Introduction

Highwall Mining (HWM) is an advanced semi-mechanized method where coal is extracted from exposed seams after opencast mining becomes uneconomical.
While it offers higher recovery with minimal manpower, the safety management and operational control are critical due to risks of slope failure, equipment malfunction, and gas build-up. This blog explains the operational sequence, safety protocols, DGMS regulations, and key exam points for mining managers.

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⚙️ 1. Sequence of Highwall Mining Operations

1. Site Preparation & Bench Design
• Final highwall must be stable with adequate drainage and berms.
• Geological mapping and SSR (Slope Stability Report) mandatory.
2. Installation of Launch Vehicle
• Positioned parallel to highwall face; pushbeam assembly and cutter module connected.
3. Cutting & Extraction Process
• Cutter module cuts coal through sequential pushbeams (~6 m each).
• Coal conveyed through beams to launch vehicle and onto surface conveyor.
4. Monitoring & Real-Time Control
• Remote CCTV, laser guidance, and gyroscopic navigation ensure accuracy.
• Gas sensors, vibration detectors, and telemetric control used.
5. Withdrawal & Maintenance
• After cutting a web, the module is withdrawn, serviced, and aligned for next web.
• Area is monitored for roof collapse or subsidence.

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🧱 2. DGMS Safety Management Requirements

Area	DGMS Regulation / Circular	Key Requirement
Equipment Approval	CMR 2017 Reg. 99	DGMS approval of HWM system before use
Electricals	CMR 2017 Reg. 108	Flameproof & intrinsically safe systems
Slope Safety	CMR 2017 Reg. 106	Stability analysis & SSR every 6 months
Gas Monitoring	CMR 2017 Reg. 153	Methane concentration ≤ 1.25% in return air
Operation Control	DGMS Circular 01 of 2015	Defines design, barrier pillar width, slope monitoring
Training	Mines Vocational Training Rules	Specialized training for HWM operators

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🦺 3. Safety Practices in Highwall Mining

• Slope Monitoring:
  Instruments like radar, extensometers, and prisms for real-time tracking.
• Drainage Control:
  Prevents infiltration and toe erosion — vital for slope stability.
• Barrier & Web Pillars:
  Must be scientifically designed as per HWM geometry and strength parameters.
• Fire & Gas Precaution:
  No smoking zones; continuous monitoring of methane and CO.
• Operation Suspension:
  HWM operation must stop during rainfall, lightning, or seismic activity.
• Communication & Control:
  Dual wireless control, CCTV backup, and alert system required.

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📘 4. DGMS Exam Relevance

Typical DGMS exam questions focus on:

• HWM operating sequence
• Safety measures under CMR 2017
• Design of web/barrier pillars
• Gas and ventilation standards
• Slope failure management

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⚡ 5. Quick One-Liners

• Launch vehicle is foundation of HWM operation.
• Cutter module penetration: ~300 m.
• SSR required every 6 months.
• DGMS Tech Circular 01/2015 covers HWM safety.
• Flameproof electricals under Reg. 108.
• Methane limit: 1.25% (Reg. 153).
• Operations must stop during rainfall or lightning.

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🎯 25 MCQs – Highwall Mining Operations & Safety

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Q1. The main regulatory approval for HWM operation is under:
A. Reg. 99 CMR 2017
B. Reg. 123 MMR 1961
C. Reg. 230 CMR 2017
D. Mines Act Sec. 12
E. DGMS Manual 1985
Answer: A.
Solution: Reg. 99 mandates DGMS approval for mechanized mining systems.

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Q2. The stability of the highwall is governed by which regulation?
A. Reg. 104
B. Reg. 106
C. Reg. 153
D. Reg. 55
E. Reg. 195
Answer: B.
Solution: CMR 2017 Reg. 106 covers slope stability.

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Q3. The methane limit in return air during HWM operation should not exceed:
A. 0.5%
B. 1.0%
C. 1.25%
D. 1.5%
E. 2.0%
Answer: C.
Solution: DGMS sets methane limit at 1.25% under Reg. 153.

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Q4. DGMS Tech Circular governing Highwall Mining safety is:
A. 03/2018
B. 01/2015
C. 05/2020
D. 06/2012
E. 02/2010
Answer: B.
Solution: DGMS Tech Circular 01 of 2015 defines HWM operational guidelines.

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Q5. HWM operations must be stopped during:
A. Shift change
B. Night shift
C. Rainfall or lightning
D. Coal quality inspection
E. Ventilation stoppage
Answer: C.
Solution: Safety protocol mandates stopping during rainfall or lightning.

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Q6. SSR (Slope Stability Report) is prepared:
A. Weekly
B. Monthly
C. Every 3 months
D. Every 6 months
E. Annually
Answer: D.
Solution: SSR must be reviewed every six months.

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Q7. Barrier pillar width depends on:
A. Seam thickness
B. Machine geometry
C. Rock strength
D. Slope angle
E. All of the above
Answer: E.
Solution: Multiple parameters influence pillar design.

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Q8. The main purpose of drainage at highwall toe is:
A. Aesthetic improvement
B. Water sampling
C. Preventing slope failure
D. Washing coal
E. None
Answer: C.
Solution: Drainage prevents water-induced slope weakening.

