Reef Adjacent To Structures at TauTona Mine, AngloGold Ashanti South African Operations
DE DAVIES
Section Manager
TauTona Mine, AngloGold Ashanti South African Operations
SYNOPSIS
The paper describes the extraction of reef adjacent to geological structures in the Carbon Leader Reef Section at TauTona Mine. Traditionally long wall mining has left feasible and economical blocks of ground adjacent to structures when negotiating major geological features. This meant that mining through an up- throw fault, rolling to the reef elevation on the displaced side of the fault left reef in the long wall. High grade areas were abandoned and gold was sterilized.
In these tight economic times and with the need to continuously improve safety standards the need arose to develop a technique to extract these blocks economically and safely. It was believed that the structures in these abandoned areas were de-stressed and could now be mined in small volumes at a high grade.
The term RATS is an acronym derived from “reef adjacent to structures” and aptly describes the process of identifying and extracting these blocks. The viability of this method was addressed in terms of the mine design, underground investigations and financial risks.
The paper concludes with an analysis of the successes achieved to date.
1 INTRODUCTION
TauTona Mine is one of the AngloGold Ashanti Southern Africa operations. It is close to the town of Carletonville in the province of Gauteng and about 70km south-west of Johannesburg. TauTona is 46 years old and employs ± 4 000 people. Mining operations are conducted at depths ranging from 1,800m to 3,500m at which the world’s deepest stoping sections are found.
TauTona Savuka Ergo
Mponeng Western Ultra Deep Levels
Tau Lekoa Moab Khotsong Great Noligwa Kopanang
Figure 1: The geographical map of TauTona Mine
2 TauTona’s values are:
People are our business… Our business is people.
Safety is our first value: We place people first and correspondingly put the highest priority on safe and healthy practices and systems of work. We are responsible for seeking out new and innovative ways to ensure that our workplaces are free of occupational injury and illness. We live each day for each other and use our collective commitment, talents, resources and systems to deliver on our most important commitment… to care.
We treat each other with dignity and respect: We believe that individuals who are treated with respect and who are entrusted to take responsibility respond by giving their best. We seek to preserve people’s dignity, their sense of self-worth in all our interactions, respecting them for who they are and valuing the unique contribution that they can make to our business success. We are honest with ourselves and others, and we deal ethically with all of our business and social partners.
We value diversity: We aim to be a global leader with the right people for the right jobs. We promote inclusion and team work, deriving benefit from the rich diversity of the cultures, ideas, experiences and skills that each employee brings to the business.
We are accountable for our actions and undertake to deliver on our commitments: We are focused on delivering results and we do what we say we will do. We accept responsibility and hold ourselves accountable for our work, our behaviour, our ethics and our actions. We aim to deliver high performance outcomes and undertake to deliver on our commitments to our colleagues, business and social partners, and our investors.
The communities and societies in which we operate will be better off for TauTona Mine having been there: We uphold and promote fundamental human rights where we do business. We contribute to building productive, respectful and mutually beneficial partnerships in the community in which we operate. We aim to leave host communities with a sustainable future.
We respect the environment: We are committed to continually improving our processes in order to prevent pollution, minimise waste, increase our carbon efficiency and make efficient use of natural resources. We will develop innovative solutions to mitigate environmental and climate risks. (Mark Cutifani, Chief Executive Officer – AngloGold Ashanti)
3 Our objective is to mine gold safely at the correct profit margin. We are a team that produces gold by believing that the workplace can be injury free. We are achieving our targets through people, we want to maximise TauTona’s contribution to AGA shareholders by exploring and managing life of mine extension opportunities and striving for continual improvement. As depicted in the following graph, safety statistics for the “RATS” operations from 2005 to 2008 proofs that mining reef adjacent to structures at depth was done safely.
Injury Statistics for “RATS” 2005 - 2008 5
4
3 Dressing Cases Loss Time Injuries 2 Serious Injuries Fatalities 1
0 2005 2006 2007 2008 •26 June 2007 Laceration Finger Tools and equipment Serious injury •07 Aug 2007 Contusion Thumb Tools and equipment Serious injury
Figure 2: Injury Statistics for RATS 2005 – 2008
At TauTona Mine gold production declined from 2005 to 2008 by 27% to 9 332kg, owing to a greater-than-scheduled decrease in volumes of ore mined. This was a result of increased seismic activity in the vicinity of the CLR shaft pillar which is being mined. Both face length and face advance were negatively affected by seismicity during 2008. (AngloGold Ashanti’s Report to Society, 2008, South Africa: Johannesburg.)
At TauTona Mine we believe in continuous improvement and therefore it is of utmost importance to review all our current processes, to find ways to make it even more effective and value creating.
The concern we have is that TauTona mine traditionally used the longwall mining method. Our gold production has decreased and a need to create additional face length arose in order to create flexibility. Because of increased seismicity, we had to change our mining strategy. To remain sustainable we decided to develop a method of extracting gold from the reef adjacent to structures without interfering with the current operations, thus enhancing our gold profile.
4 REEF ADJACENT TO STRUCTURES (RATS):
The long wall mined through an up-throw fault, rolling to the reef elevation on the displaced side of the fault and leaving reef in the hanging wall. Depicted in the following figures are the original abandoned blocks left by longwall mining and a sketch indicating reef displaced between 5 and 10 leaving reef adjacent to structures.
