Publications

Irrigation with calcium and sulphate rich mine water proved feasible and sustainable over eight years at a Mpumalanga colliery, with no significant impact on soil, surface water or groundwater. Sugarbeans, wheat, maize, potatoes and pastures were grown on a commercial scale. High calcium and magnesium suppressed potassium uptake, and waterlogging from poor site selection was the main problem.

Sets out good practice for planning, implementing, monitoring and adaptively managing land rehabilitation at surface coal mines, with generic rehabilitation objectives, implementation actions and suggested relinquishment criteria for each component. It updates guidance first issued in 1981 and revised in 2007, reflecting later changes to South African rehabilitation legislation.

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.

A framework for planning land use on rehabilitated coal mining land, built from a review of international and national regulatory and corporate guidance and from interviews with industry practitioners. The review found that existing guidance requires land to be returned as close as possible to its pre mining condition, while community needs are pushing rehabilitation towards alternative land uses that can sustain livelihoods.

No single method gives a continuous, real time report on how a coal preparation plant is performing. Mass meters converted to yield values, on-line ash and moisture monitors, load cell chutes and automatic medium density control together supply most of what is needed. Measuring discard and slimes tonnages, particularly slimes disposal, remains the weakest point in plant accounting.

Recharge factors of 23.5 per cent and 12.9 per cent were calculated at the two rehabilitated pits with complete data. The higher value reflected surface drainage towards the pit centre and eroded topsoil; the lower one, a deep pit floor with well compacted spoil and intact cover. The rates are site specific and no generic formula could be derived.

Run of mine and discard coal carried total rare earth contents of 260 and 265 ppm, above the 130 ppm cut off grade used for coal. Flotation with an emulsion binder did not raise those concentrations in either the product or the tailings streams. Calcination did, lifting totals to between 285 and 289 ppm, with most rare earths leaching within the first fifteen minutes.

Experimental studies tested ways to alleviate compaction on mine soils by combining mechanical treatment with organic material. Survival of 16 pasture species was recorded on mechanically ameliorated compacted soil, dry matter and leaf area were measured for tall fescue and cocksfoot at different levels of organic material, and soil fertility, bulk density and root biomass were tracked under irrigated and dryland grass.

Grazing trials on tall fescue pasture irrigated with gypsiferous mine water on rehabilitated mined land, run over several seasons. The work covers steer stocking rates, dry matter intake by cattle, and the factors that control pasture quality and intake, among them nitrogen fertilisation, stage of growth, sward structure and grazing intensity. Findings are reported study by study.

Builds on an earlier productivity audit that identified fluctuating bonuses and incentives as an influence on output, safety and employee stress. The work examines how salaries, production bonuses and safety bonuses are graded and distributed across employee categories, how workers perceive that distribution, and whether incentives in practice motivate production and safe working. Stress and morale are treated as measures of wellbeing.

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.

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.