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Q9. The maximum cutter module depth in HWM is:
A. 100 m
B. 150 m
C. 300 m
D. 500 m
E. 1000 m
Answer: C.
Solution: Depth limit is around 300 m.

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Q10. HWM is best suited for:
A. Very thick seams
B. Deep underground seams
C. Thin near-surface seams
D. Steep seams
E. Highly folded seams
Answer: C.
Solution: Economically feasible for thin seams near surface. 

Q11. The main factor contributing to highwall fires in coal mines is:
A. Hydraulic oil leakage
B. Spontaneous heating of exposed coal faces
C. Blasting vibrations
D. Fault movement
E. Overburden erosion
Answer: B.
Solution: Exposed coal reacts with oxygen and moisture, causing spontaneous heating and fire risk.

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Q12. The slope stability radar (SSR) primarily measures:
A. Gas concentration
B. Vibration frequency
C. Slope deformation and displacement rate
D. Sound intensity
E. Moisture content
Answer: C.
Solution: SSR continuously tracks slope movement to detect failures before collapse.

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Q13. The DGMS circular 01/2015 focuses on:
A. Mine drainage systems
B. Dust suppression
C. Slope stability monitoring and reporting
D. Explosive storage
E. Electrical earthing
Answer: C.
Solution: The circular provides slope safety and monitoring guidelines for opencast & highwall mines.

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Q14. Ideal pillar spacing in Highwall Mining is decided based on:
A. Seam thickness and rock strength
B. Coal quality
C. Lighting condition
D. Water presence
E. Operator experience
Answer: A.
Solution: Geotechnical parameters such as seam height and uniaxial compressive strength determine spacing.

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Q15. Drainage at the toe of highwall is necessary to:
A. Increase coal production
B. Prevent water accumulation and slope failure
C. Cool machinery
D. Store sediment
E. Reduce noise levels
Answer: B.
Solution: Proper drainage ensures dry and stable slope toes, improving overall wall stability.

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Q16. SSR data in slope monitoring is generally recorded at intervals of:
A. Every 5 minutes
B. Every 15 minutes
C. Every 30 minutes or real-time continuous
D. Once a day
E. Once a week
Answer: C.
Solution: SSR can log data continuously or every 30 minutes depending on system configuration.

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Q17. Which of the following is not a slope failure indicator?
A. Cracks near the crest
B. Tilting of poles
C. Reduced radar displacement rate
D. Bulging at toe
E. Sudden change in SSR displacement vector
Answer: C.
Solution: Reduced displacement means stability; other options indicate impending failure.

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Q18. The critical slope height for stability depends primarily on:
A. Depth of the mine
B. Rock density and cohesion
C. Surface temperature
D. Wind speed
E. Coal seam thickness
Answer: B.
Solution: Rock cohesion and density directly influence stable slope height limits.

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Q19. In case of slope movement detected beyond threshold, immediate action should be:
A. Increase monitoring interval
B. Continue operation carefully
C. Stop operations and evacuate area
D. Inform only safety officer
E. Spray water
Answer: C.
Solution: DGMS mandates immediate shutdown and area evacuation on unsafe movement.

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Q20. The factor of safety (FoS) for highwall slopes must be:
A. <1.0
B. 1.0
C. 1.1–1.2
D. ≥1.3
E. 2.0
Answer: D.
Solution: Minimum FoS of 1.3 ensures stable slope design under static conditions.

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Q21. Which of the following instruments complements SSR data for accuracy?
A. Extensometers & prisms
B. Barometers
C. Gas detectors
D. Anemometers
E. Altimeters
Answer: A.
Solution: Extensometers and prisms validate radar data through displacement readings.

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Q22. Fire risk in highwall benches can be reduced by:
A. Coal wetting & sealing with inert material
B. Increasing oxygen flow
C. Opening new faces rapidly
D. Removing vegetation
E. Using timber supports
Answer: A.
Solution: Fire risk is minimized by isolating air contact and sealing coal exposures.

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Q23. Which DGMS regulation covers stability of highwalls and benches?
A. Reg. 106 (CMR 2017)
B. Reg. 125
C. Reg. 177
D. Reg. 153
E. Reg. 132
Answer: A.
Solution: Reg. 106 defines slope design, monitoring, and bench stability norms.

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Q24. The slope radar must be recalibrated:
A. After 1 year
B. After every rain or blasting event
C. Only after a failure
D. Every 6 months
E. Never required
Answer: B.
Solution: Rain and blasting affect readings; recalibration ensures accuracy.

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Q25. Final slope stability report (SSR) for DGMS approval must include:
A. Production graphs only
B. SSR data, FoS, drainage, and monitoring plan
C. Lighting arrangement
D. Operator log sheets
E. Conveyor maintenance records
Answer: B.
Solution: DGMS requires detailed SSR reports with stability analysis and design validation.

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                     ✅ Conclusion 

Slope stability is not just a design parameter — it’s the first line of defense in Highwall Mining safety.
DGMS Circular 01/2015 emphasizes continuous monitoring, SSR-based slope management, and timely data interpretation to prevent highwall disasters.
Understanding these systems and their statutory requirements under Reg. 106, CMR 2017 is crucial for all DGMS exam candidates.

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