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                              Introduction 

Depillaring is the final stage of the Bord and Pillar mining method where the coal pillars left for support are systematically extracted.
This operation is one of the most hazardous in underground mining due to potential roof falls, air blasts, and gas emissions.
The Directorate General of Mines Safety (DGMS) provides strict regulatory control through CMR 2017, Reg. 111–116 to ensure safe extraction.

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⚒️ Objective of Depillaring

• To recover maximum coal safely from developed areas.
• To maintain roof stability during extraction.
• To minimize surface subsidence and environmental impact.
• To comply with DGMS safety and statutory rules.

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🏗️ Common Depillaring Methods

1. Split and Fender Method:
• Traditional and most used method.
• Pillars are split by galleries (splits) and extracted through fenders.
• Roof supports maintained by stooks or cogs.
2. Arcwall Method:
• Curved extraction front for better control.
• Reduces stress concentration and air blast risk.
3. Strip Method:
• Extraction in narrow strips along dip direction.
• Suitable for thick seams and mechanized depillaring.
4. Blasting Gallery (BG) Method:
• Used in thick seams (>4.5 m).
• Large galleries are created and roof caved by blasting.
5. Longwall Caving (Partial Pillar Extraction):
• Combines depillaring with mechanized longwall faces.

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⚙️ CMR 2017 – Key Provisions (Reg. 111–116)

• Reg. 111: DGMS permission mandatory before depillaring.
• Reg. 112: Support plan must be approved and displayed.
• Reg. 113: No goaf should be left unsealed.
• Reg. 114: Proper ventilation and fire control required.
• Reg. 115: Systematic monitoring for roof convergence.
• Reg. 116: Record of extraction, stowing, and subsidence maintained by manager.

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🔒 Safety Measures during Depillaring

• Detailed survey and marking of old workings.
• Installation of tell-tales to monitor roof movement.
• Ventilation control to prevent gas build-up.
• Use of flameproof equipment in gassy seams.
• Stowing or controlled caving to fill goaf.
• Regular supervision by competent officials.
• Training for rescue and firefighting preparedness.

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🧭 DGMS Circulars Related to Depillaring

• Tech Circular 02/2010: Roof & slope stability precautions.
• Tech Circular 03/2013: Use of monitoring instruments.
• General Circular 05/2016: Barrier & ventilation management.
• Exam Circular 01/2021: Updated syllabus guidance for depillaring.

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⚡ Quick Revision Notes

• Reg. 111–116 → Depillaring operations.
• Split & Fender → most common method.
• CO₂ and CH₄ monitoring → mandatory.
• DGMS permission required.
• Goaf → must be sealed properly.
• Flameproof equipment → compulsory in gassy seams.

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🎯 25 DGMS Exam MCQs – Depillaring Methods & Safety

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Q1. Depillaring is the process of:
A. Developing new galleries
B. Extracting coal from pillars
C. Driving shafts
D. Stowing waste
E. Draining water
Answer: B.
Solution: Pillars are extracted to recover remaining coal.

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Q2. Which regulation deals with depillaring permission?
A. Reg. 110
B. Reg. 111
C. Reg. 112
D. Reg. 107
E. Reg. 115
Answer: B.
Solution: Reg. 111 of CMR 2017 covers DGMS permission for depillaring.

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Q3. The Split and Fender method is used for:
A. Shaft sinking
B. Coal pillar extraction
C. Stone drivage
D. Roof bolting
E. Ventilation
Answer: B.
Solution: It’s the standard depillaring method.

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Q4. Stowing during depillaring helps to:
A. Increase production
B. Fill goaf and control subsidence
C. Improve air quality
D. Seal old galleries
E. None
Answer: B.
Solution: Stowing fills voids to support strata.

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Q5. Flameproof equipment is compulsory in:
A. Surface mines
B. Opencast benches
C. Gassy seams
D. Non-coal mines
E. Workshops
Answer: C.
Solution: As per DGMS, gassy seams need flameproof gear.

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Q6. The major hazard during depillaring is:
A. Roof fall
B. Dust
C. Water inrush
D. Poor visibility
E. Noise
Answer: A.
Solution: Roof fall is common due to loss of support.

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Q7. Arcwall method is designed to:
A. Increase speed
B. Reduce air blast
C. Reduce gas
D. Improve drainage
E. Enhance lighting
Answer: B.
Solution: Curved extraction front reduces air-blast impact.

