This paper focuses on the stability analysis and
support design of the coal mine tunnel excavated in weak
rock mass in an Indonesian underground coal mine
through numerical simulations using the FLAC3D
software. The PT Gerbang Daya Mandiri (GDM) coal
mine situated in Indonesia was selected as a mine site in
this study. According to the results of a series of numerical
simulations, the stability of the mine tunnel decreases by
increasing the depth and stress ratio. Ground control
problems, for example falling roof, sidewall collapse, and
floor heave are expected unless an appropriate support
system is anticipated. Three support systems, including
friction rockbolt, steel arch, and shotcrete are discussed as
methods to stabilize the roof and sidewalls of the mine
tunnel. From the simulated results, the steel arch is
considered to be the most effective support method when
compared with other support systems. The steel arch
which is installed with closer space and larger crosssection delivers a better stability control to the roof and
sidewalls of the mine tunnel. Although the stability of the
roof and sidewalls of the mine tunnel can be maintained
effectively by the steel arch support, the occurrence of
floor heave is expected when the mining depth is increased.
To control the floor stability of the mine tunnel, three
techniques by applying cablebolt, invert-arch floor, and
grooving method are therefore investigated and discussed.
Based on simulated results, the heaving of the floor is well
controlled after the cablebolt, invert-arch floor, and
grooving methods are applied. Nevertheless, it is found
that controlling the floor heave by cablebolt support could
be the most suitable method comparing with other support
systems in terms of the installation process, providing flat
and safe working conditions of the floor, and economy.
Additionally, the cablebolt with closer row space and
longer length works more effectively to control the heaving
problem of the floor.
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