Figure 3: Geological complexity of TauTona Figure 4: Abandoned blocks adjacent to Mine structures
Reef left in hanging
OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO RATS Reef band Fault
OOOOOOOOOOOOOOOOOOOOOOOOOOOOOO Reef band
Figure 5: Sketch indicating reef displaced between 5 and 10 metres leaving reef adjacent to structures
5 METHODOLOGY
Support design:
The support design was based on the Fall of Ground Management Process (FOGM) with specific reference to mine wide design guidelines – FOGM 1 and the Local area design guidelines – FOGM 2. FOGM 1 is aimed at the prevention of rock burst and FOGM 2 is aimed at the prevention of rock bursts and fall of ground.
FOGM 1: Mine wide design guidelines used
Both modelling and seismic trends must indicate that the planned RATS mining are sufficiently removed from current working places not to have any interaction. No mining into the stressed abutments at the top or bottom of a long wall including pillars. All access ways must be positioned under mined out ground where no stress changes will occur due to the new mining activity.
FOGM 2: Local area design guidelines used
In order not to mine into existing excavations all stoping and development must be clearly indicated and avoided. To leave crush pillars against major faults. To consider preconditioning of prominent dykes.
Design considerations
We assumed that shallow mining conditions would prevail as the area had been de-stressed with the original mining. Due to the regeneration of stress in the back areas, the stress would now be zero. Careful modelling shed some light on the expected stress conditions. The initial elastic modelling indicated stresses of approximately 7 MPa. It was thus assumed that the back area stress would be between 0 MPa and 10 MPa.
Stope closure is a combination of elastic convergence and in-elastic bed separation – especially in the hanging wall. This bed separation is at maximum close to the stope face and decreases in magnitude further away (into the hanging wall). It was unknown how much of this bed separation would be visible and what affect it would have on the planned mining.
6 Ideally, the support installed must prevent the first bed from falling, thereby supporting the additional layers in the hanging wall. The first layer is however unknown, but drilling support into the hanging wall will improve the integrity of the initial support system design. If drilling is impossible, the support design may have to be adjusted as soon as the stoping has commenced and new information becomes available.
Low closure rates were expected, thus stiff active support had to be designed. Because the expected closure rates could not be determined, yielding support was considered. Low seismic rates were probable, but close to abutments the seismic risks increased.
The possibility of back break conditions on large spans could not be disregarded. As proven by the platinum mines breaker lines of packs were often used to prevent back break from forming up to the face area. With packs on the gullies and limited panel spans, these breaker lines would not be required.
Support design
The standard approach is to use the accident statistics for the applicable geotechnical settings at the mine for the past 5 years to determine the fallout thickness to be supported. From this the support resistance and energy absorption criteria can be calculated. The support standard is then designed to meet these criteria.
In this case the accident statistics is not applicable as the geotechnical setting is totally different. There are no accident statistics available for this geotechnical setting on TauTona.
With so many unknowns and a “new” geotechnical setting, a different approach to support design was required. Without accident statistics the next option was to try and pre-determine a likely fallout thickness. The most likely fallout thickness is up to the first well defined bedding plane consisting of quartzite.
The bottom contact between the Greenbar and the quartzite has practically no cohesion and can be assumed to determine a likely thickness (2m above the reef contact). This relates to a support resistance criterion of 53 kN. The next bedding plane is the top contact of the Greenbar, a further 2m above the bottom contact, relating to a support resistance criterion of 106 kN.
The current support standard of elongates (Profile props) spaced 1m by 1,6m gives a support resistance capability of 125 kN and can therefore support at least up to the top contact of the Greenbar.
7 On a larger scale, including the packs in the equation and assuming 20 metre long panels, the same support standard gives a support resistance capability of 200 kN and can support up to 7,5 metres of dead weight (wedge).
Fallout thickness: Maximum of 3.5 metres?
3 Reef left behind ?
2 2m Greenbar
1 2m Fault
Quartzite Beam
Mined out Area 1 = Quartzite beam (53kN) 2 = Greenbar zone (106kN) 3 = Total deadweight (200kN)
Figure 6: FOGM 2 – Support strategy
If the separation is in excess of 7,5 metres, additional packs or in-stope pillars will be considered.
Mined out on reef Mined out off reef Mined out on reef
<5m In-stope pillars against the major fault 5m
2m 2m
Figure 7: FOGM 2 – Support strategy
8 After considering all the above and careful modelling the following support design was established:
180mm to 200mm diameter Profile props. Pre-stressed packs (75cm by 150cm) on the gully shoulders. No backfill. In-stope roof bolting would be required. Continuous closure monitoring.
180mm to 200mm diameter Profile Pre-stressed packs (75cm by 150cm) props. (No Backfill) on the gully shoulders Figure 8: Photos of 116 – 83 Stope indicating installed support units
9
2m max Dip 1.5m max 7m max
3.0m max 4.5m max Blasting barricade and sweepings line; 4.5m max from the face 1.6m 1.0m
1.8m 1.6m
Legend: Pre-stressed pack (75cm x 150 cm) Pre-stressed Profileprop (180mm) Splitset (1.5m) Camloc prop
Figure 9: Support standard for RATS mining (face length less than 20m)
2m max Dip 1.5m max 7m max
3.0m max 4.5m max 6m max Blasting barricade and sweepings line; 4.5m max from the face 1.6m
1.0m
1.8m 1.6m
Legend: Pre-stressed pack (75cm x 150 cm) Pre-stressed Profile prop (180mm) Splitset (1.5m) Camloc prop
Figure 10: Support standard for RATS mining (face length in excess of 20m)
10 Financial Risks:
Blocks were identified and prioritized according to the set criteria for inclusion in the Business Unit Plan. The reef adjacent to structures was identified by the Mineral Resources Department and each one was allocated with a specific block number. These blocks were prioritized according to their volume and grade, their current infrastructure utilisation and their proximity to current working places. A multi disciplinary risk assessment followed after a financial evaluation was done.
