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

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Presentation on theme: "1Copyright © Xstrata plc Tensionable Tendons Phil Howes Tahmoor Colliery."— Presentation transcript:

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

2 2Copyright © Xstrata plc 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.

3 3Copyright © Xstrata plc 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

4 4Copyright © Xstrata plc 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.

5 5Copyright © Xstrata plc Strata TARP

6 6Copyright © Xstrata plc 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.

7 7Copyright © Xstrata plc 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.

8 8Copyright © Xstrata plc 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

9 9Copyright © Xstrata plc  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

10 10Copyright © Xstrata plc 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.

11 11Copyright © Xstrata plc 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.

12 12Copyright © Xstrata plc 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.

13 13Copyright © Xstrata plc Hilti Ultra X Strand

14 14Copyright © Xstrata plc Tendon Installation Tools and Practices

15 15Copyright © Xstrata plc Redesigned reamer

16 16Copyright © Xstrata plc 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  a

17 17Copyright © Xstrata plc 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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