Remote Reading Tell-tale Systems in Underground Mines Chris Wagner

Strata Engineering (Australia) Pty Ltd

Outline

• What is the Remote Reading Tell-tale System? • The original “Tell-tale” • The Remote Reading Tell-tale (RRTT) • The RRTT System • Benefits of the system • Limitations of the system • Where has it been used?

• Where to from here

Strata Engineering (Australia) Pty Ltd

What is the Remote Reading Tell-tale (RRTT) System?

• Based on the original dual height mechanical Tell-tale developed in in the UK in the 1980’s • The RRTT system is an approved intrinsically safe (IS) electronic Tell-tale system which allows real time measurement of roof displacement to a surface computer • The RRTT system was developed by Golder RMT UK in the late 1990’s following the success of the mechanical Tell-tale

Strata Engineering (Australia) Pty Ltd

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The Original “Tell-tale” Purely visual indicator Uses a traffic light system, Green, Yellow and Red Has mm display for more accuracy Two indicators connected to stainless steel wires with spring anchors Indicates displacement above and within the roof bolted horizon

The Remote Reading Tell-tale (RRTT)

• Looks the same as the standard mechanical Tell-tale • Easily installed and in a similar manner to the original • Built within the instrument is a coil and ferrite core for each anchor • As the roof moves downwards, the coil moves over the ferrite and induces an electric charge which varies the inductance. • The variation in inductance is then converted to displacement • Accurate to 0.1 of a mm

Ferrite Core “B" Ferrite Core "A" Water seals Spring Anchor Coil "A" Coil "B" Stabiliser Drip tray Electronics "A" Indicator "B" Indicator

The Remote Reading Tell-tale System - Basic Set Up

Computer, barrier & comms.

Daisy chain of Tell-tales installed in roadways and cut-throughs Underground Interrogation Unit (powered by an IS 12v power supply)

From Surface to Seam

• The mine can chose to run a twisted pair wire (telephone line) from the surface to the proposed location of the Interrogation Units or alternatively, connect the system to an existing underground phone line.

• The 12v IS power supply is set –up as required for each Interrogation Unit • The surface barrier unit, communications and PC (including the supplied software) are then set-up prior to going underground • Once the above is completed and tested the underground installation commences

Basic Connection of the Interrogation Unit and Tell-tales 1. Interrogation Unit is installed on the rib and connected to the 12v IS power supply by the mine electrician 2. Twin-core wire from the surface is then connected to the Interrogation Unit 3. Finally, a simple twist and crimp connection is made to the first Tell-tale or connecting cable

Software Set-up

• Once underground connection has been completed, all existing Tell tales are identified and labelled in the software • Trigger levels are set – standard levels are typically as per those shown on the visual indicators: - Green (0-25mm) - Yellow (25-50mm) - Red (50-75mm) Note: these levels can be changed in the set-up of the software if different triggers are warranted • Following the initial set-up, each time a new Tell-tale is added to the daisy chain, the Interrogation Unit identifies it and flags it in the software ready to be labeled

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Benefits of the RRTT System

REAL-TIME Monitoring (100 Tell-tales can be read in under 20 minutes) • Less demand on man-power • The Remote Reading Tell-tale is contact-less, minimising the potential for mechanical failure • Requires very low power • Internal electrics are fully sealed and are therefore not sensitive to moisture • Ability to set high reading frequencies and specific trigger levels • Access to gassy and sealed off areas • Allows on-going monitoring of remote or high areas • Is easily integrated with existing database software • Cost

Limitations of the RRTT System

• A maximum of 100 Tell-tales and / or 2km of connecting wire can be monitored on any one underground Interrogation Unit however, if less than 100 Tell-tales are installed, the length of connecting cable can be increased beyond the 2km typical maximum.

• Currently the system can only monitor 4 x underground interrogation units per PC and therefore a maximum of 400 x Tell-tales per surface PC

Some Site Examples

1. West Mine - Germany

• Use: monitoring maingate conditions during the retreat of LW 183 • Set up in single entry maingate (limited personnel access) • Roadway was kept open during longwall retreat (using standing support) to allow roof monitoring inbye of the face • 67 Tell-tales installed along the daisy chain • Approx. 1.3km of roadway monitored • Depth of Cover of >1000m • Twisted pair line had to be run ~12km into the mine

Output from West Mine in Germany - During LW Retreat

West Mine Germany – Individual Tell-tale

15 10 5 0 25 -D ec 30 25 20 27 -D ec 29 -D ec

Station 52, 862m Face Distance 52 AA

31 -D ec 02 -Ja n

Date

04 -Ja n

52 BB

2 0 6 4 10 8 20 18 16 14 12 06 -Ja n 08 -Ja n 10 -Ja n

Acceleration in displacement in the bolted horizon when LW was <4m from Tell-tale

LW Retreat - West Mine Germany 19 December 2001. Face Position 882m.