Feasible
Blocks
X
X X X
Not Feasible
Figure 11: Identified RATS blocks
11 Recovered kilograms were determined by using the Basic Mining Equation (BME) Model. The initial blocks identified indicated 29479m2 in total. After we added a 50% discount it resulted in 1413.5 kg broken gold from the stopes. The average values of these blocks were 3481cmg/t. It is important to note that the initial assessments were done only from plans and a discount factor was added when underground investigations and geological information became available. This BME model indicated a yield of 25.1g/t.
Greenfield Plan BME FACE LENGTH m 1 300 x FACE ADVANCE m 4.50 = TOTAL m2 m² 29 497 x ON REEF PERCENTAGE % 50.80% = REEF m2 m² 14 984
x ON REEF cmg/t cmg/t 3 481 x RD = kg GOLD EX STOPES kg 1 413.517 + VAMPING kg kg 0 + REEF DEVELOPMENT kg kg 0 = TOTAL kg BROKEN kg 1 413.517 +/- U/G INVENTORY kg 0 = GOLD HOISTED kg 1 413.517 +/- SURFACE INVENTORY (SHAFT) kg 0 = GOLD DELIVERED TO PLANT kg 1 413.517 +/- PLANT INVENTORY kg 0 = GOLD CALLED FOR kg 1 413.517 x MINE CALL FACTOR % 74.00% x RECOVERY FACTO % 97.57% GOLD RECOVERED Kg = 1 020.585
WIDTHS, TONNES, YIELD R3 481 STOPING WIDTH cm 100.0 MILLING WIDTH cm - TOTAL TONS HOISTED (REEF & WASTE) t 40 607 TONS MILLED t 40 607 YIELD (GRADE RECOVERED) g/t 25.1
Figure 12: Total available gold (not discounted)
12 The next step was to determine whether these blocks would be financially viable to mine. Due to the mining risk this model allowed us to use variable parameter values to determine feasibility. Firstly the total incline square meters were used. A 50% discount was added to establish the available square meters to be mined. This allowed us to group blocks together according to accessibility and locality. Tonnages and contents of these blocks were calculated. Stoping and development costs were determined by using rand/m² and rand/m cost. This variable model allowed us to use different units: gold price, rand/m, or rand/m² to determine profits or losses in the different blocks or group of blocks.
The initial financial evaluation indicated that these blocks would be feasible to mine and could be extracted at a profit, thus enhancing the current gold profile.
0.0271 PILLAR NO SECTION 7 - FINRISK FINAL TAU TONA MINE- SECTION 311 DATE 1 LPI TOTAL STOPING COSTS INCLUDING STORES (BUDGET 2005)
% M² % M² UNIT COSTS USED IN INVESTIGATION MCF Plant REC. GOLD PRICE MINED FLTING Item Unit Costs % % R / Kg. STOPING R/ton 85.03 97.57 80,000 NEW DEVELOPMENT R/ton FLAT END RE-EQUIPPING R/m
DEVELOPMENT SHEET LEVEL LINE PANELS UNIQUE PILLAR No. FINAL STOPE SHEET BLOCK No. ALL
STOPING TO BE DONE FACTORS GOLD PRICE INCLINED M² CW SW VALUE REEF DIP STOPE STATS BLOCK No. BLOCK % GROUNDGROUND AVAILABLE AVAILABLE - FLT DISCOUNT(MRIS) (MRIS) GRADE TONS CONTENTS MCF Plant REC. Total REC. R / Kg. 100% 60% 0% cm. cm. cm.g/t x° g/m² ORE Kilograms Au % % % 26 13027 7816 7816 23.0 100 3333 22.5 90.32 21182 706 28 4290 2574 2574 23.0 100 3829 22.5 103.77 6976 267 36 40875 24525 24525 23.0 100 4205 22.5 113.96 66463 2795 85.03 97.57 82.96 80,000 70 11855 7113 7113 23.0 100 4421 22.5 119.81 19276 852
TOTAL 70047 42028 42028 23.0 100.0 4056 22.5 109.93 113896 4620 RECOVERED GOLD, KG. 3,832.965 SW Full Width 100.0 113896 TOTAL REVENUE (RANDS) 306,637,216 DEVELOPMENT COSTS STOPING COSTS FINANCIALS WORKING PLACE METRES H W SG TONS R/m *Dev COST R/ton M2 COST (R/M2 COST Item IN RANDS 30 851 7500 225000 264 HLGE 3.4 3.0 2.78 42028 2094 88,007,051 REVENUE 306,637,216 RAW / CON.X/C 3.4 3.0 2.78 0 0 0 CROSSCUT 105 3.2 3.0 2.78 2802 7500 787500 281 R/rec.gm. 80.00 RAISE + SLUSHER 450 3.0 1.8 2.78 6755 7500 3375000 500 COSTS BOXHOLE 120 1.2 2.4 2.78 961 7500 900000 937 STOPING COSTS 88,007,051 TRAVELLINGWAY 2.4 3.0 2.78 0 0 0 DEVELOPMENT COSTS 5,287,500 TOTAL 705 11369 *Standard VR TREATMENT COSTS 5,287,500 465 0 PLANNED DEV.RATE; m / mth 0 DIAMOND DRILLING COST 0 ESTIMATED TIME TO COMPLETION: mths #DIV/0! 16.13 AVG Tons / M TOTAL MINING COST 93,294,551 R/rec.gm. 24 TREATMENT AND OTHER COSTS PROFIT / LOSS 213,342,665 DIRECT COST + PORTION OF OTHER COSTS ** R/rec.gm. ITEM TONS 55.7 UNIT COST (R/t & R/m)Treatment TOT.STOPE TREAT.UNIT COST Full Width Profit/Revenue % 69.57 STOPING, (R/ton) 113896 0 0 0 DEVELOPMENT, (R/ton) 6755 0 TOT.DEV. TREAT. TOT.DEV. COST TOTAL ENGINEERING (Rand) 0 0 FLAT RE-EQUIPPING, (R/ton) 0 TOTAL TREATMENT DIAMOND DRILLING (Metres) 0 0
