial but availability
and production has started to increase. Much of this section's equipment is
already on the mine and the only capital expenditure required is that for the
continuous miner and possibly a third Stamler thin seam hauler. Additional
support needs to be installed to keep the parting up. In the mining trial the parting
behaves well and forms a strong beam under which safe working conditions
exist.
In the financial model an extraction rate equivalent to 10 years of mining was
used. An average daily production of 1400 RO.M. tons per day for 10 years
means that a total extraction of 99.55% of the possible RO.M. tons can be
achieved. The Net Present Value (N.P.v) is R 27,206mil. at a discount rate of
15% and at the yield equivalent to 13.5% ash content. The corresponding I.RR
is 305.2%. The distorted and high I.RR is the result of very low capital
expenditure due to the fact that much of the capital equipment has been
regarded as sunk costs. Furthermore it must be kept in mind that this is not a
stand-alone mine but forms an additional reserve block to the current mining
reserve. The real cash flow, at a discount rate of 15% and yield equivalent to
13.5% ash content, is listed in Table 13 and illustrated in Fig. 9.1. The effect of
the annual 10% escalation in the capital expenditure is pronounced in year 2010.
Table 13. Cash flow.
Year
Real Cash Flow
(Mil. Rands)
Accumulated cash
flow (Mil. Rands)
I
!
2003
2004
2005
2006
2007
-2,884
8,861
9,847
3,936
r,"76
15,823
19,759
_
.
-
AA
I
2010~·
2008
2009
8,020
8,358
6,244
-3,678
3,140
4,459
27,779
36,137
42,381
38,703
41,843
46,302
101 2012
management input in addressing the risks, auditing the health and safety issues
and the training of people to familiarize them in the working of those more difficult
mining conditions. Better training and difficult mining conditions will add to more
expensive labour. In the financial model the additional labour costs has been
added to the contractor's rate.
It is recommended that a similar study is undertaken on the thin seam resources
below 1.2 m. Heights ranging from 1.0 m to 1.2 m are regarded as intermediate
seam heights in many countries. It is further recommended that short-wall mining
methods are investigated for the whole of the thin seam resource within the
height range of 1.0 to 1.4 m. Many overseas countries, especially the U.S.A,
make successfully use of short-wall mining methods and achieve good
production rates under these conditions.
To conclude, one must stress the fact that thin seam mining is only one of the
avenues, and probably the most difficult, to increase the potential resource of
high grade export and metallurgical coal. The successful and economic
exploitation of the thin seam coal reserve at Dorstfontein Mine will impact on the
potential for further investigation of similar deposits which may lead to the
successful establishment of small scale mining operators from previously
disadvantaged communities.
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Southern Africa, Vol. 2. Geological Society of South Africa, Johannesburg, p.
2011-2022.
20. Stewardson, M.C. and Saunderson, RD. 1999. South Dorstfontein: The
Geology. Reserves and Grade of the No.2 Seam. (Unpub.) Internal Report:
AngloVaal Minerals, 76pp.
105 21. Van der Merwe, J. N. and Madden, B.J. 2002. Rock Engineering for
Underground Coal Mining. Published under the auspices of SIMRAC and
SAIMM, p. 50 - 52 and 201.
22. Van Zyl. W., 2001. Memo: Ventilation standards for continuous miner sections.
Internal report: Dorstfontein Coal Mine, pp. 2.
23. Winter, M.F., Cairncross, B. and Cadle, A.B. 1987. A genetic Stratigraphy for
the Vryheid Formation in the northern Highveld Coalfield. South Africa. South
African Journal of Geology, Vol. 90 NO.4. Geol. Soc. of S.A, Johannesburg,
p. 333 - 343.
24. Woodruff, S.D. 1966. Methods of Working Coal and Metal Mines. Vo1.3.
Pergamon Press, New York, p. 3 - 109, 224 - 254.
25. SAMREC. 2000. South African Code for reporting of mineral resources and
mineral reserves (The SAMREC Code). Prepared by The South African Mineral
Resource Committee (SAMREC) under the auspices of the South African
Institute of Mining and Metallurgy, pp. 41.
26. The South African Coal Processing Society. 2002. Coal Preparation in South
Africa. Compiled by: The South African Coal Processing Society,
Johannesburg, p. 38 - 43.
106 ANNEXURES Annexure 1. Thin seam coal deposits of major producing countries.
Annexure 2.
U.S.A. Tax.
Annexure 3. Wirth brochure.
Annexure 4. Stamler BH10 brochure.
Annexure 5.
Development of a floor and roof classification applicable to collieries.
Annexure 6. Geotechnical analysis.
Annexure 7. Cash flow sheet.
Annexure 8. Capital expenditure.
Annexure 9. Operational costs.
Annexure 10. Escalations.
107 ANNEXURE 2 REDUCED SEVERANCE TAX RATE FORTHINSEAM
COAL PRODUCED FROM NEW MINES
Information contained herein is of a general nature and should be used only as a reference and not
a substitute for tax laws or tax regulations.
Coal severance activities are subject to both a State tax, equal to the greater of 4.65 percent of gross receipts
(less credits) or 75 cents per ton minimum tax on coal, and a local tax equal to 0.35 percent of gross receipts.
Fortax years beginning after April11 , 1997, coal severance activities associated with new underground mines
or underground mines not in production between October 14, 1996 and April 11 , 1997 are subject to a reduced
severance tax rate if the seam thickness of such mines is forty-five inches or less. The determination of actual
seam thickness would be based upon a report by a professional engineer who uses an isopach mapping technique.
For qualified mines with a seam thickness of less than thirty-seven inches, the State tax equals the greater
of 0.65 percent of gross receipts (less credits) or 75 cents per ton. The local tax remains at 0.35 percent of gross
receipts.
For qualified mines with a seam thickness between thirty-seven inches and forty-five inches, the State tax
equals the greater of 1.65 percent of gross receipts (less credits) or 75 cents perton. The local tax remains at 0.35
percent of gross receipts .
If a coal processor purchases coal from a qualified thin seam mine then additional processing activities
associated with such coal would be subject to the same reduced tax rate as applicable to the initial severance
activity. However, processors must maintain a log with records of qualified tons and receipts subjectto alternative
tax rates .
Thin seam coal produced from qualified mines remains subjecttothe 75 cents minimum tax. The minimum
tax provides some degree oftaxequity among all West Virginia coal producers. Absentsuch an equalizer, qualified
mines subject to preferential tax rates would enjoy a significant competitive advantage over other West Virginia
mines. The minimum tax provisions should mitigate potential losses of employment, production and tax receipts
at those mines not subject to preferential tax rate treatment.
Taxpayers must separately account coal receipts subject to the three alternative State tax rates of 4 .65
percent, 0.65 percent and 1.65 percent. The following may provide some guidance:
Example 1:
, I
Kl MiningCOinpany begins operations. at a new low,seam min.e. First year COal'
sales tota1200;000 10nsa1$30.00 per ton,: The seam thickness as.d~ermined by
isopach mapping techtliques is less than 37 inches. The fotlowi~g taxcalculatjons
Iilpply:
.
. I
§11~12B
Tax
..
Tax:
~
T r
. State Minimum
200,000 tons X $0. 75/to!:' ..
§ 11-:-13A Tax
. .
Gross Receipts: 200,000 tons x$30:00/ton
Tax Rate on Receipts: .0 ;65% + ·0;35%. r ". ':"';'!:-.=
..Gross Tax: ,
State
Local
..
' Ann!laIEX:e~ption Credit:
=
.... Net Tax:
... .
.. .
~;
•
:! I
;:
."
;,....
l S~ateShare: (0.65/1.00)·X$59,500 =$38.,675 .
Net MilO~murnT~~: ($150,000 ~$38;675)
Total Tax(~ncluding local share): .
$ 6,000,000 ..
X
$
- $
r::!
..
=
-
4:
.$
1.0% ,. '-",
60,000
_;; 500
59\500 , .
....
111,325
170,825
"
Example 2:
. MSM Mining Company begins operations at two new low seam mines, First year coal sales total 300,000
tons at $30.00 per ton. The seam thickness as determined by isopach mapping techniques is less than
.37 inches at Mine A '(production = '100,000 tons) and between 37 and 45Jnches at Mine B (production
= 200,000 tons). The following tax calculations apply:
.
