GROUND SUPPORT
Paul Moore reviews
some new technology
and successes of
existing solutions in
both rockbolting and
shotcreting
Call for reinforcements
round support was a major subject
matter at the Deep Mining 2017
conference held in Perth from March 28-
30 and organised by the Australian Centre for
Geomechanics (ACG). DSI Underground’s Senior
Manager Business Development Federico
Scolari discussed the company’s development of
a bolt, based on a frictional, inflatable bolt
combined with an internal additional load-
bearing element, namely the Dynamic Omega-
Bolt. The paper presents a specific version of a
dynamic inflatable bolt, where both outer profile
and inner element are manufactured by a 2 mm
thick steel plate.
Its denomination is Dynamic Omega-Bolt ® 35
and the outer profile has a steel cross-section of
326 mm² and loading capacity of 160 kN and the
internal ‘C’ element has an ultimate tensile load
of 70 kN and a cross-sectional area of 154 mm².
The additional internal ‘C’ element is not in
direct contact with the rock and the load will be
transferred to it only due to the total
deformation of the external friction component.
The internal profile yields along its total length
since it is point anchored. Based on the grade of
steel used for the point anchored element, an
elongation of > 15% can be expected.
For a 3 m bolt length, the point anchored
component can undergo more than 450 mm of
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60 International Mining | AUGUST 2017
elongation prior to failure. The internal and
external elements cooperate to reach the
maximum peak load, however, the external
profile reaches its breaking point first, while the
internal element remains intact.
Testing on Dynamic Omega-Bolt by
Canmet
Laboratory drop tests conducted at the
CanmetMINING laboratories suggest that under
dynamic loading, the bolt exhibits a peak tensile
strength based on the frictional element
The DSI Dynamic Omega-Bolt associates the
well-known advantages of inflatable friction
bolts such as fast, clean and safe installation,
with an improved capacity of
energy/deformation absorption from the
internal point anchored element
The Normet D-Bolt is a rock reinforcement
element comprised of a smooth steel bar with a
number of deformed sections that act as anchor
points along its length
combined with a residual loading capacity from
the internal element. Failure of both elements of
the bolt corresponds to an average absorption
of 35 kJ of energy due to steel elongation. The
residual loading capacity is in the range of 70 kN
and it is intended to retain the dead load of
broken rock slabs generated by an event of a
sudden release of energy, as long as sufficient