russell thomas gas drainage coordinator – appin colliery november 2014

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Update on Outburst Management at AppinGas & Coal Outburst Committee - Wollongong

Russell ThomasGas Drainage Coordinator – Appin CollieryNovember 2014

Russell Thomas, Gas Drainage Coordinator - Appin Colliery, November 2014

Update on Outburst Management

Slide 2

1. Outbursts during Dyke Extraction

2. Alterations to Appin Outburst Management Plan


Outbursts During Dyke Extraction

Slide 3

• Dykes are extracted by shotfiring ahead of longwall extraction

• Multiple small outbursts have resulted:• Usually small amounts of material

(~10t)• Usually small amounts of gas

(<100m3)• >90% methane gas composition• Above 10m3t-1 total gas content.

• No personnel exposed – all outbursts triggered remotely

• Locations of outburst identified through tight regime of gas sampling

Typical Outburst Cone

~750-1000mm


Management of Outburst Risk in Dyke

Slide 4

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ZONE A

ZONE B

ZONE C

ZONE D

• Multiple categories of risk management• “Zone A” – no restrictions• “Zone B” – corresponds to Gas Pressure of less than

500kPa, and accounts for small pockets of gas against the dyke – relieving shots required before slotting

• “Zone C” – above Appin’s threshold – no slotting• “Zone D” – 3m3t-1 above Appin’s threhsold – no

rotary/percussive in coal or cinder

• Geological inspections at maximum intervals of a week to identify changes, particularly additional structures adjacent to dyke

• Close spacing of gas content cores – approx 10m spacing along length of dyke


Analysis of Outbursts during Dyke Extraction

Slide 5

• Multiple outbursts at approx 10-16m3t-1 during shotfiring

• No outbursts below Appin’s Outburst threshold

• All reasonably small outbursts• Based on this experience, it appears the

current Outburst Threshold Appin use is appropriate

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CM - Remote Mining

Dyke - Shotfiring

Outburst Threshold


Alteration to Outburst Management Plan

Slide 6

• Appin & West Cliff amalgamation is getting close – first roadway from West Cliff to Appin holed during November 2014

• Appin & West Cliff have different ways of managing the outburst risk – each evolving of time based on the circumstances of the mine

• Process undertaken to review the processes at each mine and use “best practice” in each area. Artwork Courtesy Iain Brown


Comparison of Outburst Management at Appin and West Cliff

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• Comparing Appin & West Cliff Outburst Management Practices (Core location, Hole Patterns, Thresholds) revealed 15x gas regimes.

• Appin & West Cliff practice approximately the same outburst management techniques in 3 of these (including undrained areas which are not normally mined)

• Appin & West Cliff practice different outburst management techniques in 12 gas regimes.

• Outburst Management techniques used in each regime at each pit were compared and evaluated against the risk at Appin, and best practice determined.

• Multiple stages of consultation undertaken, including workforce reps, and Appin & West Cliff gas drainage personnel. Steps included:

• Initial review by Appin Gas Drainage dept• Full review by Outburst Risk Review Team• Review by Appin HSEC committee• Shift briefings to workforce• Risk assessment on proposed changes• More Shift briefings to workforce• Final review by General Manager, Manager of

Mining Engineering and Site Check Inspector


The case to raise thresholds?

Slide 8

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MG901 9-10ct TG901 12-13ctTG901 13-14ct MG707 5-6ctTG707 6-7ct TG707 0-1ctMG705 24-25ct TG705 0-1ctTG706 0-1ct MG704 22-23ctMG702 9-10ct MG703 18-19ctWest Cliff Level 2 Threshold Current Appin ThresholdOld Appin Threshold

• Both Appin and West Cliff use a threshold of approx 9.4m3t-1 (100% CH4) / 6.0m3t-1 (100% CO2)

• Above this threshold – West Cliff has a “Level 2” threshold of 10.0m3t-1 (100% CH4) / 7.8m3t-1 (100% CO2)

• Gas Contents that Appin has remote mined on indicate that little mining falls within this range

• Where mining falls within this range, it is generally just the edge of remote mining – with the bulk of the remote mining well above the West Cliff Level 2

• Drainage at Appin has tended to be either a spectacular failure or a complete success.

• Areas where drainage has failed are generally due to inability to drill and drain around structures

• Mining between Appin threshold and West Cliff Level 2 threshold requires heavy use of flanking holes through structure – where drainage has failed due to structure this would not be practicable

• Dyke extraction experience indicates the current threshold is appropriate

• As such, it was determined there was no case to attempt to raise Appin’s threshold


Final Outcome

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FLANK HOLES NOT REQUIRED, EXCEPT THROUGH OUTBURST PRONE STRUCTURESCORES AT 150m MAX SPACING IN DIRECTION OF PANEL

REMOTE MINING ONLY

FLANK HOLES MANDATORYCORES AT 150m MAX SPACING IN DIRECTION OF PANEL

FLANK HOLES MANDATORYCORES AT 100m MAX SPACING IN

DIRECTION OF PANEL

ORRT TO DETERMINE FLANK REQUIREMENTSCORES AT 100m MAX SPACING IN DIRECTION OF

PANEL

russell thomas gas drainage coordinator – appin colliery november 2014

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