GROUND SUPPORT
Walenstadt, Switzerland. On a test rig it is
possible to apply large energies on variable
ground support systems with variable bolt
patterns and meshes with a total support area of
3.6 m x 3.6 m in a full-scale way. The test site is
instrumented by load cells, high-speed video
analysis and accelerometers. It could be shown
that a combination of high-tensile steel mesh with
a specific bolt pattern can result in high energy
capacity surface support. Distribution of the
impact loads during the stopping process to the
different elements of the bearing support system
depends on the strength and flexibility of the
mesh and the bolt resistance and its pattern.
Given the characteristics of a structure that
attempts to reproduce the conditions of a mine,
boundary conditions are generated, which do not
allow a direct correlation of the results obtained in
the test with the results expected at the mine.
However, it allows comparisons between
systems/elements of fortification and helps to
advance our understanding of the complex
problem of ground support.
The new ground support designs, developed
over the last few years, consist of high-tensile
steel wire mesh MINAX ® , anchors and shotcrete.
Because of the use of high-tensile steel wire
(minimum 1,770 MPa) and the flexibility of the
chain-link mesh, such a support system can be
applied in areas with very high static and dynamic
stress.
“On several rockburst occasions worldwide, it
was clearly demonstrated that this type of design,
with high-tensile chain-link mesh MINAX ® , allows
high energy absorption of the dynamic loads from
periodic rockbursts, depending of the magnitude
of the incident usually without any maintenance
requirements, which is both fundamental for
guaranteeing miners’ safety and essential to
increase the productivity of mining development
ultimately.”
With this successful test series of a
reinforcement system (shotcrete with mesh, bolt
and a second mesh with cable bolts) under
dynamic conditions, Geobruggg says “we can add
experimental antecedents to the theory and
confirm that this type of support is with no doubt
a huge step forward in increasing the safety in
underground mining.”
DSI Underground’s global capability
DSI Underground has one of the most
comprehensive ground support offerings in the
industry which is reflected in the geographical
diversity of mining rock reinforcement projects it is
involved with which also includes knowledge
sharing. The APAC division recently supplied DSI
TITAN Cable Bolts to Poland which were installed
at the “Pniowek” coking coal mine of JSW SA. The
TITAN Cable Bolts were installed in the tailgate of
the highly productive longwall panel at the depth
of approximately 900 m. TITAN Cables were used
as secondary support, with the primary type being
steel arches typical in Poland. The longwall
system in this particular case used a plow to cut
the coal so there was a need to dismantle 8-10
steel arch sets (approximately 5m total length) in
the vicinity of active longwall operation (crossroad
connection - longwall working and its tailgate).
The ventilation requirements (outtake of the air
from the longwall working) and the need for
additional transportation route to the longwall (via
tailgate) created a necessity to reinforce the
tailgate. The usual practice is to collapse the
working as soon as the longwall face passes
(retreat mining) but in this case it couldn’t be
applied. The abutment pressure behind the
longwall working can cause huge problems. One
of the objectives of the application of the TITAN
Cable was to compare its performance against
much simpler lower strength solutions. A good
result, it was determined by JSW mine engineers
that the TITAN Cable performed well.
Back to Australia and DSI Underground’s fully
automated continuous colloidal grout batching
plant for pumpable cribs is now in full operation at
BMA Broadmeadow. This plant is able to deliver a
long distance surface to seam pumping system
with full digital control. All grouting parameters
can be remotely monitored to ensure quality crib
installations every time. Utilising the superior
performance of a two component CSA cement
technology, the plant has successfully broken all
previous installation records with the installation
of 40 3.8 m pumpable cribs in a single 8 hour shift
pumped over double the distance underground
and using less operators than other more
traditional systems.
In key contracts last year, major mining
contractor PYBAR Mining Services awarded DSI
Underground the supply contract for ground
support products for the Lake Cowal underground
gold mine project in New South Wales. The project
is DSI Underground’s first supply agreement on
the East Coast with PYBAR and heralds a new
DSI TITAN Cable Bolts installed at “Pniowek”
coking coal mine of JSW SA in Poland
partnership with a view to the future. Evolution
Mining’s expansion of the Cowal gold operations
in New South Wales gained approval in October
2018 with the awarding of an underground
development contract to PYBAR in February 2019.
The site has traditionally been an open pit
operation, but to increase production the
underground project was initiated and approved.
Sandvik to launch its first battery rock
bolter in 2021
Sandvik Mining and Rock Technology says it plans
to launch the mining industry’s first batterypowered
rock bolter next year, as it continues to
roll out new solutions to electrify the underground
mining space. The Sandvik DS412iE extends the
zero emissions concept to the underground rock
bolter class and opens a wide range of
possibilities for mines driven to boost their
productivity and safety with data-based analytics,
according to the company.
In its core mission of delivering productive,
secure and versatile rock support solutions,
Sandvik rock bolters have a clear track record,
according to the company. “Still, these tools’
automation and data acquisition capabilities have
not been as advanced as their production and
development drill rig counterparts,” the company
said. “Scheduled for launch during 2021, the new
Sandvik DS412iE rock bolter will complement the
intelligent family of next-generation batterypowered
underground drill rigs.”
Anssi Kouhia, Product Manager, Rock Support
Drills, said the DS412iE is basically an upgrade on its
existing Sandvik DS411. “We have received positive
feedback about that model,” Kouhia said. “We made
an accomplished model even better with more
advanced automation capabilities, improved data
acquisition and upgraded ergonomics.”
Like the battery-powered DD422iE jumbo drill,
the rig trams on battery and carries out drilling
52 International Mining | JULY/AUGUST 2020