“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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