Pillar extraction

It's the law
Queensland
Coal Mining Safety and Health Regulation, 2001
Definition, Schedule 9, Dictionary

second workings, for an underground mine, means the second phase of mining after roadways for developing the part of the mine in which the second workings are carried out have been driven.


317 Risk assessment - to decide a safe method of extraction for second workings
318 Standard operating procedure for carrying out second workings
319 Changing standard operating procedure for carrying out second workings

320 Notices to inspector - Before second workings are started at an underground mine ...
321 Stability of mine workings 
322 Preventing dangerous subsidence
323 Strata support for workings
324 Monitoring strata support
329 Emergency sealing

New South Wales

Work Health and Safety (Mines) Regulation, 2014

33 Notification of high risk activities

SCHEDULE 3 – High risk activities 
16 Secondary extraction or pillar extraction, splitting or reduction
10 (1) Sealing (other than emergency sealing) is identified as a high risk activity, but only if notice has not been given as part of a notice for secondary extraction.

These provisions may apply.

12 Driving underground roadway that is wider than 5.5 metres
13 Widening underground roadway to more than 5.5 metres
15 Formation of non-conforming pillars

These provisions may apply. It is proposed that they will each be dealt with in a separate page. The provisions have been included on an interim basis.

17 Shallow depth of cover mining 
7 Working in inrush control zone
18 Mining in outburst control zones
29 Barrier mining

24 Preparation of principal mining hazard management plan

SCHEDULE 1 – Principal mining hazard management plans-additional matters to be considered

1 Ground or strata failure
2 Inundation or inrush of any substance
7 Gas outbursts
8 Spontaneous combustion
9 Subsidence

128 Duty to notify regulator of certain incidents

(b) the detection of a concentration of methane in the general body of the air in an underground coal mine (other than in a sealed area or goaf) that is 2.5% by volume or greater,
(c) an unplanned fall of ground, roof or sides that impedes passage, extends beyond the bolted zone or disrupts production or ventilation,
(d) a failure of ground support where persons could potentially have been present,
(e) the burial of machinery such that it cannot be recovered under its own tractive effort,
(f) progressive pillar failure or creep,
(g) a sudden pillar collapse,
(m) any indication from monitoring data of the development of subsidence ...

New Zealand

Health and Safety in Employment (Mining Operations and Quarryingions) Regulations 2013


3 Interpretation



secondary workings—

(a) means the extraction of material from a place following the initial development phase; and
(b) includes pillar extraction, splitting pillars, caving, stoping, longwalling, and bottom coaling


229 Notification of high risk activities
Schedule 9 High Risk activities

Managing the risk


Unwanted events

Spontaneous combustion
Accumulation of gas
Strata control failure
Inrush
Outburst
Pressure burst

Precautions

Design

  • details of how risks from the activity will be managed (1) (4) (7)
  • details of the authoritative sources used in determining that the proposed method of work can be done safely (1)
  • information about the land above or in the vicinity of the proposed activity including land use and details of who owns or occupies any land that may be affected by subsidence (1)
  • details of the procedures for the recovery of buried and immobile mining plant in or around a goaf (1)
  • engineering plans or drawings of the activity endorsed by the individual nominated to exercise the statutory function of mining engineering manager at the mine (1) (2) (4) (5) (6) (8)
  • details of how the risks to the health and safety of workers and other persons from subsidence or sinkholes caused by the activity will be managed (1) (4)
  • a geotechnical report on the activity (2) (4)
  • details of relevant strata control in respect of the activity (2)
  • proposed sealing procedure and type of seals (3)
  • proposed location of the seals and the areas of the mine to be sealed (3)
  • predictions of the rates at which methane and other gases will accumulate in the sealed areas during and after the sealing. (3)
  • an analysis of how the risk of gas outbursts will be managed in undertaking the activity (6)
  • survey plans certified by an individual nominated to exercise the statutory function of mining surveyor at the mine (4) (6) (7)
  • details of the explosion suppression measures to be taken (8)

Development


Implementation

  • gas monitoring procedures to be carried out (1)
  • details of ventilation arrangements in respect of the activity (8)


Monitoring

  • any evidence of ignition sources being present in the areas to be sealed (1)



