Highwall Mining in Indian Coal Mines – Working, DGMS Safety Guidelines & Regulations

Highwall Mining in Indian Coal Mines – Working, DGMS Safety Guidelines & Regulations

🧾 DETAILED NOTES

1️⃣ Introduction

Highwall Mining (HWM) is an advanced method used to extract coal from exposed seams that remain after opencast mining becomes uneconomic. It combines the features of surface and underground mining, offering a safe, eco-friendly, and productive way to recover residual coal. In India, HWM has been successfully introduced by companies like SECL, SCCL, and CCL under DGMS supervision. DGMS regulates its operation through circulars and provisions under CMR 2017 – Regulations 99, 100, and 106.

2️⃣ Working Principle

Highwall Mining uses a remotely operated miner positioned at the highwall face. The machine drives a series of parallel entries (holes) into the coal seam using an extendable push beam system, cutting and conveying coal to the surface via a conveyor system.

Main components:

Highwall Miner Crawler Unit
Push Beam and Cutter Head
Conveyor System
Launch Platform and Control Cabin
Tramming Mechanism

3️⃣ DGMS Guidelines and Regulations

CMR 2017 Regulation 99 – Safe use of machinery.
Regulation 106 – Stability of benches, highwalls, and dumps.
DGMS Circular 6 of 2011 – Safety provisions for Highwall Mining operations.
DGMS Circular 7 of 2014 – Geotechnical study and slope stability requirement.
Approval from DGMS – Mandatory before deploying HWM equipment.

4️⃣ Safety Precautions

Geotechnical assessment of highwall stability.
Highwall height ≤ 50 m (unless permitted).
Remote-controlled operation from safe cabin.
No personnel entry beyond launch platform.
Regular inspection of roof/side stability.
24×7 gas and strata monitoring system.
Emergency power cutoff and fire protection system.

5️⃣ Advantages

Recovery of residual coal from highwalls.
No exposure of personnel to underground hazards.
Lower operating costs and minimal blasting.
High productivity and reduced environmental impact.

6️⃣ Limitations

Restricted to specific seam conditions (flat, uniform seams).
High equipment cost.
Limited penetration (typically 300 m).
Requires expert operation and monitoring.

7️⃣ Case Study (DGMS Report – 2015)

In a Central Coalfields Ltd. (CCL) mine, a Highwall Miner extracted 1.2 Mt coal from the leftover highwall. DGMS inspection confirmed stable operations, provided that periodic slope monitoring, drainage, and remote control operation were strictly maintained.

⚙️ QUICK ONE-LINERS (Revision Points)

HWM is a hybrid of opencast and underground mining.
DGMS Circular 6 of 2011 – Highwall mining safety.
Reg. 106 – Stability of highwall and dumps.
Max penetration length ≈ 300 m.
Operation is fully remote-controlled.
No man entry beyond launch area.
FOS (Factor of Safety) ≥ 1.3 for wall stability.
Regular slope & gas monitoring mandatory.
Used by SECL, SCCL, and CCL.
DGMS approval must precede operation.

🧮 DESCRIPTIVE MODEL QUESTION

Q. Explain the principle, advantages, and DGMS safety provisions for the use of Highwall Mining technology in Indian coal mines.

Answer:
Highwall Mining extracts coal from exposed seams by remotely operating a cutter head through the highwall face. DGMS mandates pre-assessment of wall stability (Reg. 106 of CMR 2017) and compliance with Circular 6/2011. Major benefits include improved safety, productivity, and resource recovery without underground exposure. Preventive measures include slope monitoring, gas detection, and restricted man access.

🧩 25 DGMS-Based MCQs (Dynamic Answers – A–E)

Q1. Highwall Mining is used in:

Solution: HWM combines surface operation (like opencast) with underground extraction, so 'Both' (C) is the most accurate description of its hybrid nature.

Q2. Highwall Mining extracts coal from:

Solution: HWM is used to recover coal from the highwall face left after opencast mining reaches its economic limit.

Q3. DGMS Circular related to Highwall Mining:

Solution: DGMS Tech. Circular 6 of 2011 provides specific safety provisions for HWM operations.