AS PER IN 6 IN 12 IN 18 IN 24 3rd 4th NOW AVAILABILITY AND MINING RATE MTHS MTHS MTHS MTHS YEAR YEAR WHEN CAN STOPING START ? Date : PLANNED FACE ADVANCE m./mth.: PLANNED WORKING PANELS No.: PLANNED WORKING F/ LENGTH m.: PLANNED MINING RATE m² / mth.: PLANNED AREA TO MINE m².: ESTIM.TIME TO COMPLETION Mths.:
Figure 13: Financial Model
13 IMPLEMENTATION
PILLAR INVESTIGATION PROCESS:
In the implementation process certain steps are critical to ensure all possible constraints are addressed prior to allocation of resources. A flow sheet as described in appendix 1 was used to ensure involvement of all the role players.
Geologist and Evaluator to identify all areas with Reef adjacent to Structures. CAD’s Operator and Surveyor to update the plans and add additional information. SHE Officer to compile the necessary ventilation layout for initial investigation. Mine Overseer to do initial underground investigation in conjunction with the rock engineering, ventilation and engineering assessments. Hold a workshop with all the necessary role players to do a baseline risk assessment. If blocks are inaccessible from current infrastructure an initial development layout is done in terms of the mine design. Complete pillar investigation form and ensure sign offs from all departments.
See Appendix 1 for process flow sheet, section 1 to 10, were detailed and signed off plans was used for inclusion into the mining schedule.
Figure 14: 1 and 200 Mine Plan
14 Reef adjacent to structures’ blocks were identified by using the volume, grade and kilograms allocated to the blocks. This was determined by using Krige values.
4 839m² @ 3 804cmgt 498.895kg 1 454m² @ 2 964cmgt 116.791kg 610m² @ 2822cmgt 40.882kg
2 354m² @ 4 167cmgt 265.753kg
10 583m² @ 3 648cmgt 913.691kg Green Bar erosion Channel ? ±10 000m² @ 3 648cmgt 913.691kg
Figure 15: Identified blocks by utilizing volume, value and grade
15 PROCESS:
From the pillar investigation process all relevant information was used to determine and prioritize blocks according to their volume and grade, their current infrastructure utilisation and their proximity to current working places. A multi disciplinary risk assessment was conducted and the blocks were scheduled in terms of availability, equipping and resource requirements.
For the initial blocks identified no development was required to access the blocks. Resources were allocated in terms of equipment (winches, loco’s, loaders, switches, rails, box fronts, miscellaneous stores) and labour. The 111 employees allocated to the project included stoping, equipping, horizontal transport, haulage maintenance and supervision labour. The implementation of this mining method commenced with four crews doing the equipping, ventilation, support and establishment of the blocks. Each crew consisted of a Stope Team Leader, Miners Assistant, four Rock Drill Operators - Stope and four Stope Multi Task Crew members.
A crew movement and section build-up schedule was drawn up and implemented. Stoping of the reef adjacent to structures commenced in June 2005.
Due to the fact that the throw of the faults determined the face length short panels were designed with a face length between 10 and 20 metres. Most of these structures generally strike North East. The reef at TauTona Mine dips from North to South at 22 degrees and strikes from East to West. Current box holes were used as the initial attacking point. A diagonal wide gully was mined in a western direction through the old stope until reef was intersected and continued up to the fault position. After this establishment a north gully was positioned in the centre of the block and in the direction of the fault. This establishment created the face length and opened the block for extraction according to the support design specifications. All blocks were extracted without night shift, thus doing both cleaning and blasting on day shift.
