Transcript Installation of Megabolts as Primary Supports

How megabolts installed as
primary support assist in
safely improving
development rates
ACARP Roadway Development Operators Workshops - October 2011
Introduction
Three types of megabolts installed from
continuous miner
Post grouted megastrands – MW9
● Resin anchored, torque-tensioned megaflex bolts - TTX
● Resin anchored, post groutable fibreglass rib bolts
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MW9 Megabolt
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Most commonly
installed megabolt is
the barrel & wedge
version – MW9
Fully bulbed using
spiral rib wire for max
load transfer
Up to 11 m long cables
installed from miner in
LW installation roads
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MW9 – Nth Goonyella face road
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MW9 advantages
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42 mm hole – no reaming
Single 1,000 mm resin capsule
with resin retainer
Resin pushed up hole with bolt
– no conduit
Collar fittings attached after
bolt installed
No bearing plate or bolt head to
catch on walkway
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MW9 advantages
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Tension within 5 mins of
installation
Tension using system
hydraulics or intensifier
9 to 20 t pre-tension can be
achieved depending whether
system hydraulics or
intensifier used
No air needed on miner
Provides immediate point
anchor support of 57 t
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Important considerations
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Bolt is point anchored until
grouted
Anchor length designed to
take capacity of bolt – depends
on rock type at anchor horizon
Pull tests must be done to
determine if anchor can take
full capacity of bolt
This ungrouted bolt is loaded
to 45-50 tonnes
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MW9 grouting
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Top down grouted using grout
lance – quickest grouting
method
Grouting done within
designated time or distance
advanced – depends on
conditions
Heavy conditions may require
grouting within 24 hrs
Good conditions (intersections)
can be left for more than a week
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MW9 grouting
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Grout generally reaches
sufficient strength (30 to 40
MPa) within 24 hrs
Readily & easily audited
Regular auditing has greatly
improved quality of
installation
Grouting non-compliance now
less than 5%
Good installation reduces
likelihood of remedial roof
support
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MW9 developments
Mechanised insertion
● Lobster from Conway
Engineering
● Being used at Angus
Place
● Favourable reports so
far
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MW9 developments
Resin grouting using Minova
Carbothix
● Immediate roof support
● Remote pumping
● Quicker grouting
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Megaflex TTX
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Torque-tensioned
TT bolt becoming more in
demand
56 t and 48 t versions
56 t generally requires 28
mm hole
48 t a 27 mm hole
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TTX – advantages
No exposure to high
pressure tensioner
hydraulics
● Reduced injuries from
handling tensioners
● Quicker installation than
hydraulically tensioned
cables
● Combo dolly
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Combo dolly – no changing dollies
Mixing
Tightening
Inner socket engages hex drive
Outer socket engages nut
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TTX – advantages
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Roller race between nut &
washer reduces friction
Race is shrouded to keep
bearing free of dirt or mud
7 t bolt tension from 320
Nm drill torque
Minimal protrusion from
roof – important in low
seams
Removing hex drive
reduces protrusion further
– as little as 115 mm
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TTX – advantages
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Wires are anchored in the bolt
head using button heads forged
on end of each wire – maintains
max collar strength
B&W anchor typically reduces
cable collar capacity by approx
10%
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TTX – advantages
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Increased load transfer from
spiral wire
Groutable version being
developed – will require 42
mm dia. hole
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Limitations of torque-tensioned cables
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Reduced bolt pre-tension compared to hydraulic
tensioning
Possible use of torque multipliers
‐ Slows down installation
‐ Failure of torque multiplier can delay production
‐ Possible safety issues
May need modifications to head-plate of drill mast to
accommodate bolt and/or dolly
Full resin encapsulation difficult for cables > 4 m
Load transfer lower than for bulbed cables
If bulbed then larger hole dia. & bigger resin capsule
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Groutable FG rib bolt
42 t capacity
● Cuttable
● 42-45 mm drill hole
● Point anchored initially
● Breakout nut
● High torsion strength –
stalls rib bolting rigs
● 17 t collar capacity
● Shear strength of 14 t
● SG of 1.9 to 2.1 – separates
in washery
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Groutable FG rib dowel - advantages
Immediate rib support
● Hollow centre - post groutable
with thixotropic grout
● Full encapsulation vital in
heavy rib conditions
● Easily audited
● No secondary rib support
required – maximises
development rates
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