Towards the Failure Probability of Coal Pillars: a Review of Intact and Failed Cases in South Africa

Aircraft and ground based measurements at Kleinkopje Colliery showed spontaneous combustion to be a significant source of fine particles, with PM2.5 concentrations 91 per cent higher inside a combustion plume than outside it. Sulphur dioxide, nitrogen dioxide and carbon dioxide were also raised in plume, and benzene and toluene were detected. Average particle size was below one micron.

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.

Relinquishment criteria follow from the agreed post-mining land use. The land use is the goal and the criteria measure whether it has been reached. The guideline sets out a framework for approving those criteria at each mining phase, from the initial environmental management plan through to decommissioning, and compares South African practice with Australian, Canadian and international guidance.