,
§ 11-128 Tax
State Minimum Tax: ,300,000 tons x $0.75/Um
=,
$
=
$ 9,000,000
='
x
225,000
'§ 11-13ATax
Gross Receipts: 300,000 tons x $l0.00/ton
Tax Rate of Receipts:
(100,000 tons x $30,.Oojton)/$9,000,000 x 0,65%
(200,000 tons x $30,OQ/ton)/$9,000,000 x 1.65%
1;3167% + 0.35%
Gross Tax:
State
Local
AnnUal Exemption Credit:
NetTax: .
"
State Share: (1.3167/1 i6667)x$149,500 == $118,105
Net Minimum Tax: ($225,000 -$118,105)
Total 'Tax:
,1.6667%
150,000
,
500
$ 149,500
$
=
+ 106,895
=
$
256,395
Example 3:
JM ~ining Comp~ny 'Produces 1,000,000 tons from various mineS 'l hat have ,been; in .operation for ;
" several years, Coal from tbese mines is sold undercontractfot'$30.00perton. JM reopenstow'Pr()fit , Mine, a low seam (i.e.; lessthan ~7inc~es): not i~ operatio~ since 1989: JM sellt; 1501000190S of coal . , from lowiProfitMine,at an average p.rice of $25.00Lperton. JMalsoopensNewMine ,a nd sells 100;000 toriS of coal fromthismir'le .at an ·average of $24.00 .per ton, The seam thickriess .as determined by ,~; isopach'mappingtechniquesis less.than 37 inches at Low Profit (prdduCtlort ;,. 1'50;000) and between
.37 inches and 45 inches at New Mille (production''.:.' 100,000 tons). JM aisC);has.a CQalloadirig FacilItY ,['
Cl'edit'equal to $30,000; Ihefollowingtax calculations apply: ,.
L
I
.I
I.
'
..
I
I :i
I ,
1
§ .1-1 -128 Tax
.
,
.
'
"1~::
I:,
.
. .
,
., ::_
. ' '.
i
.
i:
;;_
.
r
-~
••
:". I
",; State Minimu'ril Tax: 1,250,000 tons x$0.75/ton , 1 .
(1 ,OO07()00+, 15~,00~+100,()OO) ,
',
§11-13AJax
'.
,'., .
" .. GrossReceipts:1,000,OoO'tonsx$30.00/ton . " . , . ,'. . + 1S0jOOOtons
'){:$25.00/ton
"
. :
.. .
",
. I'
T
+"100,OOOtonsx$24:00/ton . I : T<lxRate ot'Receipts:
...
";
'"
,
''' (1 :000,000 tons x$3ttOO/tori)!$36,150;OOOX4;£;5% (150,000tons:X$25200/ton)/$36,150,OOOxO:6s% " .. ;(100,000 to:n s ,x$24.00jton)/$36j15Q,000x ,1.65% . " ~;036% + ,.0.35% •
. , ..
, , ':
"
.' Gro$sTax: ; , ;
State ' Local ·
Credits (Coal LoadiAg :L&'ExemptiOn); , ,1 , N~t Tax: ..
','
.
: "
'
'S,t at eShare: (4.036/:ll:'3861x$1;~55,ooo= $1,430,900 ;, Net Minimum Tax: ($937,;500 - '$1;430,909) , '
,
,.
1
. •
Totai ,:Tax:
, x.
4:386% $ 1,585,500 · ' .. 30500
$1 ;55S:000 If you have further questions regarding reduced severance tax for thin seam coal, please contact the Sales Tax Unit, Internal
Auditing Division, A question in writing should be submitted to:
West Virginia State Tax Department Internal Auditing Division - Sales Tax Unit Post Office Box 425 Charleston, West Virginia 25322-0425 You may also telephone (304) 558-3333 or toll-free at: 1-800-982-8297
ANNEXURE 1 Fonnel' USSR
Geological Parameter's
Definition of thin seams
Seam dip
1.2 m
!(48 inches)
Gentle to very
steep
USA
Spain
~
~
Mainly flat
0-90
500m
(1,640 ft)
Seam depth
300- 1,1 00 m
(984-3,609 ft)
Reserves calculated
to a depth of
1,000 ft
Coal strength
Roof
Variable
6.4% sandstone
8.0% limestone
Rest shale
Mostly clay shales
Donetz and LvovVolynsky
Variable
Generally good and
strong. Frequent
draw slate
Medium
Wide areas but
thickness in
seams varies
over area
Fairly dry when
worked above
drainage table
Normally undisturbed
Floor
Extent of Seams
Water
Mostly dry, but
some very wet
Faults
Normally undisturbed
Cleat
Mostly well defined
Spontaneous combustion
Variable risk
Not generally well
defined
Variable risk
Methane
Variable emission
Generally low emission
Quality
Coking coal
Often coking and
low sulphur
United Kingdom
0.91 m
(36 inches)
0-45
Mostly 0-6
1,100 m
(3,609 ft)
Strong, variable
Strong, variable
Fragmented
Hard
Shale
Variable
Mostly clays
Northumberland,
Durham, Yorkshire and Derbyshire
Mostly dry
Highly disturbed
Mainly undisturbed
Czechoslovakia
1.0 m
(39 inches)
0-16 51%
16-3634%
+36 15%
400-600 m
(1,312-1,968 ft)
Some at 1,000 m
p,281 ft)
Hard
-
Ostrava Karvina
Highly disturbed
except Wales and
Scotland
Mostly well defined
-
-
Low risk in thin seams
-
-
Mainly gassy
All gassy
Often coking
High quality coking
coal
Annexure 1. Thin seam coal deposits of major producing countries (Clark et at, 1982)
1.0 m
(39 inches)
0-10 39%
1 0-4554%
+45 7%
0-800 m
(0-2,625 ft)
Sandstone, silts
and conglomerates
Sandstone silts
-
Colombia
j
J
Flat to steep
-
I
-
•
I
Variable
.
•
and Eastern
Bohemia
-
Low emission
Poland
-
-
-
Disturbed
Mostly weIl defined
Mainly gassy
Variable
I
·
•
Low risk
Mainly non-gassy
-
France
Belgium
Germany
Geological Parameters
Definition of thin seams
Seam dip
Seam depth
1.0 m
(39 inches)
0-20 47%
20-45 46%
+45 7%
-
Coal strength
-
Roof
-
0.6m
1(24 inches)
0-45
mostly 0-30
0.7m
(28 inches)
0-10 63%
10-20 9.5%
+20 275%
275-1,160m
(902-3,806 ft)
Maximum
Variable
Competent shale and
sandstone
Floor
Extent of Seams
Nord, Pas de
Calais, Cevennes
1,200 m
(3,937 ft)
Soft but hard in the
Saar
Shale, sandy
shale in thin seams
Good shale and sandstone Shales, sandy
shales
Charieroi-Namur,
Aachen and
Liege
lower Saxony
-
-
Faults
-
Undisturbed
Mainly undisturbed Undisturbed
Variable
Mostiywell
defined
·
-
Variable risk
·
-
Low emission
Coking coal
Spontaneous combustion
Methane
Quality
Mostly well defmed
Mainly gassy
-
Anthracite
,
-
5-70
-
-
-
-
Svoge Basin and
Balkan field
-
·
Some gassy
-
Hard sandy shales
Widely distributed
-
Romania
150-300 m
(492-984 ft)
-
-
Cleat
1.3 m
(51 inches)
10-90
mostly -45
Flat or slight 69 7%
10-25
22.4%
+25
7,9%
Mostly <200 m
(656 ft)
Water
Mostly dry
Bulgslia
China
Highly disturbed
Low risk
Some gassy
Anthracite
Annexure 1 cont. Thin seam coal deposits of major producing countries (Clark et at, 1982)
Valea-liului and
Anina
Dry
Highly disturbed
Not generally weH
defined
Mainly gassy
Coking coal
ANNEXURE 3 Low Seam Coal Header H4.30 Low Seam Coal Header WIRTH PAURAT H4.30 1. The H4.30 Low Seam Coal Header
comb ines the strength, robu stness
and versatility of WIRTH PAURAT's
heavy-duty road header range with
the ability to cut and load mine­
rals, such as coal, potash, salt, etc.
at a very high production rate.
The Coal Header with a weight of
approx. 50 t is designed to with­
stand the toughest of under ground
co nditions dUI'ing long periods of
use. It can deal with rock inclusions,
washouts and undulations in the
seam .
