6th September 2016 Investigation into Roof-fall MG 102 C Heading 18 to 19 CT
POINTS TO NOTE
Statements in the reports from Terry Medhurst (Principal Geotechnical Engineer — PDR Engineers) and Lesley Munsamy (Lead Geotechnical Engineer — T&S AAC) indicate the following
Megabolts should be part of primary support and 1.8m long bolts in primary development is insufficient.
HAS THE MINE IMMEDIATELY IMPLEMENTED INSTALLING MEGABOLTS?
At present there is no accepted approach to evaluate the combined effects of bending and suspension for roof support design.
Strata conditions suggest that the use of visible signs of damage for triggers are limited resulting in a heavy reliance on the use of roof convergence monitoring for assessing stability.
Roof convergence TARP triggers must be reviewed.
HAS THE MINE IMPLEMENTED TRAP TRIGGER REVIEW?
Empirical tools do not seem to be reliable and must be used with caution.
Based on current knowledge, conditions at Grosvenor appear outside the current empirical database for roof support design.
Empirical tools must be supplemented with numerical analysis based on site specific geotechnical data.
It is probable that there would be almost no visible signs or triggers available to monitor conditions other than a reliance on roof displacement.
STATES THAT NO EFFECTIVE EVALUATION TOOLS, OUTSIDE DATABASE FOR SUPPORT DESIGN ETC.
HOW ARE STRATA CONDITIONS SO DIFFERENT AT GROSVENOR THAN OTHER GOONYELLA MIDDLE SEAM UNDERGROUND MINES?
IS GROSVENOR MINE ALIGNED DIFFERENTLY TO CLEATS AND GEOLOGICAL STRESSES THAN THE OTHER MINES.
Confidence in the risk management and change management processes should be clearly established with regards to strata management.
The Mine must be able to demonstrate that the risk management process can adequately address concerns raised in the above-mentioned reports and that the risk is at an acceptable level.
Clarification is required in terms of the ability of the operation to identify, analyse, evaluate and treat risk as well as monitor and review the effectiveness of controls with respect to strata management going forward.
NO DIRECTIVES ISSUED.
GROSVENOR JUST CONTINUES TO PROGRESS AS THE SSE AND SENIOR MANAGEMENT DECIDE
USING WORDS SUCH AS “CLARIFICATION, CONFIDENCE” ETC MEAN NOTHING
06.09.2016. Fall Investigation Interviews + comments MRE – Grosvenor Coal Mine –