Q4. Highwall Mining operation is:

Solution: The entire operation of the miner inside the seam is remote-controlled from a safe cabin on the surface.

Q5. Regulation dealing with wall stability:

Solution: Regulation 106 of CMR 2017 specifically covers the stability of benches, highwalls, and dumps.

Q6. Typical penetration of Highwall Miner:

Solution: The penetration depth is typically limited to around 300 meters due to navigation and conveying constraints.

Q7. Factor of safety for slope stability:

Solution: A minimum Factor of Safety of 1.3 is the standard geotechnical requirement for long-term highwall stability.

Q8. Highwall Miners operate without:

Solution: HWM is a continuous cutting method that does not require drilling and blasting (explosives).

Q9. Launch platform location:

Solution: The miner operates from a launch platform (bench) prepared at the base of the exposed highwall seam.

Q10. Main advantage of HWM:

Solution: The primary safety advantage is that no personnel enter the underground entries, as it's fully remote-controlled. (This is a better answer than the original prompt's "Reduced manpower").

Q11. Primary hazard in HWM:

Solution: The entire operation depends on the geotechnical stability of the highwall; a slope failure would be catastrophic.

Q12. Equipment used for coal recovery:

Solution: The machine uses a 'push beam' system which also contains the conveying system to transport coal back to the launch platform.

Q13. Highwall height generally limited to:

Solution: DGMS guidelines often cap the highwall height for HWM operations at 50m unless special permission is granted.

Q14. DGMS approval is required:

Solution: Introducing a new, high-capacity mining method requires prior permission and safety clearance from DGMS.

Q15. Monitoring system in HWM:

Solution: Slope stability radar and prism-based total stations are standard geotechnical tools for monitoring highwall movement.

Q16. DGMS Circular 7/2014 focuses on:

Solution: This circular deals with slope and dump stability analysis, which is directly applicable to highwall safety.

Q17. Coal recovery in HWM depends on:

Solution: All these geological and geotechnical factors determine the feasibility and extent of HWM.

Q18. Worker entry beyond highwall face:

Solution: The method is designed to be fully remote-controlled, and personnel entry into the driven entries is strictly prohibited.

Q19. Power source for Highwall Miner:

Solution: HWMs are powerful machines that run on high-voltage electricity supplied via a trailing cable.

Q20. The maximum slope angle for highwall:

Solution: The stable angle depends on rock mechanics, but it is generally much steeper than a dump slope (28°) and well below 45° for safety. The final angle is determined by a geotechnical study.

Q21. DGMS mandates inspection of slope:

Solution: Regular visual inspection (often daily) and instrumented monitoring (weekly/monthly or as per plan) are required. Weekly is a standard minimum for formal checks.

Q22. Major Indian company using HWM:

Solution: SECL (South Eastern Coalfields Ltd), along with SCCL and CCL, are the primary users of HWM technology in India.

Q23. Risk assessment before HWM is done by:

Solution: A thorough geotechnical risk assessment of the highwall stability is the most critical step before deployment.

Q24. Primary benefit of HWM:

Solution: HWM achieves all three: it improves safety (no men underground), increases recovery (extracts locked coal), and eliminates blasting.

Q25. DGMS regulates HWM under:

Solution: As HWM is predominantly used in coal mines in India, it is regulated under the Coal Mines Regulations (CMR) 2017.

🔗 INTERNAL LINKS

Related Topic	Read More On...
Opencast Safety	Small Opencast Manager Appointment
Slope Stability	Design & Monitoring of Pit/Dump Slopes
DGMS Syllabus	DGMS Exam Syllabus 2025 - CMR & MMR Guide
CMR 2017	CMR 2017 Part 2 - Working & Supervision Rules

🚜 Prepare for DGMS Exams the Smart Way!

Master DGMS circulars, mining regulations, and advanced technologies with Online Mining Exam – India’s 1st Online Mining Academy.

Detailed Mechanized Mining Notes
DGMS Circulars Explained
5000+ Topic-wise MCQs

👉 Visit: www.onlineminingexam.com
📞 Call/WhatsApp: 9971114020

Download Highwall Mining Notes & Practice MCQs Now!

Online Mining Exam