Cradle to grave
Roof bolts stabilise the rock structure in a deep-level underground mine.
have no roof support, or support was limited to
intersections only,” says Murray.
Roof bolts are available in many forms and
the methods to attach them to the rock mass
are as varied. Full column resin bolts, resin
point anchors, and mechanical anchors are
the most common support systems used in
South Africa. “Initially, mines started using
mechanical anchors and resin-anchored roof
bolts in the mid 1970s,” explains Murray.
“All South African mines currently operate
with systematic roof support and mines
conducting secondary extraction in workings
that were developed with no, or limited,
systematic support, install systematic support
prior to mining,” he adds.
One of the most common flaws is
excessive bolt spacing, which may result in
failure between bolts, which in turn
can cause a fall of ground. However,
establishing the position of the bolt with
any real accuracy can take significant
time, which may negatively impact on
production.
“Excessive bolt spacing can result in
failures between bolts and serious falls of
ground, but conversely, using too many
bolts due to incorrect smaller spacing
can be costly and more time-consuming.
Establishing where to position the next
roof bolt takes time, which negatively
impacts production,” says Murray.
Monitech has developed and patented
the Monitech Roof Bolt Placement
System (RBPS), which indicates correct
bolt positioning for the operator.
Roof bolts work with the ground to create
a stable rock structure. They are the first
line of defense to protect mineworkers
from the hazards of ground falls. Just how
significant is correct placement of roof
bolting in underground mining?
The principal objective of roof bolting
is to help the rock mass support itself.
Nick Murray, chief sales and marketing
officer at Monitech, a South African
company that specialises in mining safety
and monitoring solutions, says the most
significant development in coal mine
ground control during the previous
century was the introduction of roof
bolting during the 1940s and 1950s.
Rightly so, from an engineering
standpoint, roof bolts have proved to be
more effective than the wooden timbers
they replaced.
“Roof bolts promised to dramatically
reduce the number of roof fall accidents
and they were hailed as ‘one of the
great social advances of our time’. Roof
bolting also emerged at a time of rapid
technological advancement in the coal
industry and greatly accelerated the
transition to trackless rubber – tyred face
haulage, as seen in the report compiled by
Christopher Mark,” says Murray.
Case studies also proved that roof
falls could be largely eliminated, and
productivity increased dramatically.
Again, in the words of Christopher
Mark, “Roof bolting has been adopted
more rapidly than any other new
technology in the history of coal mining
mechanisation.”
Today, roof bolting is by far the most
common support system used in South
African collieries. “Historically, South
African mines mined in areas that were
very stable and it was common practice to
The importance of placing roof bolts
Today, roof bolts are key in safeguarding workers in an underground mining operation.
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MAY 2019 MINING MIRROR [39]