2. The H4.30 is capable of cutting
In operation the drum not only
4. The main frame of the machine is
and loadi ng a cross-section up to
cuts but also crushes and conveys
constructed from solid cast steel
3.5 m wide and up to 2.80 m high
from a single central position.
the material onto the loading
apron. Cutting is carried out by
components to give it the necessary
mass to react the cutting forces
With an overall height of only
tungsten carbide tipped point
within the compact overall dimen­
1,000 mm the machine can operate
attack picks arranged in a double
sions. The individual components
in cross-sections only 1.1 m high
spiral around the drum. Wear
are bolted together for ease of
resistant steel scrolls convey the
assembly and transport as well as
cut material to the loading apron,
service inside the production area.
on plain floor conditions,
and also protect the pick boxes
3, The machine is equipped with a
and limit pick penetration. The
The crawler tracks are integ rated
WIRTH PAURAT "He lix" cutting
loading apron behind the drum
into the main frame, each track
drum powered by two water­
conveys the material by the two
being independently driven by an
cooled and water-tight electric
loading sta l's on the chain con­
electric, AC, motor, with variable
motors via epicyclic gearboxes.
veyol'.
speed by inverter control.
The cutting drum is divided into
three sections - a centre drum and
The crawlers are fitted with 500 mm
two outer drums.
wide track plates. The crawlers
have sufficient power to enable the
machine to operate on tramming
gradients up to
- ..","__M""""-----"'­
~M
+/- 18 degl'ees.
5, The machine is equipped with a
high capacity roller chain
powered by the two load ing star
The main valves are operated
The switchgear for all the motors
by a radio remote control system.
on the machine and the main
circuit breaker for the power
supply, are all contained in one
7. As standard the machine is de­
drives. The conveyor transports
contactor case located on the
signed for use with an electrical
right hand side of the machine.
power su pply rated 1000 V / 50 Hz.
All motors are protected against
The electrical system can also be
both thermal and current over­
modified for use with other
load as well as against earth
voltages and 60 Hz frequency.
leakage.
The machine can also be supplied
Start and stop buttons for all
the cut and crushed material from
the loading apron to the rear of the
machine. The tail of the conveyor
can be raised, lowered and slewed
from side to side hydraulically en­
abling it to load almost any muck
haulage system.
6. All drives, i.e. crawlers, conveyor,
cutting drum and loading stars
are electrically driven. All other
functions of the machine are
operated hydraulically. The power
pack comprising tank, pumps with
water electric motor, filters, coolers
etc. is located on the right hand
side of the machine. Preset level
and temperature switches protect
fOI' use in gassy mines in full
motors as well as ampmeters and
the system which is suitable for
compliance with the regulations
fault indication lamps are located
use with both normal mineral oil
of the relevant governing autho­
at the control panel. Emergency
and HF-C fire resistant fluids, resp.
rities.
stop buttons are provided at
several points around the machine.
8. On the left hand side of the
machine is the wet dust collection
system installed, which in com­
bination with the unique water ­
spray system offers excellent dust
absorbtion for good visibility at
low consumption of water to
reduce mud spillage at the floor.
Low Seam Coal Header WIRTH PAURAT H4.30
Technical Data:
List of technical data for WIRTH PAURAT H4.30
Machine Overall
Weight
Lenght
Height
Cutting heigth
Cutting width
,;,
,(~\,,/
, \
50 t
12100
mm
1000 mm
1100-2800 mm
3500 mm
/
Crawler Tracks
JI
L
Speed
t - -
I
" ."\.
" :,..'
~
; /")
'j
~
''''~~f>' " ,
':'
'<,
/
/
i
Drive
0-30 m/min
AC-motors
Cutting Drum
Installed power
Diameter
2 x 200 kW
1000 mm
. Hydraulics
Installed power
45 kW
Electrics (standard)
Voltage
Frequency
Maschinen- und Bohrgel'ate Fabrik GmbH
P.O. Box 1660
41806 Erkelenz
Germany
Telephone: + 492431 83-0
Telefax: +49243183-267
e-mail: [email protected]
www.wirth-drilling.com
1000 V
50 Hz
ANNEXURE 4 ANNEXURE 5 ification
ent of a roof and floor cl
Ie to colli
Ie
P.
et Ie mur en
elner Klassi1ikation von Dach uno
Die
BU
ERY
35
anwendbar fur
D. C. OLDROYD, Genmin, WitbanK, South
ben
ca
Coal measures strata together with cual mining may be viewed very much as special cases with regard
to rocy. engineering considerations. The strata are frequently laminated, generally weak and
e in character and thickness over relatively-short distances. Coal mining is typically
~hly mechanized resulting in rapid geographical expansion and large areas of exposed roof, sides
and floor. A roof and floor classification system for use bya major coal mining operation needs to
be based un tests that enable large numbers of samples to be tested,
samples from the
strata,' in ways that are related to the COmmonest forms of strata control problems.
Les terrains de charbon et l'exploitation de charbon peuvent etre considercs co~me des cas
particuliers de mecanique de roches. Le terrain est souvent stratifie~ normalement faible et
variable en propriete et epaisseur sur des distances limitees. L'exploitation de charbon est bien
mecanisee, ce qui a comme consequence l'expansion geographique rapide et l'exposition de terrains
dans lesquels le tOit, Ie mur et les parois. Une classification du toit et du mur, appliquee par un
-important, Goit etre basee sur des tests d'un grand nembre d'echantillons, y inclus des
de roches faihles, d'une telle fa90n que Ies problemes classiques de comportement de
terrains en charbonnages sont abordes.
Das Kohlcngcbirge und der Abbau von Kuhle konnen als Spezialfalle in der Gebirgsmechanik betrachtet
Die Schichten sind haufig laminiert, allgeimen wenig fest und Uber relativ kurze
£ntfernungen veranderlich in GeprUge und Machtigkeit. Die mechanisicrtc Gewinnung von Kohle ergibt
einen sc:mellen Abbaufortschri t t mit grossen
von freigelegtem Dach, Stoss und Sohle
Das
einer Dach-und Sohlenklassifikation fUr den Gebrauch in einer Kohlenindustrie-Gruppe muss auf
Versuchen beruhen, die es ermoglichen eine grosse Anzahl von Proben zu nehmen, einschliesslich
sol chen von geringster Festigkeit, und das auf die allUiglichen Probleme der Gebirgsbeherrschung
',ugen ist.
~erden.
INTRODUCTIO;o;
The econumic coal measures of South Africa
occur predominantly in the Middle Ecca stage,
and to a much lesser extent in the Upper Ecca
and Nolteno stages, of the Karoo system. The
Karoo system is of Permian age thus making the
South African coal measures somewhat younber
than their European counterparts.
Tlle coal bearing strata consist chiefly of
sandstones with subordinate shales, carbonaceous
shales, siltstones and mudstones.
Many of the coal measures strata are
inherently weay. while others are highly
susceptible to weathering. Significant
variation in the rroperties and thicknesses of a
particular stratum over short horizontal
distandes is also a notable feature of many of
the coalfields, as is the occurrence of dolerite
intrusions in the form of both dyy.es and sills.
The majority of underp,round coal is extracted
by mea:lS u!~ mechanized bord and r.illar l:1etllOds
from seams lying at shallow depths.
Consequently, mos~ mines experience a rapid rate
Eurock' 92. Thomas Tollold. london, 1992
uf geographical expansion resulting in 'vast
expanses of exposed roof, sides and floor being
created, many of which have to be maintained
for long periods of time, particularly if
pillar extraction is contemplated.
THE NEED FOR A COAL MEASURES CLASSIFICATION
A number of tests are available for the
determination of rock
and other properties such as durability and the potential for swell. The carrying out of these tests is guverned by guidelines laid down by the ISp,r·j (ref. 1). Similarly, well-established rOc~ mass classification systems exist which have proven themselves in numerous practical applications. When dealing with the soft rocks of coal measures strata, however, there are certain drawbacks with regard to the use of these tests and classification systems
These include: i 1 T:1e tests or classification parameters may not relate directly to actual strata behaviour in coal mine roadways. 197
EUROCK '92
ii) Sample rreparation requirements and test
procedures may make it impossible to test
weak strata so that the behaviour of these
strata has to be inferred from experience.
iii) The tests are typically costly, time
consuming and can only be conducted in
specialist laboratories. This presents
significant difficulties when very large
numbers of tests are required such as
during the feasibility stage of a major
coal mining project.
iv) Rock mass classification systems will
frequently assign the same class to a wide
range of coal mine roofs.
c·
TRANS-NATAL'S ROOF AND FLOOR CLASSIFICATION
The Coal Division of Genmin's Rock Engineering
Department has always desired and striven to
become more p'ro-active in order to anticipate
strata control problems rather than to deal with
them only once they become apparent. In order
to do so it was essential to develop a means of
classifying coal measures strata. The size of
the department, budget constraints and the scope
of work involved meant that the following
philosophy had to be applied in devising a
suitable classification system:
i) The tests should relate to the expected
mode of failure of the strata.
ii) It should be possible to test even the
weakest material.
iii) Large numbers of tests should be able to
be conducted simply, quickly, at low cost
and in-house ..