16 RATS PLANNING: CREW MOVEMENT AND SECTION BUILD- UP
Work Place Page Block cmgt M2 @ Gang March April May June July Aug Sept Oct Nov Dec Jan ' 06 Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Jan ' 07 Feb UCL LCL 60% 120m2 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 101 13 72 4293 1931 8 A 25 50 75 100 120 120 120 120 120 120 8 B 50 50 75 100 120 120 120 120 120 120 102 14 73 4703 1106 9 83 2 26B 3049 2588 11 C 50 50 100 120 120 120 120 120 120 120 120 120 11 D 50 75 100 120 120 120 120 120 120 120 120 120 120 85 1 26A 4136 2984 12 0 50 13 0 50 87 3 26C 2594 2244 10 E 50 50 100 120 120 120 120 120 120 120 120 9 0 100 100 120 120 120 120 120 120 120 87 4 28 3829 1287 11 F 50 50 100 120 120 120 120 120 120 120 120 120 85 1287 11 0 100 100 120 120 120 120 120 120 120 107,5 15 74 4870 1591 13 0 50 75 100 100 120 120 109 16 75 4899 1746 15 G 25 25 50 100 120 120 120 120 120 120 120 120 120 120 120 120 120 17 76 2240 739 6 0 50 100 100 120 120 120 120 120 93/94 12 36H 4444 2279 10 0 100 100 100 120 120 120 120 120 120 120 9 40 50 100 120 97 5 36A 3310 4145 35
94 7 36C 4055 1724 14 H 0 25 50 70 100 120 120 120 120 120 120 120 120 120 96/97 6 36B 3982 2678 11 11 I 0 50 70 100 93/94 11 36G 4742 1918 8 50 70 120 120 120 120 120 120 120 8 0 40 97 36
GRANDTOTAL 30247 0 0 0 150 275 475 690 800 840 840 840 865 890 890 830 850 870 940 870 915 860 920 1010 840 TOTAL GANGS 0 0 0 4 6 7 7 7 7 7 7 8 8 8 8 8 8 8 8 8 8 9 9 9 TOTAL GOLD KG' s @ 4056 cmgt 0 0 0 14,9 37,7 46,85 69 80,6283,9 83,9 83,9 86,6 89,4 90,4 84,8 87,5 93,5 102 95,3 103 94 101 113,07 108
2 Year Au kg total = 1655.27 2 Year m2 total = 16460 Figure 16: Mining Schedule
17 BENEFITS OF MINING METHOD
The production profile improved from 1646m² produced in 2005 to 6579m² in 2008. The gold profile in the RATS also increased from 112 kg broken in 2005 to 592 kg’s broken in 2008. Since implementation of the project 23 864m² has been mined and yielded 1938kg broken gold.
The reef adjacent to structures became an integral part of our resources and optimized our plan. The limited window of opportunity to mine these blocks was addressed against the set criteria and included into our plan. This process enabled us to optimize the full potential to extract gold from RATS without interfering with the current operations, thus enhancing our gold profile.
We had no previous knowledge of mining reef adjacent to structures at depth therefore a unique support strategy was designed and implemented successfully. Each block have its own design in terms of mining layout and support strategy to allow the successful extraction of these blocks.
9000
8000
7000
6000
5000
4000
3000 2000 1000
0 2005 2006 2007 2008 2009 YTD Act Total m2 1646 4698 8950 6579 1991
800 700
600
500
400
300 200
100
0 2005 2006 2007 2008 2009 YTD Act Broken Gold 112 348 713 592 173
Figure 17: Production Performance actual m² and Kilograms
18 CONSTRAINTS
It was foreseeable that ventilation and cooling would be the biggest constraint. This was addressed through the implementation of proper ventilation layouts utilizing the current infrastructure.
Seismicity on structures was not excluded, but by implementing the unique support design it was proven that this risk was minimized and controlled.
Inaccessibility of the blocks prior to mining provided us with limited geological information on the reef horizon. The structures in the blocks were modeled from old geological mapping, thus creating a degree of uncertainty in terms of confidence levels in some blocks. Structural changes within the blocks when mining commenced could influence the successful extraction of the blocks.
Interference with current mining, when mining reef adjacent to structures, posed a major risk in certain areas which could influence the volume of the current longwall operation. Re-mining in these areas could increase the seismicity, resulting in the loss of the access ways to the existing long walls. In addition layouts for ventilation were critical to ensure that ventilation conditions were conducive for mining both the areas.
A proper assessment of all existing excavations in the proposed mining area was necessary to prevent unnecessary holing into established infrastructure.
CONCLUSION
Due to the complexity of the mining environment it is inevitable that one must be able to adapt to change in order to ensure the viability of the system. This paper does not seek to obscure your mind, but rather to stimulate the thinking process.
It is imperative to not only remember the basic principles of mining but to challenge the obvious.
At TauTona Mine it was proven that mining reef adjacent to structures at depth needed a dynamic and workable plan. The unique extraction sequence per block was a major contributor to the success of this mining method. The reality is that successes and failures in blocks are inevitable. The multi disciplinary risk assessment and involvement of all services departments is imperative to ensure the success of mining reef adjacent to structures.
The content of this paper results from approximately four years of experience in mining reef adjacent to structures at depth. It was written with the objective of assisting fellow mining engineers in the planning and implementation of such a mining method.
19 ACKNOWLEDGEMENTS
The author wishes to thank the management of TauTona Mine for permission to publish this paper and all the persons who assisted in the preparation.
In addition thanks to Great Noligwa Mine for their Pillar Investigation Process Flow Sheet and Lourens Scheepers, Rock Engineering Manager, TauTona Mine who assisted with the support design.
REFERENCES
AngloGold Ashanti. (2008). Report to Society. South Africa: Johannesburg.
