Underground Mining
A Preliminary Investigation Into the Geotechnical Interpretation of Geophysical Logs
2004
Compares a full suite of downhole sondes against geotechnical core logging over the 5 m above three coal seams, for geologists and rock engineers assessing roof conditions.
What this report foundGeophysical logging of boreholes above three Witbank seams identified clay rich matrices, stiffness changes, bedding planes and the principal stress direction...
R1500,00
Geophysical logging of boreholes above three Witbank seams identified clay rich matrices, stiffness changes, bedding planes and the principal stress direction, and picked up fractures in 30 to 75 per cent of cases. Core logging found most of the same features faster, so routine use was not recommended unless stiffness and stress direction matter.
Determine Possible Means to Conduct Large Scale Frictional Ignitions Tests, and the Value of These to Coaltech
2017
A scoping exercise based on technical enquiries to mine safety organisations and discussions at an international conference, aimed at rock engineers and safety practitioners weighing test facility investment.
What this report foundNo operating full scale frictional ignition test facility was found anywhere in the world, and building one was judged expensive, impractical and unlikely to...
R1500,00
No operating full scale frictional ignition test facility was found anywhere in the world, and building one was judged expensive, impractical and unlikely to justify its cost against laboratory scale testing. Effort should instead go to small scale laboratory equipment using South African rocks, and to expanding geological data such as silica distribution and petrographic analysis.
Development of Design Procedures for Long Slender Pillars
2005
Design guidance for rib pillars, built from back analysed in situ coal tests and two dimensional modelling rather than empirical data, for rock engineers laying out high extraction panels.
What this report foundNumerical modelling produced upper and lower bound strength formulae for rib pillars, the lower bound covering weak roof and floor contacts.
R1500,00
Numerical modelling produced upper and lower bound strength formulae for rib pillars, the lower bound covering weak roof and floor contacts. The formulae apply between width to height ratios of 0.5 and 2.5, with linear interpolation below that, and give conservative designs above 3. Adjustments were suggested where regular joint sets occur.
Development of Seam-Specific Strength Formulae for South African Collieries
2006
Statistical back analysis of an expanded collapse database, testing power, linear and non-linear strength models, for rock engineers setting pillar safety factors.
What this report foundBack analysis of 77 collapsed and 245 uncollapsed pillar cases showed that much of the scatter in pillar strength comes from differences between coalfields, so...
R1500,00
Back analysis of 77 collapsed and 245 uncollapsed pillar cases showed that much of the scatter in pillar strength comes from differences between coalfields, so a single national formula is unrealistic. Seam specific formulae were derived for the major coalfields; Free State and KwaZulu Natal data remained too sparse. The lognormal safety factor distribution was retained.
R1500,00
Improved Utilization of Underground Coal Reserves
2016
Working reference on high extraction methods, from stooping and rib pillar extraction to auger, punch, longwall and backfilling, drawn from South African colliery experience for mine planners.
What this report foundAbout 3.19 billion tons of coal now sits underground in pillars, growing by roughly 110 million tons a year under current bord and pillar practice.
R1500,00
About 3.19 billion tons of coal now sits underground in pillars, growing by roughly 110 million tons a year under current bord and pillar practice. Pillars with a safety factor of about 1.8 or higher can be extracted successfully, and 1.5 is permissible in thin seams where the pillar width to height ratio exceeds 10.
Life sustainability of underground refuge bays of South African collieries
2023
An industry database of South African refuge bay designs set beside practice in Australia, Canada and the United Kingdom, prompted by recent underground emergencies.
What this report foundNo single global standard governs refuge bay design, and the collieries surveyed differ widely in construction, location, equipment and operating practice...
R1500,00
No single global standard governs refuge bay design, and the collieries surveyed differ widely in construction, location, equipment and operating practice, which made ranking them impractical. Areas needing attention were identified in design, construction and maintenance of the facilities that keep people alive until rescue, drawn against local law and overseas practice.
