Simulation of Regional Collapses in Bord & Pillar Workings
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.
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.
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What this report foundHeat exchanger material governs how fast ice scale forms during eutectic freeze crystallisation of dilute brine.
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Masters study of dyke and sill intrusions at collieries in the Witbank and Highveld coalfields, using thin section petrography and X-ray fluorescence, for exploration geologists.
What this report foundDolerites in the study area differ in mineral content, geometry, thickness, grain size and degree of alteration.
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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.
Improved Utilization of Underground Coal Reserves
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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.
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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.