Jager, A.J.; Ryder, J.A. (1999). “A Handbook on Rock Engineering Practice for Tabular Hard Rock Mines”.
Le Roux, W.L. (1979). “Mine Ventilation Notes for Beginners”.
Lurie, J. (1984). “South African Geology for Mining, Metallurgical, Hydrological and Civil Engineering.
Ritson, T.P. (1997). “Surveying for Mine Surveyors”.
Storrar, C.D. (1987). “South African Mine Valuation”.
20 APPENDIX 1: PROCESS FLOW SHEETS SECTION 1 TO 10
WORKING PLACE PILLAR No.
BLOCK No.
TAUTONA MINE
FLOW SHEET FOR PILLAR INVESTIGATION FILE
MRM Pillar geologist. W O R K I N G P L A C E Section 1 completed. Sign: Sign: Date:Date:
MRM CAD Operator. Section 2 completed. Sign: Date:
MRM Senior Evaluator Section 3 completed. Sign: Date:
Section Surveyor. Section 4 completed. Sign: Date:
MO Old areas. Section 5 completed. Sign: Date:
MRM Planning officer. s. o N K C O L B Section 6 completed. Sign: Date:
MRM Pillar Geologist - FINRISK. Section 7 completed. Sign: Date:
Rock Engineering Department. Section 8 completed. Sign: Date:
SHE Department. Section 9 completed. Sign: Date:
Engineering Department Section 10 completed. Sign: Date:
Summary AP IL L R N o.
Geology Manager Section 11 completed. Sign: Date:
Section Manager Section 11 completed. Sign: Date:
MRM Manager. Section 11 completed. Sign: Date:
Flow sheet for Pillar Investigation
21
WORKING PLACE PILLAR No.
BLOCK No.
TAUTONA MINE SECTION 1 PILLAR GEOLOGIST W O R K I N G P L A C E
i) Review available information: 1:200 stope sheets
1:200 development sheets
Assay tracings
ii) Complete updates: Strike lines
Faulting
Facies type
RIH/RIF B L O C K N o s.
iii) Determine: RGSW
Hazardous conditions
iv) Transfer onto geological investigation sheet:
v) Transfer to CAD: P I L L A RA L I P L o. N
Signature :- Date:
Section 1: Pillar Geologist
22
TAUTONA Appendix GEOLOGICAL INVESTIGATION MINE PILLAR No. Geologist: Date: BLOCK No. Working place: Plan scale 1: 1000
Refer to Stope sheet: and Development sheet: RGSW cm. STOPING STYLE U/C F/W
Historic sampling in the adjacent panels indicate cmg/t.
It is proposed by Geology to
Facies type:
ORIS: Geological comments: INCLINED M2 : INSERT A COPY (1: 100) CW (cm) :
SW (cm):
GRADE (CMG/T) :
INSERT A PLAN COPY (1: 1000) ON NEXT PAGE
Rock Engineering comments:
This pillar CAN / CANNOT be mined safely. This pillar CAN / CANNOT be mined safely.
Geological Investigation
23 WORKING PLACE PILLAR No.
BLOCK No.
TAUTONA MINE SECTION 2 - CAD OPERATOR/DRAFTSPERSON
CHECKLIST W RO K IN G P L A C E i) Update geological information on CAD/Microstation
ii) Create print of area under investigation
iii) Check updates with pillar geologist
iv) Attach copy of print to geological investigation sheet
v) Attach copy of print to old area investigation sheet B L CB O KL Ns. o P I L L A R N o.
Signature :- Date:
Section 2: CAD Operator
24 WORKING PLACE PILLAR No.
BLOCK No.
TAUTONA MINE SECTION 3 - SENIOR EVALUATOR
CHECKLIST E C A L P G IN K R O W i) Review available information:
ii) Capture relevant peripheral sampling:
iii) Evaluate block No's: s. o N K C O L B
ORIS:
Inclined M2
CW (CM)
SW (CM)
GRADE (Cmg/t)
kriged
conventional o. N R A L IL P
ORIS
Signature :- Date:
Section 3: Senior Evaluator
25 WORKING PLACE PILLAR No.
BLOCK No.
TAUTONA MINE SECTION 4 - SECTION SURVEYOR
CHECKLIST W O R K I N G P AL C E
MCF :- (%) LOW: MOD: HIGH: PRF :- (%) LOW: MOD: HIGH:
All additional pegs required in place :- (Y/N) Plans up to date :- (Y/N) Layouts out and signed by all depts. :- (Y/N) Old gold / Lockup :- tons @ g/t
= 0 kg Au
Estimated tons and contents of mud in x/cut: B OL C K N s.o Remarks:
SIGNATURES:
Chief Gold Loss Officer: Date:
Section Surveyor: Date: o. N R A L L I P
Section 4: Section Surveyor
26 WORKING PLACE PILLAR No.
BLOCK No.
TAUTONA MINE SECTION 5 - M/O UNDERGROUND INVESTIGATIONS
CHECKLIST W O RK I NG P A L C E i) State of working places: Haulage ______
X/Cut ______
Timber ______bay ______
T/Way ______
B/Holes ______B L O CK N o s.
