Publications

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.

A regional scheme to collect, treat and re-use mine water in the Upper Olifants River Catchment has merit, with the mines best placed to start it through a dedicated mine water company that brings in the water services authorities. Water legislation supports the scheme provided the regulator allocates mine water as a resource. Viability rests on the tariffs mines and water users pay.

Sub-seams within the No 2 Seam were characterised at a single test site using lithology, seam thickness, proximate analysis, petrography and geophysical logs, and a paleoenvironmental model was built from them. Wireline logs separated coal from interburden but could not resolve the individual zones, because the physical differences are too subtle. Better sedimentological models gave better reserve and resource estimates.

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 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.

Emission factors derived from measured South African seam gas data give simple models for methane released by underground mining, surface mining and coal after mining. Applied across the industry they put total methane emissions at 52 000 to 93 000 tons a year. The models follow the IPCC Tier 2 approach using country specific factors.

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.

Government and industry aeromagnetic data over the Witbank Coalfield were merged into one set of maps and GIS compatible files, and roughly 1200 dyke traces were interpreted from them. Purchase of a 200 m line spacing government survey removed the need for infill flying. One participating company valued advance knowledge of a single underground dyke at about R15 million.

Compares labour intensive mechanised drill and blast underground mining with capital intensive bord and pillar using continuous miners, and adds the option of substituting locally made goods for imported supplies. Input data came from two mines running both types of section under comparable geological conditions, covering worker numbers, skill profiles, cost structures and import dependence, then calibrated to industry totals to drive a socio-economic model.

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.

Dolerites in the study area differ in mineral content, geometry, thickness, grain size and degree of alteration. Plagioclase textures indicate fractionation at different depths in the crust for the Witbank and Sasolburg intrusions, and the olivine content points to separate magma sources for two of the sills. Fine crystalline dolerite, including chilled margins and bifurcations, alters most readily.