Abstract:
‘Roof support awaiting time’ (RSAT) is a term used at Goedehoop Colliery’s
Simunye Shaft to describe the potential production time lost due to the
continuous miner (CM) standing idle waiting for roof support to catch up.
Investigations revealed that in 2013, Simunye Shaft had approximately
1400 hours of RSAT, which suggests that the mine could have potentially
produced an additional 280 000 t of coal. This project consisted of two
parts. Firstly, the causes of the high RSAT and means to improve the
situation were investigated. Secondly, as insisted by mine management, the
CM cutting sequence was investigated as a possible cause of high RSAT.
Machine-related challenges due to the roofbolter installing support too
slowly, geological conditions (mostly hard roof conditions and slips),
logistical challenges pertaining to the CM cutting sequence, man-related
challenges related to operator fatigue, re-support, operator inexperience,
and the absence of support targets were identified as main contributors to
RSAT. Furthermore, results showed that the roofbolters in the sections at
Simunye Shaft are slower than the CMs. A target of 28% reduction in RSAT
was set. Experts from Kennametal and Fletcher were consulted to find
solutions for the identified causes. In total, eight solutions for RSAT were
identified, but the solution that contributed most significantly to reducing
RSAT was to use hard roof drill bits as a standard product at Simunye
Shaft. Calculations showed that by using hard roof drill bits, RSAT can be
reduced by 43%, which is more than the specified 28% target.
The cutting sequences at Kriel, Greenside, and Simunye Shaft, together
with three newly developed cutting sequences, were simulated using the
UCMS (Underground Coal Mining Simulation) program. A re-aligning
principle was incorporated into the newly developed cutting sequences to
align the cutting sequences to general support work and to reduce RSAT. A
decision matrix revealed that a cutting sequence in which boxing takes
place in R3 (third road to the right of the belt road) and in which the realigning
principle has been incorporated will be the best option for Simunye
Shaft. The recommended cutting sequence will lead to a 5% increase in
production.
Description:
The work presented in this paper was carried out as partial fullfilment for the degree
BEng (Mining Engineering)
I would like to thank L.M. Mphasha, my mentor at the mine,
and J.A. Maritz, my supervisor at the University of Pretoria,
for their guidance and support.