Mapping of Old Bords and Pillars Revisited
2019
Desktop review of recent unmanned aerial and underwater vehicle systems and how they compare with borehole scanning, for engineers assessing the stability of old underground workings.
What this report foundMapping abandoned, inaccessible bord and pillar workings comes down to two options: borehole deployed laser or sonar scanning, or sensors carried in by...
R1500,00
Mapping abandoned, inaccessible bord and pillar workings comes down to two options: borehole deployed laser or sonar scanning, or sensors carried in by unmanned vehicles. Drone mounted laser scanning for air filled voids and sonar carried by small submersibles for flooded workings were judged the most promising, but intrinsic safety, deployment and the risk of losing equipment still favour borehole methods for occasional use.
More Effective Use of Disposable Dust masks
Underground field trials, laboratory seal tests and operator questionnaires at two collieries, covering mask selection, fit, issue records and service time. For ventilation and occupational hygiene staff.
What this report foundDust masks worn by load haul dump operators passed 200 mg of filter loading in an average of 1.7 hours, and continuous miner, shuttle car and roofbolt...
R1500,00
Dust masks worn by load haul dump operators passed 200 mg of filter loading in an average of 1.7 hours, and continuous miner, shuttle car and roofbolt operators reached the same point within two to five hours. Every mask failed laboratory fit testing. An eight hour service life is too long.
Participative Management Employee Participation in the Wealth of Mining Companies, an Employee Share Ownership Participation Scheme Focus
2004
Postgraduate dissertation on share ownership in South African mining, drawing on British and American precedent and a worker attitude survey. For human resources and empowerment planners.
What this report foundEmployee share ownership participation schemes are presented as a route to spreading mining wealth more widely after apartheid.
R1500,00
Employee share ownership participation schemes are presented as a route to spreading mining wealth more widely after apartheid. They differ from profit sharing and pension arrangements in holding only the employer's own equity and in enlarging the company's capacity to borrow. Acceptance of such schemes in the South African mining industry was tested through an attitude survey of workers.
Project 2.9.6 Preventing Cutting Head Methane Emissions On Continuous Miners
2020
Simulation work on face ventilation in mechanised coal sections, with methane sources modelled from the cut face, gathering arms, conveyors and shuttle cars. For ventilation engineers and equipment manufacturers.
What this report foundComputational fluid dynamics, checked against underground measurements, mapped ventilation flow and methane concentration around continuous miner headings for...
R1500,00
Computational fluid dynamics, checked against underground measurements, mapped ventilation flow and methane concentration around continuous miner headings for straights and splits, single and double scrubbers, side and straight scrubber discharges, jet fans, brattices and force columns. It showed the earlier physical test work cannot predict contaminant flow for larger machines or altered scrubber layouts.
Review of Current and Expected Underground Coal Mining Methods and an Evaluation of the Best Practices Associated with These
2010
Review of underground coal production systems in South Africa set against practice in Australia, China and the United States, with guidance on equipment choice and section planning.
What this report foundSouth African underground sections average about 60 000 t a month, against 130 000 to 160 000 t for single pass bolter miner units on continuous haulage, while...
R1500,00
South African underground sections average about 60 000 t a month, against 130 000 to 160 000 t for single pass bolter miner units on continuous haulage, while the better sections target 1.4 to 1.6 Mt a year. Australian longwalls deliver 5 to 7 Mt a year from one face, compared with 3 to 5 Mt at the two local wall operations.
Simulation of Regional Collapses in Bord & Pillar Workings
2018
Three dimensional modelling of a documented subsidence event in the Witbank coalfield, aimed at reserves in the seam above old workings that current pillar strength formulae sterilise.
What this report foundFinite element simulation reproduced the rapid collapse of bord and pillar workings in the 2 Seam at a Witbank colliery, showing that progressive pillar...
R1500,00
Finite element simulation reproduced the rapid collapse of bord and pillar workings in the 2 Seam at a Witbank colliery, showing that progressive pillar deterioration triggers snap through of a strong sandstone plate in the overburden. Too little was known about the chosen collapse to back out a real pillar safety factor, so the calibration goal was not met.