Introduction

Highwall Mining (HWM) is a remote-controlled, surface-based mining system used to recover coal from final highwalls in opencast mines. It bridges the gap between opencast and underground mining, enabling economic recovery of coal seams that are otherwise uneconomical to mine by surface methods.
This blog covers key components of HWM systems, DGMS requirements for machinery design, and 25 exam-based MCQs.

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⚙️ Main Components of a Highwall Mining System

1. Launch Vehicle (Base Unit):
• Anchored on the surface bench near the highwall.
• Pushes and retrieves the pushbeam train.
• Houses hydraulic systems, winches, and operator control cabin.
2. Cutter Module (Cutter Head):
• Mechanically excavates coal using rotating drums or augers.
• Equipped with electric motors and hydraulic actuators for efficient cutting.
• Mounted with bit segments to suit different seam hardness.
3. Pushbeam System:
• Modular steel structures (typically 6 m each).
• Form a continuous conveying path to carry coal from cutter to surface.
• Equipped with chain conveyor or auger screw inside.
4. Tramming & Retrieval System:
• Pushes beams sequentially and retrieves them post-cutting.
• Uses hydraulic pusher arms for smooth engagement.
5. Control Cabin / Operator Station:
• Remotely controls the entire process.
• Monitors cutting, conveyor load, gas detection, and machine alignment.
6. Power & Communication System:
• Electric supply (via trailing cable).
• Wireless telemetry for data exchange with sensors and cameras.

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🧠 Cutter Module Design & DGMS Safety Parameters

Parameter	Typical Range / Requirement
Cutter Power	250–300 kW
Drum Diameter	1.0–1.5 m
Seam Thickness	2.5–6.0 m
Pushbeam Length	6.0 m
Max Penetration Depth	300–400 m
Control System	Remote with interlocks
Monitoring	CCTV + gas & vibration sensors

DGMS Technical Guidelines:

• Machines must have flameproof enclosures in gassy areas.
• DGMS Tech Circular 01 of 2015 mandates slope stability, mechanical design & automation checks.
• Regular inspection logbooks for every 24-hour cycle are compulsory.

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🦺 Safety Features & DGMS Compliance

1. Interlocks: Prevent machine movement without power isolation.
2. Emergency Stop: Dual-line kill switch system at control and launch unit.
3. CCTV & Gas Monitoring: Continuous remote surveillance.
4. Slope Monitoring System (SSR): Detects wall movement >5 mm/hour.
5. Dust Suppression: Water spray nozzles on cutter head and conveyor.
6. Preventive Maintenance: Daily inspection by mechanical engineer (Reg. 126, CMR 2017).

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📘 DGMS Relevance in Exam

• Questions on equipment, automation, and safety design frequently appear in DGMS First Class (Coal) and Second Class Manager exams.
• Common MCQ topics: pushbeam design, cutter head power, slope safety, and DGMS circulars.

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🧾 25 MCQs – Highwall Mining Equipment & Cutter Module Design 

Q1. The main working unit of a Highwall Miner is the:
A. Launch Vehicle
B. Cutter Module
C. Conveyor Head
D. Feeder Breaker
E. Dump Hopper
Answer: B.
Solution: The cutter module performs coal extraction at the highwall face.

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Q2. The power rating of a typical cutter head motor is about:
A. 50 kW
B. 100 kW
C. 250–300 kW
D. 500 kW
E. 800 kW
Answer: C.
Solution: Typical HWM cutter power ranges between 250–300 kW.

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Q3. Each pushbeam in an HWM system is approximately:
A. 2 m long
B. 4 m long
C. 6 m long
D. 8 m long
E. 10 m long
Answer: C.
Solution: Standard pushbeam modules are 6 m each.

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Q4. DGMS mandates use of flameproof machinery under which conditions?
A. Opencast operations
B. Gassy seam working
C. Surface blasting
D. Workshop repair
E. Conveyor belt area
Answer: B.
Solution: Flameproof systems are mandatory in gassy environments.

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Q5. The chain conveyor inside pushbeams is used to:
A. Support beams
B. Convey coal from cutter to surface
C. Power the cutter head
D. Detect gas
E. Provide alignment
Answer: B.
Solution: Chain conveyors carry coal from the face to the launch vehicle.

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Q6. The launch vehicle is positioned at:
A. Top of dump
B. Highwall bench edge
C. Workshop
D. Pit bottom
E. Loading station
Answer: B.
Solution: It remains fixed at the highwall bench, pushing beams into seam.

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Q7. Which system retrieves pushbeams after cutting?
A. Feeder breaker
B. Hydraulic retrieval arm
C. Belt reclaimer
D. Winch
E. Cable dragger
Answer: B.
Solution: Retrieval is by hydraulic arms controlled from the launch unit.