The achievement of these aims was considered
worth losing a ~ree of accuracy for.
Roof Classification
Roof failure in South African coal mines is
predominantly governed by the frequency of
laminations or bedding planes and their
propensity to open and separate, and by the bord
width. This is in accordance with the formula
for tensile stresses in a fixed beam which gives
the maximum tensile stress, P, developed in a
beam of unit width as:
P
= ~
2t
where:
~
g
B
t
(1)
strata density
gravitational acceleration
bord width
beam thickness
Tests designed to indicate the potential for
roof failure must therefore indicate the
frequency of bedding planes and laminations, and
their potential to open. During 1982 the
introduction of a Coal Rock Structure Rating
(CRSR) system was considered. This was based on
three parameters; ROD, the results of impact
splitting tests and a parameter related to joint
condition and groundwater.
In coal measures strata it is impractical to
satisfactorily distinguish between drilling
induced and natural fractures in the rock.
Therefore, the ROD was discarded from the system
although it is still determined for all strata
that are of interest and used, where .necessary,
to assist in interpretation.
198
Fig.l.
Impact splitting test
The third parameter proved difficult tu
determine. Furthermure, .irrespecti ve of the
roof type, special support precautions are
taken at all geological discontinuities
exceeding 2m in length. Joints, therefore,
unless they are exceptionally closely spaced
have no influence on systematic roof support
design. Cunsequently, in 1983 it was decided to
confine the determination of roof ratings to
the results of impac't splitting tests.
Impact Splitting Tests
The impact splitLing test involves imparting
a constant impact to a length of cor,e every
O,02m. The resulting fracture frequency is
then used to determine a roof rating.
The instrument used is very simple (Fig. 1).
It consists of an angle iron base which holds
the core. Mounted on this is a tube containing
a chisel with a mass of 1, 5\<:g and a blade width
of 25mm. The chisel is dropped onto the core
from a constant height according to core size,
lOOmm for TNW (60mm dia.) and 64mm for NO
(48mm dla.).
The impact splitter causes weak or poorly
cemented bedding planes and laminations to open
under duress thus giving an indication of
likely behaviour in situ when subjected to
bending stresses, in some instances compour.ded
by blasting.
When designing coal mine roof support, 2m of
strata above the immediate roof are tested. If
the roof horizon is in doubt then all strata
from the lowest likely horizon to 2m above the
highest likely horizon are tested so that all
the potential horizons may be cumpared. For
shaft boreholes the full length of strata is
tested (ref. 2).
The strata is divided into geotechnical units
which are very often shorter than the units
described by the geulogist. The ROD for each
unit is determined and any geological
discontinui ties are noted. The units are then
tested and a mean fracture spacing for each
unit is obtained. Using either equation (2a)
or (2b) an individual roof rating for each unit
is determined.
For fs S 5
For fs >5
rating
rating
4fs
2fs + 10
(2a J (2b ] PAPER 35: BUL)DEF1Y AND ULUhU 1
~ere: fs = fracture spacing in cm
for example, a · uni t 1, 2m long v.'i th 8 fractures
'Iill have a mean fracture spacing.of IScm and a
mit rating of 40.
This value may be used to classify the
individual strata units (Table 1) but for coal
mine roofs the individual ratings are adjusted
to obtain a roof rating for the first 2m of
roof. The immediate roof unit will have a much
greater influence on roof conditions than a unit
2m abo ve the roof. Consequently, the unit
ratings are weighted according to their position
in the roof by using equation (3).
Weighted rating = rating x 2( 2 - h)t
where: h
t
(3)
mean unit height above the roof (m)
thickness of unit (m)
The weighte'd ratings for all units are then
totalled to give a final roof rating. For
example, a coal mine roof has three units;
O-0.8m; · 0.8-1.3m and 1.3- 2.8m above the coal
seam with ratings of 25, 32_~~8, respectively.
r:;."-(-'\~ the purpose of determining a weighted
r~~~ng the last unit is regarded as being from
1.3-2 . 0m above the coal seam. From equation 3
the weighted ratings at the mean heights of
O.4m, 1.OSm and 1.6Sm are 64 , 30 . 4 and 3.9 ,
respectively. The final roof rating is
therefore: 64+30 . 4+3.9 = 98 . 3.
After many years of experi ence and hav i ng
collected data from numerous sites the
classification given in Table 1 has been arrived
at. Good agreement between expected and actual
roof conditions has been found when using this
rating system .
Table 1. Unit and coal roof classification system Uni t Rating
,\ C.< -102717
.L8 -
28 - 32
) 32
Rock Class
Roof Rating
Very Poor
Poor
Moderate
Good
Very Good
<39
40 - 69
70 - 99
100 - 129
>1 30
Floor Classification
The floor classification system was developed
in late 1988/early 1989 for the' feasibility
study to the T-project which was investigating
the extraction of torbanite and its, conversion
to syncrude . Torbanite is found in the N°5 coal
seam of the Highveld coalfield (Fig. 6) which is
notorious for poor floor conditions . Floor
strata are liable to swell and degrade due to
water . The mechanical action of mining
equipm~nt is also a major contributory factor to
the degradation of the floor. In the light of
the above it was decided to base the floor
classification system on unconfined swelling
strain and slake durability tests . In order to
adhere to the aforementioned testing ' phi l osophy
it has been necess ary to modify the suggeste d
_ methods as laid down by the ISRM.Only the
,
U
modifications will be discussed here, for full
details of the test methods the rea der should
refer to the 15?M sugge s ted methods (ref.l).
Duncan Swell Test
The Duncan swell test measures the unconfined
swelling strain in one or more directions when
a sample of rock is immersed in water. When
testing borehole cores from coal measures
strata it is only necessary to measure the
swelling strain perpendicular to the
laminations since, in rocks liable to swell,
the swelling strain perpendicular to the
laminations will greatly exceed that in other
directions.
Samples are not prepared but are chosen with
their ends approximately paral l el. This
reduces the costs and time involved and, above
all, allows the testing of weak samples that
would otherwise break up during machining.
The test procedure requires that swelling
displacement should continue to be recorded
until it reaches a constant level or passes a
pea~ .
This can be extremely time consuming
and, for practical purposes, is not necessary.
For the vast majority of specimens, 90% or more
of their final swell will have taken place by
the time 30 minutes have elapsed. For this
reason a 30 minute swelling strain is
determined. A sample undergoing testing is
shown in Fig.2.
The swelling strain, ~30, is calculated as
follows:
S30
=
d
30
x 100",£ (4)
L
where: d
L
30
swelling displacement after 30
minutes
ini tial length of the sample.
At the end of the test the sample is
immediately removed from the water . It is then
assigned a rating from 1-6 according to its
condition. A rating of 1 being assigned to an
undisturbed sample and a rating of 6 to a
totally degraded one (fig.3) . The swell index
of the sample is then determined by mu11iplying
the swelling strain by the condition rating.
Fig . 2. Duncan swe ll tes t
199
EUROCK '92
TllC more than 250 Duncan swcll and slcJ..-.c
durability indices were carefully compared.
The approach was to rate the various
lithologies with regard to their potential to
swell or, weather based on all availabe
in for mation. Ranges of the two indices, with
appropriate descriptions, were then chosen t o
fit the majorjty of da ta. The remaining
anomal ies were then dealt wi th by fine
adjustments to the ranges . The final ranges
arrived at are given in Table 2.
Table 2. Swelling and slake durability floor
classification.
.
: ',:. '.: ~ :,: ~ ~.
, ".
.~:;;~.
'. '
"" ,',
.' .~.
.".;:\.~.~~~:~.f~ ~.~ h;r:; t ;~..,~.:;" .. / ; .~; . . .:.:", . ~"
; ' ~'.:' ..
Rating
!"" "':";:;
Description
. ,~ , : ~~if.};,;·'i' :',:L'.:2; ·,~L,;,:· _·; :.;' , :~; X·;j.:.
c
Fig.3. Samples after Duncan swell test. From
left to right condition ratings are:
5; 3 and 1
Slake ~ability Test
This te~t assesses the resistance offered by a
rock sample to weakening and disintegration when
subjected to two standard cycles of drying and
wetting. The department had equipment
manufactured - which conforms fully to the ISRM
guidelines - with four drums thus allowing four
~amples to be tested at a time.
