Abstract:
This paper investigates the conditions leading to the indefinite termination
of production in four critical primary panels at an underground coal mining
operation, the observed shortcomings in the mining approach, and the
proposed strategy to mine through the affected panels. Initial assessment
of the abandoned panel conditions indicated time-dependent strata failure,
(i.e. bolted roof failure overrunning intersections), which occurred from
mere minutes to up to four weeks post-production, with and without prior
warning of failure. This prompted the constant re-supporting of back areas,
which raised safety and productivity concerns. Investigation of the initial
mining conditions revealed that the failures were due to a critical
combination of factors, the chief of which was isolated horizontal stress.
Other factors that were initially overlooked by the mine (i.e. influence of
hydraulic stress, misinterpretation of borehole data), resulted in the
conditions being described as abnormal. Remedial actions were determined,
and in so doing, a new strategic approach was formulated to thoroughly
address all failure concerns. The four panels were explicitly planned to
serve as the main intake and return airways for the recently commissioned
secondary ventilation shaft, as well as providing access to millions of tons
in proven coal reserves. It is thus imperative to mine the panels. A
feasibility study showed that the proposed strategy set for implementation
would be financially viable.
