Underground Mining
Underground Trials of Seismic-counter and Goafing Characteristics in Pillar Extraction
2003
Underground trials at South African collieries of a seismic early warning instrument first developed for an Australian longwall, with analysis of how roof layers fail during pillar extraction.
What this report foundA stand-alone device was built that detects micro-seismicity within 100 m of the roof and raises an alarm when preset thresholds are exceeded, giving early...
R1500,00
A stand-alone device was built that detects micro-seismicity within 100 m of the roof and raises an alarm when preset thresholds are exceeded, giving early warning of goafing. Input parameters proved not to vary with geotechnical setting. Man-made noise triggering false alarms remained the main obstacle, addressed by signal conditioning and sensor placement.
Update of Coal Pillar Data Base, Strength Formula and Probability of Failure for South African Coal Mining
2012
Reviews how the failed and intact pillar record, tributary area loading and the safety factor concept have developed since 1960, for rock engineers and regulators.
What this report foundFailures continued after the safety factor approach was adopted, in pillars created both before and after it, so the record of failed workings has kept growing...
R1500,00
Failures continued after the safety factor approach was adopted, in pillars created both before and after it, so the record of failed workings has kept growing since the original 27 cases. The database was updated and re-analysed to revise the strength formula and to set out the probability of failure associated with pillar designs.
Verification of the New Coal Pillar Strength Formula and Investigations Into the Prediction of Pillar Life in Witbank and Highveld Coalfields
2004
Covers pillar load and strength estimation, the limits of tributary area theory, and the extraction gains available from revised strength formulae, for rock engineers designing bord and pillar workings.
What this report foundLaboratory testing showed coal specimen strength rising linearly with width to height ratio and falling exponentially with specimen size, the size effect...
R1500,00
Laboratory testing showed coal specimen strength rising linearly with width to height ratio and falling exponentially with specimen size, the size effect becoming insignificant beyond about 2 m diameter. The slope of that relationship was the same for coals from different mines, while the intercept varied with specimen size.