The slaking fluid used is in all instances
water.
.
The International Standard calls for a
representative sample comprising ten rock lumps,
each weighing 40-60g. The size of core used by
Trans-Natal means that 40-60g lumps can only be
obtained from the more competent rock types. If
only these rock are tested then the results
would be biased towards good floor conditions.
For this reason the lump requirement has been
modified to 20-30g unprepared lumps (Fig.4).
The drying periods have been shortened from
2-6 hours to lYz-2 hours in order to speed up the
procedure and because the lumps are smaller.
Fig.5 shows the retained portions after the
samples of Fig.4 had been tested.
The slake durability index (second cycle),
I , is calculated as follows:
d2
Id2
where: A
C
C x 100% A
Swell
index
Slake
durabili ty
index
A
Good
<
B
Moderate
1 - 3
14 - 26
C
Poor
3.1 - 15
26.1 - 36
D
Very Poor
1
> 15
<
1<1
) 36
There is not al wa ys c omplete correlation
between the two indices. In these
circumstances the index suggesting pOOrer floor
conditions dictates the rating.
Each floor is then de scribed to a depth of
0.6m according to the rating and thickness of
each unit, e.g. Borehole
BNI4:A(0.32)/C(0.25)/A. The last layer is
usually not given a thickness because it goes
beyond 0.6m. Finally the condition of the
immediate floor is classified according to
Table 3.
( 5)
dry mass prior to testing (g)
dry mass after two slaking cycles
(g)
Treatment of Results
The brief from the T-Project management team
was that the results should be descriptive and
unambiguous.
Conventionally a high swell index implies a
poor rock, conversely a high slake durability
index implies a good rock. To avoid confusion
it was decided to present the slake durability
index as 100 - I . Both floor indices
d
therefore increas~ as expected floor conditions
get worse.
200
Fig.4.
A weathering dolerite and shale prior
to slake durability testing
PAPER 35: BUDDERY AND OLDROYD
the classific3tions assigned to those boreholes
with known conditions. Furthermore, the
classifications assigned to the exploration
holes c orrelated to other available geological
data and made sense wh en plotted on a plan of
the reserves.
BTRATIORAPHY
DESCRIPTION
UNIT
Legend
Figures 7 and 8
T:":~:~ ,!} ,:;:~,...
"'1).""; '
~
Good
~ ...
("'"'f"~!'~1,~.~,~~.~~;;:;;:·~~,=-zr;~tW~;$;':;·:::~Ml'wmIWl
Moderate
Poor
(=:.5.
Table 3
Samples from Fig.4. alter testing
Floor classification system
Description
Basis of classification
Good
A/a to a depth
Possibly
Poor
A/a to a depth <O.4m
The first figure in the
bracket refers to the
thickness of A/B and the
second figure to the
underlying C/D.
e.g. BN14(O.32/0.25)
Poor
~
O.4m
Fig.6.
Generalised stratigraphic section,
N°5 coal seam, T-Project and legend
for ligures 7 and 8
C/D in the immediate
floor. The figure in
the bracket refers to
the . thickness of C/D.
e.g. BN37(O.12)
T-PROJECT
Sadly the T-Project never got off the ground.
Had it done so it would have required massive
capital investment. Consequently, the
feasibility study had to be conducted to a high
degree of confidence. Previous experience with
the 5 seam floor and to a lesser extent the 5
seam roof meant that rock engineering
considerations would play a major part in mine
design, equipment selection and contamination.
Since the classification approach used by the
Rock Engineering Department (RED)-was novel and
untried the project management decided to test
the classification system against known
conditions. Three holes were drilled at the
nearby Matla Colliery. The location of these
holes was not made known to the RED. Neither
was a plan of the location of the exploration
boreholes made available. When given the
results for the individual boreholes the project
management team expressed themselves happy with
Fig.7.
Expected roof conditions,
T-Project
201
EUROCK'92
the information it was possible to
determine
levels of contamination for
the roof and floor. For example, no roof
contamination was expected from the longwalls
of the nature of the roof whereas
for bor,d and pillar panels contamination was
expected tQ be lOcm for good roofs and 200m for
moderate roo"'s. Floor contamination was
expected to vary from Scm for a
with a
floor to 50cm for bord and pillar
poor floor.
were expected to have a
consistent in-panel extraction factor of 92%.
For ribpilla.T" panels this was 82% with a
moderate floor
to 78% with a poor
floor.
Although the T-Project was shelved the
project management team consider that from a
technical perspective the feasibility study was
a complete succe~s.
Fig.8. Expected floor conditions, T-Project The management team chose to reduce the number
of classes to two for each of the roof and floor
plans. Thus the roof was rated moderate or good
and the floor poor or moderate (Figs. 7 and 8).
This information was then applied in a number
of ways. After considering all potential mining
methods it was decided that longwall mining
would be applied in areas where poor coal seam
roof a~d floor conditions existed and the
possibility of geological disturba~ces was
minimal. Ribpillar mining would be applied in
complex areas where the coal seam
roof and floor conditions were ma~ageable.
Mechanised bord and pillar mining would be
applied in main and
entries, areas
where surface structures needed to be protected
and in
panels not Buited to longwall
ribpillar mining and where the coal Beam roof
and floor conditions were manageable.
202
CONCLUSIONS
Since its successful contribution to the
T-project the Trans-Natal roof and floor
classification system has been
to
further major projects as'well as on a much
smaller scale. Trans-Natal's mine and project
management both view it as an essential tool ir
the investigation of greenfield sites and mine
extensions .. It has proven particularly
valuable in shaft design (ref.2). The manner
of the presentation of the resu'lts means that
mine and project management are able to
envisage the expected conditions in terms of
their own experience.
The authors make no claims regarding their
classification system other than that it
successfully meets the needs of a rock
engineering department which is
t
provide a meaningful service to a major' coal
producer. It is not generally applicable to
other minerals and strata types.
\
REFERENCES
1. ISRM. Suggested methods for
swelling and slake-durability index
properties. Committee on Laboratory TestE
document 2, part 2, final draft, Nov 1972.
2. OLDROYD D.C. and BUDDERY P.S. The design
a~d support of inclined shafts through cae
measures strata, the use of rock
classification. ibid.
ANNEXURE 6 TOTAL COAL HOLDINGS SOUTH AFRICA (PTY) LTD
DORSTFONTEIN COAL MINE
TESTS ON BOREHOLE SAMPLES OF THE PARTING BETWEEN THE 2 LOWER AND UPPER
SEAMS
1. INTRODUCTION
Tests on the borehole samples of the parting between the 2 Lower and Upper seams are
required to determine:
(i) Whether the parting can be supported using conventional roofbolting methods to
allow the safe mining of the lower seam only.
The feasibility of mining the parting with a continuous miner if it cannot be safely
supported.
(ii) The following tests were conducted:
(i) Rock mechanics - impact splitter compressive strength (ii) Mining
- "J" factor (cutting) 'W' factor (wear) 2. ROCK MECHANICS
2.1 Impact Splitter Tests
This test was devised by rock engineering practitioners of the then Genmin group in 1982
and is used throughout the industry and particularly by the Ingwe Group. Roof failure in
predominantly governed by the frequency of lamination or bedding planes, their propensity
to open and the bord width. The impact splitter causes weak or poorly cemented bedding
planes and laminations to open up under duress, thus giving an indication of likely in situ
behaviour when subjected to bending stresses.
The rating system requires 2m of strata above the immediate roof to be tested. The
borehole core is tested in geotechnical units preferably of about a half a metre in length. A
mean fracture spacing for each unit is obtained and an equation used to determine the unit
rating and the roof rating.
These were in-house tests. The results of the 3 borehole cores that were tested are:
DF 326
UNIT
POSITION
(m)
RATING
CLASSIFICATION
DF 327
CLASSIFICATION
RATING
OF 322
RATING
CLASSIFICATION
I
1.5-2.0
1.0-1.5 0.5-1.0
0-0.5 i
2m Roof
112.0
110.0
60.0
24.8
Very Good
Very Good
Very good
Moderate
110.0
110.0
24.3
20.0
227
Very Good
175
i
Very Good
Very Good
Moderate
Moderate
110.0
110.0
21.1
22.5
Very Good
175
Very Good Very Good
Moderate Moderate
Very Good
Despite the weighting of the individual units according to their position in the roof, the very
competent upper units results in the overall classifications of the roof being "Very Good".
The classification of the lower units that form the first 0,5 to 1,Om of the roof is of greater
significance and this zone is classified as "Moderate".
