Block Caving - A Cost-Effective Underground Mining Method
Block caving is a very efficient underground mining method. Its costs are lower than other mining methods per tonne mined. In addition, it requires a lower ventilation requirement. It also allows for a more flexible use of equipment, such as LHDs.
In block cave mining, a section of the rock mass is
undercut and then collapses into excavations. These form ore extraction
drawpoints.
Cost-effectiveness
Compared with other mining methods, block caving is
one of the most cost-effective ways to mine copper and gold. It also reduces
the need for surface waste disposal. However, it requires substantial planning
and infrastructure and a long lead time. This method can be more sensitive to
world events than other mining techniques, making it a riskier investment.
To develop a block cave, access shafts are
excavated to a level below the ore body. Horizontal tunnels, known as haulage
tunnels, are then dug benearth the ore body. These are followed by a series of
upward-sloping tunnels, known as raises. Blasting is used to create these, and
large rock funnels, called drawbells, are excavated beneath the undercut level.
A major challenge for block cave mining is the
ability to fracture the rock mass and generate enough fragmentation to support
long-life drawpoints and excavation tunnels. This requires preconditioning,
which is a comprehensive process that includes destressing and fracturing the
in situ rock mass.
Safety
Block caving is a safe mining method, but it
requires special skills and equipment. Mining machinery manufacturers have been
developing automated systems to increase safety. Caterpillar has developed a
system for loading and hauling that is specifically designed for block caving,
making it safer for miners.
This system will enable real-time mapping of cave
material movement, which can help minimise dilution and improve recovery. It
will also allow miners to design cave layouts that are more efficient. It will
also help reduce mine safety risks and environmental impacts.
The technology has already been tested at Ridgeway
Deeps and was found to be effective. It will be available on the market next
year. Its development is supported by the mining industry and the University of
Western Australia. Increasing numbers of PEAs and feasibility studies are
recommending the use of this technique. This is a good sign that the future of
block caving is bright. It can be used for both new mines and for extending the
life of open pits.
Environmental impact
The success of block caving means mining companies
are turning to it for deeper ore bodies that could not be mined profitably
using traditional methods. However, deeper rocks are stronger and less
fractured, so they require a lot more support to allow for natural caves to
form. This means that companies need to give nature a helping hand, using
technologies such as remote operation and collision avoidance systems for
hydraulic breakers.
The development sequence for a block cave begins
with the establishment of access drifts around the ore body. Once this is done,
a grid of crosscuts are developed for workers and equipment. A new level is
then developed above the first drift, and mining begins. Blasting and hydraulic
breaking are used to break up the ore.
The key to successful block cave mining is a
well-designed development, which allows for the creation of undercuts that will
automatically collapse when the orebody is undercut. The dimensions of the
undercuts are important, as they determine the speed at which ore is drawn down
through the drawpoints and transferred to the transfer raises. Insufficient
undercuts can lead to a loss of productivity and may cause the cave roof to
stabilize or even collapse.
Technology
Increasingly, mining companies are considering
block caving as an alternative to developing new mines or extending the life of
existing open pits. The method involves drilling access shafts into an ore
deposit and excavating a network of tunnels underneath the surface. These
tunnels are known as haulage tunnels and are linked by upward-sloping rock
funnels called raises. They are excavated by blasting from a central location
called an undercut.
Block caving has several advantages over other
underground mining methods. It offers higher production rates and lower
operating costs. It also reduces the amount of waste rock generated by a mine,
as it is buried below ground level.
However, the process requires significant initial
investment and long lead times. It can take up to 20 years for a large-scale
block cave to be established. Furthermore, the method is not suitable for all
ore bodies. The rocks should be competent, with good permeability and low
fracture energy.
Comments
Post a Comment