A telltale (mm) Total Movement (mm) 30 20 10 0 80 70 60 50 40

Early roof displacement around 300m outbye of the longwall Surge in displacement following the passing of the longwall Distance from Face Line (m) Summary of all Tell-tales as LW approaches

2. Daw Mill – United Kingdom

• Use: monitoring sealed longwall • Why? For access to equipment behind stoppings at a later date.

• 13 Tell-tales installed along daisy chain in a single entry maingate • Standard Trigger Levels set: - Green 0-25mm - Yellow 25-50mm - Red 50-75mm

Stoppings Daw Mill Colliery – UK - Location Plan LW Stop Position 301’s 31’s 13 x Tell-tales

Output from Daw Mill Colliery, UK Trigger levels exceeded – Yellow Trigger (25-50mm) on the A Anchor = bolted horizon

50 45 40 15 10 5 0 35 30 25 20 Daw Mill Colliery, UK RRTT Daw Mill Colliery, 301's MG 365m TT13 A Reading 340m TT11 A Reading 360m TT12 A Reading 320m TT10 A Reading 365m TT13 Total 340m TT11 Total 360m TT12 Total 320m TT10 Total Date Location of trigger level events

3. Marathon Petroleum Gas Cavern – West Virginia US

• Use: monitoring roof movement in gas cavern • 64 Tell-tales running a 10 minute reading interval • Due to shape of cavern, complex connection topology required • Several 3 and 4-way connections had to be made • Interrogation unit set up on surface rather than underground • Approx. 1.5km of connecting cable in system

Marathon Petroleum Gas Storage Cavern - West Virginia USA Movement Recorded on EN +100 (Channel 31) Cavern and Connection Layout 100ft

20 Marathon Petroleum Gas Storage Cavern - Movement on EN +100 in Days Bolted height (A) Total Movement to 5m (A+B) 18 16 14 12 10 8 6 4 2 0 10/08/2009 11/08/2009 12/08/2009 Date Indicates majority of movement occurring in the bolted horizon 13/08/2009 14/08/2009

2 0 8 6 4 20 18 16 14 12 10

Marathon Petroleum Gas Storage Cavern - Detailed Section of Movement (hours) Bolted Height (A) Total Movement to 5m (A+B) Ability to pin-point when the movement started (hours) Time

4. Experimental Mine - Indonesia

• Use: monitoring roof movement during roadway development of run outs and retreat pocketing • 20 x roof extensometers (4 x anchor as opposed to dual height Tell-tale) • 21 x rib extensometers • 8 x stress cells • Use was made of the Portable Readout Unit as opposed to the underground interrogation unit and surface PC

Experimental Mine - Indonesia

• All monitoring sites were wired back to an individual location underground where they were able to be read utilising the hand-held Portable Readout Unit

Hand-held Portable Readout Unit 4 x Anchor Remote Reading Extensometer

Indonesia Experimental Mine - Layout Retreat development of run outs and pockets

Roof Exto Telltales shown.....

Rib Exto Telltales shown.......

Stress cells shown.................

Roof Extensometer No. 3

Results from Roof Exto 3 – During Development of Run-outs and Pocketing Increase in roof displacement measured as pocketing retreats closer to Exto 3 Limited movement measured above the bolted horizon

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5. Angus Place Colliery – NSW Australia

Use: monitoring roof displacement during the driveage of first pass and subsequent widening in LW 970’s installation road • 30 x dual height Tell-tales installed in both the installation and bleeder roadways • Installation road located approx. 9km into the mine • Underground interrogation unit was installed in the crib room approx. 200m outbye of the installation road • During initial site visit, full surface to seam set-up completed and 12 x Tell-tales were installed • Remaining Tell-tales were installed either off the miner as development advanced or outbye by the mine site Geologist • RRTT system has been integrated into the mine’s existing access exto database

970 Panel Angus Place Colliery – Layout Majority of red Tell-tales installed at the face off the miner Green Tell-tales installed outbye of face during initial site visit and set-up

LW 970 Installation Road – 38m from MG Intersection Overall very limited amount of displacement (ie, <7mm) Initial surge in displacement as miner developed towards TG end of roadway Displacement is confined to the bolted horizon (ie, A anchor)

LW 970 Installation Road – 90m from MG Intersection – Mid-face Int Overall very limited amount of displacement (ie, <8mm) Initial surge in displacement as miner developed towards TG end of roadway Note the limited surge in displacement recorded during the formation of the intersection

LW 970 Installation Road – 200m from MG Intersection Surge as a result of roadway widening Minor ongoing movement following roadway widening measured in the bolted horizon only – overall limited (ie, <10mm) displacement

Where To Next?

Mine Plan and Trigger Level Integration (i) Colour immediately shows Engineer trigger level exceeded and (ii) displacement amount also plotted

- SMS and email alerts for Tell-tales which have exceeded the prescribed trigger level - Software upgrades including; (i) Network server installation with the ability for multiple users to review the data simultaneously and remotely (ii) Improved system diagnostics