2.2
Uniaxial Compressive Strength Tests
As the name uniaxial compressive strength (UCS) implies, in these tests a load is applied in
one direction only with no lateral confinement In this case the load was applied at right
angles or near right angles to the laminae. The results of these tests therefore rather reflect
the intrinsic strength of the material and not the strength of the roof when subjected to
bending stresses that result in the de-lamination of the roof beam.
These tests were done at CSIR Mingtek. Three specimens from each of two borehole cores
were tested. The results are tabulated below.
I
SPECIMEN PARTICULARS
CSIR
SPECIMEN
No. 2339­
UCS - 01
UCS-04
UCS -05
UCS-02
UCS-03
UCS - 06
I
TEST RESUL TS
SPECIMEN DIMENSIONS
CLIENT No.
DIAMETER
(mm)
DENSITY
(kglm3)
UCS
(MPa)
MODE OF
FAILURE
DF329
DF329
OF 329
60,7
60,6
60,6
2450
2380
2450
99,2
95,0
98,8
XA
XA
XA
OF 331
OF 331
OF 331
60,3
60,2
60,2
2450
2510
2470
97,3
110,3
111,7
XA
XA
XA
XA: Partial cone development
3.
MINING
3.1
"J" Factor Tests
This test is used extensively by Joy Mining Machinery to predict the cutting rate of a
machine such as a continuous miner. The "J" factor is determined by the controlled drilling
of a specimen of the material that is to be cut. The oJ" factor is the average depth of 5 holes
in millimetres multiplied by 10. Material with "J" factors above 500 can be cut and becomes
easier to cut as the number gets larger.
These tests were doneat CSIR Miningtek. Four specimens from one borehole were tested.
The results of the tests are tabulated below.
SPECIMEN PARTICULARS
CSIR No.
CLIENT No.
01 Top
OF328
01 Bot.
OF328
02 Top
OF328
02 Bot.
DF328
-.
3.2
I
"J" FACTOR
TEST 1
220
282
176
186
TEST 2
210
245
194
237
TEST 3
204
257
188
215
AVER. + STD.
211,1±8,O
261,1±19,2
186,1±9,3
212,3±25,6
"W" Factor Tests
The 'W' factor or wear factor is some indication of the pick wear that will result from both
the abrasive material in the rock and the manner in which the material is found in the
matrix. Bit wear takes place when drilling the holes to determine the "J" factor. This wear
expressed in thousands of an inchis the "W' factor. "W' factors range from 0,000 to 0,018,
with long life having a 'W' factor under 0,003.
These tests were done at CSIR Miningtek. The results of the tests are tabulated below.
SPECIMEN PARTICULARS
CSIR No.
CLIENT No.
DF328
01 Top
DF328
01 Bot.
DF328
02 Top
02 Bot.
DF328
4.
CONCLUSIONS
4.1
Impact Splitter Tests
I
TEST 1
0,0034
0,0032
0,0025
0,0039
I
"W"FACTOR
! TEST 3
TEST 2
0,0046
0,0039
0,0032
0,0034
0,0027
0,0027
0,0049
0,0032
AVER. + STD.
0,0040±0,0006
0,0033±0,0001
0,0026±0,0001
0, 0040±O, 0009
The classification of the lower units of the roof as "Moderate" indicates that the roof can be
supported provided about OAm of the rockbolt can be anchored in the competent
sandstone above the 2 Upper seam. This means that a 0,9m long bolt can only be used if
the parting and the upper seam together are not more than 0,5m thick. Rows of 4 full
column anchored rockbolts every 1,5 m will be required. A reduction in the density may be
possible but that will depend on observations of favourable roof behaviour over a period of
time.
4.2
Uniaxial Compressive Strength Tests
The UCS of the specimens tested varied between 95.0 and 111,7 MPa. As stated in section
2.1, this test does indicate the ability of the parting to withstand the de-laminating bending
stresses that occur in the roof. What it does indicate is that this material can be transformed
into a competent beam if de-lamination is prevented by clamping the layers together.
4.3
"J" Factor Tests
"J" factors of between 282 and 176 indicate that the parting will be difficult to cut. Rock with
"J" factors below 500 can be cut if the rock is highly laminated or fractured and provided
high operating costs can be tolerated.
4.4
"W" Factor Tests
The results show that pick life will be greatly reduced as the majority of the
greater than 0,003.
M G SPENGLER "w' factors
are
I
ANNEXURE 7 Stnsltlvlty
Oparaflng Co.ts
0.00%
Stlllng Price (Export)
0.00%
Seiling Price (Domestic)
0.00%
YIeld
0.00%
Production
0.00%
c:Q'pllIIll!xpandltlll'll
0.00%
TolIIl
Period
Oomfontaln
2.003
2.004
2.005
314 85.2%
267 377 85.2% 321 852% 321 82.08
96,38
82.91
97.35
2,005
2,007
2.005
2.009
377 85,2% 321 377 85.2% 321 377 85,2% 321 852%
2.0101
TOOO's
3,514
85.2% 2,993
377 321 3141 85.2%1 2671 85.2% 267 I
RIton
104,37
122,54
87.89
103.19
93,16
109,38
98,75
115,94
104,68
122,90
110,96
130,27
123411 130.82
144,901 153.59
I
Alton
46,00
8.49
TOOO's
1
2,99iT
2Sn
3211
3211 18.85 321 190 131 48.76
9.00
19.98 321 190 131 51.69
9.54
21.18 321 190 131 '$27.77
8.5000
238.05
$27.77
8.7500
242.99
'$27.77
9.0074
250.13
$27.77
9.2723
257.49
'$27.77
9.5450
265.06
$27.77
9.8257
Rlton
$31.84
8.5000
268.96
RIton
216.01
165.03
174.93
185.43
198.55
208.35
ROOO's
140.441
55.345
69.02:7
71.157
74.608
77,588
48,924
50,382
27,226
16.942
9,265
1,710
3,796
$iton
$IR
1,436
3,187
343
1,616
54,666
31,203
31,217
.14
23,463
4,534
18,930
623
8.351
9,958
8.861
305·2%1
nt rate
377 .2.884 1
8.881
1
8,246
1,522
3,378
363
1,663
56.584
33.030
33,090
·59
23.553
5,084
18,489
135
6,607
11.728
9.847
9.847 1
25,665
18.033
8,740
1,613
3,581
385 1,712 58.576
35.012
35,075
·64
23.564
2,190
21.374 140 16,265
4,969
3.936
3,
54.79
10.11
22.45 321 190 131 58.08
10.72
2379 267 158 109 61.56
11.38
25.22 267 158 109 65.26 1205 26.74 267 158 109 272.86
$2777
10.1147
280.89
$27.77 104122 289.15
$2777
10.7184
297.65
$2777
11.0337
306.41
220.85
234.10
248.15
263.03
278.82
80.703 51,844 28,859 17.­
9,821 1,813 4,024 83.980
53,368
30,591
18.924
10,410
1,922
4,265
459 1,668
65,036
41,699
41,775
·76
23.337
4,091
19.246
157 9,700 9,388 6,244 72,804
45,782
27,022
18.668
9,196
1,897
3,768
405 1,602 56.136
38.577
38.721
·143
17.558
75.772
47,128
408 433 1,763 60,846 37.112
37,180
.fJ7
23.534
4,682
18,872
146 7,994 1,815 62.798
39,339
39,410
·71
23.459
5,146
18.313
151 6,306 10.732
8.020
11.856
8,388
a
17,558
·424 23,844 .5.882 -3,678 28,643
17.619
9,747
1,799
3,994
430 1,649 56.152
40,954
41,044
·90
17.198
0
17.198
158 11,737 5.305
3.140
18,876
48,514
30,382
18.626
10,332 1,907 1 4,2331 4551 1,698 60.250
43,412
43,506
·94
18.838
3,138
13,700
161 5,554 7,985 4,4~
Period
Tax Computation
Tax loss
0
0
0
0
0
0
0
0
0
·6,285
-824 i
Operating profit
211,160
16,674
23,463
23,553
23,564
23,534
23,459
23,337
17,556
17,198
16,638
Capital expenditure
114,569
16,210
6,351
6,607
16,265
7,994
6,306
9,700
23,844
11,737
5,554
96,611
464
15,112
16,947
7,299
15,540
17,153
13,636
-6,265
-824
10,459
26,983
139
4,534
5,094
2,190
4,662
5,146
4,091
0
0
3,138
I
Taxable Profit
Tax payable
30%
I
Working Capital
Stocks
967
1,000
1,060
1,124
1,191
1,262
1,338
1,482
1,571
1,666
Stores (4 weeks op costs)
2
990
1,201
1,273
1,349
1,430
1,516
1,607
1,489
1,579
Debtor (6 weeks)
4
4,257
5,310
5,520
5,739
5,966
6,206
6,456
5,600
5,829
673
1,
1
6,067
Cred~or (4 weeks all costs)
4
2,852
3,506
3,713
3,931
4,163
4,409
4,669
4,261
4,513
3,362
4,005
4,140
4,260
4,426
4,577
4,734
4,310
4,466
Opening Balance
0
3,382
4,005
4,140
4,280
4,426
4,577
4,734
4,310
Yearly Movement
3,362
623
135
140
146
151
157
-424
156
779
4,
4,627,
1
Net Current Assetl(Liabilities)
4'~1
161
ANNEXURE 8 12-AUf.03
Dorstfonteln thin seam
Yea,
2003
Period:
2004
2006
2
3
1
2008
2001
2008
2009
II
II
7
4
2010
S
2011
9
2012
10
~scala1ecl capltlll expendltur.
