Causes, Symptoms, Prevention and Alleviation of Soil Compaction on Mined Land
A review of South African opencast coal experience, written for environmental officers and mine management who must correct legacy compaction and plan operations that avoid creating more.
Compaction on rehabilitated opencast land restricts effective rooting depth so severely that only a small proportion of arable and grazing areas reach their stated capability. The review sets out the causes and symptoms, argues that symptoms are usually treated without addressing the cause, and recommends site specific, resource based management, mechanisation choices weighed against compaction, and land capability standards aligned with international codes.
R1500,00
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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...
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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.
Simulation of Regional Collapses in Bord & Pillar Workings
2018
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.
What this report foundFinite element simulation reproduced the rapid collapse of bord and pillar workings in the 2 Seam at a Witbank colliery, showing that progressive pillar...
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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.
Can old bord-and-pillar workings be mapped from surface?
2016
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.
What this report foundNo surface geophysical method can map individual bords and pillars at the depths typical of the Witbank coalfield, a limit the review attributed to physics...
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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.
The Relationship Between Geological Structures and Dolerite Intrusions in the Witbank Highveld Coalfield, South Africa
2008
Structural study of dolerite dykes and sills at four collieries south of the Ogies Dyke, linking intrusion geometry to mining conditions and coal quality. For mine geologists.
What this report foundDolerite intrusion mechanisms and their metamorphic effect on coal were examined across four collieries in the south eastern Witbank Coalfield.
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Dolerite intrusion mechanisms and their metamorphic effect on coal were examined across four collieries in the south eastern Witbank Coalfield. In decreasing order of importance, intrusions cut safety by raising the risk of roof, pillar and floor failure, raise mining costs, reduce saleable tonnage, and increase waste generation and environmental risk.