Tensionable Tendons
Phil Howes
Tahmoor Colliery
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Tahmoor Colliery
 Tahmoor colliery is located approx. 30 minutes west of Wollongong.
 Mines hard coking coal from the Bulli seam.
 Is approx. 450m below the surface.
 Average seam height is 2m.
 Mining height at the face is 2.7m.
 Floor is taken to achieve the required mining height.
 Mains & gate road panels suffer extensive floor heave which must
be brushed with the CM to regain the 2.7m originally cut prior to
the panel advance.
 Normal roof support is 1.1m mesh modules & 8 x 2.1 X grade fully
encapsulated roof bolts per metre.
 4.1 tendons fully encapsulated with chemical resins installed as
required.
 8m or 10m Mega Bolts fully encapsulated installed outbye as
required.
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WHERE IT ALL BEGAN
 Brimstone No1 colliery November 1970
 Early strata monitoring systems:
•
Props
•
Wooden Wedges
•
Strata sounding
•
Worker awareness (experience)
 Strata control:
•
Props
•
Cut poor roof down with CM
•
Half round wooden slabs
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Displacement monitoring
 Above monitoring will not replace the traditional awareness of
colliery workers & officials, who are still required to observe for, &
respond to, changing ground conditions.
 Installed every intersection.
 Installed half way along every heading .
Gates & Mains
 Installed half way along every cut through.
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Strata TARP
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Strata TARP
Triggers (Face Area)
1. GREEN Level 1 Normal mining (8 x 2.1m bolts per metre)
2. YELLOW Level 2 (8 x 2.1m bolts per metre & 2 x 4.1m tendons each 2m)
 Slabbing greater than 200mm to less than 400mm for more than 3m
 Minor guttering less than/equal to 100mm.
 Minor roof buckles less than/equal to 100mm.
 Minor geological structure . Zone of jointing.
 Less than 2 bedding separation partings (each less than/equal 100mm) in
roof bolt drill hole.
 Local road widening for nitch (less than 5.5m).
 Pillar split, gas drainage stubs into L/w block.
 Minor rib spall associated with geological feature.
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Strata TARP
Response

Localised deterioration in conditions , increase support to yellow support
pattern.

Install a Tell Tale at the start of the support pattern change/geological.

Control miner guttering with 2.1m spot bolts.

Install additional rib bolts & mesh across geological structure.
Pre-existing Tell tales (outbye face)

Total (T) anchor movement greater than 30mm but not exceeding
50mm.

Response in the hazardous zone: Monitor & record readings once/shift
where more than 3 consecutive linear rates of displacement are greater
than 0 and/or 2 consecutive accelerating rates of displacement.
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Strata TARP
Trigger Reverse

Improved conditions go to green.

Authorised by development Superintendant & undermanager or
mine manager or Geotechnical Engineer.
Triggers (Face Area)
3. Orange Level 3 (8 x 2.1m bolts per metre & 2 x 4.1m tendons per
metre).
4. Red Level 4 (8 x 2.1m bolts per metre & 4 x 4.1m tendons per
metre).
• If Total anchor (T) more than 100mm STOP MINING.
• Secondary support to be installed (8m mega bolts)
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4.1m Tendons tensioned with
hydraulic tensioner
 This type of tendon had been used at Tahmoor for many
years.
 Was successfully used at the face in conjunction with the
primary.
 Fully encapsulated using 1000mm plus 800mm chemical
resins.
 Quick to install.
 Able to pre-tension tendon to 10 – 27 tonnes.
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EQUIPMENT DAMAGE
 Operators rough handling of the hydraulic tensioner.
 Not keeping equipment clean & serviceable.
 Failure to safely store the tensioner hoses between
usage.
 Failure to periodically inspect equipment for damage
so repair/replacement can be enacted.
 All of the above will lead to production loss & has
the potential to cause injury to operators.
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OH&S ISSUES
 Hydraulic tensioner heavy & difficult to lift above the
operators head causing strain injuries to operator.
 Potential for tensioner to fall or be forced under
pressure from the tendon tail injuring operator.
 Tensioner hydraulic hoses with operating pressures
up to 10,000psi at operator head height with the
potential to cause fluid injection injuries.
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Tendon that can be tensioned with
the CM bolting rig
 In 2008 ResCo approached me about trailing a
fully encapsulated 4.1m tendon (Ultrabolt) that
can be installed & tensioned by the miner bolting
rig. The cable is tensioned with a dolly spanner by
the bolting rig motor.
 I was keen to trial this new innovation as we were
having ongoing issues with equipment failure &
OH & S issues using the 4.1m barrel & wedge
tendons that required a hydraulic tensioner.
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Hilti Ultra X Strand
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Tendon Installation Tools and
Practices
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Redesigned reamer
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Why use Tendons that can be
tensioned with the CM bolting rig
 There are four good reasons:
1.
OH & S friendly
2.
Quick to install
3.
Cost effective
4.
Increased productivity
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How Tahmoor Utilises 4.1m Tendons
 The primary use of 4.1m tendons at Tahmoor is to
install tendons at the face as soon a TARP is
triggered. This is a temporary measure to allow us to
complete the current drivage. When we no longer
wheel through the above area contractors then move
in & install 8m mega bolts to a pattern determined by
our geotech team.
 The secondary use is to install tendons at the face in
areas that have been identified by our geotech team
as having the potential to fail soon after we have
mined through the area. This slows the strata
movement until mega bolts can be installed when
S/C wheeling through the area is no longer required.
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