Underground
~rth Machine
~tamler Hauler
,
.
.
15,000,000
4,400,000
r,rentllation
15,000
elemetrev
120,000
16,500
.
18,150
19,965
21,962
48,315
53147
58,462
64,308
70,738
-
-
Concrete roads
240,000
I:xlraordinary support
100000
110,000
121000
133,100
146,410
161,051
177,156
194,872
214,359
235,795
Conveyor be!! and $trvcture
900,000
1,100000
1,210,000
1,331,000
1,464,100
1610,510
1,771,561
1,946,717
2,143,589
2,357,948
78,000
85,800
94,380
103,818
114,200
125,620
138,182
152,000
167,200
183,920
Roof Brushing
250,000
275,000
302,500
332,750
366 025
402628
442890
467,179
535,897
589487
EIectrlc8I distribUtion
105,000
115,500
121050
139755
153731
169,104
186,014
204,615
225,077
247,585
Pumps and aocessories
CMOlierhaul
15,589,737
10,846,000
1,155 000
3,630,000
1,996,500
4,392,300
2,415765
5,314,583
2923,076
6,430,766
18,808,000
7,251,800
5,503.080
14,704,888
11,668,127
4,932,992
9,083,833
21,558,667
9,781,196
3,585,472
Overland oonveyor
90,000
99,000
108,900
119,790
131,769
144,946
159,440
175,385
192,923
212215
Infla$trueture
90,000
99,000
108,900
119,790
131,769
144,946
159,440
175,385
192,923
212,215
twironmental
60,000
66,000
72,600
79,860
87848
96,631
106,294
116,923
128615
141,477
~Irategic spa"",
90,000
99,000
106,900
119,790
131,769
144,946
159,440
175,365
192,923
212,215
330,000
363000
399,300
439,230
483,163
531,458
684,615
643,077
707,384
778,123
EQuipment overall
Sub total· underground
Surface
!sub total· surface
Processing
Plan! & Laboratory modlfcalion
Discard dump
Slurry pond
StrategiC spares
SUb total· proclISslng
Subtotal
Capax fees @ 4%
0Ia1 capItal expendItUre
66,000
72,600
79,860
87,846
96631
106,294
116923
128,615
141,477
155,625
111,000
122100
134,310
147,741
162,515
178,767
196,643
218308
237938
261,732
45,000
49,500
54,450
59,895
658S5
72,473
79,720
87,692
96,461
106,108
150,000
165,000
181,500
199,650
219,615
241,517
265,734
292,308
321,538
353,692
312,000
409200
450,120
496,132
644 845
599,110
669021
124,923
791,416
877,167
17,610,000
8,030 000
6,352,500
115,639,2&0
7,686,526
6,063,570
9,327,2119
22,9211,657
11,286,996
6,340,762
700,400
321,200
254,100
625,570
307,461
242,543
373,091
917,066
451,440
213,630
18,210,400
8,361,200
6,606,600
16,284,820
7,993,996
6,306,113
9,700,369
23,843,723
11,737,435
6,554,382
- - ' - - -- - ­
12-Aug.o3
Elorsffonteln tbln seam
Year
2003
Period
1
CapItal ExD<!ndlture
2004
2
2005
200II
2007
200II
20011
2010
4
6
8
7
S
3
2011
9
2012
10
ROOO'$
Unescalated capital expenditure
Underground
Wirth Machine
-
15,000,000
Stamler Houler
"-
-
4,000000
Ventilation
15,000
elemetrey
120,000
15,00D
15,000
15,000
15,000
30,000
30,000
30,000
-
30000
30,000
-
Iconcrete roads
240,000
El<traordlnary support
100,000
100,000
100,000
100,000
100,000
100,000
100,000
100000
100,000
100,000
900,000
1,000,000
1,000000
1,000000
1,000,000
1,000,000
1,000,000
1,000,000
1,000,000
1,000,000
onvevor belt and struclure
78,000
78,000
78000
78,000
78,000
78000
78,000
78,000
78,000
78.000
Roof Brushing
250,000
250,000
250,000
250,000
250,000
250,000
250,000
250,000
250,000
250,000
Electrical distribution
105,000
105000
105,000
105,000
105,000
105,000
105,000
105,000
105,000
105,000
Pumps and ac<:elI$Ories
~MOverhaul
8,000,000
8,000,000
-
1,050,000
3,000 000
1500 000
3,000,000
1500,000
3,000,000
1,500,000
3,000,000
16,808,000
8,198,000
4,648,000
11,048,000
4,1148,000
3,063,000
4,663000
11,063,000
4,5113,000
Overland conveyor
90,000
90,000
90,000
90,000
90,000
90,000
90000
90,000
90,000
90,000
Infrastructure
90,000
90,000
90,000
90000
90,000
90,000
90,000
90,000
90,000
90,000
Environmental
60,000
60,000
60,000
80,000
80000
60,000
60000
60,000
60,000
80,000
Istrateglc spares
90,000
90000
90,000
90,000
90000
90,000
90,000
90,000
90,000
90,000
330,000
330,000
330,000
330000
330,000
330,000
330,000
330,000
330,000
330,000
",qulpment averall
SUb total· underground
1,563,000
~lIrfaC.
Sub totat • surface
Processing
Plant & Laboratory modWcation
Discard dump
!sluny pond
StrategiC spares
Sub total • ~ocesslng
IsUb total
ICspex fees @ 4%
total capital expenditure
66,000
66,000
66,000
66,000
66,000
66,000
66,000
66,000
66,000
66,QOO
111,000
111000
111000
111,000
111,000
111,000
111,000
111,000
111000
111,000
45,000
45,000
45,000
45,000
45000
45,000
45000
45,000
45,000
45,000
150,000
150,000
150000
150,000
150000
150000
150,000
150,000
150,000
150,000
372,000
372,000
372,000
a72,000
372,000
372,000
372,000
372,000
372,000
372,000
17,510,000
7,300,000
5,250,000
11,760,000
6,250,000
3,786,000
5,285000
11,765,000
5,265,000
2,265,000
700,400
292,000
210,000
470000
210000
150,600
210,600
470,600
210,600
90,BOO
18,210,400
7,592,000
5,460,000
12,220,000
6,460,000
3,915,1100
6476,600
12,2311,600
5,475,600
2,355,600
ANNEXURE 9 Dorslfontein thin seam
Year
2003
Period
ODeraliog !:!.Q!itl!
