Can old bord-and-pillar workings be mapped from surface?
Desktop review updating two earlier assessments, weighing borehole scanning, robots and unmanned aerial platforms as routes to locating old workings ahead of opencast drilling and blasting.
No surface geophysical method can map individual bords and pillars at the depths typical of the Witbank coalfield, a limit the review attributed to physics rather than to technology, since the targets are small relative to their depth and conductive layers often lie above the seam. Borehole laser scanning remains the workable option, with sonar suited to flooded workings.
R1500,00
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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.