Cost estimate of opening up old areas to acess pillar: R
ii) Temperatures: a)Wet bulb:- b)Dry bulb:- iii) Development layouts or pegs required: ______
iv) Stoping layouts or pegs reqiuired: ______
v) Equipping required: ______
Cost estimate of equipping pillar: R P I L L A R N o.
vi) 2nd Escapeway: In place YES NO Condition GOOD FAIR BAD Layout required YES NO Comments ______
vii) Special requirements: ______
Signature :- Date:
Section 5: Mine Overseer U/G Investigation
27 TAUTONA OLD AREA PILLAR INVESTIGATION MINE PILLAR No. M/Overseer: Date: JUL 01 BLOCK No. Working place: Plan scale 1: 1000
3. Is the ventilation adequate? What is required?
4.Tracks: are they required? How many lengths?: Sleepers?: 5. Where do the pipes end? Peg +\- : 6. How many air/ water pipes needed? Sizes 7. Boxfronts: condition? Can they be used? Do they contain ore? 8. Are grizzlies available? Condition: 9. New B/HOLE required? 10. New T/WAY required? 11. No. of equipping shifts needed: 12. Cost of opening up (new dev excluded): R Mining comments: ESH comments:
This pillar IS / IS NOT mineable. This pillar CAN / CANNOT be mined safely. Old Area Pillar Investigation
28 WORKING PLACE PILLAR No.
BLOCK No.
TAUTONA MINE SECTION 6 - MINE DESIGN
Mine Design W O R K I N G P L A C E Provisional mining layout on CAD taking the current Geological structure on CAD, the underground investigation (App.) and Rock Engineering (App.) into account.
Cost treated (excl.dev.costs) R Development costs R Flat equipping costs, R/m R HLGE required : (metres) RAW/Conn.X/C required : (metres) X/Cut development required : (metres) Raise/slusher required : (metres) M SLUSHER + M RSE BH / Orepass required : (metres) T/Way required : (metres) Timberbay required : (metres)
Flat re-equipping required : (metres) s. o N K C O L B Total Pillar Access dev.costs : MODE R Total Capital development costsMODE : R Total Stoping costs : MODE R Total Mining costs,(excl.D/drilling)MODE : R Start date for mining Area that can be mined per year (M2) 2400 CAD Design File No. Copy of 1:1000 design to be attached.
ASSESSMENT : This pillar IS / IS NOT mineable.
Signature : Date: P I L L A R N o.
Section 6: Mine Design
29 TAUTONA Appendix F1 MINE DEVELOPMENT PLAN REQUIRED FOR PILLAR PILLAR No. M/Overseer: Date: BLOCK No. Working place: Plan scale 1: 1000
Hlge. X/Cut STICK PLAN ONTO THIS PAGE T/Way Slusher B/Hole
TOTAL Mine design/planning comments:
Mining comments:
Rock Engineering comments: ESH department comments:
Development Plan
30 0.0271 SECTION 7 - FINRISK TAU TONA MINE- SECTION 311 DATE 1 LPI TOTAL STOPING COSTS INCLUDING STORES (BUDGET 2005)
% M² % M² UNIT COSTS USED IN INVESTIGATION MCF Plant REC. GOLD PRICE MINED FLTING Item Unit Costs % % STOPING R/ton 85.03 97.57 NEW DEVELOPMENT R/ton FLAT END RE-EQUIPPING R/m
DEVELOPMENT SHEET LEVEL LINE PANELS UNIQUE PILLAR No. STOPE SHEET BLOCK No.
STOPING TO BE DONE FACTORS INCLINED M² CW SW VALUE REEF DIP STOPE STATS BLOCK No. BLOCK % GROUNDGROUND AVAILABLE AVAILABLE - FLT DISCOUNT(MRIS) (MRIS) GRADE TONS CONTENTS MCF Plant REC. Total REC. 100% 60% 0% cm. cm. cm.g/t x° g/m² ORE Kilograms Au % % 26 13027 7816 7816 23.0 100 3333 22.5 90.32 21182 706 28 4290 2574 2574 23.0 100 3829 22.5 103.77 6976 267 36 40875 24525 24525 23.0 100 4205 22.5 113.96 66463 2795 85.03 97.57 70 11855 7113 7113 23.0 100 4421 22.5 119.81 19276 852
TOTAL 70047 42028 42028 23.0 100.0 4056 22.5 109.93 113896 4620 RECOVERED GOLD, KG. SW Full Width 100.0 113896 TOTAL REVENUE (RANDS) DEVELOPMENT COSTS STOPING COSTS FINANCIALS WORKING PLACE METRES H W SG TONS R/m *Dev COST R/ton M2 COST (R/M2 COST Item IN RANDS 30 851 7500 225000 264 HLGE 3.4 3.0 2.78 42028 2094 88,007,051 REVENUE 306,637,216 RAW / CON.X/C 3.4 3.0 2.78 0 0 0 CROSSCUT 105 3.2 3.0 2.78 2802 7500 787500 281 R/rec.gm. RAISE + SLUSHER 450 3.0 1.8 2.78 6755 7500 3375000 500 COSTS BOXHOLE 120 1.2 2.4 2.78 961 7500 900000 937 STOPING COSTS TRAVELLINGWAY 2.4 3.0 2.78 0 0 0 DEVELOPMENT COSTS TOTAL 705 11369 *Standard VR TREATMENT COSTS 5,287,500 465 PLANNED DEV.RATE; m / mth 0 DIAMOND DRILLING COST ESTIMATED TIME TO COMPLETION: mths #DIV/0! 16.13 AVG Tons / M TOTAL MINING COST 93,294,551 R/rec.gm. TREATMENT AND OTHER COSTS PROFIT / LOSS 213,342,665 DIRECT COST + PORTION OF OTHER COSTS ** R/rec.gm. ITEM TONS UNIT COST (R/t & R/m)Treatment TOT.STOPE TREAT.UNIT COST Full Width Profit/Revenue % STOPING, (R/ton) 113896 0 0 0 DEVELOPMENT, (R/ton) 6755 0 TOT.DEV. TREAT. TOT.DEV. COST TOTAL ENGINEERING (Rand) 0 0 FLAT RE-EQUIPPING, (R/ton) 0 TOTAL TREATMENT DIAMOND DRILLING (Metres) 0 0
AS PER IN 6 IN 12 IN 18 IN 24 3rd 4th NOW AVAILABILITY AND MINING RATE MTHS MTHS MTHS MTHS YEAR YEAR WHEN CAN STOPING START ? Date : PLANNED FACE ADVANCE m./mth.: PLANNED WORKING PANELS No.: PLANNED WORKING F/ LENGTH m.: PLANNED MINING RATE m² / mth.: PLANNED AREA TO MINE m².: ESTIM.TIME TO COMPLETION Mths.:
Section 7: Financial Risk
31 WORKING PLACE PILLAR No.
BLOCK No.
TAUTONA MINE SECTION 8 - ROCK ENGINEERING
i) Seismics: a). Is the pillar seismically active ? Rating
b). What is its seismic history ? W O R K I N G P L A C E
ii) Stability: a). Is this a stabilising pillar ? b). Pillar and Regional stability.
iii) Development support recommendations: a). Primary :- X/cut
T/way
B/hole
Timber bay
Other B L O C K N o s.
b). Secondary :-Haulage
X/cut
T/way
iv) Stoping method:
v) Are proposed accesses overstoped?
vi) Development sequencing: P I AL L R N o.
vii) Special instructions:
ASSESSMENT : This pillar CAN / CANNOT be mined safely.
Signature : Date :
Section 8: Rock Engineering
32 WORKING PLACE PILLAR No.
BLOCK No.
TAUTONA MINE SECTION 9 - SHE DEPARTMENT i)Ventilation & Refrigeration W O R K I N G P AL C E a). Air availability in the area
b). Requirements and Layout.
ii) Temperatures: a). Wet bulb :- b). Dry bulb :- iii) What is the Kata in the area ?
iv) Nearest Refuge Bay: B L O C K N o s. o N K C O L B
v) Escape routes:
vi) Methane and water: CH4 = % H2O (l/hr) = Precautions :-
Special instructions ? P I L L A R N o. N R A L L I P
ASSESSMENT : This pillar CAN / CANNOT be mined safely.
Signature : Date
Section 9: SHE Department
33 WORKING PLACE PILLAR No.
BLOCK No.
TAUTONA MINE SECTION 10 - ENGINEERING DEPARTMENT i) Telephone requirements: W O RW K I N G A L P C E
ii) Lighting requirements.
iii) Cable requirements:
iv) Water, air and refrigeration requirements: B L O C K N os.
v) Other electrical requirements:
vi) Special instructions ? P I L L A R N o.
Signature : Date: Section 10: Engineering Department
34 PILLAR VIABILITY INVESTIGATION SUMMARY SHEET TAUTONA MINE Unique Pillar No. Working place Measured or Indicated Resource Block Nos. Area to be mined :- (M²) (70% OF TOTAL) Reef Extraction ratio :- (%) Off Reef Mining percentage :- (%) 0 Grade, (mode over full C/Width) :- (cm.g/t.) (ORIS) Stoping SINGLE or DOUBLE CUT:- #REF! Reef stripping potential :- N/A HW thickness :- (cm) Full C/Width (cm) Footwall thickness :- (cm) RGSW :- (cm) Tramming Width :- (cm) Old gold / Lockup tons @ g/t.= Kg. Au MCF for the pillar :- (%) Plant Recovery Factor :- (%) Estimated D/drilling costs, R Total Pillar Access costs :- R Total Capital costs :- R Total stoping costs :-, R Total working mining costs :-, R Gold price used :- R/Kg.
Curr.Breakeven gold price:- R/Kg. TO BE CALC. COSTS Total revenue :- R From Finrisk Total Recovered Gold :- Kg. TOTAL PRODUCTION + TOTAL PRODUCTION
LOM DCF - Operational +STORES CORPORATE PROFIT or LOSS :- R 0
FINAL ASSESSMENT : COMMENTS :-
Signature : PILLAR GEOLOGIST Date: Pillar Viability Investigation
35 Geology Manager comments: 0
ASSESSMENT : This pillar IS / IS NOT mineable.
Signature :- Date:
Chief Surveyor comments:
ASSESSMENT : This pillar IS / IS NOT mineable.
Signature :- Date:
Section Manager comments
ASSESSMENT : This pillar CAN / CANNOT be mined safely and profitably.
Signature :- Date:
Production Manager comments:
ASSESSMENT : This pillar CAN / CANNOT be mined safely and profitably.
Signature :- Date:
MRM comments:
FINAL ASSESSMENT : This pillar CAN / CANNOT be mined safely and profitably.
Signature :- Date:
Pillar Viability Investigation (continued)
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