2004
1
2
2005
2006
3
2007
4
2008
5
8
2009
7
2010
II
2011
9
2012
10
ROO~'s
leash costs· Unescalated
25,753
29,451
29,451
29,451
29,451
29,451
29,451
25,753
25,753
50.00
50.00
50.00
50.00
50.00
50.00
50.00
50.00
50.00
50.00
15,1388
18,825
18,825
18,825
18,825
18,825
18,825
15,S88
15,S88
15,669
25,753
Mining contractor costs
Rllon
Mining contractor cosls
ROOO's
Outbye costs
ROOO's
300
300
300
300
300
300
300
300
300
300
Repair and maintenance
ROOO's
2,241
2.241
2,241
2,241
2,241
2.241
2,241
2,241
2,241
2,241
Other underground costs
ROOO's
570
570
570
570
570
570
570
570
570
570
Plant costs
Rllon
7.50
7.50
7.50
7.50
7.50
7.50
7.50
7.50
7.50
7.50
Plant costs
ROOD's
2,353
2,824
2,824
2,824
2,824
2,824
2,824
2,353
2,353
2,353
laboratory & Weighbrldge
ROOO's
43S
436
436
436
436
436
436
436
436
436
ROM stockpile
ROOD's
189
189
189
189
189
189
189
189
189
189
Product stockpile
ROOO's
486
486
486
486
488
486
488
486
486
486
ServiCE! costs
ROOD's
609
609
609
609
609
609
609
609
609
609
Safety and training
ROOO's
159
159
159
159
159
159
159
159
159
159
Utility costs
ROOO's
1,200
1,200
1,200
1,200
1,200
1,200
1,200
1,200
1,200
1,200
893
Other costs
ROOD's
893
893
893
893
893
893
893
893
893
pperating fee 2,5%
ROOD's
630
720
720
720
720
720
720
630
630
630
Cash costs· Escalated
ROOD's
25,751
31,217
33,090
35,075
31,180
39,410
41,775
38,121
41,044
43,506
15,688
19,955
21,152
22,421
23,766
25,192
26,104
23,5BB
25,003
26,504
300
318
337
357
379
401
426
451
478
507
2,241
2,375
2,518
2,669
2,B29
2,999
3,179
3,370
3,572
3,786
Mining cost
Outbye costs
Repair and maintenance
Other underground costs
570
604
640
579
720
763
809
857
90B
963
2,353
2,993
3,173
3,363
3,565
3,779
4,006
3,538
3,751
3,976
Laboratory & Welghbtldge
436
462
490
520
551
564
619
656
695
737
ROM stockpile
lB9
200
212
225
239
253
2BB
284
301
319
Plant costs
Product stockpile
4B6
515
546
579
614
650
689
731
775
1121
Service costs
609
845
6B4
725
766
815
863
915
970
1,02B
Safety and training
159
169
179
189
201
213
2211
239
253
269
1,200
1,272
1,348
1,429
1,515
1,606
1,702
1,804
1,913
2,027
Other costs
893
946
1,003
1,063
1,127
1,195
1,266
1,342
1,423
1,508
[operating fee 2,5%
628
761
807
855
907
961
1,019
944
1,001
1061
Utility costs
Oorstfonteln thin seam
Year
2003
Period
~!!sh cgsts - Bito!]
BQM
2004
1
2
2005
3
2006
2007
2009
5
4
2009
6
2010
e
7
2011
9
2012
10
82.08
82.91
87.99
93.16
98.75
104.68
110.96
123.41
130.82
138.67
84.47
Mining cost
50.00
53.00
56.18
59.55
63.12
86.91
70.93
75.18
79.69
Outbye cosls
0.96
0.84
0.90
0.95
1.01
1.07
1.13
1.44
1.52
1.62
Repair and maintenance
7.14
6.31
B.69
7.09
7.51
7.97
8.44
10.74
11.38
12.07
other underground oosls
1.82
1.60
1.70
1.60
1.91
2.03
2.15
2.73
2.90
3.07
Plant costs
7.50
7.95
8.43
8.93
9.47
10.04
10.64
11.28
11.95
12.67
2.35
Laboratory & Weighbrldge
1.39
1.23
1.30
1.38
1.46
1.55
1.64
2.09
2.22
ROM stockpile
0.60
0.53
0.56
0.60
0.63
0.67
0.71
0.91
0.96
1.02
Product stockpile
1.55
1.37
1.45
1.54
1,63
1.73
1.e3
2.33
2.47
2.62
Service costs
1.94
1.71
1.82
1.93
2.04
2.16
2.29
2.92
3.09
3.26
Safety and training
0.51
0.45
0.47
0.50
0.53
0.57
0.60
0.76
0.81
0.86
6.46
Utility costs
3.82
3.38
3.58
3.60
4.02
4.27
4.52
5.75
B.l0
other costs
2.85
2.51
2.66
2.82
2.99
3.17
3.36
4.28
4.54
4.81
Operating fee 2,5%
2.00
2.02
2.14
2.27
2.41
2.55
2.71
3.01
3.19
3.38
96.36
97.35
103.19
109.38
115.94
122.90
130.27
144.90
153.59
162.81
65.96
69.92
74.11
78.56
83.27
86.27
93.57
99.18
lc.ash Cl:t!i\J:s -.Rlton Droduced
Mining cost
56.70
62.23
Outbye costs
1.12
0.99
1.05
1.11
1.18
1.25
1.33
1.69
1.79
1.90
Repair and maintenance
8.39
7.41
7.85
8.32
8.82
9.35
9.91
12.61
13.37
14.17
other underground costs
2.13
1.86
2.00
2.12
2.24
2.36
2.52
3.21
3.40
3.60
Plant costs
8.81
9.33
9.69
10.49
11.12
11.78
12.49
13.24
14.03
14.88
2.76
Laboratory & Welghbrldge
1.63
1.44
1.53
1.62
1.72
1.B2
1.93
2.45
2.60
ROM stockpile
0.71
0.62
0.66
0.70
0.74
0.79
0.84
1.06
1.13
1.19
Product stockpile
1.B2
1.61
1.70
1.81
1.91
2.03
2.15
2.73
2.90
3.07
SelVlce costs
2.28
2.01
2.13
2.26
2.40
2.54
2.69
3.42
363
3.85
Safety and trsinlng
0.59
0.53
0.56
0.59
0.63
0.86
0.70
0.69
0.95
1.01
Utility costs
4.49
3.97
4.20
4.46
4.72
5.01
5.31
6.75
7.16
7.59
other costs
3.34
2.95
3.13
3.32
3.51
3.73
3.95
5.02
5.32
5.84
Operating fee 2,5%
2.35
2.37
2.52
2.67
2.63
3.00
3.18
3.53
3.75
3.97
ANNEXURE 10 Year
~thinseam
03
1
Period
2004
2
2005
2006
2007
2008
2009
2010
2011
2012
3
4
5
6
7
8
9
10
~6.00%
6.00'*
Escalation Rates
Deflator
6.00%
Deflator fador
1.060
SA PPI
%
SA PPI Growth Factor
%
USCPI
0.00%
~
6.00%
6.00%
6.00%
6.00%
6.00%
6.00·..,
1.191
1.262
1.338
1.419
1.504
1.594
1.689
1.791
5.00%
5.00%
5.00%
5.00%
00%
5.00%
5.00%
5.00'*
1.050
1.103
1.156
1.216
1.276
1.340
1.407
l.4n
1.551
2.00%
2.00%
2.00%
2.00%
2.00%
200%
2.00%
2.00%
~I
1.000
1.020
1.040
1.061
1
1.126
1.149
1.172
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
0.00%
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
0.00%
6.00%
6.00%
6.00%
6.00%
6.00%
6.00%
6.00%
~
1.000
1.060
1.124
1.191
1.262
1.338
1.419
1.504
1.594
1.689
%
0.00%
6.00%
6.00%
6.00%
6.00%
6.00%
6.00%
6.00%
6.00%
6.00%
~
1.000
1.060
1.124
1.191
1.262
1.338
1.419
1.504
1.594
1.689
0.00%
6.00%
6.00%
6.00%
6.00%
6JlO%
6.00%
6.00%
6.00%
6.00%
1.000
1.060
1.124
1.191
1.262
1.338
1.419
1.504
1.594
1.689
%
0.00%
6.00%
6.00%
6.00%
6.00%
6.00%
6.00%
6.00%
6.00%
Railage Costs Growth Factor
1.000
1.060
1.124
1.191
1262
1.338
1.419
1.504
1.594
Por1 charges
0.00%
6.00%
6.00%
6.00%
6.00%
6.00%
6.00%
6.00%
6.00%
~~I
US CPI Growth Fador
Dollar Selling price
1%
Dollar SeHing price Growth Fador
Inland Selling price
%
Inland Selling price Growth Factor
ESKOM
ESKOM
Operating Costs
Operating Costs Growth Fador
Railage Costs
6.00%
1.
6.
Port charges Growth Factor
1.000
1.060
1.124
1.191
1.262
1.338
1.419
1.504
1.594
Transport costs
0.00%
6.00%
6.00%
6.00%
6.00%
6.00%
6.00%
6.00%
6.00%
6.00%
1.000
1.060
1.124
1.191
1.262
1.336
1.419
1.504
1.594
1.689
Transport costs Growth Factor
Capillli Expenditure
ctor
%
1.689
0.00% 10.00% 10.00% 10.00% 10.00% 10.00% 10.00% 10.00% 10.00% 10.00'lI
1.000
1.100
1.210
1.331
1.464
1.611
1.772
1.949
2.144
2.356

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