Transcript Rock Bolting for 21st Century

Installation of SDRBs into 60 MPa concrete blocks showing full resin encapsulation with resin at the borehole collar
Self Drilling Rock Bolt
Technology
for the Coal Industry
Ground Support Services Pty Ltd
March 2007
Self Drilling Rock Bolt (SDRB) Technology
Background to Self
Drilling Rock Bolts
(SDRBs)
Current SDRB System
Future SDRB
Developments
Testing SDRBs in concrete blocks
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Background to SDRBs
 SDRBs been around for at least 30 years
 developed for tunneling applications in weak or collapsing
ground
 commonly used with pumpable cement grout
 screw on fittings – wash off with water
 at least 17 SDRBs commercially available
Installation of SDRBs in civil engineering
they are simple, work well, but require manual installation & hours for cement grout to cure
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Existing SDRBs
Furen (China)
MAI (Austria)
Alwag (Austria)
DSI (Germany)
Williams
(USA)
Romtech (UK)
CarboTech (Germany)
Stainless UK
Wiborex (Germany)
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Existing Hollow Bars used for SDRBs
Ischebeck (Germany)
pierced billet
Atlas Copco (Sweden)
tube
tube
Minova-CarboTech
Wiborex (Germany)
Hilti
pierced billet
twin tubes
Williams (USA)
tube
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Conclusions on SDRBs
 SDRBs are NOT new
 SDRBs for the COAL industry should satisfy the following
criteria:

should provide immediate support at the face
 requires friction anchors or resin

have a support capacity at least equivalent to solid bolts
 requires full column encapsulation

have improved bolt installation productivity
 should be simple, repeatable & suited to automation

should be cost effective
QED: full column resin encapsulated bolt, with larger diameter than solid bolts & be logistically simple
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SDRB load transfer capacity
Load Transfer Capacity about 2 x solid bolts
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New SDRB System
Like a Machine Gun or a Nail Gun, most new technology
developments are in the equipment:
new Drill Chuck
new injection system
new Drive System
new pumps
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Pumpable Resin

full bolt encapsulation maximises roof support

no gloving, no plastic film, no under-mixing or over-mixing

perfect resin mixing every time

resin fills bearing plate & locks mesh in place

minimises water inflow from bolt holes

minimises bolt corrosion
visible resin at collar proves full encapsulation, fills bearing plate & also
locks mesh in place
© 2007 GSS Pty Ltd
full encapsulation both inside and outside bolt
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Underground trials
Nut tightened to 400Nm
confirms resin has cured
& tightens plate up to
roof
Hard Resin at collar
confirms:
•
full encapsulation
•
perfect resin mixing
Bolt end “clean”
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Conventional Solid Bolt Installation
Head Plate with
bearing plate
Drill
mast
may
also
need
new
drill
bits or
new
drill
rods
Roof
poor
mixing?
free
length
Resin
cartridge
“gloving”
“piston”
effect
Rock
Bolt
Drill
Steel
bending
Drive
Dolly
Lower
&
remove
dolly
Drill
Chuck
Logistically complex, can’t get any faster
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SDRB Installation Cycle
Drilling
Resin
Injection
Lower Drill
Chuck &
head plate
SDRB
High
thrust
but
straight
No Drive Dolly
Logistically simple
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SDRB Installation Cycle
Points to Note:

once SDRB is placed in chuck, no manual
handling

SDRB remains completely straight
throughout drilling cycle

2m hole drilled in 24 secs (83mm/sec)

plate gets pushed firmly up against mesh at
400 Nm proving resin has cured

end of bolt is completely clean
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SDRB Installation
Cycle Times to Install SDRBs
Film Clip
10
24
Fastest
10
22
27
3
10 2
Set Bolt in Chuck
10
Average
36
16
Drilling
5
Grouting
10
Slowest
0
77
20
40
39
60
80
100
Nut Tensioning
8
120
140
Seconds

Target cycle time of 60 seconds

Improvements planned for drilling cycle

PLC will enable consistently fast installation cycle times
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Target Roadway Driveage Rate 30m/shift = 120 Roof Bolts & 60 Rib Bolts
Total = 180 Bolts
Target
30m of
driveage
per shift
150 secs per standard bolt vs. 60 secs per SDRB
= 90 secs per bolt x 120 bolts = 3 bolting hours
= 90 secs per bolt x 180 bolts = 4.5 bolting hours
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SDRB future developments
Issue
Existing
Continuous
Miners
High Roadway
Driveage Rates
require more
consumables
Problem
Solution

Not designed for SDRBs

Need to be able to retro-fit
existing continuous miners –
requires good engineering
design

Very little space available
for bolting or consumables

Where to put resin tanks?

Longer term need to design
miner for SDRBs

Where to store
consumables on miner?

Needs a re-design of bolt
cassette system on miner

How to re-supply
consumables to miner?

And re-think how consumables
are re-supplied to miner
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Conclusions: SDRB System
Advantages:
 Logistically simple
 very fast bolt installation
 improved productivity
 reduces manual handling
 no drill rods, no drive dollies, no changing
drill bits, no resin cartridges, & no rotation
to mix resin
 less injuries and LTIs
 > bolt strength & > load transfer capacity
less bolts required?
 full bolt encapsulation
 equipment can be retro-fitted
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Summary: SDRB System
Future Developments:
 completed the “R” now into the production “D”
 considerable know-how on the SDRB System
 proved that the process works and achieves
original objectives
 optimising drill bits based on rock types
 refining resin gel times to suit high volume
pumping
 refining injection system
 next stage is to develop a production system
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Acknowledgements to:
ACARP
XStrata Beltana
BHP Billiton
Anglo Coal
Alminco
Thank You
For further information please contact:
Dr Peter Gray,
Ground Support Services Pty Ltd
Phone: 02 4225 7057
Email: [email protected]
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End
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Pre-tensioning & Encapsulation
You can clamp books together by applying a normal force

A pre-tensioning force compresses the rock bedding planes together

and creates an increase in shear strength = the normal force x the friction angle
on the bedding planes

this increase in shear strength is beneficial

but a normal force (pre-tensioning force) is distributed very quickly throughout
a rock mass away from the point of application
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Pre-tensioning & Encapsulation
You cannot support the books with just the same normal force (side force)
But if the books are glued together you can support them
Also it is much harder to pull books apart or get them to slide over each other, if they are glued
together rather than just being clamped together
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