Contingencies

Treatment

  • the parts of the mine’s emergency plan relevant to outbursts (6)

Escape

  • details of the escape strategy to be implemented (8)

Rescue


Recovery



Incident reports, safety bulletins and safety alerts

NSW SA 11-08 Fall of rib results in fatality

During pillar extraction using a remotely controlled continuous miner and breaker line supports, a 4 tonne slab of unsupported rib fell from the solid side without apparent warning, fatally injuring the operator. (2008)

NSW SA 01-01 Coal mine fatality from fall of roof

A continuous miner did not respond to the remote controller while beyond the last support. Two miners working their way in were severely injured by a fall of roof. One was fatally injured. (2001)

NSW SA 98-07 Windblast from newly formed goaf at shallow cover

4 rolls of pillars had been extracted without a goaf fall. The windblast whoch resulted from the initial goaf fall resulted in serious and life-threatening injuries to several miners. (1997)

NSW SA 98-04 Two pillar extraction incidents

Serious injuries to two miners, and 2 buried machines and 3 breaker line supports. (1998)

NSW SA 13-01 Faulty strata monitoring devices

Reported failure of strata monitoring devices and associated inability to identify failure. (2013)
MSHA report of investigation - Fatal rib rock burst (2013)

A continuous mining machine operator was killed, and a mobile bridge carrier operator and a mobile roof support were injured. The crew was retreat mining when a coal/rock burst occurred.
NSW Investigation report - fatality due to rib failure in extraction panel. (2011)
A miner was fatally injured when hit by unsupported rib in an extraction panel.

Resources

Manual on pillar extraction in NSW Underground Coal Mines - Part 1: Text

Manual on pillar extraction in NSW Underground Coal Mines - Part 2 - Illustrations

MSHA Coal miners handbook for roof and rib control

This is a United States government publication for training underground coal miners. (Published 1998)

MSHA Roof control plan and approval procedures

This is a United States government publication setting out their regulator's expectations when a submission is made in advance of pillar extraction. (Published 2013)

References

  1. NSW WORK HEALTH AND SAFETY (MINES) REGULATION 2014 - SCHEDULE 3 – High risk activities, s 16 Secondary extraction or pillar extraction, splitting or reduction
  2. NSW WORK HEALTH AND SAFETY (MINES) REGULATION 2014 - SCHEDULE 3 – High risk activities, s 12 Driving underground roadway that is wider than 5.5 metres AND s 13 Widening underground roadway to more than 5.5 metres AND s 15 Formation of non-conforming pillars
  3. NSW WORK HEALTH AND SAFETY (MINES) REGULATION 2014 - SCHEDULE 3 – High risk activities, s 10 Sealing (other than emergency sealing).
  4. NSW WORK HEALTH AND SAFETY (MINES) REGULATION 2014 - SCHEDULE 3 – High risk activities, s 17 Shallow depth of cover mining and SCHEDULE 1 Principal mining hazard management plans, s9 Subsidence
  5. NSW WORK HEALTH AND SAFETY (MINES) REGULATION 2014 - SCHEDULE 3 – High risk activities, s 7 Working in inrush control zone and SCHEDULE 1 Principal mining hazard management plans, s 2 Inundation and inrush
  6. NSW WORK HEALTH AND SAFETY (MINES) REGULATION 2014 - SCHEDULE 3 – High risk activities, s 18 Mining in outburst control zones and SCHEDULE 1 Principal mining hazard management plans, s7 Gas outbursts
  7. NSW WORK HEALTH AND SAFETY (MINES) REGULATION 2014 - SCHEDULE 3 – High risk activities, s 29 Barrier mining
  8. NSW WORK HEALTH AND SAFETY (MINES) REGULATION 2014 - SCHEDULE 3 – High risk activities, s 8 Roadway or drift without intersection for 250 metres
  9. NSW WORK HEALTH AND SAFETY (MINES) REGULATION 2014 - SCHEDULE 1 - Principal mining hazard management plans, s1 Ground or Strata failure
  10. NSW WORK HEALTH AND SAFETY (MINES) REGULATION 2014 - SCHEDULE 1 - Principal mining hazard management plans, s8 Spontaneous combustion
  11. Qld Coal Mining Safety and Health Regulation, 2001