erich neugebauer
TRANSCRIPT
“ROOFEX A NEW ROCK
BOLTING CONCEPT FOR
UNDERGROUND
EXCAVATION UNDER HIGH
STRESS CONDITIONS”
Erich Neugebauer
ATLAS COPCO
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Rock Reinforcement from Atlas Copco
A new way to tackle safety in underground operations
Roofex - a new rock bolting concept for underground operations under high stress conditions
Erich Neugebauer, Atlas Copco Geotechnical, Drilling and Exploration
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Background
The world markets’ persistent demand on raw materials and the continuous need
for infrastructure expansion forces the mining and construction industry to
develop underground structures in more sensitive and violent environments
… and at the same time the demand on safety is increasing.
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Background
There is a need to actively control the energy liberated from the rock mass
deformation process in high stress environments.
Large convergences in weak, yielding grounds, where deformation is a slow and an almost
static phenomenon.
Dynamic events, commonly in hard rock where energy is released in a rapid and violent
manner as in the case rock burst or earthquakes.
The ability of the support elements to yield under dynamic loading, through a
predefined controlled displacement is critical in damping the dynamic load and
minimizing rock ejection.
Existing rock bolts designed to cope with the mentioned problems strongly
depend on installation conditions, the interaction of the steel with the rock or
on the bonding agent, and this may lead to sources of concern regarding their
controlled performance.
It is now time for a new innovation in rock reinforcement!
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Roofex rock bolt
Roofex Rx8 rock bolt, is a new, highly
advanced rock bolt designed to dissipate and
control high amounts of energy liberated from
the rock mass deformation process. Through its
steel to steel interface, Roofex provides a
predictability to the system behaviour and
allows you to accurately adjust the support
needed to keep the excavation from caving in.
Designed either for static or dynamic
applications.
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Components
The key components of the
Roofex rock bolt are:
Inner steel bar
Energy absorber
Mixing / stop element
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Roofex – an ingenious design
The sliding function creates friction between the fixed energy absorbing
element and the inner steel bar which in turn absorbs the energy released from rock
movement.
The bar isolation concept assures a free linear movement to maintain the constant
sliding-load level along the entire pre-set sliding length.
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Rock mass behaviour – Support performance
Rock mass behaviour
Characteristic lines after Fenner-Pacher
System behaviour
Characteristic lines with different
support characteristics
Su
pp
ort
re
sis
tan
ce
Radial deformation
pi
R
characteristic line - stiff support
characteristic line - flexible, ductile support ROOFEX
characteristic line - soft support
progressive rock mass
relaxation, development of ground
loosening pressure
elastic rock mass
rock mass at elastic limit
Support
resis
tance
Radial deformation
pi
R
Roofex load performance
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Installation procedure
Roofex rock bolt, is easily installed using a
bonding agent that is either a cartridge
contained type (e. g. 2 component resin) or a
premixed, pumped type (e. g. cement mortar)
Cartridge type Pumped type
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Roofex monitor bolts – complete the concept
Provide easy monitoring of rock movement, verification of the performance
of the Roofex rock bolts at the same time they provide rock support.
There are two versions of the monitor bolt; the external version and the
internal version. Both designed either for static or dynamic applications.
Components
External monitor
Internal monitor
External monitor - cartridge
Working stages Installation
External monitor - pumped
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Why Roofex?
Designed to accommodate the whole
spectrum of rock mass behaviour.
By allowing a certain amount of rock
movement, Roofex releases the energy of
the rock in a fully controlled manner.
After large rock deformations or rock bursts,
where the sliding length has been consumed,
Roofex bolts are still able to cope with
prevailing residual loads, providing a reserve
load capacity to the system.
Safety in extreme environments
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Why Roofex?
The bolt is installed using conventional bolting
equipment.
The life span of the support system is
extended. Gallery can be kept open for a
longer period of time
lower total cost of operation.
Easily adapted to your operation
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Why Roofex?
The steel to steel energy absorbing interface facilitates a stable load bearing capacity which is insensitive to external conditions
reliable, predictable performance preset at the manufacturing stage.
The bolt’s behaviour can be accurately specified in numerical models, allowing the designer to pre-design the support system to the structure’s expected loading conditions and deformation span
optimised rock reinforcement design.
greater levels of safety and productivity.
Provides predictability and control
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A problem solver
Roofex is and will remain a specialty bolt,
intended for special conditions (unstable
ground, rock bursts, etc.)
The investment in Roofex bolts gives positive
benefits to the customer in a higher safety level
through predictability of the bolt’s behaviour.
The price of the bolt will be higher than a bolt for
standard applications, however the cost is
justified and easily returned by avoiding support
failures, rehabilitation and interruption of
production.
The introduction of Roofex targets mine and
tunnel designers, consultants and mining
houses who can maximize the benefits that the
product offers.
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Testing, Application and Future
Selected installation and testing sites for Roofex rock and monitor bolts are:
CANMET MMSL dynamic drop fall testing, Ottawa, Canada
IAMGOLD Mine Doyon, dynamic field testing, Rouyn-Noranda, Canada
Iberpotash, Vilafruns mine, Spain
X-Strata Copper at Kidd Creek mine, Timmins, Ontario, Canada.
Agnico Eagle at Laronde mine near Val D’Or, Quebec, Canada.
Brunswick Mining at Bathurst, New Brunswick, Canada.
Somincor, Portugal.
Cayeli and Koza mines, Turkey.
Colorado School of Mines, Edgar Research Mine, Idaho Springs, CO, USA
ZG Polkowice-Sieroszowice, KGHM Polska Miedz S.A., Polkowice, Poland.
Chwalowice, Kompania Weglowa S.A., Rybnik, Poland.
West Elk mine, Somerset, CO, USA
Elk Creek mine, Somerset, CO, USA
In the course of the development of the Roofex rock bolts, Atlas Copco has conducted an extensive
laboratory and field testing program, to commit to it’s high quality standards.
A second generation of Roofex, the Rx20, offering a load range of ca. 200 kN sliding load
and 240 kN ultimate load, has successfully passed the first field tests.
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We are committed to your
superior productivity through
interaction and innovation.
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