Operations
structural properties and being a renewable
resource. “Timber remains a cost-
effective and reliable material for mining
applications and still forms a crucial part of
the mining support systems,” she says.
Going forward, De Haas says that the
demand for timber in the mining industry
will depend largely on how effectively
timber can compete with other products.
“Timber is a renewable resource, unlike any
other support material used in mines.”
Advantages and disadvantages of
using timber in the mining industry
Timber planks stacked neatly ready to be used.
entries, and along haulage corridors,’ the
article explains. mine roof by spanning two parallel mining
props,’ the article states.
Next it describes sawn props, which have
a similar purpose to round props. The
difference is that they have more of a
permanent function in that they are often set
in mine corridors for up to 10 years. They are
also the main preference for mines because
they are simple to use. When explaining
the split props, the article mentioned that
they would normally conform to the same
standards as round props. Depending on the
original diameter, spilt props are halved or
quartered. This makes them versatile enough
to be used for other functions such as wheel
chocking and lagging. According to the
three authors, lagging is described as having
similar dimensions to planks which are used
for shoring sides of mine entries, shafts and
haulage ways. Lagging can be stacked in
two ways: lengthwise or crosswise on top of
crossbars for roof support. The article also mentions that it is possible
to rehabilitate some wood products for
other uses as well. For example, ties can be
used for railway support, but also provide
a large bearing surface against a soft or
muddy surface. In addition, after being
rehabilitated, ties can also be sawn and
sacked similar to crib blocks and be used
for pillar support.
Another category of timber product is a
header which functions as a bearing surface
against mine roofs. Also known as caps,
headers are ‘conventionally mounted in props
to fill gaps and tighten the wood structure
into the mine roof ’. The article highlights that
headers can be replaced by metal. According to De Haas, Merensky Timber
has seen a steady decrease in mining timber
demand over the years, with volumes
reducing further as a result of numerous
shaft closures. “Mining timber is expected to
decrease in line with the decrease in demand
from mines. Price increases are expected
to be inflationary, but also linked to the
demand for other timber uses,” she adds.
Some timber products serve more of a
support function and are used together
with other timber products. Crossbars are
an example of supporting timber products,
where they are usually used along with
props and headers. ‘They help support the
42 AFRICAN MINING JULY - AUGUST 2019
The last timber product described by the
journal is a wedge which is described as a
pie-shaped wood slab. Typically, the slabs
are sawn at the mill and then wedged on
top of headers to tighten the props to the
mine roof. ‘Coal mines keep a large supply of
wedges on hand since they can be used for
any purpose requiring tightening or blocking
of a support structure,’ the article says.
The future of timber use in mining
Although timber in mining continues to
face various challenges, De Haas maintains
that the use of timber in the mining
industry is still prevalent due to its unique
Advantages:
Timber is cost-effective for use in the
mining industry. The high density of
eucalyptus makes it a strong, durable
and structurally-sound product. As a
construction material, mining timber
requires none of the special equipment
needed for placing concrete or steel
supports.
Another key advantage of timber over
other support-system materials is the
safety factor. When crushed by extreme
pressure, timber collapses slowly and not
suddenly like concrete or other materials.
Timber is a renewable resource, unlike
most other support materials used in
mines. All support materials consume
energy and other resources in their creation,
construction and eventual demolition. At
each stage, this consumption can have a
significant impact on the environment
at global, regional and local levels. Using
environmentally sustainable support
materials like timber helps reduce the use
of fossil fuel energy and minimises adverse
environmental impacts.
Disadvantages:
Timber is considered more of a fire
hazard than some other support materials,
although it retains its structural strength
at high temperatures while it is burning.
Timber can shrink, swell, twist and
crack over time, although Merensky has
for decades been involved in breeding
eucalyptus species that are less prone
to wood end-splitting and thus deliver
greater strength. b
Merensky Timber
www.africanmining.co.za