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Q8. Depillaring is also called:
A. Retreat mining
B. Stowing operation
C. Panel development
D. Stoping
E. Sinking
Answer: A.
Solution: Extraction during retreat = retreat mining.

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Q9. Which gas is closely monitored during depillaring?
A. O₂
B. CO₂
C. CO & CH₄
D. N₂
E. Argon
Answer: C.
Solution: CO (fire risk) & CH₄ (explosive) critical.

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Q10. A “goaf” refers to:
A. Unmined area
B. Extracted area left void
C. Coal seam top
D. Barrier pillar
E. Drainage tunnel
Answer: B.
Solution: Goaf = area where coal is removed.

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Q11. DGMS Tech Circular 02/2010 is related to:
A. Transport safety
B. Roof and slope stability
C. Illumination
D. Haulage
E. Electrical hazards
Answer: B.
Solution: It prescribes roof and slope safety rules.

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Q12. Minimum width of barrier pillar in depillaring district:
A. 5 m
B. 8 m
C. 10 m
D. 12 m
E. As per depth
Answer: E.
Solution: Width depends on cover depth and seam strength.

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Q13. Roof movement is measured by:
A. Barometer
B. Tell-tale
C. Psychrometer
D. Flowmeter
E. Dust sampler
Answer: B.
Solution: Tell-tale measures roof convergence.

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Q14. CO₂ accumulation during depillaring indicates:
A. Blasting
B. Fire or poor ventilation
C. Roof fall
D. Leakage
E. None
Answer: B.
Solution: Fire or poor air circulation.

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Q15. The first step in depillaring is:
A. Sealing old working
B. Splitting the pillars
C. Creating haulage
D. Draining water
E. Ventilation survey
Answer: B.
Solution: Splitting creates fenders for safe extraction.

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Q16. The stook pillar is left to:
A. Improve ventilation
B. Support roof temporarily
C. Store tools
D. Mark airway
E. Measure gas
Answer: B.
Solution: Temporary support in goaf area.

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Q17. In Blasting Gallery (BG) method, the gallery height is:
A. < 3 m
B. 4.5–8.0 m
C. > 10 m
D. 2 m
E. None
Answer: B.
Solution: BG used in thick seams up to 8 m.

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Q18. Depillaring starts from:
A. Center
B. Boundary towards dip side
C. Surface
D. Barrier pillar
E. Roof
Answer: B.
Solution: Extraction proceeds from dip to rise.

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Q19. “Arcwall” method provides:
A. Flat face
B. Curved face to distribute stress
C. Longwall face
D. Horizontal extraction
E. None
Answer: B.
Solution: Curved front reduces stress concentration.

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Q20. Fire control in depillaring goaf uses:
A. Nitrogen flushing
B. Methane injection
C. Air sealing
D. Salt water
E. Steam
Answer: A.
Solution: N₂ injection inertises the atmosphere.

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Q21. Depillaring permission is issued by:
A. Manager
B. Agent
C. DGMS
D. Overman
E. Mining engineer
Answer: C.
Solution: Only DGMS grants written permission.

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Q22. Regular inspection of depillaring district is done by:
A. Fitter
B. Sardar
C. Manager & Overman
D. Blaster
E. Clerk
Answer: C.
Solution: Manager ensures safe operations.

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Q23. Main cause of air blast in depillaring:
A. Sudden goaf collapse
B. Blasting fumes
C. Over ventilation
D. Poor haulage
E. None
Answer: A.
Solution: Sudden caving creates pressure wave.

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Q24. DGMS recommends use of:
A. Manual records only
B. Roof monitoring instruments
C. Artificial ventilation
D. Overburden dumps
E. None
Answer: B.
Solution: Instruments help early hazard detection.

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Q25. The Reg. covering record of extraction & stowing is:
A. 111
B. 114
C. 116
D. 118
E. None
Answer: C.
Solution: Reg. 116 mandates records and reports.

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                     🧩 Conclusion 

Depillaring is a critical yet risky phase in coal extraction.
DGMS regulations stress proper planning, systematic extraction, and safety supervision.
By mastering Reg. 111–116, understanding methods like Split & Fender or Arcwall, and practicing MCQs, candidates can confidently handle both exam and field challenges.

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