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Q8. DGMS Tech Circular 01 of 2015 relates to:
A. Drilling
B. Slope stability & highwall safety
C. Explosive use
D. Lighting systems
E. Fire rescue
Answer: B.
Solution: Circular 01/2015 details slope and highwall safety in HWM.

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Q9. The main risk during HWM operation is:
A. Electrical shock
B. Highwall failure
C. Dust only
D. Oil spillage
E. Noise
Answer: B.
Solution: Highwall failure is a critical safety concern.

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Q10. Maximum recommended penetration depth is:
A. 100 m
B. 150 m
C. 300–400 m
D. 600 m
E. 1 km
Answer: C.
Solution: Typical depth is limited to 300–400 m for safety.

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Q11. The primary cause of slope instability during HWM operations is:
A. Rainwater infiltration
B. Poor lighting
C. Improper ventilation
D. Excessive machine vibration
E. Operator fatigue
Answer: A.
Solution: Water infiltration weakens toe and causes slope failure.

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Q12. The ideal slope angle for highwall stability in medium-strength strata is approximately:
A. 20°
B. 30°
C. 45°
D. 60°
E. 75°
Answer: C.
Solution: 45° gives safe equilibrium between stability and productivity.

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Q13. What instrument is used for real-time slope movement detection?
A. Methanometer
B. Barometer
C. Slope radar
D. Hygrometer
E. Seismometer
Answer: C.
Solution: Slope radars and prisms monitor movement continuously.

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Q14. In HWM, which component performs the actual coal cutting?
A. Launch vehicle
B. Pushbeam
C. Cutter module
D. Conveyor belt
E. Winch motor
Answer: C.
Solution: Cutter module performs mechanical coal cutting.

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Q15. Safety interlocks in HWM system are designed to:
A. Increase cutting speed
B. Ensure automatic shutdown in unsafe condition
C. Boost conveyor power
D. Maintain slope angle
E. Reduce vibration
Answer: B.
Solution: Interlocks protect machinery and personnel during faults.

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Q16. What is the typical penetration limit for each web in HWM?
A. 100 m
B. 200 m
C. 300 m
D. 400 m
E. 500 m
Answer: C.
Solution: Average safe penetration depth is 250–300 m.

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Q17. Which DGMS regulation specifies methane testing before starting any mechanical cutting?
A. Reg. 123
B. Reg. 153
C. Reg. 168
D. Reg. 177
E. Reg. 199
Answer: B.
Solution: Reg. 153 deals with gas testing and monitoring.

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Q18. The function of the launch vehicle in HWM is to:
A. Cut coal
B. Support the highwall
C. Push and retrieve the cutter module
D. Monitor gas concentration
E. Drain water
Answer: C.
Solution: Launch vehicle pushes and retrieves the module with pushbeams.

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Q19. What is the main purpose of installing toe drains below the highwall?
A. Aesthetic improvement
B. Drain surface runoff
C. Prevent slope slippage
D. Reduce gas accumulation
E. Increase coal recovery
Answer: C.
Solution: Toe drains reduce pore pressure and prevent slippage.

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Q20. Minimum width of safety berm at bench edge near highwall should be:
A. 1 m
B. 2 m
C. 3 m
D. 4 m
E. 5 m
Answer: D.
Solution: Standard safety berm width is at least 4 m.

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Q21. Which component of HWM conveys coal to surface?
A. Cutter head
B. Conveyor car
C. Launch vehicle belt conveyor
D. Hydraulic pump
E. Cable reel
Answer: C.
Solution: Conveyor belt in launch vehicle transfers coal to surface.

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Q22. Slope stability analysis in HWM is carried out using:
A. Empirical charts
B. Numerical modeling
C. Limit equilibrium & finite element method
D. Visual inspection only
E. Laboratory tests only
Answer: C.
Solution: FEM and LEM methods are standard for slope design.

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Q23. DGMS mandates slope inspection frequency during HWM operations as:
A. Once daily
B. Once weekly
C. Once every shift
D. Once monthly
E. Every 15 days
Answer: C.
Solution: Shift-wise inspection by competent person is mandatory.

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Q24. Which system integrates all gas sensors, cameras, and radar data in HWM?
A. SCADA
B. ERP
C. WRAC
D. DGMS portal
E. Mine network
Answer: A.
Solution: SCADA system provides centralized safety monitoring.

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Q25. In the event of slope failure detection, the first immediate step is:
A. Continue operation under caution
B. Evacuate personnel and shut down system
C. Increase radar frequency
D. Drain water
E. Inform DGMS only
Answer: B.
Solution: Immediate evacuation and system shutdown are statutory requirements.

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                   ✅ Conclusion 

The Highwall Mining system’s efficiency depends on its machinery reliability and DGMS-compliant design.
Understanding equipment specifications, safety interlocks, and mechanical configurations is essential for DGMS exam success and real-world mine management.

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