1Copyright © Xstrata plc Tensionable Tendons Phil Howes Tahmoor Colliery.

1Copyright © Xstrata plc

Tensionable Tendons

Phil Howes

Tahmoor Colliery


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.


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


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.


Strata TARP


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.


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.


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)

Strata TARP


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.

4.1m Tendons tensioned with hydraulic tensioner


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.


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.


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.


Hilti Ultra X Strand


Tendon Installation Tools and Practices


Redesigned reamer


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.

1Copyright © Xstrata plc Tensionable Tendons Phil Howes Tahmoor Colliery.

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